High prevalence of MDR and XDR Escherichia coli in hospital wastewater from Shiraz, Iran: ESBL and carbapenemase production

Hospital wastewater (HWW) is a significant reservoir for multidrug-resistant (MDR) bacteria and antimicrobial resistance (AMR) genes, posing serious public health risks. This study investigated the phenotypic and genotypic resistance profiles of Escherichia coli (E. coli) isolates from HWW in Shiraz, Iran. Thirty-six HWW samples (18 influent, 18 effluent) were collected weekly over six weeks from three major hospitals. E. coli isolates were identified and assessed for antimicrobial susceptibility, extended-spectrum β-lactamase (ESBL) and carbapenemase production, resistance genes, phylogroups, and sequence types (STs). A total of 68 E. coli isolates were obtained (33 influent, 35 effluent). High resistance rates were observed for ampicillin (97.1%), cefazolin, and amoxicillin/clavulanic acid (86.8%). The lowest resistance rates were to imipenem (5.9%), meropenem (13.2%), and chloramphenicol (19.1%). MDR and extensively drug-resistant (XDR) profiles were identified in 80.9% and 22.1% of isolates, respectively. ESBL production was found in 57.4% of isolates. All nine carbapenem-resistant isolates were tested by both modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM); eight (88.9%) were positive by mCIM, while all were negative by eCIM. Resistance genes detected included blaTEM (39.7%), blaCTX-M (33.8%), and blaSHV (2.9%). Three isolates carried blaOXA-48, while one carried blaIMP and another carried blaVIM. Phylogroup B2 was most frequent (22.1%), with ST131 being the dominant type (33.8%). In conclusion, HWW may serve as a potential reservoir for resistant and pathogenic E. coli isolates, indicating the importance of monitoring wastewater as a step in addressing the issue of AMR.