Mykhailo Savin
University of Bonn, Germany
Title: The emergence of colistin-resistant bacteria in wastewater from poultry and pig slaughterhouses and their dissemination into surface water
Biography
Biography: Mykhailo Savin
Abstract
Background and Objectives: Although colistin is a last resort antibiotic, it is applied regularly in animal production. Its increased use may have triggered the emergence of colistin-resistant bacteria. Hence, the aim was to investigate their occurrence in wastewater from poultry and pig slaughterhouses and to examine their emergence after the treatment process in the in-house and municipal wastewater treatment plants (WWTPs). Materials and Methods: Wastewater samples were taken during 2017-2018 along the production chains in two German pig slaughterhouses (n=53) and in its municipal WWTPs (n=36) as well as in two poultry slaughterhouses (n=72). Samples were screened for colistin-resistant bacteria using EMB medium supplemented with 3.5µg/ml colistin sulfate. The final identification was done by MALDI-TOF-MS. Antimicrobial susceptibility tests were performed by the broth microdilution method. Colistinresistant isolates were screened for the presence of colistin resistance genes (mcr 1-5) by PCR. Results: Colistin-resistant bacteria were more abundant in wastewater from the poultry slaughterhouses. Overall, 41.7% of its samples (n=30/72), including the outflows of the in-house WWTP, were found positive. The percentage of positive samples from the pig slaughterhouses and its mWWTPs was lower at 18.0% (n=16/89). Out of 46 samples, a total of 106 colistin-resistant strains were obtained. Among these, the majority belonged to E. coli (39.6%), followed by E. cloacae complex (28.3%), K. pneumoniae (27.4%) and R. ornithinolytica (4.7%). The mcr-1 gene was detected in 69.0% of the E. coli strains (n=29/42), in 13.8% of the K. pneumoniae strains (n=4/29) and in 3.3% of the strains from the E. cloacae complex (n=1/30). Conclusions: Colistin-resistant bacteria were detected in wastewater throughout the production chains as well as in the effluents and preflooder of the in-house and municipal WWTPs. This could pose a threat to human health and needs to be further investigated.