Prevalence and clinical relevance of carbapenem-resistant bacteria in untreated hospital wastewater

Objective To analyze the prevalence, genomic characteristics and clinical relevance of carbapenem-resistant bacteria in untreated hospital wastewater, and to provide a reference basis for in-hospital assessment of public health situation and prevention of cross-infection.Methods In March 2023, wastewater was collected from the general wastewater pipe of the hospital and the U-shaped wastewater pipe of the ward sink, and the drug-resistant bacteria were isolated by using LB solid plates containing meropenem (2 μg/ml) for species identification, drug sensitivity analysis, carbapenenase gene PCR detection and whole genome sequencing. The genome sequence was identified for drug resistance genes. Retrospective research was used, combining multilocus sequence typing (MLST) and single nucleotide polymorphism (SNP) analysis, to compare their homology with clinical isolates of the same quarter.Results 56 strains of carbapenem-resistant gram-negative bacteria were isolated from hospital wastewater, including 13 genera of Pseudomonas, Aeromonas and Trichomonas, etc. 39 isolates carried carbapenemase genes involving blaKPC、blaNDM、blaIMP、blaVIM、blaIND、blaOXA-58-like、blaOXA-48-like and blaOXA-427-like. blaKPC-2 and blaIMP-8 are major carbapenemase genes in total hospital effluent and ward effluent, respectively. Pseudomonas aeruginosa carrying blaIMP-101 was also identified in our institution. 4 wastewater isolates and 11 clinical isolates were screened for inclusion in the SNP analysis, in which 2 strains of clinical and wastewater origin, ST11 Klebsiella pneumoniae, are highly homologous.Conclusion The presence of multiple multi-drug resistant conditionally pathogenic bacteria in untreated hospital wastewater has the potential risk of spreading drug-resistant genes in the environment. The highly homologous Klebsiella pneumoniae isolated from hospital wastewater and clinics indicates the close association between hospital wastewater and clinical infections. Hospitals need to strengthen the monitoring of drug-resistant bacteria and drug-resistant genes in the wastewater environment, to prevent the widespread dissemination of drug-resistant bacteria and drug-resistant genes in hospital wastewater and to prevent nosocomial infections caused by drug-resistant bacteria in wastewater.