Main research question/goal
What is the effect of low doses of antibiotics in feed as a consequence of carry-over, on selection of resistant bacteria and transfer of resisance genes in the animal gut? This is the central research question of the Crosscontam project. By carry-over from medicated to non-medicated feed cross contamination of feed with antibiotics may occur. Since 2014, carry-over is mainly located in Belgium at the level of transport and pig farms and to a much smaller extent in feed companies.
By animal experiments, we determine the concentration of antibiotics in the pig gut when pigs are fed with low doses of antibiotics (carry-over level of 3%, based on the legally acceptable level of carry-over of coccidiostatics, 2009/8/EG). We analyse doxycycline as well as the combination of sulphonamide/trimethoprim. Via in vitro experiments with pure cultures and with a fermentation system that mimics a part of the pig gut we study the influence of low concentrations of antibiotics on resistance development. Because of recent developments in the legislation concerning carry-over, a level of 1% carry-over is also taken into account. Besides a quantitative risk model is developed by which the exposure of animals to antibiotics as a consequence of carry-over in feed is estimated.
This project has shown that low concentrations of antibiotics in feed may result in rather high concentrations in the gut, even at 3% carry-over. The type of antibiotic (and thus the bioavailability) determines the gut concentrations. For doxycycline we showed that very low carry-over concentrations (1%) may cause resistance selection. Estimation of exposure by the developed model indicated that cross contamination is a general phenomenon and is consequently impossible to avoid in practice. Based on these results we recommend a general reduction of the use of medicated feed for administration of antibiotics. These results were disseminated via posters and oral presentations at national and international symposia and were also published in scientific journals. They contribute to the PhD research of Laura Peeters and Thijs De Mulder.
CODA-CERVA - Centrum Onderzoek Diergeneeskunde & Agrochemie
Ugent - Fac. Diergeneeskunde