Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA.
Appl Environ Microbiol. 2012 Sep;78(18):6683-8. doi: 10.1128/AEM.01119-12. Epub 2012 Jul 13.
Mannheimia haemolytica, Pasteurella multocida, and Bibersteinia trehalosi have been identified in the lungs of pneumonic bighorn sheep (BHS; Ovis canadensis). Of these pathogens, M. haemolytica has been shown to consistently cause fatal pneumonia in BHS under experimental conditions. However, M. haemolytica has been isolated by culture less frequently than the other bacteria. We hypothesized that the growth of M. haemolytica is inhibited by other bacteria in the lungs of BHS. The objective of this study was to determine whether P. multocida inhibits the growth of M. haemolytica. Although in monoculture both bacteria exhibited similar growth characteristics, in coculture with P. multocida there was a clear inhibition of growth of M. haemolytica. The inhibition was detected at mid-log phase and continued through the stationary phase. When cultured in the same medium, the growth of M. haemolytica was inhibited when both bacteria were separated by a membrane that allowed contact (pore size, 8.0 μm) but not when they were separated by a membrane that limited contact (pore size, 0.4 μm). Lytic bacteriophages or bactericidal compounds could not be detected in the culture supernatant fluid from monocultures of P. multocida or from P. multocida-M. haemolytica cocultures. These results indicate that P. multocida inhibits the growth of M. haemolytica by a contact- or proximity-dependent mechanism. If the inhibition of growth of M. haemolytica by P. multocida occurs in vivo as well, it could explain the inconsistent isolation of M. haemolytica from the lungs of pneumonic BHS.
绵羊肺炎支原体、多杀性巴氏杆菌和蜂房哈夫尼菌已在肺炎性大角羊（BHS；Ovis canadensis）的肺部中被发现。在这些病原体中，绵羊肺炎支原体已被证明在实验条件下可导致 BHS 致命性肺炎。然而，绵羊肺炎支原体的培养分离率低于其他细菌。我们假设绵羊肺炎支原体的生长受到 BHS 肺部中其他细菌的抑制。本研究的目的是确定多杀性巴氏杆菌是否抑制绵羊肺炎支原体的生长。尽管在单独培养时两种细菌均表现出相似的生长特征，但在与多杀性巴氏杆菌共培养时，绵羊肺炎支原体的生长受到明显抑制。这种抑制在对数中期被检测到，并持续到静止期。当在相同的培养基中培养时，当两种细菌通过允许接触的膜（孔径 8.0μm）而不是通过限制接触的膜（孔径 0.4μm）分离时，绵羊肺炎支原体的生长受到抑制。在多杀性巴氏杆菌的单独培养物或多杀性巴氏杆菌-绵羊肺炎支原体共培养物的培养上清液中，均未检测到溶菌噬菌体或杀菌化合物。这些结果表明，多杀性巴氏杆菌通过接触或接近依赖的机制抑制绵羊肺炎支原体的生长。如果多杀性巴氏杆菌对绵羊肺炎支原体生长的抑制作用在体内也存在，那么它可以解释为何在肺炎性 BHS 的肺部中无法一致地分离出绵羊肺炎支原体。
