engleski

Hospital wastewater: a reservoir and dissemination route for ESBL- and carbapenemase-producing enterobacteria

The emergence of extended-spectrum β-lactamases (ESBLs)- and especially carbapenemases in Enterobacterales has led tolimited therapeutic options ; therefore, it is critical to fully understand all potential pathways of their transmission, especiallyin high-risk sources such as hospital wastewater. The aim of this study was to isolate and characterize ESBL- andcarbapenemase-producing Enterobacterales (CRE) from untreated wastewater of two major hospitals in Zagreb, Croatia. Phenotypic testing was performed to identify ESBL or carbapenemase producers. Antibiotic susceptibility was tested by agardisk diffusion and broth microdilution methods. Genotypic antibiotic resistance profiles of isolates were analyzed by PCRand whole genome sequencing (WGS), while molecular epidemiology was studied by PFGE and MLST. Sixty-nine ESBL and 90 CRE isolates were isolated from hospital wastewater ; all were multidrug resistant and were mostlyidentified as Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Enterobacter cloacae complex. Among ESBL isolates, blaCTX-M-15 was the most prevalent ESBL gene, while among CRE isolates, bla KPC-2 and bla NDM-1 were the mostfrequently detected carbapenemases, especially in Citrobacter spp. followed by bla OXA-48, especially in K. pneumoniae . Themost frequently detected sequence types included clinically relevant variants E. coli ST131 ( bla CTX-M-15/ bla TEM-116) andST541 ( bla KPC-2), K. pneumoniae ST101 ( bla OXA-48/ bla NDM-1) and E. cloacae ST277 ( bla KPC-2/ bla NDM-1). WGS alsoshowed that these isolates contained resistance genes to multiple antibiotic classes and a diverse plasmidome previouslyassociated with clinically relevant ESBL or carbapenemases. Finally, analysis of the genomic context of bla CTX-M, bla OXA-48, and bla KPC-2 showed that these genes were associated with mobile genetic elements, particularly transposons andinsertion sequences, indicating the potential for mobilisation. Conclusions Our results suggest that hospital wastewater is a reservoir for critical priority pathogens that exhibit resistance mechanismsto antibiotics critical to human health and provide a pathway for their dissemination in water systems. Effective treatment ofthis wastewater with advanced treatment methods such as UV and ozone treatment must therefore be ensured to reduce orstop the spread of resistant bacteria and ARGs in the natural environment.

Antimicrobial resistance (AMR) ; Hospital wastewater

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