Extended-Spectrum Beta-Lactamase-/AmpC Beta-Lactamase-Producing Enterobacteriaceae in Broiler Farms: Transmission Dynamics at Farm Level

Abstract

The occurrence of extended-spectrum beta-lactamase- (ESBL) and/or AmpC beta-lactamase- (AmpC) producing Enterobacteriaceae in livestock, especially in broiler fattening flocks, has been demonstrated in previous studies. Nevertheless, data on transmission routes of these resistant bacteria into the fattening farms are rare. Therefore, seven broiler fattening flocks were investigated for the occurrence of ESBL-/AmpC-producing Enterobacteriaceae during the course of the fattening period with the special focus on horizontal transmission routes. ESBL-/AmpC-producing Enterobacteriaceae from both individual animals and their housing environment were isolated at different time points and the housing environment was even sampled before the arrival of the chickens. All obtained ESBL-/AmpC-producing Enterobacteriaceae were examined for their bacterial species, Escherichia coli phylogroup, and occurrence of resistance genes. Selected isolates were further analyzed via whole-genome sequencing. All seven investigated flocks were tested positive for ESBL-/AmpC-producing Enterobacteriaceae with widely varying prevalence between the flocks. In one flock, the ESBL-/AmpC-producing Enterobacteriaceae were already detected in the housing environment before the arrival of the animals. In general, among the different types of ESBL-/AmpC-producing Enterobacteriaceae determined E. coli harboring a bla gene was the most frequent. Using whole-genome analyses we observed a horizontal transmission of ESBL-/AmpC-producing Enterobacteriaceae through contaminated housing environment as two flocks consecutively fattened in the same farm harbored closely related ESBL-producing isolates. This demonstrates the influence of a previous fattened flock on the ESBL-/AmpC-status of a following broiler flock and, therefore, the importance of hygiene measures on farm level.

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.…”

“…Due to the small number of SNP differences between the isolates, a transmission or exchange of these ESBL E. coli between the barns of the same farm is very likely. It was previously shown that (ESBL‐) E. coli can survive the cleaning and disinfection procedures in the chicken barns which finally leads to a spread and the colonization of broiler chickens on the same farms (Luyckx et al ., 2015a,b; Daehre et al ., 2017). Interestingly, the two clusters differ in up to 629.4 SNPs Mbp −1 indicating that two different clonal lines of ST‐117 strains were introduced into the same flock.…”

“…We previously investigated up to 150 samples from the fattening period of seven flocks each showing that there is an overall highly diverse E. coli population on these fattening farms (Daehre et al ., 2017). Together with the results from this study, we could show that not only one prominent vertical or horizontal transmission route of ESBL producers exists.…”

“…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). However, it still remained unclear whether the resistant bacteria are permanently and repeatedly transferred along the whole broiler production chain with each production cycle, or if this transfer only occurs occasionally and certain strains, once introduced on the farm, are circulating constantly.…”

“…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.…”