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. In March 2023, untreated wastewater in the wastewater treatment station of the Second Affiliated Hospital of Soochow University and wastewater in the U-shaped wastewater pipes of the hand-washing sinks in 26 wards were collected, centrifuged and diluted, 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. The results showed that 56 carbapenem-resistant gram-negative bacteria were isolated from hospital wastewater, originating from 13 genera, of which 17 were isolated from the total hospital wastewater, with Aeromonas spp. as the most dominant genus (35.3%, 6/17), and 39 were isolated from the wastewater of 17 wards, with Pseudomonas spp. as the most dominant genus (30.8%, 12/39). All common wastewater isolates from our hospital were multidrug-resistant bacteria, with up to 100% resistant to some second-and third-generation cephalosporins. A total of 8 carbapenemase genes originated from wastewater isolates, including blaKPC, blaNDM, blaIMP, blaVIM, blaIND, blaOXA-58-like, blaOXA-48-like, and blaOXA-427-like. 39 wastewater isolates carried the carbapenemase genes, and the total wastewater of the hospital carried the highest isolation rate of blaKPC-2 bacteria (35.3%, 6/17) and the highest isolation rate of blaIMP-8 bacteria (31.8%, 7/22) were found in the wastewater from 26 wards. 14 wastewater isolates were found to carry both carbapenemase genes, with a total of 6 combinations. A new blaIMP-101 isoform was also identified for the first time. 4 wastewater isolates and 11 clinical isolates were screened for inclusion in the SNP analysis, in which only 15 SNPs differed between the two strains of ST11 Klebsiella pneumoniae of clinical and wastewater origin, which was highly homologous. In 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.

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. In March 2023, untreated wastewater in the wastewater treatment station of the Second Affiliated Hospital of Soochow University and wastewater in the U-shaped wastewater pipes of the hand-washing sinks in 26 wards were collected, centrifuged and diluted, 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. The results showed that 56 carbapenem-resistant gram-negative bacteria were isolated from hospital wastewater, originating from 13 genera, of which 17 were isolated from the total hospital wastewater, with Aeromonas spp. as the most dominant genus (35.3%, 6/17), and 39 were isolated from the wastewater of 17 wards, with Pseudomonas spp. as the most dominant genus (30.8%, 12/39). All common wastewater isolates from our hospital were multidrug-resistant bacteria, with up to 100% resistant to some second-and third-generation cephalosporins. A total of 8 carbapenemase genes originated from wastewater isolates, including blaKPC, blaNDM, blaIMP, blaVIM, blaIND, blaOXA-58-like, blaOXA-48-like, and blaOXA-427-like. 39 wastewater isolates carried the carbapenemase genes, and the total wastewater of the hospital carried the highest isolation rate of blaKPC-2 bacteria (35.3%, 6/17) and the highest isolation rate of blaIMP-8 bacteria (31.8%, 7/22) were found in the wastewater from 26 wards. 14 wastewater isolates were found to carry both carbapenemase genes, with a total of 6 combinations. A new blaIMP-101 isoform was also identified for the first time. 4 wastewater isolates and 11 clinical isolates were screened for inclusion in the SNP analysis, in which only 15 SNPs differed between the two strains of ST11 Klebsiella pneumoniae of clinical and wastewater origin, which was highly homologous. In 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.

Objective:To understand the clinical prevalence and drug resistance of Raoultella ornithinolytica, and to analyze the drug-resistant characteristics of carbapenem-resistant strains. Methods:A total of 83 clinical isolates of R.ornithinolytica, identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry between May 2015 and December 2020, were collected. Clinical information, drug-resistant phenotype, and carbapenemase gene of the carbapenem resistant strains were analyzed. Homology of the resistant strains was examined by pulse-field gel electrophoresis (PFGE). The molecular characteristics of plasmids, drug resistance genes and virulence genes were determined by whole genome sequencing (WGS), and a phylogenetic tree was constructed based on core single-nucleotide polymorphisms(core-SNPs) for evolutionary analysis of the carbapenem-resistant strains. Results:All 83 clinical isolates were confirmed as R.ornithinolytica, of which 11 strains were resistant to carbapenem antibiotics. The resistant strains were mainly sourced from the drainage fluid and wound secretions of patients in surgery, intensive care unit and oncology department. In addition to carbapenems resistances, the 11 strains were also resistant to cephalosporins, cephamycins, and aztreonam, while maintaining good in vitro activity to levofloxacin, tigecycline and colistin. Carbapenemase gene detection showed that 8 strains carried the bla IMP-4, 3 carried bla KPC-2, of which 1 strain carried both bla IMP-4 and bla KPC-2, and 2 strains carried both bla IMP-4 and bla NDM-1. PFGE results showed 7 banding types and 4 epidemic strains. WGS identified plasmid replicon types carried by the 11 strains of R. ornithinolyticus including IncFIA, IncFIB, IncHI1B, IncU, repB and Col, along with 10 additional types of drug resistance genes. Iron carrier related virulence genes entB, fyu, ybt and irp were detected in all carbapenem-resistant strains. Phylogenetic analysis showed that Ro6348 and Ro6050, Ro7401 and Ro7242, Ro8647 and Ro5832, and Ro9907 and Ro8856 were grouped together, while Ro8454, Ro7349 and Ro7326 were located on different branches. Conclusions:The overall drug resistance of R. ornithinolytica closely resembles Klebsiella pneumoniae and carries a variety of drug-resistant genes, but differs from domestic K.pneumoniae in that its carbapenemase is mainly IMP-4. PFGE and phylogenetic analysis results suggest that the strain has a tendency of mutual transmission in hospital, which deserves more attention.