Carriage of extended-spectrum β-lactamases in pig farmers is associated with occurrence in pigs

Abstract

Livestock may serve as a reservoir for extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE). The objectives of this study were to determine the prevalence of carriage with ESBL-PE in pig farmers, family members and employees, and its association with carriage in pigs. Rectal swabs were taken from 2388 pigs (398 pooled samples) on 40 pig farms and faecal samples were obtained from 142 humans living or working on 34 of these farms. Presence of ESBL-PE was determined by selective plating (agar). ESBL genes were analysed by PCR or microarray analysis, and gene sequencing. Genotypes and plasmids were determined by multilocus sequence typing and PCR-based replicon typing for selected isolates. ESBL genes were detected in Escherichia coli from eight humans (6%) (blaCTX-M-1, n = 6; blaTEM-52, n = 1 and blaCTX-M-14, n = 1) on six farms. In 157 pig isolates (107 pooled samples) on 18 farms (45%) ESBL genes were detected (blaCTX-M-1, n = 12; blaTEM-52, n = 6; and blaCTX-M-14, n = 3). Human and pig isolates within the same farm harboured similar ESBL gene types and had identical sequence and plasmid types on two farms (e.g. E. coli ST-453, blaCTX-M-1, IncI1), suggesting clonal transmission. For the remaining farms, sequence types, but not plasmid types, differed. Human ESBL carriage was associated with average number of hours working on the farm per week (OR = 1.04, 95% CI 1.02-1.06) and presence of ESBLs in pigs (OR = 12.5, 95% CI 1.4-111.7). Daily exposure to pigs carrying ESBL-PE is associated with ESBL carriage in humans.

Extended-spectrum β-lactamase- and pAmpC-producing Enterobacteriaceae among the general population in a livestock-dense area

“…People who worked or lived on a farm were excluded from this study. However, it is already known that broiler and pig farmers and their family members have a higher prevalence of ESBL/pAmpC carriage, and contact with animals was identified as risk factor in two studies [4,6,12]. Prevalence was 27%e33% for broiler farmers [4,6] and 13% for persons living or working on ESBL/pAmpCpositive pig farms [12].…”

“…In addition, it was unknown which farms were ESBL/pAmpC-positive. In the Netherlands, in the period just before this study (2009e2011), 100% of broiler farms [4,6] and 45% of pig farms were ESBL/pAmpCpositive [12], but for other types of farms, this prevalence is unknown. Finally, selection bias may have occurred due to the twostep selection process of participants.…”

“…ESBL/pAmpC-producing Enterobacteriaceae (ESBL/pAmpC-E) were initially only observed in human health care [2,3], but they are increasingly detected in the community [2,4e8] as well as in companion animals [9,10], livestock [2e4, 9,11,12] and meat [2,3,13]. Potential routes of transmission of ESBL/pAmpC-E to humans are via the food chain [2,3], by direct contact with animals [4] or indirectly via the environment [11,14].…”

The association of ESBL-producing Enterobacteriaceae (ESBL-E) carriage in humans with pigs

“…[2]. Genetic similarities of ESBL genes, plasmid types and sequence types (STs) suggested a likely transmission between humans and pigs on the same farms.…”

Antibiotic residues and resistance in the environment

“…livestock as a reservoir for ESBL (Extended Spectrum Beta-Lactamase) -producing bacteria is increasingly being recognized as a threat to human health care (Dohmen, 2015).…”