engleski

Carbapenem-resistant enterobacteria and genes in wastewater from municipal wastewater treatment plants in Croatia

Bacterial carbapenem resistance, especially among Enterobacteriaceae, is a major public health problem and wastewater treatment plants (WWTPs) can promote its spread in the environment. In this work we describe the occurrence of carbapenem-resistant coliforms and carbapenemase genes and the characteristics of carbapenemase- producing enterobacteria from municipal wastewater in Croatia. Conventional culturing was performed to monitor coliform bacteria and quantitative PCR to monitor 5 carbapenemase (CP) genes in the influent and effluent of 7 Croatian WWTPs in two seasons. Carbapenem-resistant enterobacteria were isolated on CHROMagar mSuperCARBA plates from the effluent of the largest WWTP (Zagreb) and identified by MALDI-TOFF. Antimicrobial susceptibility profiles and carbapenemase production were assessed phenotypically. Detection of CP genes was performed by PCR and sequencing of selected amplicons or by whole genome sequencing (WGS). Molecular epidemiology was assessed by PFGE and WGS. In general, levels of total and carbapenem- resistant coliforms were significantly reduced but not eliminated by conventional treatment in most WWTPs. CP genes, blaKPC-3, blaNDM and blaOXA-48- like, were sporadically detected, while blaIMP and blaVIM were frequently enriched during treatment and were influenced by specific features of the WWTPs. A total of 200 carbapenem-resistant enterobacteria were isolated from Zagreb WWTP effluent. Most isolates (144/200) produced carbapenemases and were confirmed as Enterobacteriaceae, with the predominant taxa identified as Klebsiella (33%), Enterobacter (24%), and Citrobacter (25%). All Klebsiella isolates were multidrug-resistant, of which 6% were pandrug-resistant. Most Klebsiella isolates were grouped into 8 pulsotypes ; among these, two were predominant and belonged to a novel Klebsiella lineages, ST1697 and ST3590, which may be a hybrid of the recombination of the Klebsiella quasipneumoniae and Klebsiella pneumoniae genomes. The predominant CP genes among these isolates were blaOXA-48, blaNDM-1 and blaKPC-2, whereas blaVIM-1 and blaIMP-13 were rarely detected. 40% of Klebsiella isolates were resistant to colistin, and a novel plasmid-encoded mcr-4.3 gene was detected for the first time in pandrug-resistant Klebsiella pneumoniae. Our results suggest that improvements in WWTP technologies are needed to minimize the risk of environmental contamination with key opportunistic enteric pathogens and CP genes and the resulting public health impact.

Carbapenem resistance ; carbapenemase ; wastewater

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