Abstract
Mycoplasma pneumonia caused by Mycoplasma bovis (M. bovis) is associated with severe inflammatory reactions in the trachea and lungs and can be difficult to treat with antibiotics. Biofilms play a significant role in the persistence of bacteria and contribute to chronic lesions. A recent study showed that polymicrobial interactions of species are an important factor in biofilm formation, but the detailed mechanism of biofilm formation of M. bovis remains unknown. Assuming multiple pathogen infections in bovine respiratory disease complex, this study examined the characterization of the polymicrobial relationship between M. bovis and Trueperella pyogenes (T. pyogenes) during biofilm formation. Bacterium-like aggregation structures (> 10 µm), which were assumed to be biofilms of M. bovis in vivo, were observed adhering to the cilia in calves with Mycoplasma pneumonia. M. bovis released extracellular matrix to connect with neighboring bacteria and form a mature biofilm on the plate. Biofilm formation in co-culture of M. bovis and T. pyogenes tended to increase compared to that in single culture of these bacteria. Additionally, some large aggregates (> 40 µm) composed of M. bovis and T. pyogenes were observed. The morphological characteristics of this biofilm were similar to those observed in vivo compared to a single culture. In conclusion, the polymicrobial interaction between M. bovis and T. pyogenes induced biofilm formation, which was associated with increased resistance to antimicrobial agents, thereby exacerbating the progression of chronic Mycoplasma pneumonia.