Antimicrobial Resistance Pattern and Phenotypic Characterization of Staphylococcus Aureus and Escherichia Coli Isolated from High Vaginal and Urethral Swab Specimens

Abstract

Background: Antimicrobial resistance (AMR) among urogenital bacterial pathogens is an increasing global public health concern, particularly in low- and middle-income countries. High vaginal and urethral infections are commonly associated with Staphylococcus aureus and Escherichia coli, which frequently exhibit multidrug resistance. Monitoring antimicrobial susceptibility and phenotypic characteristics of these pathogens is essential for effective treatment and infection control. Objective: This study aimed to determine the antimicrobial resistance patterns and phenotypic characteristics of Staphylococcus aureus and Escherichia coli isolated from high vaginal and urethral swab specimens and to assess factors associated with multidrug resistance. Methods: A hospital-based cross-sectional study was conducted among 240 clinically suspected patients at a tertiary care hospital from March 2025 to November 2025. High vaginal and urethral swab specimens were collected aseptically and processed using standard microbiological procedures. Bacterial identification was performed through colony morphology, Gram staining, and biochemical characterization. Antimicrobial susceptibility testing was carried out using the Kirby–Bauer disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Multidrug resistance (MDR), methicillin-resistant Staphylococcus aureus (MRSA), and resistant Escherichia coli isolates were determined phenotypically. Statistical analyses including chi-square test and logistic regression were performed, with p < 0.05 considered statistically significant. Results: Among the 240 specimens collected, 168 (70.0%) demonstrated significant bacterial growth, while 60 (25.0%) showed no growth and 12 (5.0%) revealed mixed growth. Of the culture-positive isolates, Escherichia coli was the predominant pathogen accounting for 80 (47.6%) isolates, followed by Staphylococcus aureus comprising 64 (38.1%) isolates. The highest culture positivity was observed among patients aged 26–35 years (79.6%), which showed a statistically significant association with bacterial infection (χ² = 9.85, p = 0.020). Phenotypic characterization demonstrated that 93.8% of S. aureus isolates were coagulase-positive and 87.5% fermented mannitol, whereas 93.8% of E. coli isolates showed lactose fermentation and 90.0% were indole-positive. Antimicrobial susceptibility analysis revealed high resistance of E. coli against ampicillin (81.2%), cotrimoxazole (56.2%), and ceftriaxone (42.5%), while high sensitivity was observed for imipenem (95.0%) and nitrofurantoin (85.0%). Similarly, S. aureus exhibited marked resistance to penicillin (78.1%), erythromycin (37.5%), and ciprofloxacin (34.4%), whereas vancomycin (96.9%) and gentamicin (75.0%) demonstrated high effectiveness. Multidrug resistance was detected in 38 (47.5%) E. coli isolates and 24 (37.5%) S. aureus isolates. MRSA prevalence among S. aureus isolates was 34.4%. A significant association was identified between previous antibiotic exposure and MDR infection (χ² = 15.37, p < 0.001). Inpatient participants showed significantly higher MRSA prevalence compared to outpatients (54.5% vs. 23.8%; p = 0.009). Logistic regression analysis further demonstrated that previous antibiotic use (AOR = 3.54, 95% CI: 1.89–6.61, p < 0.001) and inpatient admission status (AOR = 2.11, 95% CI: 1.14–3.89, p = 0.017) were independent predictors of MDR infection. Conclusion: The study demonstrated a high burden of antimicrobial resistance among urogenital bacterial pathogens, with Escherichia coli and Staphylococcus aureus as the predominant isolates. The notable prevalence of multidrug resistance and MRSA highlights the need for continuous antimicrobial surveillance, rational antibiotic use, and effective infection prevention strategies to reduce resistant urogenital infections.