Risk factors for Tetracycline resistance gene tet(W) & Class 1 integron abundance in Dutch pig farms

Abstract

Antibiotic resistance is an undeniable public health threat. Humans, animals, and the environment are closely interlinked reservoirs for the transmission of antimicrobial-resistant bacteria and genes. Contacting domesticated animals is an exposure to human acquisitions of ARGs and mobile genetic elements, which can transfer via the food chain, indirect & direct contact routes. Farmers in swine farms are in a particular situation where they can acquire ARGs from their pigs. The study aimed to identify risk factors for tetracycline gene tet(W) and class 1 integron abundance in Dutch pig farmers. Data from 33 multiplier Dutch pig farms from 2011-2012 were analyzed using a linear mixed-effects regression modeling technique. This method was appropriate for exploring the association between farm risk factors based on the human questionnaire answered by farmers and the relative abundance of tet(W) and intl1 gene copies calculated and normalized from the qPCR on fecal samples of farmers and pooled samples from pigs. Tet(W) and intl1 data were analyzed separately. Descriptive analyses including t-tests on the relative abundance of tet(W) and intl1 depicted a decreasing trend in humans. The result of the two models indicated that the second sampling time (12 months) was associated with the decreased relative abundance of tet(W) and intl1 in humans. In the tet(W) model, self-administering antibiotics to pigs and living on the pig farm were positively and significantly associated with the relative abundance of tet(W) in humans. In the intl1 model, hours spent per week on washing sows and removing manure of weaner piglets were identified as significant farm risk factors. In conclusion, risk factors in the study indicated that there has been a combination of direct and indirect transfer of resistant genes from pigs to farmers. Longer exposure in hours to pigs is associated with a higher relative abundance of tet(W) in humans.