Livestock-Associated Methicillin-resistant Staphylococcus aureus (LA-MRSA) has emerged in pigs globally. Pig farms act as a reservoir of LA-MRSA. In the Netherlands, the prevalence of LA-MRSA in slaughter pigs was 99.5% in 2015. Through exposure to animals and dust, farms are at risk for acquiring LA-MRSA. In the Netherlands MRSA colonization in the general population and in hospitals is very low. Strict infection control measures are implemented in hospitals (‘search and destroy’) to prevent spread of MRSA of people who are at risk of being MRSA-positive. With the introduction of LA-MRSA, all people working with living pigs and veal calves are considered as risk for being LA-MRSA positive and are included in the search and destroy program with quarantine and additional diagnostics. Infections with multidrug-resistant microorganisms, including LA-MRSA are a burden for patients, health care staff, and finances of health care institutions.

 The recent adaptation of LA-MRSA to humans in Denmark, and the recently observed unexplained cases of LA-MRSA patients in Dutch hospitals, highlights the need to prevent LA-MRSA transmission. At this moment, there are no intervention measures in pig production to reduce LA-MRSA in pigs. In a pilot microbiome study, we identified several bacterial species negatively associated with colonization of LA-MRSA in piglets. To identify and isolate bacterial strains that will effectively outcompete LA-MRSA when used as a pre-colonization microflora, strain level metagenomics followed by high throughput strain identification will be used. Subsequently these competing strains should be produced and applied nasally as live bacteria in newborn piglets, in order to limit or eradicate LA-MRSA outgrowth in the piglet nasopharynx. Prevention of LA-MRSA colonization will reduce the transmission risk of LA-MRSA from piglets to farm workers through dust. We aim to study the effect of this bacterial inference on transmission of LA-MRSA from pigs to humans by i) identifying competing bacterial species that might be included in a microflora to be used in pigs, ii) studying the efficacy of pre-colonizing piglets, and iii) estimating the risk reduction for MRSA transmission to humans as a result of reduced environmental contamination.

In this project, an interdisciplinary group works together with an industrial partner to identify bacterial species that compete with LA-MRSA for production of a microflora that can be administered to pigs for modulation of the nasal microbiome. The outcome of this project will be a novel intervention procedure based on protecting the piglets for colonization with LA-MRSA by competitive-exclusion.

• prof. dr. ir. L.A. (Lidwien) Smit
• prof. dr. ir. D.J.J. (Dick) Heederik
• dr. A Fluit
• A.A. (Abel) Vlasblom
• prof. dr. J.A. (Jaap) Wagenaar
• dr. B. (Birgitta) Duim
• dr. A.L. (Aldert) Zomer

• Marjolein Kluytmans-van den Bergh
• Gerard van Eijden