Prevalence and quantitative analysis of ESBL and AmpC beta-lactamase producing Enterobacteriaceae in broiler chicken during slaughter in Germany

Abstract

Food producing animals are considered a reservoir for Extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase (AmpC) producing Enterobacteriaceae. Therefore, meat is discussed to be a potential source for the transmission of these resistant bacteria to humans. There is only limited information about the quantitative load of ESBL-/AmpC-producing Enterobacteriaceae in different sample matrices during slaughter and their distribution in the slaughterhouse environment. Therefore, the aim of this study was to determine the prevalence as well as quantitative load of ESBL-/AmpC-producing Enterobacteriaceae in caecum, skin and filet samples of different broiler chicken flocks during slaughter in Germany. In addition, environmental samples were taken during slaughter of the respective flocks. To gain insights into possible transmission routes of ESBL-/AmpC-producing Enterobacteriaceae, the corresponding phylogroup and beta-lactamase genes were determined for selected isolates.ESBL-/AmpC-producing Enterobacteriaceae were detected during slaughter of all seven investigated flocks. On average, 47% (83/175) of caecum, 55% (96/175) of skin, 28% (49/175) of filet and 28% (25/89) of environmental samples harboured ESBL-/AmpC-producing Enterobacteriaceae. Prevalence varied widely between the flocks as well as between the different sample matrices. In about half of the caecum (23/40) and skin (19/40) samples as well as 85% (17/20) of the filet samples, the number of putative ESBL-/AmpC-producing Enterobacteriaceae (cefotaxime resistant Enterobacteriaceae) was below quantification limit. The median of cefotaxime resistant Enterobacteriaceae was 2.5 × 103 cfu/g in caecum, 1.5 × 103 cfu/g in skin and 1.5 × 102 cfu/g in filet samples. The median of cefotaxime resistant Enterobacteriaceae was, depending on the sample matrix, 1–4 log units below the median of total Enterobacteriaceae. Using real-time PCR, in 82% (629/767) of the cefotaxime resistant Enterobacteriaceae at least one of the investigated beta-lactamase genes blaCTX-M, blaSHV, blaTEM, blaAmpC-CIT was detected. The respective resistance genes of 322 isolates were further sequenced. The predominant bla-gene was blaCMY-2 (48%), followed by blaSHV-12 (23%).A contamination from the broiler chicken to the slaughterhouse environment and vice versa seems probable as isolates of the same species and phylogroup, encoding the same resistance genes were detected in all matrices during slaughter of the respective flock as well as in the slaughterhouse environment.