Epidemiology of ESBL - About pigs and humans

Extended spectrum beta-lactamases (ESBL) are an emerging concern in public health. Transmission of ESBL from livestock to humans may occur through direct contact with livestock. This thesis focused on the presence of ESBL in pigs, the pig farming community and pig slaughterhouse workers. Risk factors for ESBL carriage in humans were determined next to risk factors for the occurrence of ESBL in pigs. Genetic characteristics of ESBL-producing E. coli were determined longitudinally in pigs, humans and dust on pig farms and cross-sectionally from slaughterhouse workers at different occupational tasks. Frequent contact with pigs carrying ESBL was associated with human ESBL carriage. In addition, the possibility of airborne transmission of ESBL genes was suggested. Slaughterhouse workers were more likely to carry an ESBL when working at the beginning of the slaughter process than after chilling of the pig carcasses. The presence of ESBL in pigs declined over time. The incidental use of cephalosporins was associated to the presence of ESBL carrying pigs on farms. Farm management practices on biosecurity were associated with a lower probability of ESBL in pigs on farms. In both humans and pigs, blaCTX-M-1 was most frequently detected. On several farms, identical combinations of ESBL genes, sequence types and plasmid (sub)types were detected in E. coli isolates from humans and pigs. Prolonged carriage of ESBL in pig farmers was observed incidentally. Considering their daily intensive contact with livestock, the epidemiological associations found, and the genetic similarities, clonal transmission is likely to occur between pigs and pig farmers.