Colistin-Resistant Enterobacteriaceae Isolated From Process Waters and Wastewater From German Poultry and Pig Slaughterhouses

Mykhailo Savin; Gabriele Bierbaum; Khald Blau; Marijo Parcina; Esther Sib; Kornelia Smalla; Ricarda Schmithausen; Céline Heinemann; Jens A Hammerl; Judith Kreyenschmidt

doi:10.3389/fmicb.2020.575391

Colistin-Resistant Enterobacteriaceae Isolated From Process Waters and Wastewater From German Poultry and Pig Slaughterhouses

Front Microbiol. 2020 Oct 30:11:575391. doi: 10.3389/fmicb.2020.575391. eCollection 2020.

Authors

Affiliations

¹ Institute of Animal Sciences, University of Bonn, Bonn, Germany.
² Institute for Hygiene and Public Health, Medical Faculty, University of Bonn, Bonn, Germany.
³ Institute for Medical Microbiology, Immunology and Parasitology, Medical Faculty, University of Bonn, Bonn, Germany.
⁴ Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany.
⁵ Department for Biological Safety, German Federal Institute for Risk Assessment, Berlin, Germany.
⁶ Department of Fresh Produce Logistics, Hochschule Geisenheim University, Geisenheim, Germany.

Abstract

Due to the high prevalence of colistin-resistant Enterobacteriaceae in poultry and pigs, process waters and wastewater from slaughterhouses were considered as a hotspot for isolates carrying plasmid-encoded, mobilizable colistin resistances (mcr genes). Thus, questions on the effectiveness of wastewater treatment in in-house and municipal wastewater treatment plants (WWTPs) as well as on the diversity of the prevailing isolates, plasmid types, and their transmissibility arise. Process waters and wastewater accruing in the delivery and unclean areas of two poultry and two pig slaughterhouses were screened for the presence of target colistin-resistant bacteria (i.e., Escherichia coli, Klebsiella spp., Enterobacter cloacae complex). In-house and municipal WWTPs (mWWTPs) including receiving waterbodies were investigated as well. Samples taken in the poultry slaughterhouses yielded the highest occurrence of target colistin-resistant Enterobacteriaceae (40.2%, 33/82), followed by mWWTPs (25.0%, 9/36) and pig slaughterhouses (14.9%, 10/67). Recovered isolates exhibited various resistance patterns. The resistance rates using epidemiological cut-off values were higher in comparison to those obtained with clinical breakpoints. Noteworthy, MCR-1-producing Klebsiella pneumoniae and E. coli were detected in scalding waters and preflooders of mWWTPs. A total of 70.8% (46/65) of E. coli and 20.6% (7/34) of K. pneumoniae isolates carried mcr-1 on a variety of transferable plasmids with incompatibility groups IncI1, IncHI2, IncX4, IncF, and IncI2 ranging between 30 and 360 kb. The analyzed isolates carrying mcr-1 on transferable plasmids (n = 53) exhibited a broad diversity, as they were assigned to 25 different XbaI profiles. Interestingly, in the majority of colistin-resistant mcr-negative E. coli and K. pneumoniae isolates non-synonymous polymorphisms in pmrAB were detected. Our findings demonstrated high occurrence of colistin-resistant E. coli and K. pneumoniae carrying mcr-1 on transferrable plasmids in poultry and pig slaughterhouses and indicate their dissemination into surface water.

Keywords: Enterobacter cloacae complex; Escherichia coli; Klebsiella pneumoniae; colistin resistance; mcr genes; slaughterhouse; wastewater; zoonotic microorganisms.