Longitudinal Monitoring Reveals Klebsiella Quasipneumoniae as the Main Contributor to Carbapenem Resistance in a Hong Kong Hospital Wastewater Discharge Line

Abstract

Testing hospital wastewater (HWW) is potentially an effective, long-term approach for monitoring trends in antimicrobial resistance (AMR) patterns in health care institutions. Over a year, we collected wastewater samples from the clinical and non-clinical sites of a tertiary hospital and from a downstream wastewater treatment plant (WWTP). We focused on the extent of carbapenem resistance among Enterobacteriaceae isolates given their clinical importance. Escherichia coli and Klebsiella spp. were the most frequently isolated Enterobacteriaceae species at all sampling sites. Of the 232 Klebsiella spp. isolates, 100 (43.1%) were multi-drug resistant, of which 47 were carbapenem-resistant. Most of these carbapenem-resistant isolates were Klebsiella quasipneumoniae (CRKQ). All CRKQ (n=43) were isolated from the wastewater of a clinical site that included intensive care units, which also yielded significantly more multi-drug resistant (MDR) isolates compared to all other sampling sites. Among the CRKQ, blaGES-5 genes (n=42) were the primary genetic determinant of carbapenem resistance. During one particular month, three different CRKQ isolates were found in HWW and the influent and effluent flow of the WWTP. The blaGES-5 genes, flanking regions and upstream integron-integrase regions of these isolates shared >99% sequence similarity. The influent isolate was phylogenetically close to K. quasipnuemoniae isolates from wastewater collected in Japan and its blaGES-5 gene and surrounding sequences were >99% identical to blaGES-24 genes found in Japanese isolates. Our results suggest that testing samples from sites located closer to hospitals may better reflect hospital AMR patterns related to antibiotics usage and support antibiotic stewardship programs compared to samples collected further downstream. Moreover, testing samples collected regularly from WWTPs may reflect the local and global spread of pathogens and their resistances.

Keywords: Hospital wastewater, Carbapenem resistance, Klebsiella spp., Klebsiella quasipneumoniae, WGS