Extended-Spectrum-Beta-Lactamase- and Plasmid-Encoded Cephamycinase-Producing Enterobacteria in the Broiler Hatchery as a Potential Mode of Pseudo-Vertical Transmission

Abstract

Antimicrobial resistance through extended-spectrum beta-lactamases (ESBLs) and transferable (plasmid-encoded) cephamycinases (pAmpCs) represents an increasing problem in human and veterinary medicine. The presence of ESBL-/ pAmpC-producing commensal enterobacteria in farm animals, such as broiler chickens, is considered one possible source of food contamination and could therefore also be relevant for human colonization. Studies on transmission routes along the broiler production chain showed that 1-day-old hatchlings are already affected. In this study, ESBL-/pAmpC-positive broiler parent flocks and their corresponding eggs, as well as various environmental and air samples from the hatchery, were analyzed. The eggs were investigated concerning ESBL-/pAmpC-producing enterobacteria on the outer eggshell surface (before/after disinfection), the inner eggshell surface, and the egg content. Isolates were analyzed concerning their species, their phylogroup in the case of Escherichia coli strains, the respective resistance genes, and the phenotypical antibiotic resistance. Of the tested eggs, 0.9% (n ϭ 560) were contaminated on their outer shell surface. Further analyses using pulsed-field gel electrophoresis showed a relationship of these strains to those isolated from the corresponding parent flocks, which demonstrates a pseudo-vertical transfer of ESBL-/pAmpC-producing enterobacteria into the hatchery. Resistant enterobacteria were also found in environmental samples from the hatchery, such as dust or surfaces which could pose as a possible contamination source for the hatchlings. All 1-day-old chicks tested negative directly after hatching. The results show a possible entry of ESBL-/pAmpC-producing enterobacteria from the parent flocks into the hatchery; however, the impact of the hatchery on colonization of the hatchlings seems to be low.IMPORTANCE ESBL-/pAmpC-producing enterobacteria occur frequently in broilerfattening farms. Recent studies investigated the prevalence and possible transmission route of these bacteria in the broiler production chain. It seemed very likely that the hatcheries play an important role in transmission and/or contamination events. There are only few data on transmission investigations from a grandparent or parent flock to their offspring. However, reliable data on direct or indirect vertical transmission events in the hatchery are not available. Therefore, we conducted our study and intensively investigated the broiler hatching eggs from ESBL-/pAmpCpositive broiler parent flocks as well as the hatchlings and the environment of the hatchery.KEYWORDS antibiotic resistance, Enterobacteriaceae, broiler chicken, hatchery, ESBL, pAmpC, AmpC

Environmental adaptation and vertical dissemination of ESBL‐/pAmpC‐producing Escherichia coli in an integrated broiler production chain in the absence of an antibiotic treatment

“…Isolates of fattening flocks C/41, F/74 and E/74 occurred with different prevalence in the respective fattening flocks (flock C/41: 73.1%, flock E/74: 26.4%, flock F/74: 5.7%). The second strain set included 42 isolates from investigations of seven different broiler production chains covering all detected genetic profiles (phylogroup + ESBL‐/pAmpC gene) to get an overall impression on cellulose and curli production in different resistant isolates from the whole broiler production chain (Daehre et al ., 2017; Projahn et al ., 2017) (Tables S1 and S2). Isolates of the first set showed both, production of cellulose and curli, regardless of the flock prevalence, whereas in the second one, various phenotypes were determined (Fig.…”

“…This is in concordance with our findings that the resistant bacteria were introduced into the hatchery via contaminated eggshells and the hatchery acts as a bottleneck for the spread of these strains (Projahn et al ., 2017). …”

“…ESBL‐/pAmpC‐producing E. coli originate from individual animal samples (cloacal swabs) and environmental samples (swabs and housing environment) of different stages of the broiler production chain (parent flock, hatchery, fattening farm) collected in Germany during the years 2014 and 2015 (Daehre et al ., 2017; Projahn et al ., 2017). …”

“…Therefore, different transmission scenarios of the resistant bacteria in the broiler production pyramid are discussed: A transmission from prior stages into the fattening farms (Giovanardi et al ., 2005; Dierikx et al ., 2013; Nilsson et al ., 2014; Huijbers et al ., 2016) as well as an insufficient cleaning and disinfection procedure in the chicken barns (Hiroi et al ., 2012; Luyckx et al ., 2015b). We recently showed a pseudo‐vertical transfer of resistant bacteria from the parent flocks into the hatchery via contaminated eggshells (Projahn et al ., 2017). In addition, it was proved by whole genome analyses that there is in fact a horizontal transfer of ESBL producers between consecutively fattened flocks regardless of cleaning and disinfection procedures (Daehre et al ., 2017).…”

“…To investigate the top‐down transmissions across all stages of the broiler production chain (parent flock, hatchery, fattening flock/barn), we analysed 44 ESBL‐/pAmpC‐producing E. coli from two different broiler production chains (chain C and F) which were not treated with antibiotics by whole genome analyses (Daehre et al ., 2017; Projahn et al ., 2017). Ten ESBL‐/pAmpC‐positive strains from parent screening samples (S) and other parent or fattening flocks (A/11, B/41, D, E/73) showing the same phylogroup and resistance genes that were found in chain C or F, respectively, were also included to show a potential circulation of certain strains within the broiler production chain (please see Fig.…”