Occurrence of vanA/vanM-positive vancomycin-resistant Enterococcus faecium in hospital wastewater associated with clinical infections in Guangzhou, China: A genomic epidemiological study.

BACKGROUND

The emerging ST80 vancomycin-resistant Enterococcus faecium (VREfm) lineage, linked to the increases of clinical infections in China and Japan, raises concerns about environmental transmission. Hospital wastewater systems are recognized reservoirs for antimicrobial-resistant bacteria, but their role in disseminating ST80 VREfm remains unclear. This study investigates VREfm prevalence in hospital wastewater and genomic links between patients and hospital wastewater.

METHODS

From December 2023 to May 2024, a total of 262 wastewater samples were collected from three hospitals in Guangzhou, China. VREfm was identified using vancomycin-supplemented media. Antimicrobial susceptibility was assessed using the broth dilution method. Ninety-five patient-derived VREfm genomes in the same hospitals were included. Whole-genome sequencing and bioinformatic analysis were performed to reveal genomic characterizations and genetic transmission links.

RESULTS

VREfm was detected in 54.6 % (143/262) of samples. All isolates carried vanA, with 25.9 % (37/143) co-harboring vanA and vanM. The dominant ST80 lineage (43.4 %, n = 62) was linked to recent regional prevalence. A novel sequence type ST2460, belonging to CC17, emerged as the second most prevalent (27.2 %, n = 39). ST80 isolates exhibited enriched antimicrobial resistance genes, correlating with multidrug resistance phenotypes and high resistance rates. Genomic analysis revealed that 95.7 % (132/138) of ST80 isolates from wastewater and patients exhibited close genetic relatedness (median of SNP = 19, IQR: 14-23) and were linked within cross-source transmission networks, supported by the high similarity of a shared p23VRE019-like plasmid.

CONCLUSIONS

Hospital wastewater is a critical reservoir for high-risk VREfm clones, particularly the outbreak-associated ST80 lineage. The persistence of VREfm in effluents and evidence of cross-source transmission underscores the urgent need for enhanced environmental surveillance. Integrated strategies addressing environmental reservoirs are essential to combat the growing threat of VREfm.