Abstract
In recent years, extended-spectrum β-lactamases (ESBL) producing bacteria have been found in livestock, mainly as asymptomatic colonizers. The zoonotic risk for people working in close contact to animal husbandry has still not been completely assessed. Therefore, we investigated the prevalence of ESBL-producing Escherichia spp. in livestock animals and workers to determine the potential risk for an animal-human cross-transmission.In Mecklenburg-Western Pomerania, northeast Germany, inguinal swabs of 73 individuals with livestock contact from 23 different farms were tested for ESBL-producing Escherichia spp. Two pooled fecal samples per farm of animal origin from 34 different farms (17 pig farms, 11 cattle farms, 6 poultry farms) as well as cloacal swabs of 10 randomly selected broilers or turkeys were taken at each poultry farm. For identification, selective chromogenic agar was used after an enrichment step. Phenotypically ESBL-producing isolates (n = 99) were tested for CTX-M, OXA, SHV and TEM using PCR, and isolates were further characterized using multilocus sequence typing (MLST). In total, 61 diverse isolates from different sources and/or different MLST/PCR results were acquired. Five farm workers (three from cattle farms and two from pig farms) harbored ESBL-producing E. coli. All human isolates harbored the CTX-M β-lactamase; TEM and OXA β-lactamases were additionally detected in two, resp. one, isolates. ESBL-producing Escherichia spp. were found in fecal samples at pig (15/17), cattle (6/11) and poultry farms (3/6). In total, 70.6% (24/36) of the tested farms were ESBL positive. Furthermore, 9 out of 60 cloacal swabs turned out to be ESBL positive. All isolated ESBL-producing bacteria from animal sources were E. coli, except for one E. hermanii isolate. CTX-M was the most prevalent β-lactamase at cattle and pig farms, while SHV predominated in poultry. One human isolate shared an identical MLST sequence type (ST) 3891 and CTX-M allele to the isolate found in the cattle fecal sample from the same farm, indicating a zoonotic transfer. Two other pairs of human-pig and human-cattle E. coli isolates encoded the same ESBL genes but did not share the same MLST ST, which may indicate horizontal resistance gene transfer. In summary, the study shows the high prevalence of ESBL-producing E.coli in livestock in Mecklenburg- Western Pomerania and provides the risk of transfer between livestock and farm workers.
Highlights
Extended- spectrum β-lactamases (ESBL) are mainly plasmid-encoded enzymes providing an extended resistance to β-lactam antibiotics and can be produced by a variety of different bacteria, such as Enterobacteriaceae or nonfermenting bacteria [1, 2]
38 isolates were of supposed clonal origin, as they were found in the same sample source and showed identical multilocus sequence typing (MLST) and PCR results
Five of 73 (6.8%) farm workers carried ESBL-producing E. coli and all were employed at farms with positive livestock fecal samples (Table 1)
Summary
Extended- spectrum β-lactamases (ESBL) are mainly plasmid-encoded enzymes providing an extended resistance to β-lactam antibiotics and can be produced by a variety of different bacteria, such as Enterobacteriaceae or nonfermenting bacteria [1, 2]. The risk of zoonotic transfer from livestock to people with close contact to these animals is still largely unknown, but some studies have implicated a transfer of ESBLproducing E. coli or ESBL genes from poultry or pigs to farm workers [15,16,17,18]. Besides this direct zoonotic transfer, other routes as foods of animal origin may be a risk factor for human colonization or infection [19, 20]. ESBL-producing bacteria are found in livestock, and in companion animals [8, 21], zoo animals [22] and wild animals [23,24,25,26]
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