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

Due to the high prevalence of colistin-resistant in poultry and pigs, process waters and wastewater from slaughterhouses were considered as a hotspot for isolates carrying plasmid-encoded, mobilizable colistin resistances ( 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., , spp., 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 (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 and were detected in scalding waters and preflooders of mWWTPs. A total of 70.8% (46/65) of and 20.6% (7/34) of isolates carried 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 on transferable plasmids ( = 53) exhibited a broad diversity, as they were assigned to 25 different I profiles. Interestingly, in the majority of colistin-resistant -negative and isolates non-synonymous polymorphisms in were detected. Our findings demonstrated high occurrence of colistin-resistant and carrying on transferrable plasmids in poultry and pig slaughterhouses and indicate their dissemination into surface water.