Objectives Farm animals may serve as a reservoir for (multi)resistant bacteria, such as extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae. Animal to man transmission may occur through (in)direct contact during work, which may thus pose an occupational health hazard. In humans, infections with ESBL producing Enterobacteriaceae are associated with high mortality, morbidity and costs. We investigated the prevalence of carriage with ESBL producing Enterobacteriaceae in pig farmers, their family members, and their employees and associations between presence of ESBLs among animals and humans.
Methods Rectal swabs were taken from pigs on 40 Dutch conventional pig farms (60 per farm) and stool samples were obtained from 142 humans living and/or working on 34 of these farms (farmers, family members and employees). Sampling was repeated after 6 months. Presence of ESBL-producing bacteria was determined by selective plating and ESBL genes were analysed by microarray analysis and gene sequencing. Questionnaires were used to determine antimicrobial use, hygiene, contact with animals and/or meat, and other relevant determinants.
Results ESBL genes, mostly CTX-M-1, TEM-52 en CTX-M-14, were determined in pig isolates on 17 farms (43%) and in isolates from 8 participants (6%). ESBL genes determined in farmers corresponded to those detected in pigs on their farm. ESBL carriage was more likely in farmers working on ESBL positive farms (OR > 10). After 6 months ESBL genes were determined in isolates from 8 farmers (6%). Only 2 of these farmers carried ESBL genes in both stool samples obtained with a 6 months interval.
Conclusions We found a strong association between ESBL carriage in farmers and ESBL occurrence on the farm. Repeated sampling indicates that ESBL carriage is not persistent in this human study population.