Jayarao B M, Oliver S P
Department of Animal Science, University of Tennessee, Knoxville 37901-1071.
J Dairy Sci. 1992 Apr;75(4):991-7. doi: 10.3168/jds.S0022-0302(92)77841-2.
A total of 117 isolates representing four Streptococcus species and 20 isolates representing two Enterococcus species from bovine mammary secretions were examined for resistance to streptomycin, kanamycin, and gentamicin. Resistance to streptomycin (85.4%) was most prevalent, followed by kanamycin (19%) and gentamicin (2.2%). Minimum inhibitory concentration of streptomycin for most organisms examined ranged from 16 to 250 micrograms/ml. For kanamycin, the minimum inhibitory concentration for most organisms was .5 to 62.5 micrograms/ml. Minimum inhibitory concentration for gentamicin was lower than for kanamycin. Two strains each of Streptococcus uberis and Enterococcus faecalis had minimum inhibitory concentration for streptomycin of greater than 2000 micrograms/ml, and two strains of E. faecalis had similar minimum inhibitory concentration for kanamycin. The minimum bactericidal concentration for all organisms was one to four times higher than minimum inhibitory concentration. None of the organisms evaluated was found to carry plasmids. Transfer of antibiotic resistance in plasmid-free strains was not achieved by mobilization with the aid of plasmid pAD1, indicating the absence of conjugative transposons. These data suggest that expression of aminoglycoside resistance of Streptococcus and Enterococcus species of bovine origin is likely due to factors other than plasmids or conjugative transposons.
对从牛乳腺分泌物中分离出的代表4种链球菌的117株菌株和代表2种肠球菌的20株菌株进行了链霉素、卡那霉素和庆大霉素耐药性检测。对链霉素的耐药性最为普遍（85.4%），其次是卡那霉素（19%）和庆大霉素（2.2%）。大多数检测菌株对链霉素的最低抑菌浓度为16至250微克/毫升。对于卡那霉素，大多数菌株的最低抑菌浓度为0.5至62.5微克/毫升。庆大霉素的最低抑菌浓度低于卡那霉素。乳房链球菌和粪肠球菌各有两株对链霉素的最低抑菌浓度大于2000微克/毫升，两株粪肠球菌对卡那霉素的最低抑菌浓度与此相似。所有菌株的最低杀菌浓度比最低抑菌浓度高1至4倍。未发现所评估的任何菌株携带质粒。在无质粒菌株中，借助质粒pAD1进行动员未能实现抗生素耐药性的转移，这表明不存在接合转座子。这些数据表明，牛源链球菌和肠球菌氨基糖苷类耐药性的表达可能是由质粒或接合转座子以外的因素引起的。
