Date Full Report Received


Date Abstract Report Received



Primary Investigator:

Many bacterial pathogens of pigs can be found in the tonsils, and the tonsils can act as a reservoir for these pathogens, allowing them to persist in a herd. The goal of this study was to characterize the bacterial community, or microbiome, in the tonsils of healthy pigs and further to compare the tonsillar community in healthy pigs to that in pigs with known infectious diseases. We used a combination of bacterial culture, the traditional method, and current culture-independent techniques, which allowed us to identify many difficult-to-culture bacteria. This study provides the first detailed characterization of the bacterial community, or microbiome, found in porcine tonsils. We identified bacteria found in the tonsils of normal, healthy pigs, and found a diverse mixture of aerobic and anaerobic bacteria that were primarily non-pathogenic commensal organisms. We then compared these to bacteria found in pigs with known infectious diseases. In many herds with disease, we saw increased numbers of the bacterial pathogens in the tonsils as well as a shift in the remainder of the bacterial community. For example, in a herd with chronic Streptococcus suis problems, there were significantly more Streptococcus in the tonsils than we found in healthy herds, as well as reduced numbers of several of the types of commensal bacteria. It is not yet clear whether a shift in the community allows the pathogen to increase or acquisition of the pathogen shifts the rest of the community; it will take additional experimental infection studies to answer this question. We also observed an effect of antibiotics on the normal bacterial community. In herds treated with antibiotics, we frequently saw increased numbers of anaerobic organisms in the tonsils, and a shift in the overall community. Whether this shift affects the subsequent acquisition of pathogens or development of disease is not known, although a parallel would be the effect of antibiotics on human intestinal bacteria.
Contact information: Dr. Martha H. Mulks
Department of Microbiology & Molecular genetics
Michigan State University
East Lansing, MI 48824
Email: mulks@msu.edu
Phone: 517-884-5365