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

This study analyzed Escherichia coli isolates from hospital wastewater (HWW) in Shiraz, Iran, to assess antimicrobial resistance patterns. From 36 influent and effluent samples, 68 E. coli isolates were identified, showing alarmingly high resistance to ampicillin (97.1%) and amoxicillin/clavulanic acid (86.8%), while resistance to carbapenems remained relatively low. Most isolates (80.9%) were multidrug-resistant (MDR), and 22.1% were extensively drug-resistant (XDR). Extended-spectrum β-lactamase (ESBL) production was detected in 57.4% of isolates, with resistance genes such as blaTEM, blaCTX-M, and blaSHV frequently found. Carbapenemase genes blaOXA-48, blaIMP, and blaVIM were also present. Phylogroup B2, including high-risk clone ST131 (33.8%), predominated. The findings highlight that hospital wastewater is a critical reservoir for MDR and pathogenic E. coli, emphasizing the need for regular wastewater monitoring to curb the spread of AMR.