Lees P, Illambas J, Pelligand L, Toutain P-L
Royal Veterinary College, Hawkshead Campus, Hatfield, Hertfordshire AL9 7TA, United Kingdom.
Toxalim, Université de Toulouse, INRA, ENVT, 23, Chemin des Capelles-BP 87614, 31076 Toulouse, France.
Vet J. 2016 Dec;218:60-64. doi: 10.1016/j.tvjl.2016.11.006. Epub 2016 Nov 17.
The in vitro pharmacodynamics of oxytetracycline was established for six isolates of each of the calf pneumonia pathogens Mannheimia haemolytica and Pasteurella multocida. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and bacterial time-kill curves were determined in two matrices, Mueller Hinton broth (MHB) and calf serum. Geometric mean MIC ratios, serum:MHB, were 25.2:1 (M. haemolytica) and 27.4:1 (P. multocida). The degree of binding of oxytetracycline to serum protein was 52.4%. Differences between serum and broth MICs could not be accounted for by oxytetracycline binding to serum protein. In vitro time-kill data suggested a co-dependent killing action of oxytetracycline. The in vitro data indicate inhibition of the killing action of oxytetracycline by serum factor(s). The nature of the inhibition requires further study. The outcome of treatment with oxytetracycline of respiratory tract infections in calves caused by M. haemolytica and P. multocida may not be related solely to a direct killing action.
对溶血性曼氏杆菌和多杀性巴氏杆菌这两种犊牛肺炎病原体的六个分离株，分别测定了土霉素的体外药效学指标。在两种基质中测定了最低抑菌浓度（MIC）、最低杀菌浓度（MBC）以及细菌时间-杀菌曲线，这两种基质分别是 Mueller Hinton 肉汤（MHB）和犊牛血清。血清与 MHB 的几何平均 MIC 比值分别为 25.2:1（溶血性曼氏杆菌）和 27.4:1（多杀性巴氏杆菌）。土霉素与血清蛋白的结合程度为 52.4%。血清和肉汤 MIC 之间的差异不能用土霉素与血清蛋白的结合来解释。体外时间-杀菌数据表明土霉素存在协同依赖性杀菌作用。体外数据表明血清因子会抑制土霉素的杀菌作用。这种抑制作用的性质需要进一步研究。土霉素治疗由溶血性曼氏杆菌和多杀性巴氏杆菌引起的犊牛呼吸道感染的效果可能不仅仅与直接杀菌作用有关。
