Acute Antimicrobial Resistance Patterns of Pseudomonas aeruginosa and E. coli Clinical Isolates

Abstract

Antimicrobial resistance among Gram-negative bacteria is a growing global health concern, particularly in hospital settings, where opportunistic pathogens contribute to severe infections. Pseudomonas aeruginosa and Escherichia coli are common causes of healthcare-associated infections and frequently demonstrate multidrug resistance, limiting therapeutic options. Objective: To determine the antimicrobial resistance patterns and prevalence of multidrug-resistant strains of Pseudomonas aeruginosa and Escherichia coli isolated from clinical specimens in a tertiary care hospital. Methods: A retrospective observational study was conducted at the University of Veterinary and Animal Sciences, Lahore, Pakistan, from June 2025 to December 2025. A total of 60 clinical isolates (30 Pseudomonas aeruginosa and 30 Escherichia coli) obtained from various specimens, including urine, sputum, blood, pus, wound swabs, and catheter tips, were analyzed. Bacterial identification was performed using standard microbiological techniques. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method in accordance with established clinical laboratory standards. Antibiotics tested for Pseudomonas aeruginosa included ceftazidime, piperacillin-tazobactam, ciprofloxacin, gentamicin, amikacin, imipenem, and colistin, whereas Escherichia coli isolates were tested against ampicillin, ceftriaxone, ciprofloxacin, gentamicin, amikacin, meropenem, and nitrofurantoin. Multidrug resistance was defined as resistance to three or more antimicrobial classes. Data were analyzed using SPSS, with descriptive statistics used for frequencies and percentages, and chi-square and independent t-tests applied for comparisons, with p < 0.05 considered statistically significant. Results: A total of 60 bacterial isolates were analyzed. The mean age of patients associated with Pseudomonas aeruginosa isolates was 48.97 ± 16.32 years, while for Escherichia coli it was 49.53 ± 15.06 years; there was no significant difference between groups (p = 0.889). Pseudomonas aeruginosa demonstrated the highest resistance to ciprofloxacin (56.7%), gentamicin (53.3%), and ceftazidime (50.0%), while the lowest resistance was observed for colistin (13.3%). Escherichia coli showed the highest resistance to ampicillin (70.0%) and ceftriaxone (63.3%), with lower resistance to meropenem and nitrofurantoin (20.0%). Overall, 56.7% of isolates were identified as multidrug resistant. No statistically significant difference in the prevalence of multidrug resistance was observed between the two organisms. Conclusion: A high prevalence of antimicrobial resistance and multidrug-resistant strains was observed among Pseudomonas aeruginosa and Escherichia coli isolates, highlighting the urgent need for continuous antimicrobial surveillance, rational antibiotic prescribing, and strengthened antimicrobial stewardship programs to control the spread of resistant pathogens in healthcare settings.