Quantitative PCR analysis of Mycoplasma suis shedding patterns during experimental infection

Abstract

The uncultivable hemotrophic bacterium Mycoplasma suis causes infectious anemia in pigs worldwide. The mechanisms by which M. suis is transmitted from pig to pig are largely unknown. Thus, the present study aimed at investigating urine, feces, saliva, nasal and vaginal secrets as well as environmental samples for the presence of M. suis DNA to get insights into potential transmission routes. Seven pigs were experimentally infected with M. suis KI3806. Samples were taken for 8 days post infection (p.i.). A quantitative LightCycler msg1 PCR was used to detect and quantify M. suis. Shedding was found in saliva as well as nasal and vaginal secrets from day 6 p.i. on with a quantity of 3.4×102 to 2.7×105M. suis/swab. In urine M. suis DNA could be detected in 100.0% of the samples from day 6 p.i. on with a quantity of 4.7×102 to 6.3×105M. suis per mL. When shedding patterns were correlated to the median bacterial blood loads shedding was observed at loads of 2.0×109–7.0×1010M. suis per mL blood. No M. suis DNA could be amplified from feces. Dust and water samples of the pig drinking troughs were positive for M. suis on days 2 and 6 post infection, air samples were M. suis-negative throughout the experiment. Our results indicate that blood independent direct transmission as well as indirect transmission via environmental contamination could play a role in the epidemiology of M. suis infections.