A periodical of the Faculty of Natural and Applied Sciences, UMYU, Katsina
ISSN: 2955 – 1145 (print); 2955 – 1153 (online)
ORIGINAL RESEARCH ARTICLE
Ikemesit Udeme Peter1*, Obike Onyedikachi Chijindu2, Justina Nnenna Ngwu3, Akunna Perpetua Emeruwa4,5,, Ijeoma Onyinye Okolo6 and Mohammed Ismaila Danjuma7
1Department of Microbiology, Faculty of Basic Medical Sciences, Federal University of Allied Health Sciences, Trans-Ekulu, Enugu, Nigeria
2Department of Clinical Pharmacy, Faculty of Pharmaceutical Science, University of Nigeria, Nsukka
3Department of Dental Therapy, Faculty of Dental Health, Federal University of Allied Health Science, Trans-Ekulu, Enugu, Nigeria
4Department of Microbiology and Parasitology, David Umahi Federal University of Health Science, Uburu, Ebonyi State, Nigeria
5International Institute for Infectious Disease, Biosafety and Biosecurity, Uburu, Ebonyi State, Nigeria
6Department of Biochemistry, Faculty of Basic Medical Sciences, Federal University of Allied Health Science, Trans-Ekulu, Enugu, Nigeria
7Department of Nursing Sciences, Faculty of Health Sciences, Federal University of Lokoja, Kogi, Nigeria
*Correspondence: ikemesitpeter@gmail.com
The increasing prevalence of biofilm-forming and carbapenemase-producing Gram-negative Bacilli (GNB) in catheterized patients is linked to significant clinical challenges, including persistent infections, prolonged hospital stays, and higher colonization rates. To address these issues, establishing localized antimicrobial resistance (AMR) surveillance data is critical for guiding effective patient management and implementing robust infection prevention and control strategies. This study analyzed 200 indwelling urinary catheters (IUCs) from hospitalized patients using standard microbiological techniques, with isolates characterized using the VITEK 2 system. Phenotypic screening for biofilm production and carbapenem resistance was conducted using the Congo Red Assay and the Carba NP Test, respectively. Carbapenemase genes were identified via Polymerase Chain Reaction (PCR) with specific primers. Of the 200 samples, 164 (82.0%) were positive for GNB, with 87 (43.5%) identified as biofilm producers. Carbapenem resistance was confirmed in 89 (44.5%) isolates using CRE agar and the Carba NP Test. The distribution of carbapenemase genes among GNB isolates was as follows: blaKPC (29.5%), blaNDM (100%), blaVIM (13.5%), blaOXA (100%), and blaIMP (20.0%). Antibiogram analysis revealed high resistance rates (54.5%-100%) to amoxicillin-clavulanic acid, trimethoprim-sulfamethoxazole, ceftriaxone, meropenem, and ertapenem. However, susceptibility was observed to nitrofurantoin, ciprofloxacin, and Gentamicin, suggesting their potential as empiric treatments for GNB infections in catheterized patients. The study highlights the importance of adhering rigorously to structured catheter care protocols, including daily assessment of catheter necessity and strict adherence to aseptic techniques during insertion and maintenance. Regular training for healthcare staff on best practices for catheter management is essential to reduce colonization rates and improve clinical outcomes for patients at risk of carbapenem-resistant GNB (CR-GNB) infections. These findings highlight the urgent need for localized AMR surveillance and targeted infection control measures to mitigate the growing threat of multidrug-resistant GNB in healthcare settings.
Keywords: Gram-negative Bacilli (GNB), Biofilm forming, carbapenemase, Indwelling Urinary Catheters
Indwelling urinary catheters are a vital component of clinical care, used to manage urinary incontinence and retention, measure urine output, and support patients recovering from surgical procedures or various medical conditions (Drake et al., 2024). It is estimated that approximately 25% of hospitalized patients require the use of urinary catheters; however, this intervention is associated with a heightened risk of urinary tract infections (UTIs). Research indicates that 70-80% of nosocomial infections acquired within healthcare facilities are linked to catheter-associated urinary tract infections (CAUTIs) (Asmare et al., 2024; Puro et al., 2022). Furthermore, short-term use of indwelling catheters is correlated with an increased incidence of UTIs that may persist even after catheter removal. In instances of long-term catheterization, the occurrence of bacteriuria is anticipated in a significant majority of users. Consequently, healthcare professionals must be vigilant in addressing potential complications such as symptomatic UTIs and recurrent catheter blockages. By adopting comprehensive management strategies, providers can optimize patient outcomes and enhance the quality of care for individuals who depend on indwelling urinary catheters.
Indwelling urinary catheters are widely recognized for their role in promoting bacterial colonization within the body, which can lead to hospital-associated infections (Niveditha et al., 2012; Stickler et al., 2014; Stærk et al., 2024). The most common pathogens responsible for catheter-associated urinary tract infections (CAUTIs) are Gram-negative bacilli (GNB), including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, and Acinetobacter baumannii (Flores-Mireles et al., 2019). Recent studies have shown that K. pneumoniae, A. baumannii, E. coli, and P. aeruginosa account for 13.3–53.3%, 8–25%, 18.5–40.5%, and 7.1–20.2% of CAUTIs, respectively (Asmare et al., 2024; Oumer et al., 2021; Awoke et al., 2019; Kołpa et al., 2018). The risk of urinary tract infections (UTIs) is linked to the duration of catheter use. The prevalence of bacteriuria increases daily by an estimated 3% to 10%, and nearly all patients with an indwelling catheter will develop bacteriuria after 30 days of catheterization (Kulbay et al., 2024; Warren, 2001).
The frequent use of catheterization in healthcare settings presents a significant challenge, as bacteria have the propensity to colonize and contaminate these devices, resulting in the formation of biofilms. The duration for which a urinary catheter remains in place correlates with an increased likelihood of biofilm development by these organisms, potentially predisposing patients to both asymptomatic and symptomatic urinary tract infections (UTIs). Catheter-associated urinary tract infections (CAUTIs) are identified as the most prevalent adverse events associated with indwelling urinary catheter use (Wald, 2008; Tambyah, 2000). Notably, CAUTIs are often asymptomatic, and only 3% of affected individuals will progress to develop bacteremia with a urinary isolate (Nakawuki et al., 2022).
Bacteria can proliferate in biofilms on the surfaces of catheters, which are organized communities of microorganisms encased in a self-produced extracellular polymeric matrix (Niveditha et al., 2012). The formation of these biofilms poses significant challenges in healthcare environments, resulting in persistent and recurrent infections as well as device-related infections. Biofilm-producing bacteria possess the ability to persist on both abiotic and biotic surfaces. This bacterial population may transition between indwelling urinary catheters and vulnerable patients, or alternatively, from patients to catheters. The presence of a catheter increases the patient’s susceptibility to infections by facilitating access for uropathogens to the bladder through both its external and internal surfaces, where biofilms can establish on the catheters and the uroepithelium (Stickler, 2008). Although exposure to antibiotics may temporarily delay the onset of bacteriuria in catheterized patients, such effects are typically short-term. The presence of biofilm-forming bacteria is of considerable medical concern, as they frequently exhibit reduced susceptibility to antimicrobial agents. Furthermore, the close spatial arrangement of cells within a biofilm can promote the exchange of plasmids, thereby enhancing the dissemination of antimicrobial resistance (Niveditha et al., 2012).
Several studies have highlighted the complexity of bacterial populations found in the urine and blood cultures of catheterized patients. Notably, there has been a significant rise in the presence of Extended-Spectrum Beta-Lactamase (ESBL) and carbapenemase-producing Enterobacteriaceae species (Bebell et al., 2017; Tolera et al., 2018; Musinguzi et al., 2019; Amisu et al., 2019). These developments indicate a growing resistance to multiple antibiotic classes.
Carbapenems represent one of the limited treatment options available for multidrug-resistant (MDR) Gram-negative bacilli, including those that produce beta-lactamases genotype. The presence of a urinary catheter is envisaged as a significant risk factor for the development of carbapenem-resistant Gram-negative bacilli (CR-GB) bacteremia. Additional risk factors encompass the utilization of central venous catheters, the presence of other indwelling devices, and patient admission to intensive care units (ICUs). The transmission of carbapenemase-producing Enterobacterales (CPE) can occur both between hospitals and within individual healthcare facilities. Transferring patients from institutions with high rates of CPE to different facilities may lead to the introduction of these organisms into previously unaffected areas. Carbapenem-resistant strains, particularly Pseudomonas aeruginosa and Acinetobacter baumannii, pose substantial challenges in terms of treatment due to their intrinsic resistance mechanisms, capacity to acquire further resistance genes, and their ability to form biofilms. These biofilms can impair immune system clearance and compromise the efficacy of antibiotics. Currently, the emergence of carbapenemase production is recognized as a significant mechanism of drug resistance. Pathogens that produce carbapenemase, including Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-β-lactamase (NDM), present critical challenges in the management of patients with urinary catheters. These enzymes confer resistance to carbapenems, which are vital for the treatment of severe Gram-negative infections, and are often encoded on mobile genetic elements that facilitate rapid dissemination. The rising prevalence of these pathogens has been linked to adverse clinical outcomes, including persistent infections, prolonged hospital stays, and higher rates of colonization.
Research indicates that the proliferation of carbapenemase-producing bacteria in Nigeria is contributing to a significant increase in mortality rates associated with various bacterial infections within the region (Nomeh et al., 2022; Ilang et al., 2023a; Joseph et al., 2023; John-Onwe et al., 2023).
Indwelling urinary catheters (IUCs) can contribute to urinary incontinence and retention, and their use is linked to the risk of device-related healthcare-associated infections (HCAIs). Low-income countries, including Nigeria, encounter significant challenges in implementing effective preventive measures. These challenges encompass inadequate environmental hygiene, characterized by microbial colonization of drainage bags, catheter insertions performed outside of sterile operating environments, and non-compliance with catheter care protocols. Additionally, factors such as poor infrastructure, insufficient medical equipment, understaffing, overcrowding, and the prevalence of rapidly deteriorating underlying health conditions exacerbate the risk of biofilm formation and the transmission of carbapenemase-producing Gram-negative bacilli. Such factors may lead to colonization of indwelling urinary catheters and pose enhanced risks to less susceptible patients. Currently, there is a dearth of epidemiological data concerning biofilm-forming and carbapenemase-producing organisms among patients with IUC in Nigeria. Previous studies on catheter-associated urinary tract infections (CAUTI) (Amisu et al., 2019; Sharif et al., 2020; Bashir et al., 2020) have primarily overlooked the prevalence of biofilm-forming and carbapenemase-producing bacteria in these patients. Consequently, significant knowledge gaps remain regarding the prevalence of these organisms and their associated antibiotic resistance profiles within Nigeria. To facilitate the effective management of patients with IUC and to implement comprehensive infection prevention and control measures, it is imperative to establish current and localized antimicrobial resistance (AMR) surveillance data. Such information is vital for addressing the spread of AMR associated with indwelling urinary catheters.
Patients who were not catheterized were excluded from this study. The research was conducted within the Departments of Obstetrics and Gynaecology, Intensive Care Unit (ICU), and Surgical services. Approval was obtained from the Institutional Ethical Committee of the University of Calabar Teaching Hospital, located in Cross River State, Nigeria, at latitude 4° 57.4’ N and longitude 80° 19’ 10.2” E (Edemekong et al., 2025), prior to the collection of samples. This study complied with the ARRIVE guidelines (Animal and Human Research: Reporting of In Vivo and In Vitro Experiments) for the reporting of experiments involving both animal and human subjects (https://arriveguidelines.org). To protect participant confidentiality, all identifiable information was anonymized during data collection and analysis.
A total of 200 indwelling urinary catheters were collected from hospitalized patients over three months. All patients admitted to the wards were eligible for study participation within 48 hours after admission. The urinary catheters were removed as directed by the reviewing medical personnel during their rounds. The tip of each catheter was aseptically cut about 2-3 cm below the balloon point with a disinfected pair of scissors and immediately placed into Brain-Heart infusion broth. This sample was transported in a cooler box to the microbiology laboratory within 30 minutes to maintain sample integrity, following standard protocols. The samples were then sent to the Microbiology Laboratory at the University of Calabar, where cultures were performed to identify the bacterial species. Bacterial culture isolations were carried out using standard techniques. After overnight incubation, a loopful of the catheter tip turbidity broth culture was seeded onto CHROMagar™ Acinetobacter, cetrimide agar, MacConkey agar, and Klebsiella ChromoSelect Selective Agar (Sigma-Aldrich, Darmstadt, Germany). These were incubated at 37°C for 24 to 48 hours. The colonial appearances, which included red, green, pink, and purple (mucoid) growths, indicated the presence of Acinetobacter baumannii, Pseudomonas aeruginosa, E. coli, and Klebsiella pneumoniae, respectively. To proceed with identification, the isolated colonies were further screened using the Gram staining technique and various biochemical tests, including the oxidase test, indole test, catalase test, urease test, citrate test, coagulase test, and triple sugar iron (TSI) test, along with the TSI slant and butt test (Tille, 2015). The bacteria were also identified using the VITEK-2 Automated System (BioMérieux, France).
By growing isolates on Congo red agar (CRA), the phenotypic characterization of Gram-negative bacilli strains that produce biofilms was carried out. The CRA was made by mixing 37 g/L of Brain Heart Infusion broth (bioMérieux, France) with 50 g/L of sucrose, 10 g/L of agar, and 0.8 g/L of Congo red dye (Peter et al., 2022). After being autoclaved separately, Congo red was added to the mixture that had cooled to 55°C. After being streaked onto the agar, the isolates were cultured for 24 hours at 37°C. When bacterial polysaccharides interact with the Congo red dye, biofilm-producing bacteria form black colonies, but non-biofilm-producing bacteria stay red. Following incubation, bacteria that produced biofilms were identified by their strong black, black, or reddish-black colonies with a hard, crystalline texture. Conversely, isolates exhibiting Bordeaux-red or smooth red colonies were designated as non-biofilm producers (Peter et al., 2022).
In this study, the antibiotic resistance profiles of Gram-negative bacilli (GNB) isolates were evaluated against twelve antibiotics. The antibiotics tested included amoxicillin-clavulanic acid (20/30 µg), ceftriaxone (30 µg), cefotaxime (30 µg), ceftazidime (30 µg), cefepime (30 µg), nitrofurantoin (10 µg), trimethoprim-sulfamethoxazole (1.25/23.75 µg), gentamicin (5 µg), ciprofloxacin (5 µg), ertapenem (10 µg), imipenem (10 µg), and meropenem (10 µg) (Oxoid, UK). Susceptibility testing was conducted on Mueller-Hinton agar (Sigma-Aldrich, Darmstadt, Germany) using the Kirby-Bauer disk diffusion method, following the standardized guidelines provided by the Clinical and Laboratory Standards Institute (CLSI) (CLSI, 2021; Edemekong et al., 2025). Bacterial growth around the antibiotic discs was observed, and the zones of inhibition were measured using a metric ruler. The results were interpreted in accordance with the 2021 CLSI guidelines.
The initial screening for carbapenemase production in Gram-negative bacilli (GNB) was conducted based on the susceptibility profiles of the isolates to imipenem and meropenem. Isolates of GNB that demonstrated resistance to ertapenem, imipenem, and/or meropenem were identified as potential carbapenemase producers. These isolates were subsequently evaluated using a chromogenic medium known as Chromatic Carbapenem-resistant Enterobacteriaceae agar, which consists of a Chromatic Carbapenem-resistant Enterobacteriaceae agar base supplemented with 1% Chromatic CRE (Liofilchem, Province of Teramo, Italy) (CLSI, 2021). In this evaluation, two to three separate colonies of GNB isolates were suspended in 3 mL of normal saline and inoculated onto the Chromatic CRE agar. The confirmation of carbapenemase production was established by observing the growth of specific pigmented colonies of GNB on the Chromatic CRE agar. The identification of bacterial species was performed in accordance with the chromogenic color code specified in the manufacturer’s instructions (Liofilchem, 2020).
This was done to ensure the accuracy and reliability of the test. The culture media were assessed for sterility by incubating the batch of sterilized solidified media at 37 °C for 24 hours, and their quality was checked by seeding the agar plates with the control bacteria strain. For the carbapenemase production positive strain, Escherichia coli ATCC 25922, K. pneumoniae ATCC BAA 1705 [American Type Culture Collection (ATCC)] were used, while K. pneumoniae ATCC BAA 1706 was used for the carbapenemase production negative control.
Carbapenemase production was also confirmed via the Carba NP test, a rapid colorimetric assay based on the hydrolysis of carbapenem by carbapenemase enzymes (Bouslah et al., 2020). Isolates that produce carbapenemase turn the solution from red to yellow, indicating positive results.
All carbapenem-resistant isolates underwent molecular analysis to detect specific carbapenemase-encoding genes using PCR. The following genes were targeted: (i) blaKPC, (ii) blaNDM, (iii) blaVIM, (iv) blaOXA, and (v) blaIMP (Saleem et al., 2025; Shahid et al., 2023; Nomeh et al., 2023a). PCR was conducted via the following protocol. First, we performed DNA extraction via a standard boiling method. Second, we performed PCR amplification using specific primers for the abovementioned genes. Finally, the amplified products were run on a 1.5% agarose gel, stained with ethidium bromide, and visualized under UV light
The distribution of Gram-negative bacilli (GNB) across the analyzed samples revealed a high prevalence rate of 164 (82.0%) in catheter tips collected from hospitalized patients. Among the identified isolates, Escherichia coli was the most predominant, accounting for 35.0% of cases. This was followed by Klebsiella pneumoniae at 19.5% and Pseudomonas aeruginosa at 16.5% as shown in Table 1. In contrast, Acinetobacter baumannii was the least frequently isolated, representing only 11.0% of the GNB identified. These findings highlight the significant role of catheter-associated colonization by GNB in hospital settings, with E. coli emerging as the leading pathogen in this context.
A total of 87 (43.5%) Gram-negative bacilli were biofilm producers, as shown in Figure 1. In different wards, the prevalence was as follows, as presented in Figure 1. Surgical (n=31/15.5%): Acinetobacter baumannii (n=3/1.5%), Pseudomonas aeruginosa (n=6/3.0 %), E. coli (n=15/7.5%), Klebsiella pneumoniae (n=7/3.5%). Obstetrics and Gynaecology, (n=47/23.5%), Acinetobacter baumannii (n=5/2.5 %), Pseudomonas aeruginosa (n=10/5.0%), E. coli (n=26/13.0%), Klebsiella pneumoniae (n=12/6.0%). ICU (n=9/4.5%), Acinetobacter baumannii (n=0/0.0%), Pseudomonas aeruginosa (n=3/1.5 %), E. coli (n=4/2.0%), Klebsiella pnuemoniae (n=2/1.0%).
The Antibiotic resistance and Susceptibility of Gram-negative bacilli are presented in Figure 2. The Antibiotic Resistance proportion of Gram-negative bacilli was as follows:
Acinetobacter baumannii (n=22), amoxicillin-clavulanic acid R=16(72.7%), S=6(27.3%), ceftriaxone R= 22(100%), cefotaxime R=13 (59.1%), S=8(36.3%), ceftazidime R=(100%), S=0(0.0 %) cefepime R= 10(45.5%), S=12(54.5%), nitrofurantoin R=4 (18.2%), S=18(81.8%), trimethoprim-sulfamethoxazole R= (100%), S=0(0.0 %), Gentamicin R= 2 (9.1%), S=20(90.9%), ciprofloxacin R=0(0.0 %) S=22(100%), Ertapenem R= 15 (68.2%), S=7(31.8%), imipenem R= 13 (59.1%), S=9 (40.9%), meropenem R= 12 (54.5%), S=10 (45.5%).
Pseudomonas aeruginosa (n=33), amoxicillin-clavulanic acid R=33(100%) S=0(0.0 %), ceftriaxone R=30 (90.9%) S= 3(9.1 %), cefotaxime R=21 (63.6%), S=12(36.3%), ceftazidime = 33(100%) S=0(0.0 %), cefepime R= 33(100%) S=0(0.0 %), nitrofurantoin R=9 (27.3%), S=24(72.7%), trimethoprim-sulfamethoxazole R= (100%), S=0(0.0 %), Gentamicin R=0(0.0 %), S=33 (100%), ciprofloxacin R=0(0.0 %), S=33(100%), Ertapenem R=33 (100.%) S=0(0.0 %, imipenem R= 18 (54.5%), S=15 (45.5%), meropenem R= 33 (100%), S=0(0.0%).
E. coli (n=70), amoxicillin-clavulanic acid R=70(100%), S=0(0.0%), ceftriaxone R=70(100%), S=0(0.0%), cefotaxime R=70(100%), S=0(0.0%), ceftazidime R=70(100%), S=0(0.0%), cefepime R=41 (58.6%), S=29 (41.4%), nitrofurantoin R=17 (24.3%), S=43(61.4%), trimethoprim-sulfamethoxazole R= 70(100%) S=0(0.0%), Gentamicin R=15(21.4%), S=55 (78.57%), ciprofloxacin S=70(100%) S=0(0.0%), Ertapenem R=70(100 %, S=0 (0.0.%), imipenem R= 41 (58.6%), S=29 (41.4%), meropenem R= 51 (72.9%), S=19(27.1%).
Klebsiella pnuemoniae (n=39), amoxicillin-clavulanic acid R=29 (74.4%), S=10(25.6%), ceftriaxone R=39(100%), S=0(0.0%), cefotaxime R=25(64.1%), S=14(35.9%), ceftazidime R=39(100%), S=0(0.0%), cefepime R=21 (53.8%), S=18 (46.2%), nitrofurantoin R=4(10.3%), S=35(89.7%), trimethoprim-sulfamethoxazole R= (100%) S=0(0.0%), Gentamicin R=15(38.5%), S=24 (61.5%), ciprofloxacin R= 16(41.0%) S=23(59.9%), Ertapenem R=39(100 %, S=0 (0.0 %), imipenem R= 18 (46.2%), S=22 (56.4%), meropenem R= 31 (79.5%), S=8(20.5%).
In Figure 3, Carbapenem-resistant Enterobacteriaceae agar and Carba NP Test confirmed 89 (44.5%) Gram-negative bacilli that are carbapenem-resistant. This comprises Acinetobacter baumannii (n=12/%), Pseudomonas aeruginosa (n=18/9.0 9.0%), E. coli (n=41/20.5%), and Klebsiella pneumoniae (n=18/9.0 9.0%). In different wards, the isolation rate of Gram-negative bacilli was as follows.
Surgical (n=17/8.5): Acinetobacter baumannii (n=2/1.0 %), Pseudomonas aeruginosa (n=5/2.5 %), E. coli (n=8/4.0 %), Klebsiella pneumoniae (n=2/1.0 %).
Obstetrics and Gynaecology (n=29/14.5 %): Acinetobacter baumannii (n=3/1.5%), Pseudomonas aeruginosa (n=10/5.0 %), E. coli (n=10/5.0 %), Klebsiella pneumoniae (n=6/3.0 %).
Intensive Care Unit (n=43/21.5 %): Acinetobacter baumannii (n=7/3.5 %), Pseudomonas aeruginosa, (n=3/1.5%), E. coli (n=23/11.5 %), Klebsiella pnuemoniae (n=10//5.0 %).
The Overall occurrence of Carbapenemase Genes in Gram-negative bacilli: blaKPC 59(29.5 %), blaNDM, 89(100 %), blaVIM, 27 (13.5 %), blaOXA 89(100 %), and blaIMP 40 (20.0 %) is presented in Figure 4.
According to hospital wards, the prevalence of the carbapenemase gene was as follows:
Surgical
blaKPC (n=16/8.0)-Acinetobacter baumannii (n=1/%), Pseudomonas aeruginosa, (n=5/%), E. coli (n=8/4%), Klebsiella pnuemoniae (n=2/ %).
blaNDM (n=17/8.5 %)- Acinetobacter baumannii (n=2/1.0 %), Pseudomonas aeruginosa, (n=5/2.5 %), E. coli (n=8/4.0 %), Klebsiella pnuemoniae (n=2/1.0 %).
blaVIM (n=7/3.5)-Acinetobacter baumannii (n=0/0.0 %), Pseudomonas aeruginosa, (n=2/ %), E. coli (n=4/%), Klebsiella pnuemoniae (n=1/ %).
blaOXA (n=17/ 8.5)- Acinetobacter baumannii (n=2/%), Pseudomonas aeruginosa, (n=5/%), E. coli (n=8/4%), Klebsiella pnuemoniae (n=2/ %).
blaIMP (n=10/5.0)-Acinetobacter baumannii (n=2%), Pseudomonas aeruginosa, (n=3/%), E. coli (n=3/%), Klebsiella pnuemoniae (n=2/%).
blaKPC (n=21/10.5 %)- Acinetobacter baumannii (n=3/1.5%), Pseudomonas aeruginosa, (n=3/%), E. coli (n=9/%), Klebsiella pnuemoniae (n=6/%).
blaNDM (n=29/14.5 %)-Acinetobacter baumannii (n=3/1.5%), Pseudomonas aeruginosa, (n=10/5.0 %), E. coli (n=10/5.0 %), Klebsiella pnuemoniae (n=6/3.0 %).
blaVIM (n=7/3.5)-Acinetobacter baumannii (n=0/0.0%), Pseudomonas aeruginosa, (n=2/ %), E. coli (n=3/ %), Klebsiella pnuemoniae (n=2/%).
blaOXA (n=29/14.5 %)- Acinetobacter baumannii (n=3/1.5%), Pseudomonas aeruginosa, (n=10/5.0 %), E. coli (n=10/5.0 %), Klebsiella pnuemoniae (n=6/3.0 %).
blaIMP (n=14/7.0) -Acinetobacter baumannii (n=1/%), Pseudomonas aeruginosa, (n=5/5.0 %), E. coli (n=3/5.0 %), Klebsiella pnuemoniae (n=6/3.0 %).
blaKPC (n=22/11.0 %)-Acinetobacter baumannii (n=5/%), Pseudomonas aeruginosa, (n=1/%), E. coli (n=9/11.5 %), Klebsiella pnuemoniae (n=7/ %).
blaNDM (n=43/21.5%)-Acinetobacter baumannii (n=7/3.5 %), Pseudomonas aeruginosa, (n=3/1.5%), E. coli (n=23/11.5 %), Klebsiella pnuemoniae (n=10//5.0 %).
blaVIM (n=13/6.5 %)- Acinetobacter baumannii (n=1/3.5 %), Pseudomonas aeruginosa, (n=0.0/%), E. coli (n=4/1 %), Klebsiella pnuemoniae (n=8/ %).
blaOXA (n=43/21.5%)- Acinetobacter baumannii (n=7/3.5 %), Pseudomonas aeruginosa, (n=3/1.5%), E. coli (n=23/11.5 %), Klebsiella pnuemoniae (n=10//5.0 %).
blaIMP (n=16/8.0)-Acinetobacter baumannii (n=2/%), Pseudomonas aeruginosa, (n=3/1.5%), E. coli (n=8/%), Klebsiella pnuemoniae (n=3/%).
Table 1: Distribution of Gram-negative bacilli in Catheter tip Samples
| Gram-negative bacilli | Surgical (n=89) | Obstetrics and Gynaecology (n=50) | Intensive Care Unit (n=61) | Frequency (%) |
|---|---|---|---|---|
| Acinetobacter baumannii | 6(3.0) | 11(5.5) | 5(2.5) | 22(11.0) |
| E. coli | 21(10.5) | 35(17.5) | 14(7.0) | 70(35.0) |
| Pseudomonas aeruginosa | 16(8.0) | 14(7.0) | 3(1.5) | 33(16.5) |
| Klebsiella pnuemoniae | 13(6.5) | 19(9.5) | 7(3.5) | 39(19.5) |
| Total | 56(28.0) | 79(39.5) | 29(14.5) | 164 (82.0) |
Figure 1: Frequency of Biofilm-forming Gram-negative Bacilli
Figure 2: Radar chart showing the antibiotic resistance proportion of Gram-negative bacilli
Figure 3: Phenotypic Carbapenem-resistant Enterobacteriaceae agar and Carba NP Test confirmed Carbapenem-resistant Gram-negative bacilli
Figure 4: Prevalence of Carbapenemase Genes in Gram-negative bacilli from different hospital wards
Figure 5(a): Gel image showing amplification of blaNDM at 350bp.
Lane M: Molecular size marker (50bp ladder, Invitrogen, U.S.A®) was used to estimate the base pair size of the amplicons
Lane 1-7= Acinetobacter baumannii, Lane 8-15= Pseudomonas aeruginosa, Lane 16-23= E. coli, Lane 24-39= Klebsiella pnuemoniae
Figure 5(b): Gel image showing amplification of blaOXA at 450bp. A 50bp ladder was used to estimate the base pair size of the amplicons
Lane M: Molecular size marker (50bp ladder, Invitrogen, U.S.A®) was used to estimate the base pair size of the amplicons
Lane 1-5= Acinetobacter baumannii, Lane 6-11= Pseudomonas aeruginosa, Lane 12-16= E. coli, Lane 17-26= Klebsiella pnuemoniae
Figure 5(c): Gel image showing amplification of blaVIM at 550bp. A 50bp ladder was used to estimate the base pair size of the amplicons
Lane M: Molecular size marker (50bp ladder, Invitrogen, U.S.A®) was used to estimate the base pair size of the amplicons
Lane 1-7= Acinetobacter baumannii, Lane 8-12= Pseudomonas aeruginosa, Lane 13-19= E. coli, Lane 20-26= Klebsiella pnuemoniae
Figure 5(d): Gel image showing amplification of blaKPC at 800bp. A 50bp ladder was used to estimate the base pair size of the amplicons
Lane M: Molecular size marker (50bp ladder, Invitrogen, U.S.A®) was used to estimate the base pair size of the amplicons
Lane 1-7= Acinetobacter baumannii, Lane 8-12= Pseudomonas aeruginosa
Figure 5(e): Gel image showing amplification of blaIPM at 500bp. A 50bp ladder was used to estimate the base pair size of the amplicons.
Lane M: Molecular size marker (50bp ladder, Invitrogen, U.S.A®) was used to estimate the base pair size of the amplicons
Lane 1-7= Acinetobacter baumannii, Lane 8-15= Pseudomonas aeruginosa, Lane 16-21= E. coli, Lane 22-27= Klebsiella pnuemoniae
Discussion
The study found that Gram-negative bacilli colonized 164 (82.0%) cases, of catheter tips. Among these, Escherichia coli was the most prevalent at 35.0%, followed by Klebsiella pneumoniae, with Acinetobacter baumannii being the least common at 11.0%. Research indicates that the Gram-negative bacilli identified in Table 1 are commonly isolated from urine samples of both catheterized and non-catheterized patients with urinary tract infections (UTIs), highlighting their potential as human uropathogens (Niveditha et al., 2012; Sharif et al., 2020; Nakawuki et al., 2022; Asmare et al., 2024). Even though the urine samples from these patients did not explicitly assess for asymptomatic bacteriuria (ASB) (Asmare et al., 2024), the colonization of these bacteria in catheter tips raises concerns about the associated risk for both ASB and UTIs. It is essential to note that ASB has been frequently observed in all patients who were catheterized for 30 days or less (Warren, 2001; Luu et al., 2022; Asmare et al., 2024). The presence of these pathogens increases the likelihood of developing UTIs, which can lead to serious complications, especially in individuals with underlying health issues or compromised immune systems. While current literature extensively covers ASB and UTIs in catheterized patients, there remains a critical need for further research to investigate the clinical outcomes following the removal of indwelling urinary catheters (IUCs). Understanding these outcomes is crucial for developing effective management strategies and minimizing the risk of infection after catheter removal.
The high prevalence of Gram-negative bacilli identified in our study suggests areas where improvements can be made. Factors such as host-related pathogen colonization, the need for improved urinary catheter maintenance, and more effective drainage bag care are crucial. Addressing these concerns could significantly reduce catheter colonization rates. Additionally, enhancing education around catheter care practices, particularly regarding the importance of hand hygiene when handling drainage bags, can further improve outcomes. By adhering to CDC guidelines for the prevention of catheter-associated urinary tract infections (CAUTIs) and promoting best practices in catheter care, we can work toward decreasing the risk of catheter-related infections (Gould et al., 2019; Health Protection Surveillance Centre, 2011).
Regarding biofilm assay, the Congo Red method is recognized for its rapidity, sensitivity, and reproducibility. A notable advantage of this method is that the colonies remain viable on the medium. In the present study, 43.5% of Gram-negative bacilli exhibited in vitro biofilm production as determined using Congo Red agar. In comparison, a related study reported biofilm production rates of 60% and 73% in cases of catheter-associated urinary tract infections (Niveditha et al., 2012; Reid, 1992). Biofilms represent the predominant phenotype of nearly all bacteria in their natural environments, irrespective of whether they are pathogenic or environmental. Significant quantities of Gram-negative bacilli were isolated from the catheter tip and shaft, demonstrating a strong capacity of these isolates to colonize foreign bodies within the bladder. The process of biofilm formation facilitates bacterial attachment and colonization on the catheter surface, which likely contributes to successful colonization in the affected patients.
Gram-negative bacilli that produce biofilms exhibit a notable resistance to immune factors and antibiotic therapy, frequently resulting in chronic urinary tract infections (UTIs). In general, free-floating bacterial cells can be effectively eliminated using antibiotic concentrations established through Minimum Inhibitory Concentration (MIC) studies, which indicate the lowest concentration of an antibiotic that prevents visible bacterial growth. However, to successfully eradicate cells embedded within biofilms, concentrations often exceeding 100 times the MIC of the relevant antibiotics are necessary. This substantial increase in required antibiotic concentration arises not only from the protective nature of the biofilm matrix but also from its complex architecture, which serves as a barrier to drug penetration. Consequently, the effective management of such infections necessitates substantial efforts to develop innovative therapeutic agents that either inhibit biofilm formation or promote the detachment of these biofilms, which could greatly enhance treatment efficacy. Biofilms are implicated in a range of persistent infections that are not adequately addressed by traditional antibiotic therapies (Peter et al., 2022). Their formation contributes to the propagation of antibiotic resistance among hospital-acquired pathogens, as biofilms can foster higher mutation rates and facilitate the transfer of genes related to resistance. Thus, overcoming infections linked to device-associated biofilm organisms often requires the removal of the infected implant in conjunction with antibiotic treatment (Peter et al., 2022). Another key aspect of biofilm bacteria is their physiological heterogeneity. This characteristic influences bacterial growth rates and metabolic activities, driven by interbacterial signaling, toxin accumulation, and alterations in the local microenvironment (Uduku et al., 2023). While these so-called persister cells are not inherently resistant to antibiotics, their association within biofilms contributes to their survival during antibiotic treatment. Addressing these challenges through innovative approaches could lead to more effective management of biofilm-related infections.
The antibiotic resistance patterns illustrated in Figure 2 indicate that a significant proportion of the isolates in this study demonstrate resistance to one or more commonly utilized antibiotics, including cephalosporins, carbapenems, and trimethoprim-sulfamethoxazole, with resistance rates varying from 18.2% to 100%. Previous investigations have highlighted the implications of Gram-negative bacilli that exhibit resistance to the assessed antibiotics (Nomeh et al., 2022; Ilang et al., 2023a; Joseph et al., 2023; John-Onwe et al., 2023). This notable resistance pattern may arise from insufficiently guided antibiotic prophylaxis before catheterization, as well as ongoing empirical therapy for infections associated with Gram-negative bacilli, such as pneumonia, skin and soft tissue infections, or unspecified septicemia. Additionally, it is critical to identify the determinants of carbapenem resistance in bacterial pathogens. While numerous isolates express carbapenemase, others may develop resistance through alternative mechanisms, such as porin loss (Atrissi et al., 2021) and biofilm formation, as observed in this study. Addressing these issues is imperative for enhancing treatment approaches and mitigating the impact of antibiotic resistance.
Additionally, Gentamicin, nitrofurantoin, and ciprofloxacin were effective against the Gram-negative bacteria. Their judicious application in the clinical care of these patients will reduce prolonged hospital stays and treatment costs.
Non-carbapenemase-producing strains that target carbapenems and β-lactam antibiotics are frequently associated with multidrug resistance (MDR). Mutations in AmpC and its regulatory genes are often linked to Pseudomonas aeruginosa's resistance to novel β-lactam antibiotics and β-lactamase inhibitor combinations (Barceló et al., 2022). On the other hand, plasmid-encoded AmpC is primarily found in resistant Enterobacterales (Philippon et al., 2002). Among the efflux pump systems, the AcrAB-TolC RND system is the most commonly described (Chetri et al., 2019). Additionally, mutations in porin proteins, particularly OmpC and OmpF, can inhibit the entry of carbapenems into the bacterial cell (Masi et al., 2017).
A total of 89 (44.5%) of Gram-negative bacilli were identified as carbapenemase producers through the CRE agar and Carba NP Test. Previous research conducted in Sudan, South Africa, Egypt, Uganda, and Nigeria has shown varying rates of carbapenem resistance among Gram-negative bacilli, reported at 83%, 68%, 62.7%, 28.6%, and 11.9%, respectively (Elbadawi et al., 2021; Perovic et al., 2016; Amer et al., 2016; Okoche et al., 2015; Yusuf et al., 2014). Given the current trends, it is essential to acknowledge that carbapenem resistance is likely to increase in low- and middle-income countries (LMICs) in Africa, primarily due to the unrestricted use of these antibiotics. The CRE agar and Carba NP Test findings indicated resistance rates of Acinetobacter baumannii (n=12, 6.0%), Pseudomonas aeruginosa (n=18, 9.0%), Escherichia coli (n=41, 20.5%), and Klebsiella pneumoniae (n=18, 9.0%). These resistance patterns highlight a concerning trend, particularly since carbapenems are often used as a last line of defense. To tackle this challenge, it is crucial to address the increasing use of carbapenems in both community and hospital settings, alongside improving infection control measures. By implementing effective infection prevention strategies and promoting antimicrobial stewardship programs, we can ensure the judicious use of antibiotics. Additionally, investing in the development of new antibiotics that target these resistant strains is an essential step forward. A collaborative and multifaceted approach is key in combating the rising threat posed by carbapenemase-producing Acinetobacter, E. coli, Klebsiella pneumoniae, and Pseudomonas species. Through concerted efforts, it is possible to improve public health outcomes and enhance treatment options for individuals affected by these resistant infections (Mulani et al., 2019; Jean et al., 2022).
In our study, the most frequently identified carbapenemase-encoding genes were blaNDM and blaOXA, both found in 89 samples (100%). The New Delhi metallo-beta-lactamase (NDM), classified as group B in the Ambler classification, is an enzyme capable of degrading a wide range of beta-lactam antibiotics, including carbapenems. Notably, NDM was primarily identified in K. pneumoniae, E. coli, P. aeruginosa, and Acinetobacter baumannii. Our findings are consistent with those reported in Ethiopia, Mexico, Sudan, India, South Africa, Saudi Arabia, and other Middle Eastern countries (Gashaw et al., 2024; Nieto-Saucedo et al., 2023; Elbadawi et al., 2021; Perovic et al., 2016; Deshpande et al., 2010; Kumarasamy et al., 2010; Sonnevend et al., 2015). NDM is particularly concerning due to its ability to rapidly spread among different bacterial species through horizontal gene transfer, which can lead to the emergence of extensively drug-resistant infections (Gashaw et al., 2024). The blaNDM gene has demonstrated potential for rapid dissemination, as observed in Turkey and other countries worldwide (Karabay et al., 2016; Gashaw et al., 2024). Furthermore, its frequent association with different antibiotic resistance determinants indicates the potential for co-transfer, necessitating comprehensive strategies to address this pressing issue in antibiotic resistance management.
Our study highlights the global distribution of carbapenemases, with a particular focus on the predominance of the blaOXA gene in the Middle East and Africa (Suay-García et al., 2019). We found an even distribution of blaOXA genes among various Gram-negative bacterial isolates, similar to the distribution of the blaNDM gene. The prevalence of the blaOXA-51-like gene in our study aligns with previous research conducted in Egypt (Abouelfetouh et al., 2019) and South Africa (Anane et al., 2020), but it was higher than what was reported in a study from Jimma, which indicated a prevalence of 63.1% (Sewunet et al., 2022). This increase may be attributed to the higher proportion of Gram-negative bacilli strains found in the catheter tip samples we evaluated, compared to earlier studies. We did not explore the regulatory mechanisms that may contribute to the increased expression of blaOXA-51-like enzymes. As such, we can only hypothesize about their potential role in contributing to the phenotypically resistant isolates, which could be further influenced by factors such as changes in membrane permeability or the action of efflux pumps that expel antimicrobials from bacterial cells. Additionally, in the case of Pseudomonas aeruginosa, the carbapenem resistance could be as the result of the carbapenemases gene, and it is also more plausible that this resistance is primarily due to porin loss, a mechanism suggested by previous research (Atrissi et al., 2021), which impairs the bacterium's ability to uptake carbapenem antibiotics effectively. This nuanced understanding of resistance mechanisms is crucial for developing targeted interventions to combat these multidrug-resistant pathogens.
We found the following carbapenemase-encoding genes: blaKPC in 59 cases (29.5%), blaVIM in 27 cases (13.5%), and blaIMP in 40 cases (20.0%). Notably, the presence of these genes is concerning due to their association with resistance to carbapenem antibiotics, which are often used as a last line of defense against serious infections caused by Gram-negative bacteria.
Despite the critical implications of these findings, the literature on the prevalence of such genes remains sparse. Noteworthy studies addressing this issue include those conducted by Garza-Ramos et al. (2023), Nomeh et al. (2023), Ilang et al. (2023b), Garza-González et al. (2023), Ogba et al. (2022), and López-García et al. (2018), which provide valuable insights into the dynamics of resistance mechanisms in clinical settings. Given the high lethality rate linked to infections from carbapenem-resistant Gram-negative bacilli (CR-GNB), underscores the importance of risk assessment at both the hospital and ward levels. This involves not only identifying the specific mechanisms of resistance but also ensuring meticulous care in the maintenance of urinary catheters and drainage bags.
By adhering to stringent catheter care protocols, we can significantly reduce the rates of urinary catheter colonizationa major contributor to infection risks. Moreover, strict adherence to the guidelines established by the Centers for Disease Control and Prevention (CDC) for preventing catheter-associated urinary tract infections (CAUTIs) is essential. These measures will play a vital role in mitigating the risk of catheter-related infections, thereby protecting patient safety and preventing the spread of nosocomial infections by enhancing overall infection control strategies within healthcare settings.
Conclusion
This study reports the biofilm and carbapenemase potential of Gram-negative bacilli colonizing the catheter tip of hospitalized patients. Drugs such as Gentamicin, nitrofurantoin, and ciprofloxacin have been proven effective and can serve as an empirical treatment for infections caused by Gram-negative bacilli colonizing the catheter tips of hospitalized patients. Also, rigorous adherence to structured catheter care protocols is a key strategy for reducing the prevalence of urinary catheter colonization of this strain, which serves as a significant gateway for infections. Regular training for healthcare staff on best practices for catheter management, including daily assessment of the necessity of catheters and proper aseptic technique during insertion and maintenance, is vital. Furthermore, strict adherence to evidence-based guidelines regarding the prevention of catheter-associated urinary tract infections (CAUTIs) will enhance patient safety and quality of care. By adopting these detailed and constructive measures, we can effectively mitigate the risk of catheter-related infections and improve overall clinical outcomes for patients at risk of CR-GNB infections.
CONFLICT OF INTEREST
None
FINANCIAL SUPPORT
None
ETHICS STATEMENT
All experiments in this study were performed following ARRIVE guidelines regarding Animal and human subjects. Documentation is available from the corresponding author upon reasonable request.
REFERENCES
Abouelfetouh, A., Torky, A. S., & Aboulmagd, E. (2019). Phenotypic and genotypic characterization of Carbapenem-resistant Acinetobacter baumannii isolates from Egypt. Antimicrobial Resistance and Infection Control, 8, 1–9. [Crossref]
Amer, W. H., Khalil, H. S., & Abd ELWahab, M. A. A. (2016). Characterization of carpabenem resistant Enterobacteriaceae in risk factors, phenotypic and genotypic characterization of carbapenem resistant Enterobacteriaceae in Tanta University Hospitals, Egypt. International Journal of Infection Control, 12, 1–11. [Crossref]
Amisu, M. A., Awobusuyi, J., Salako, B. L., Mutiu, W. B., & Ojongbede, M. (2019). Localization of urinary tract infection in catheterized adults patients: Experience with the bladder washout technique. Tropical Journal of Nephrology, 14(2), 113–120.
Anane, Y. A., Apalata, T., Vasaikar, S., Okuthe, G. E., & Songca, S. (2020). Molecular detection of carbapenemase-encoding genes in multidrug-resistant Acinetobacter baumannii clinical isolates in South Africa. International Journal of Microbiology, 1, 10–23. [Crossref]
Asmare, Z., Awoke, T., Genet, C., Admas, A., Melese, A., & Mulu, W. (2024). Incidence of catheter-associated urinary tract infections by Gram-negative bacilli and their ESBL and carbapenemase production in specialized hospitals of Bahir Dar, northwest Ethiopia. Antimicrobial Resistance and Infection Control, 13, 10–21. [Crossref]
Atrissi, J., Milan, A., Bressan, R., Lucafò, M., Petix, V., & Busetti, M. (2021). Interplay of Opdp porin and chromosomal carbapenemases in the determination of carbapenem resistance/susceptibility in Pseudomonas aeruginosa. Microbiology Spectrum, 9, e01186-21. [Crossref]
Awoke, N., Kassa, T., & Teshager, L. (2019). Magnitude of biofilm formation and antimicrobial resistance pattern of bacteria isolated from urinary catheterized inpatients of Jimma University Medical Center, Southwest Ethiopia. International Journal of Microbiology, 20, 19–21. [Crossref]
Barceló, I. M., Jordana-Lluch, E., Escobar-Salom, M., Torrens, G., Fraile-Ribot, P. A., Cabot, G., Mulet, X., Zamorano, L., Juan, C., & Oliver, A. (2022). Role of enzymatic activity in the biological cost associated with the production of AmpC β-lactamases in Pseudomonas aeruginosa. Microbiology Spectrum, 10, e02700-22. [Crossref]
Bashir, M., Umar, A. B., & Bilyaminu, M. (2020). Determination of bacteria associated with urinary catheters from patients suffering from urinary tract infections. Dr. Sulaiman Al-Habib Medical Journal, 2(1), 20–23. [Crossref]
Bebell, L. M., Ngonzi, J., Bazira, J., Fajardo, Y., Boatin, A. A., & Siedner, M. J. (2017). Antimicrobial-resistant infections among postpartum women at a Ugandan referral hospital. PLOS ONE, 12(4), e0175456. [Crossref]
Bouslah, Z. (2020). Carba NP test for the detection of carbapenemase-producing Pseudomonas aeruginosa. Médecine et Maladies Infectieuses, 50, 466–479. [Crossref]
Chetri, S., Bhowmik, D., Paul, D., Pandey, P., Chanda, D. D., Chakravarty, A., Bora, D., & Bhattacharjee, A. (2019). AcrAB-TolC efflux pump system plays a role in carbapenem non-susceptibility in Escherichia coli. BMC Microbiology, 19, 210. [Crossref]
Clinical and Laboratory Standards Institute. (2021). Performance standards for antimicrobial susceptibility testing (31st ed.). CLSI.
Clinical and Laboratory Standards Institute. (2022). Performance standards for antimicrobial susceptibility testing (32nd ed.). CLSI Supplement M100.
Deshpande, P., Rodrigues, C., Shetty, A., Kapadia, F., Hedge, A., & Soman, R. (2010). New Delhi Metallo-beta lactamase (NDM-1) in Enterobacteriaceae: Treatment options with carbapenems compromised. Journal of Association of Physicians of India, 58, 147–149.
Drake, M. J., Clavica, F., Murphy, C., & Fader, M. J. (2024). Innovating indwelling catheter design to counteract urinary tract infection. European Urology Focus, 10, 713–719. [Crossref]
Edemekong, C. I., Chukwujekwu, A. G., Okorie, M. E., Udenweze, E., Obodoechi, I. F., Ogbonna, I. P., & Livinus, N. P. (2025). Evaluation of antibacterial activity of selected medicinal plant on extended spectrum β-lactamase producing Salmonella enterica serovar Typhimurium. UMYU Scientifica, 4(1), 28–36. [Crossref]
Elbadawi, H. S., Elhag, K. M., Mahgoub, E., Altayb, H. N., Ntoumi, F., Elton, L., McHugh, T. D., Tembo, J., Ippolito, G., Osman, A. Y., Zumla, A., & Abdel Hamid, M. M. (2021). Detection and characterization of carbapenem resistant Gram‐negative bacilli isolates recovered from hospitalized patients at Soba University Hospital, Sudan. BMC Microbiology, 21, 136. [Crossref]
Flores-Mireles, A., Hreha, T. N., & Hunstad, D. (2019). Pathophysiology, treatment, and prevention of catheter-associated urinary tract infection. Topics in Spinal Cord Injury Rehabilitation, 25(3), 228–240. [Crossref]
Garza-González, E., Bocanegra-Ibarias, P., Bobadilla-Del-Valle, M., Ponce-de-León-Garduño, L. A., Esteban-Kenel, V., Silva-Sánchez, J., Garza-Ramos, U., Barrios-Camacho, H., López-Jácome, L. E., & Colin-Castro, C. A. (2021). Drug resistance phenotypes and genotypes in Mexico in representative gram-negative species: Results from the INVIFAR network. PLOS ONE, 16, e0248614. [Crossref]
Garza-Ramos, U., Silva-Sánchez, J., López-Jácome, L. E., Hernández-Durán, M., Colín-Castro, C. A., Sánchez-Pérez, A., Rodríguez-Santiago, J., Morfín-Otero, R., Rodriguez-Noriega, E., & Velázquez-Acosta, M. D. (2023). Carbapenemase-encoding genes and colistin resistance in Gram-negative bacteria during the COVID-19 pandemic in Mexico: Results from the Invifar Network. Microbial Drug Resistance, 29, 239–248. [Crossref]
Gashaw, M., Gudina, E. K., Ali, S., Gabriele, L., Seeholzer, T., Alemu, B., Froeschl, G., Kroidl, A., & Wieser, A. (2024). Molecular characterization of carbapenem-resistance in Gram-negative isolates obtained from clinical samples at Jimma Medical Center, Ethiopia. Frontiers in Microbiology, 15, 1336387. [Crossref]
Gould, C. V., Umscheid, C. A., Rajender, Agarwal, K., Kuntz, G., & Pegues, D. A. (2019). Guideline for prevention of catheter-associated urinary tract infections. Centers for Disease Control and Prevention. cdc.gov
Health Protection Surveillance Centre (2011). Guidelines for the Prevention of Catheter-Associated Urinary Tract Infection. Published on behalf of SARI by HSE Health Protection Surveillance Centre, 2011. ISBN 978-0-9551236-9-6
Ilang, D. C., Peter, I. U., & Iroha, I. R. (2023a). Antibiotic resistance profile of clinical importance biofilm forming extended spectrum beta-lactamase and carbapenemase phenotype in Gram-negative bacteria isolates. International Journal of Pharmacognosy and Life Science, 4(2), 120–127. [Crossref]
Ilang, D. C., Peter, I. U., & Iroha, I. R. (2023b). Characterization of VIM, VEB and CTX-M beta-lactamase gene in Escherichia coli and Pseudomonas aeruginosa isolated from urine samples of patients visiting a tertiary hospital in Abakaliki. International Journal of Medical Sciences and Pharma Research, 9(4), 7–11. [Crossref]
Jean, S. S., Harnod, D., & Hsueh, P. R. (2022). Global threat of carbapenem-resistant Gram-negative bacteria. Frontiers in Cellular and Infection Microbiology, 12, 823684. [Crossref]
John-Onwe, B. N., Aniokete, U. C., Ibiam, F. A., Peter, I. U., Iroha, C. S., & Iroha, I. R. (2023). Dissemination of multidrug-resistant, extensively drug resistant and pandrug-resistant Pseudomonas aeruginosa isolates among in-patients and out-patients in a multi-profile health care settings. Journal of Advances in Microbiology, 23(10), 109–115. [Crossref]
Joseph, I. S., Okolo, I. O., Udenweze, E. C., Nwankwo, C. E., Peter, I. U., Ogbonna, I. P., & Iroha, I. R. (2023). Comparison of antibiotic-resistant pattern of extended spectrum beta-lactamase and carbapenem resistant Escherichia coli isolates from clinical and non-clinical sources. Journal of Drug Delivery and Therapeutics, 13(7), 107–118. [Crossref]
Karabay, O., Altindis, M., Koroglu, M., Karatuna, O., & Aydemir, Ö. A. (2016). The carbapenem-resistant Enterobacteriaceae threat is growing: NDM-1 epidemic at a training hospital in Turkey. Annals of Clinical Microbiology and Antimicrobials, 15, 1–6. [Crossref]
Karampatakis, T., Tsergouli, K., & Behzadi, P. (2023). Carbapenem-resistant Klebsiella pneumoniae: Virulence factors, molecular epidemiology and latest updates in treatment options. Antibiotics, 12, 234. [Crossref]
Kołpa, M., Wałaszek, M., Gniadek, A., Wolak, Z., & Dobroś, W. (2018). Incidence, microbiological profile and risk factors of healthcare-associated infections in intensive care units: A 10 year observation in a provincial hospital in Southern Poland. International Journal of Environmental Research and Public Health, 15(1), 112. [Crossref]
Kulbay, A., Joelsson-Alm, E., Amilon, K., & Tammelin, A. (2024). Asymptomatic bacteriuria and urinary tract infection in geriatric inpatients after indwelling urinary catheter removal: A descriptive two-centre study. Infection Prevention in Practice, 6, 100411. [Crossref]
Kumarasamy, K., Toleman, M., Walsh, T., & Al. E. (2010). Emergence of a new antibiotic resistance mechanism in India, Pakistan, and the UK: A molecular, biological, and epidemiological study. The Lancet Infectious Diseases, 10, 597–602. [Crossref]
Liofilchem. (2020). Chromogenic medium for the detection of carbapenem-resistant Enterobacteriaceae.
López-García, A., Rocha-Gracia, R. D. C., Bello-López, E., Juárez-Zelocualtecalt, C., Sáenz, Y., Castañeda-Lucio, M., López-Pliego, L., González-Vázquez, M. C., Torres, C., & Ayala-Nuñez, T. (2018). Characterization of antimicrobial resistance mechanisms in carbapenem-resistant Pseudomonas aeruginosa carrying IMP variants recovered from a Mexican hospital. Infection and Drug Resistance, 11, 1523–1536. [Crossref]
Luu, T., & Albarillo, F. S. (2022). Asymptomatic bacteriuria: Prevalence, diagnosis, management, and current antimicrobial stewardship implementations. The American Journal of Medicine, 135, 236–244. [Crossref]
Masi, M., Réfregiers, M., Pos, K. M., & Pagès, J. M. (2017). Mechanisms of envelope permeability and antibiotic influx and efflux in Gram-negative bacteria. Nature Microbiology, 2, 17001. [Crossref]
Mulani, M. S., Kamble, E. E., Kumkar, S. N., Tawre, M. S., & Pardesi, K. R. (2019). Emerging strategies to combat ESKAPE pathogens in the era of antimicrobial resistance: A review. Frontiers in Microbiology, 10, 539. [Crossref]
Musinguzi, B., Kabajulizi, I., Mpeirwe, M., Turugurwa, J., & Kabanda, T. (2019). Incidence and etiology of catheter-associated urinary tract infection among admitted patients at Kabale Regional Referral Hospital, South Western Uganda. Advances in Infectious Diseases, 9, 183–196. [Crossref]
Nakawuki, A. W., Nekaka, R., Ssenyonga, L. V. N., Masifa, G., Nuwasiima, D., & Nteziyaremye, J. (2022). Bacterial colonization, species diversity and antimicrobial susceptibility patterns of indwelling urinary catheters from postpartum mothers attending a tertiary hospital in Eastern Uganda. PLOS ONE, 17(1), e0262414. [Crossref]
Nieto-Saucedo, J. R., López-Jacome, L. E., Franco-Cendejas, R., Colín-Castro, C. A., Hernández-Duran, M., Rivera-Garay, L. R., Zamarripa-Martinez, K. S., & Mosqueda-Gómez, J. L. (2023). Carbapenem-resistant Gram-negative bacilli characterization in a tertiary care center from El Bajio, Mexico. Antibiotics, 12, 1295. [Crossref]
Niveditha, S., Pramodhini, S., Umadevi, S., Kumar, S., & Stephen, S. (2012). Isolation and the biofilm formation of uropathogens in the patients with catheter-associated urinary tract infections (UTIs). Journal of Clinical and Diagnostic Research, 6(9), 1478–1482. [Crossref]
Nomeh, L. O., Federica, O. I., Joseph, O. V., Moneth, E. C., Ogba, R. C., Nkechi, O. A., Peter, I. U., Akpu, P. O., Edemekong, C. I., & Iroha, I. R. (2023). Detection of carbapenemase-producing Escherichia coli and Klebsiella pneumoniae implicated in urinary tract infection. Asian Journal of Research in Infectious Diseases, 2(1), 15–23. [Crossref]
Nomeh, O. L., Chukwu, E. B., Ogba, R. C., Akpu, P. O., Peter, I. U., Nwuzo, A. C., & Iroha, I. R. (2022). Prevalence and antibiogram profile of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae among patients with urinary tract infection in Abakaliki, Nigeria. International Journal of Pathogen Research, 11(3), 14–28. [Crossref]
Ogba, R. C., Nomeh, O. L., Edemekong, C. I., Nwuzo, A. C., Akpu, P. O., Peter, I. U., & Iroha, I. R. (2022). Molecular characterization of carbapenemase encoding genes in Pseudomonas aeruginosa from tertiary healthcare in South Eastern Nigeria. Asian Journal of Biology, Genetic and Molecular Biology, 12(4), 161–168. [Crossref]
Okoche, D., Asiimwe, B. B., Katabazi, F. A., & Kato, L. (2015). Prevalence and characterization of carbapenem-resistant Enterobacteriaceae isolated from Mulago National Referral. PLOS ONE, 10(8), e0135745. [Crossref]
Oumer, Y., Dadi, B. R., Seid, M., Biresaw, G., & Manilal, A. (2021). Catheter-associated urinary tract infection: Incidence, associated factors and drug resistance patterns of bacterial isolates in Southern Ethiopia. Infection and Drug Resistance, 14, 2883–2894. [Crossref]
Patil, H. V., Patil, V. C., Patange, A. P., & Khan, M. A. (2024). Antibiotic resistance profiles of extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL)-producing Klebsiella pneumoniae isolates from diabetic foot ulcers: Implications for treatment strategies. Cureus, 16, e66089. [Crossref]
Perovic, O., Micro, F. S. A., Micro, M., Britz, E., Chb, M. B., & Chetty, V. (2016). In practice molecular detection of carbapenemase-producing genes in referral Enterobacteriaceae in South Africa: A short report. South African Medical Journal, 106(10), 975–977. [Crossref]
Peter, I. U., Okolo, I. O., Uzoeto, H. O., Edemekong, C. I., Thompson, M. D., Chukwu, E. B., Mohammed, I. D., Ubom, I. J., Joseph, O. V., Nwuzo, A. C., Akpu, P. O, and Iroha, I. R (2022). Identification and Antibiotic Resistance Profile of Biofilm-forming Methicillin-Resistant Staphylococcus aureus (MRSA) Causing Infection among Orthopedic Wound Patients. Asian Journal of Research in Medical and Pharmaceutical Science, 11(4): 45-55. [Crossref]
Philippon, A., Arlet, G., & Jacoby, G. A. (2002). Plasmid-determined AmpC-type beta-lactamases. Antimicrobial Agents and Chemotherapy, 46(1), 1–11. [Crossref]
Puro, V., Coppola, N., Frasca, A., Gentile, I., Luzzaro, F., & Peghetti, A. (2022). Pillars for prevention and control of healthcare-associated infections. Antimicrobial Resistance and Infection Control, 11(1), 1–13. [Crossref]
Reid, G., Charbonneau-Smith, R., Lam, D., Kang, Y. S., Lacerte, M., & Hayes, K. C. (1992). The bacterial biofilm formation in the urinary bladder of spinal cord injured patients. Paraplegia, 30(10), 711–717. [Crossref]
Saleem, M., Moursi, S. A., Altamimi, T. N. A., Alharbi, M. S., Alaskar, A. M., Hammam, S. A. H., Rakha, E., Syed Muhammad, O. I., Almalaq, H. A., & Alshammari, M. N. (2025). Prevalence and molecular characterization of carbapenemase-producing multidrug-resistant bacteria in diabetic foot ulcer infections. Diagnostics, 15(2), 141. [Crossref]
Sewunet, T., Asrat, D., Woldeamanuel, Y., Aseffa, A., & Giske, C. G. (2022). Molecular epidemiology and antimicrobial susceptibility of Pseudomonas spp. and Acinetobacter species from clinical samples at Jimma Medical Center, Ethiopia. Frontiers in Microbiology, 13, 951857. [Crossref]
Shahid, M., Saeed, N. K., Ahmad, N., Shadab, M., Joji, R. M., Al-Mahmeed, A., Bindayna, K. M., Tabbara, K. S., Ismaeel, A. Y., & Dar, F. K. (2023). Molecular screening of carbapenem-resistant K. pneumoniae (CRKP) clinical isolates for concomitant occurrence of beta-lactam genes (CTX-M, TEM, and SHV) in the Kingdom of Bahrain. Journal of Clinical Medicine, 12(24), 7522. [Crossref]
Sharif, F. B., Aminu, A., & Idris, A. M. (2020). Catheter associated urinary tract infection among patients attending some selected hospitals in Kano Metropolis. Bayero Journal of Medical Library Science, 5(2), 174–179.
Sonnevend, Á., Ghazawi, A., Hashmey, R., Jamal, W., Rotimi, V., & Shibl, A. (2015). Characterization of carbapenem-resistant Enterobacteriaceae with high rate of autochthonous transmission in the Arabian Peninsula. PLOS ONE, 10(7), e0131372. [Crossref]
Stærk, K., Andersen, K., Hjelmager, J. S., Jensen, L. K., Jørgensen, B. M., Møller-Jensen, J., Lund, L., & Andersen, T. E. (2024). Effect of bladder catheterization on bacterial interference with asymptomatic Escherichia coli strain 83972 in an experimental porcine model of urinary tract infection. The Journal of Infectious Diseases, 229(4), 1–9. [Crossref]
Stickler, D. J. (2008). Bacterial biofilms in patients with indwelling urinary catheters. Nature Clinical Practice Urology, 5(11), 598–608. [Crossref]
Stickler, D. J. (2014). Clinical complications of urinary catheters caused by crystalline biofilms: Something needs to be done. Journal of Internal Medicine, 276(2), 120–129. [Crossref]
Suay-García, B., & Pérez-Gracia, M. T. (2019). Present and future of carbapenem-resistant Enterobacteriaceae (CRE) infections. Antibiotics, 8(3), 122. [Crossref]
Tambyah, P. A., & Maki, D. G. (2000). Catheter-associated urinary tract infection is rarely symptomatic. Archives of Internal Medicine, 160(5), 678–682. [Crossref]
Tolera, M., Abate, D., Dheresa, M., & Marami, D. (2018). Bacterial nosocomial infections and antimicrobial susceptibility pattern among patients admitted at Hiwot Fana Specialized University Hospital, Eastern Ethiopia. Advances in Medicine, 2018, 2127814. [Crossref]
Uduku, N. D., Chinwe, I. F., Happiness, O., Immaculate, N. M., Favor, N. O., Peter, I. U., Aniokete, U. C., & Iroha, I. R. (2023). Antibiotics susceptibility profile of biofilm-forming bacteria isolated from soybean milk drinks sold in Abakaliki metropolis, Nigeria. Advances in Research, 24(6), 168–176. [Crossref]
Wald, H. L. (2008). Indwelling urinary catheter use in the postoperative period. Archives of Surgery, 143(6), 551. [Crossref]
Warren, J. W. (2001). Catheter-associated urinary tract infections. International Journal of Antimicrobial Agents, 17(4), 299–303. [Crossref]
Yuan, P. B., Dai, L. T., Zhang, Q. K., Zhong, Y. X., Liu, W. T., Yang, L., Chen, D. Q., & Ponraj, V. P. (2024). Global emergence of double and multi-carbapenemase producing organisms: Epidemiology, clinical significance, and evolutionary benefits on antimicrobial resistance and virulence. Microbiology Spectrum, 12(1), e00008-24. [Crossref]
Yusuf, I., Arzai, A. H., Haruna, M., Sharif, A. A., & Getso, M. I. (2014). Detection of multidrug resistant bacteria in major hospitals in Kano. Brazilian Journal of Microbiology, 45(3), 791–798. [Crossref]