Antibiotic-resistant bacteria, antibiotic resistance genes, and antibiotic residues in wastewater from a poultry slaughterhouse after conventional and advanced treatments

Mykhailo Savin,Ricarda Maria Schmithausen,Alexander Voigt,Johannes Alexander,Norman Hembach,Thomas Schwartz,Judith Kreyenschmidt,Esther Sib,Gabriele Bierbaum,Jens Andre Hammerl

doi:10.1038/s41598-021-96169-y

Abstract

Slaughterhouse wastewater is considered a reservoir for antibiotic-resistant bacteria and antibiotic residues, which are not sufficiently removed by conventional treatment processes. This study focuses on the occurrence of ESKAPE bacteria (Enterococcus spp., S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp.), ESBL (extended-spectrum β-lactamase)-producing E. coli, antibiotic resistance genes (ARGs) and antibiotic residues in wastewater from a poultry slaughterhouse. The efficacy of conventional and advanced treatments (i.e., ozonation) of the in-house wastewater treatment plant regarding their removal was also evaluated. Target culturable bacteria were detected only in the influent and effluent after conventional treatment. High abundances of genes (e.g., blaTEM, blaCTX-M-15, blaCTX-M-32, blaOXA-48, blaCMY and mcr-1) of up to 1.48 × 106 copies/100 mL were detected in raw influent. All of them were already significantly reduced by 1–4.2 log units after conventional treatment. Following ozonation, mcr-1 and blaCTX-M-32 were further reduced below the limit of detection. Antibiotic residues were detected in 55.6% (n = 10/18) of the wastewater samples. Despite the significant reduction through conventional and advanced treatments, effluents still exhibited high concentrations of some ARGs (e.g., sul1, ermB and blaOXA-48), ranging from 1.75 × 102 to 3.44 × 103 copies/100 mL. Thus, a combination of oxidative, adsorptive and membrane-based technologies should be considered.

Highlights

Slaughterhouse wastewater is considered a reservoir for antibiotic-resistant bacteria and antibiotic residues, which are not sufficiently removed by conventional treatment processes
No target ESKAPE bacteria were detected in the effluent after subsequent ozone treatment
This study provides insights regarding the occurrence and impact of ESKAPE bacteria, including ESBL-producing E. coli, antibiotic resistance genes (ARGs) and antimicrobial residues, in wastewater samples from a German poultry slaughterhouse that might be disseminated to the environment

Summary

Introduction

Slaughterhouse wastewater is considered a reservoir for antibiotic-resistant bacteria and antibiotic residues, which are not sufficiently removed by conventional treatment processes. German slaughterhouses commonly treat their wastewater by different physicochemical and/or biological methods This results in a moderate to high removal of nutrients and a reduction of the bacterial load by 1.1–3.4 log units[6,11,12]. Ozone treatment has been shown to exhibit a high reduction efficacy of 98.4% against facultative pathogenic bacteria and their antibiotic resistance genes (ARGs)[12]. In German municipal WWTPs, microbial reduction to below the detection limit ( 101 cell equivalents per 100 mL) was recently reported in the case of additional advanced treatment technologies (ozonation and ultrafiltration)[13]. Upgrading WWTPs with advanced treatment technologies bears additional costs associated with high energy consumption, additional personnel and posttreatment of the effluents[12,14]

Objectives

Methods

Results

Conclusion