Urinary tract infections associated with catheter use are among the most frequently encountered healthcare-associated infections. These infections are particularly prevalent in patients who require prolonged hospitalization or intensive care management. The widespread use of indwelling urinary catheters has significantly contributed to the burden of such infections in hospital settings . Catheterization disrupts the natural defense mechanisms of the urinary tract, facilitating the entry and colonization of microorganisms. In addition, pathogens can adhere to catheter surfaces and form biofilms, which enhance their persistence and reduce susceptibility to antimicrobial therapy. Several risk factors influence the development of these infections, including the duration of catheterization, underlying comorbid conditions, and prolonged hospital stay. Microorganisms may reach the urinary tract either by ascending along the external surface of the catheter or through contamination of the internal lumen. A diverse range of microorganisms are implicated in CAUTI, with Gram-negative bacilli being the most common pathogens. Frequently isolated organisms include Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus species. Gram-positive bacteria such as Enterococcus species and Staphylococcus aureus also contribute to these infections. The emergence of antimicrobial resistance has become a major challenge in the management of CAUTI. Multidrug-resistant organisms, capable of resisting multiple classes of antibiotics, are increasingly encountered in clinical practice. This rise in resistance is largely associated with inappropriate and excessive use of antimicrobial agents. Production of enzymes such as extended-spectrum beta-lactamases and carbapenemases further limits the effectiveness of commonly used antibiotics. Consequently, drugs that were previously effective, including fluoroquinolones and cotrimoxazole, are now showing reduced efficacy. Although certain antibiotics like carbapenems and aminoglycosides remain relatively effective, resistance to these agents is also emerging, raising serious concerns. In this context, continuous surveillance of local antimicrobial resistance patterns is essential. Generating institution-specific data can help guide appropriate empirical therapy and improve patient outcomes. Therefore, the present study was undertaken to evaluate the bacterial profile and antimicrobial resistance patterns in CAUTI, with particular emphasis on multidrug resistance.

Study Design and Setting This study was designed as a descriptive cross-sectional study and conducted in the Department of Microbiology at Navodaya Medical College Hospital & Research Centre, Raichur, a tertiary care teaching hospital Study Period The study was carried out over a 12-month duration from January to December 2023 Study Population Urine samples were obtained from catheterized patients who were clinically suspected to have catheter-associated urinary tract infection. Both hospitalized patients and selected outpatient cases were included in the analysis. Sample Selection All eligible bacterial isolates recovered during the study period were included. To avoid duplication bias, only the first isolate obtained from each patient was considered for analysis. Inclusion Criteria • Patients with indwelling urinary catheters • Clinically suspected CAUTI cases • Presence of significant bacteriuria • Non-repetitive bacterial isolates Exclusion Criteria • Samples showing insignificant growth • Contaminated specimens • Repeat isolates from the same patient • Non-bacterial isolates including fungi Specimen Collection and Processing Urine samples were collected under aseptic precautions from the catheter sampling port after appropriate disinfection. The collected specimens were transported promptly to the microbiology laboratory to minimize the risk of contamination and ensure accurate results. Semi-quantitative culture techniques were employed using calibrated loops for inoculation onto CLED agar and blood agar. The inoculated plates were incubated at 37°C for 18–24 hours. Significant bacteriuria was determined based on colony counts consistent with standard microbiological criteria. Identification of Isolates Bacterial identification was performed using conventional microbiological techniques. These included assessment of colony morphology, Gram staining, and a series of biochemical tests such as catalase, coagulase, oxidase, indole, citrate utilization, urease activity, and triple sugar iron reactions. Antimicrobial Susceptibility Testing The antimicrobial susceptibility profile of isolates was determined using the disc diffusion method on Mueller–Hinton agar. Results were interpreted according to established clinical laboratory standards. Antibiotics tested included agents commonly used in the treatment of urinary tract infections. Assessment of Multidrug Resistance Isolates were categorized as multidrug resistant if they exhibited resistance to at least one antimicrobial agent in three or more different classes of antibiotics. Data Analysis The collected data were compiled and analyzed using descriptive statistical methods. Results were expressed as frequencies and percentages, and antibiograms were prepared to depict susceptibility patterns. Ethical Considerations Approval for the study was obtained from the Institutional Ethics Committee

A total of isolates from catheter-associated urinary tract infection (CAUTI) cases were analyzed. Gram-negative organisms predominated. Escherichia coli was the most frequently isolated pathogen, followed by Klebsiella pneumoniae. Other Gram-negative organisms included Klebsiella oxytoca, Pseudomonas aeruginosa, Proteus spp., Citrobacter spp., and Enterobacter spp. Gram-positive organisms such as Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Enterococcus spp., and beta-hemolytic streptococci were less common. (Table 1) Table 1: Distribution of Uropathogens in CAUTI Organism Frequency (n) Percentage (%) Escherichia coli 45 40.9 Klebsiella pneumoniae 12 10.9 Klebsiella oxytoca 4 3.6 Pseudomonas aeruginosa 3 2.7 Proteus spp. 2 1.8 Citrobacter spp. 4 3.6 Enterobacter spp. 2 1.8 Staphylococcus aureus 3 2.7 CoNS 14 12.7 Enterococcus spp. 3 2.7 Beta-hemolytic streptococci 3 2.7 Total 110 100 Gram-negative isolates showed very high resistance to ampicillin, with most isolates resistant. Cephalosporins and fluoroquinolones also showed reduced sensitivity. Better sensitivity was observed with carbapenems, piperacillin–tazobactam, and aminoglycosides, indicating their continued effectiveness in CAUTI. (Table 2) Table 2: Antibiotic Sensitivity Pattern of Gram-negative Isolates (%) Antibiotic Sensitivity (%) Ampicillin 0–10 Amoxicillin-clavulanate 30–50 Piperacillin–tazobactam 70–90 Ceftriaxone 30–50 Cefotaxime 30–45 Ciprofloxacin 20–40 Cotrimoxazole 40–60 Nitrofurantoin 60–80 Imipenem 80–95 Meropenem 75–90 Amikacin 75–90 Gram-positive isolates showed low sensitivity to fluoroquinolones, while doxycycline, vancomycin, and linezolid demonstrated high sensitivity, indicating their reliability in treating Gram-positive infections. (Table 3) Table 3: Antibiotic Sensitivity Pattern of Gram-positive Isolates (%) Antibiotic Sensitivity (%) Ciprofloxacin 25–40 Cotrimoxazole 50–65 Doxycycline 80–95 Tetracycline 80–95 Vancomycin 85–100 Linezolid 85–100 High resistance was observed among Gram-negative isolates to beta-lactams, cephalosporins, and fluoroquinolones, suggesting widespread beta-lactamase production. Emerging resistance to carbapenems was also noted, though they remain largely effective. (Table 4) Table 4: Antibiotic Resistance Pattern of Gram-negative Isolates (%) Antibiotic Resistance (%) Ampicillin 90–100 Cephalosporins 50–70 Fluoroquinolones 60–80 Cotrimoxazole 40–60 Carbapenems 10–25 Amikacin 10–25 A high proportion of Gram-negative isolates demonstrated resistance to multiple antibiotic classes, fulfilling criteria for multidrug resistance. Klebsiella pneumoniae and Escherichia coli showed the highest MDR rates. (Table 5) Table 5: Multidrug Resistance Pattern Organism MDR Trend Escherichia coli High Klebsiella pneumoniae Very high Pseudomonas aeruginosa Moderate–high Gram-positive organisms Moderate

The distribution of pathogens in the present study indicates a clear predominance of Gram-negative organisms in catheter-associated infections. Among these, Escherichia coli was the most frequently isolated organism, followed by Klebsiella pneumoniae. Similar findings have been reported in multiple studies, which highlight the dominance of Gram-negative bacilli in hospital-acquired urinary infections (9,10). The presence of opportunistic pathogens such as Pseudomonas aeruginosa and Proteus species further supports the nosocomial nature of these infections. These organisms are well recognized for their ability to survive in hospital environments and acquire resistance mechanisms, thereby contributing to persistent infections (10,11). A concerning observation was the reduced effectiveness of several commonly prescribed antimicrobial agents. This pattern is consistent with earlier reports and is likely related to excessive and inappropriate antibiotic use, which promotes the selection of resistant strains (12–14). The reduced effectiveness of beta-lactam antibiotics may be explained by the production of beta-lactamase enzymes, including extended-spectrum beta-lactamases. Increasing resistance to fluoroquinolones also reflects their widespread empirical use in clinical settings (13–15). In contrast, relatively higher sensitivity was observed with carbapenems and aminoglycosides, indicating their continued efficacy against many isolates. However, emerging resistance even to these agents is concerning and has been documented in recent studies (16). Gram-positive organisms, although less common, showed good susceptibility to vancomycin and linezolid. These antibiotics continue to be reliable treatment options for infections caused by resistant Gram-positive pathogens (17,18). The high proportion of multidrug-resistant isolates observed in this study is alarming. Infections caused by organisms resistant to multiple drug classes pose a major challenge to effective management, often resulting in poorer clinical outcomes, longer inpatient care, and greater financial burden on healthcare systems.. Factors such as prolonged catheterization, underlying illnesses, and irrational antibiotic use contribute significantly to this problem (19,20). These findings emphasize the need for continuous monitoring of antimicrobial resistance patterns at the institutional level. Regular antibiogram analysis can guide clinicians in selecting appropriate empirical therapy and help improve patient outcomes (21). In addition, strict infection control practices, including proper catheter care, minimizing unnecessary catheterization, and maintaining aseptic techniques, are essential in reducing the incidence of CAUTI (20,21).

The findings of this study underscore the growing challenge posed by multidrug-resistant organisms in catheter-associated urinary tract infections. The observed resistance patterns highlight the need for careful selection of antimicrobial therapy. Strengthening infection prevention strategies, optimizing catheter use, and promoting rational prescribing practices are essential steps in addressing this issue.

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