Mycoplasma bovis dans le complexe respiratoire bovin et propriétés de cyto-adhésion in vitro

Mycoplasmas frequently infect cattle, causing especially respiratory diseases. Mycoplasma bovis is the most important pathogenic species in countries free of bovine contagious pleuropneumonia. This species was frequently isolated in Belgium from cattle with respiratory disease. Furthermore, associations were often observed with pasteurellas and bovine respiratory syncytial virus. Of these M. bovis isolates, many were resistant to several antimicrobial agents which are used in cattle practice, except to fluoroquinolones. Inasmuch the high frequency of M. bovis isolation and antibiotic resistances, it is very important to understand the pathogenicity of this bacteria in order to optimize prophylactic tools. Therefore, the study of the cytadherence of M. bovis is essential since it represents the first step of the bacterial infection. According to our experimental results, PG45 is not representative of field isolates because of its low adherence rates to various cell lines. This could be explained by the high number of subcultures of this pathogenic strain underwent since its first isolation, which sharply contrasts with other isolates. M. bovis adheres specifically to bovine bronchial epithelial cells in primary culture. Proteins such as variable surface proteins C and F are involved in this step as observed by decreased adherence rates after trypsinization of mycoplasma cells or addition of monoclonal antibodies.