Abstract
Background and aims: Municipal wastewater may contain pathogenic and antimicrobial-resistant bacteria (ARB), posing public health risks. This study investigated bacterial frequency, antimicrobial resistance (AMR), ESBL production, and resistance and virulence genes in wastewater from Shahrekord, Iran. Methods: In this cross-sectional study, 384 wastewater samples were collected from June 2023 to May 2024. Bacterial identification, antimicrobial susceptibility, and ESBL production were assessed using standard methods and CLSI guidelines. β-lactamase genes (BLACTX-M, BLATEM, and BLASHV) and species-specific virulence genes were detected by PCR. Data were analyzed descriptively. Results: Among the 384 wastewater samples, 195 bacterial isolates were recovered exclusively from influent samples, while no isolates meeting the predefined culture and identification criteria were recovered from the primary sedimentation, secondary biological treatment, or final effluent samples. The isolates included Staphylococcus aureus (45.6%, n=89), Enterococcus faecalis (18.5%, n=36), Pseudomonas aeruginosa (18.5%, n=36), and Acinetobacter baumannii (17.4%, n=34); Salmonella and Shigella were not detected. Phenotypic ESBL production occurred in 58.8% of A. baumannii, 83.3% of P. aeruginosa, 66.3% of S. aureus, and 25.0% of E. faecalis. BLACTX-M was the predominant β-lactamase gene in A. baumannii (29.4%) and P. aeruginosa (36.1%). The most frequent virulence genes were exoS in P. aeruginosa (80.5%), efa in E. faecalis (100%), and fimH in A. baumannii (82.3%); the highest frequency in S. aureus was 16.8%. Conclusion: Municipal wastewater contained clinically relevant bacteria with substantial ESBL production and diverse virulence determinants, emphasizing the need for continuous surveillance and effective control measures.