Citation:

Hoelle, J., J. Johnson, B. Johnston, B. Kinkle, L. Boczek, H. Ryu, AND S. Hayes. Survey of US wastewater for carbapenem-resistant Enterobacteriaceae. JOURNAL OF WATER AND HEALTH. IWA Publishing, London, Uk, 17(2):219-226, (2019). https://doi.org/10.2166/wh.2019.165

Impact/Purpose:

Carbapenem antibiotics have been effective against multi-drug resistant Gram-negative bacilli and a mainstay of therapy for infections due to such organisms. Carbapenem-resistant E. coli (CREC) are increasingly prevalent, mainly due to the emergence of novel carbapenemases. The associated carbapenemase genes are frequently found on mobile genetic elements and have the potential to spread to other Gram-negative bacteria. Although CREC have been recognized primarily in health care settings, investigators at the US Environmental Protection Agency proposed that antimicrobial resistance surveillance involving sewage isolates could be informative as to the occurrence and dissemination of specific clonal groups or sequence types within a given community or population. This study is follow on research to preliminarily survey wastewater from different sites in the US for antibiotic-resistant E. coli to ESCs and carbapenem, to characterize the resulting isolates for presence of carbapenemase and ESBL genes, and identify sequence types that have been associated with extraintestinal infections in humans.

Description:

A survey for the presence of antibiotic-resistant E. coli was undertaken by collecting samples from seven geographically dispersed US wastewater treatment plants (WWTPs). Samples were collected at each WWTP in cool and summer months and cultured using selective media. The resulting E. coli isolates were characterized for resistance to imipenem, ciprofloxacin, cefotaxime and ceftazidime, presence of carbapenemase and extended spectrum beta lactamase (EBSL) genes, and phylogroups and sequence types (STs). The survey identified 322 antibiotic-resistant (AR) E. coli isolates and the associated resistance profiles, with 65 of these being imipenem-resistant. Of the 65 carbapenem-resistant E. coli (CREC) isolates, 62% contained ≥ 1, and 31% contained ≥ 2, of nine studied carbapenemase and ESBL genes. The most common carbapenemase gene detected was blaVIM and two instances of blaKPC were found, but the gene panel was negative for many of the CREC isolates. Carbapenem resistance was seen in pathogenic E. coli phylogroups (B2 & D) and STs (1193, 405, 648) as well as commensal phylogroups (A & C). The occurrence of CREC in wastewater is a potential concern because this matrix may serve as a reservoir for gene exchange and thereby increase the risk of AR bacteria (including CR) being disseminated into the environment and thence back to humans.

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