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

Dynamics of cefotaxime resistant Escherichia coli in broilers in the first week of life

Extended-spectrum beta-lactamase producing E. coli (ESBL-E) are wide spread among broilers, with the highest prevalence among individual birds at broiler production farms. Previous research describes low prevalences among individual birds at arrival at the farm (below 30%), and a rapid increase up to 100% within the first week. Our goal was to investigate whether this rapid increase was due to latent contamination of ESBL-E or to contamination at the broiler farm. Two broiler groups, one hatched at a conventional hatchery and the other individually hatched in an ESBL-free environment, were housed individually in an experimental ESBL-free environment. A third group was hatched at a conventional hatchery and kept at a conventional broiler farm. The birds were sampled daily during the first week after hatch and tested for the presence of ESBL-E. In addition ESBL-E presence in eggs that were not incubated was investigated. All birds and eggs came from one ESBL-E positive parent flock. ESBL/AmpC genes, plasmids and E. coli sequence types were determined for a selection of isolates. ESBL-E was never found in the two groups kept in the ESBL-free experimental environment or in the sampled eggs, whereas all broilers sampled at the conventional farm became positive for ESBL-E within three days. One dominant E. coli strain (ST88) carrying bla_CTX-M-1 gene on an IncI1/pST3 plasmid was found in parent and broiler samples. We conclude that the rapid increase in ESBL-E prevalence in the first week of life is not caused by a latent contamination of the majority of birds at arrival, but that this increase must be caused by other factors.

Investigation of Extended-Spectrum and AmpC β-Lactamase-Producing Enterobacteriaceae from Retail Seafood in Berlin, Germany

Retail seafood in Berlin, Germany, was investigated to detect the prevalence and quantitative load of Enterobacteriaceae that produce extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase (AmpC). A total of 160 raw seafood samples were screened for the presence of these bacteria using MacConkey agar supplemented with 1 mg/L cefotaxime after nonselective enrichment. Isolated species were subsequently identified using matrix-assisted laser desorption-ionization time-of-flight analysis. ESBL and AmpC production was tested by the disk diffusion method, and ESBL and AmpC genes were characterized using real-time and conventional PCR assays with DNA sequencing. Spread plating was used for quantification of ESBL- and AmpC-producing Enterobacteriaceae. Overall, these bacteria were detected in 21.3% of seafood samples (34 of 160 samples) with prevalences of 22.5 and 20% for shrimp and bivalves, respectively. Of the positive samples, 91.2% contained an ESBL- or AmpC-producing Enterobacteriaceae load of <100 CFU/g (lower detection limit), and 8.8% contained 100 to 1,000 CFU/g. Among the 45 Enterobacteriaceae isolates, Klebsiella pneumoniae (13 isolates) and Escherichia coli (12 isolates) were the predominant species. ESBL and AmpC genes were detected in 33 isolates, with the majority of isolates harboring bla_CTX-M (27.3%), bla_CMY (21.2%), or bla_DHA (21.2%). Our study highlights the hazard associated with seafood containing ESBL- and AmpC-producing Enterobacteriaceae in Germany. Even though the contamination levels were low, the high prevalence of ESBL- and AmpC-producing Enterobacteriaceae in seafood might be of concern to public health because of the potential transmission of these bacteria from seafood to humans through the food chain.

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

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_CMY-2 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.

The occurrence of CTX-M-25-producing Enterobacteriaceae in day-old broiler chicks in Japan

Day-old chicks from 3 hatcheries were placed on bedding paper and brought to a commercial broiler farm between January and July 2016. Sixty-six samples of the paper, which were stained with meconium droppings of the chicks, were collected and examined for isolation of cephalosporin-resistant Enterobacteriaceae. Cefotaxime (CTX)-resistant Klebsiella pneumoniae (1 isolate) and Enterobacter cloacae (4 isolates) were isolated from 5 (7.58%) of the 66 samples. Conjugation experiments revealed that the bla_CTX-M-25 gene conferring CTX resistance was transferred from the K. pneumoniae isolate and 2 of the 4 E. cloacae isolates to Escherichia coli DH5α via IncA/C plasmids carrying the gene. Our results suggested that the bla_CTX-M-25 gene originating from chicks may be spread among commercial broiler farms.