Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA.
Appl Environ Microbiol. 2010 Feb;76(4):1008-13. doi: 10.1128/AEM.02086-09. Epub 2009 Dec 28.
Mannheimia (Pasteurella) haemolytica is the only pathogen that consistently causes severe bronchopneumonia and rapid death of bighorn sheep (BHS; Ovis canadensis) under experimental conditions. Paradoxically, Bibersteinia (Pasteurella) trehalosi and Pasteurella multocida have been isolated from BHS pneumonic lungs much more frequently than M. haemolytica. These observations suggest that there may be an interaction between these bacteria, and we hypothesized that B. trehalosi overgrows or otherwise inhibits the growth of M. haemolytica. Growth curves (monoculture) demonstrated that B. trehalosi has a shorter doubling time ( approximately 10 min versus approximately 27 min) and consistently achieves 3-log higher cell density (CFU/ml) compared to M. haemolytica. During coculture M. haemolytica growth was inhibited when B. trehalosi entered stationary phase (6 h) resulting in a final cell density for M. haemolytica that was 6 to 9 logs lower than expected with growth in the absence of B. trehalosi. Coculture supernatant failed to inhibit M. haemolytica growth on agar or in broth, indicating no obvious involvement of lytic phages, bacteriocins, or quorum-sensing systems. This observation was confirmed by limited growth inhibition of M. haemolytica when both pathogens were cultured in the same media but separated by a filter (0.4-microm pore size) that limited contact between the two bacterial populations. There was significant growth inhibition of M. haemolytica when the populations were separated by membranes with a pore size of 8 mum that allowed free contact. These observations demonstrate that B. trehalosi can both outgrow and inhibit M. haemolytica growth with the latter related to a proximity- or contact-dependent mechanism.
绵羊肺炎支原体是唯一一种在实验条件下能引起大角羊（Ovis canadensis）严重支气管肺炎和快速死亡的病原体。矛盾的是，比氏贝氏菌（Pasteurella trehalosi）和多杀巴斯德氏菌从大角羊肺炎肺部中分离出来的频率比绵羊肺炎支原体高得多。这些观察结果表明，这两种细菌之间可能存在相互作用，我们假设比氏贝氏菌过度生长或以其他方式抑制绵羊肺炎支原体的生长。生长曲线（单一培养）表明，比氏贝氏菌的倍增时间更短（约 10 分钟对约 27 分钟），并且始终达到比绵羊肺炎支原体高 3 个对数的细胞密度（CFU/ml）。在共培养中，当比氏贝氏菌进入静止期（6 小时）时，绵羊肺炎支原体的生长受到抑制，导致绵羊肺炎支原体的最终细胞密度比没有比氏贝氏菌生长时低 6 到 9 个对数。共培养上清液不能抑制琼脂或肉汤中的绵羊肺炎支原体生长，表明没有明显涉及裂解噬菌体、细菌素或群体感应系统。当两种病原体在相同的培养基中培养但通过限制两者之间接触的孔径为 0.4 微米的过滤器（0.4 微米的孔径）分开时，对绵羊肺炎支原体的有限生长抑制证实了这一观察结果。当种群通过允许自由接触的孔径为 8 微米的膜分离时，对绵羊肺炎支原体的生长有明显的抑制作用。这些观察结果表明，比氏贝氏菌可以过度生长并抑制绵羊肺炎支原体的生长，后者与接近或接触依赖机制有关。
