Stuart J G, Zimmerer E J, Maddux R L
Department of Biological Sciences, Murray State University, Kentucky 42071.
Vet Microbiol. 1992 Feb;30(2-3):213-22. doi: 10.1016/0378-1135(92)90115-a.
Forty-eight clinical isolates of Streptococcus suis were examined for antibiotic sensitivity and the presence of plasmid DNA. It was determined that isolates from this study showed a substantial increase in resistance to erythromycin (ery), clindamycin, and tetracycline (tet) compared to a similar study conducted five years earlier. Eleven of the 48 isolates contained plasmid DNA as revealed by DNA isolation and gel electrophoresis. Plasmid DNA from four strains resistant to the above three antibiotics was tested for the ability to transform an antibiotic sensitive recipient. No transformation of antibiotic resistance could be demonstrated. In other experiments, the above four strains, along with four plasmid-negative triply resistant strains were tested for the ability to transfer tet or ery resistance to tet and ery sensitive recipients by conjugation. In each mating, antibiotic resistance was transferred at frequencies averaging 2.4 x 10(-6) recombinants/recipient for ery and 3.4 x 10(-6) recombinants/recipient for tet resistance. DNA from each clinical specimen, as well as the recombinants mentioned above was probed with tn916. Autoradiographs revealed that several clinical isolates and recombinants bound the probe. It is concluded that conjugation of antibiotic resistance in these clinical strains is possibly mediated by a transposon similar to tn916.
对48株猪链球菌临床分离株进行了抗生素敏感性和质粒DNA检测。结果表明，与五年前进行的一项类似研究相比，本研究中的分离株对红霉素（ery）、克林霉素和四环素（tet）的耐药性大幅增加。通过DNA分离和凝胶电泳发现，48株分离株中有11株含有质粒DNA。对上述三种抗生素耐药的四株菌株的质粒DNA进行了转化抗生素敏感受体能力的检测。未证明抗生素耐药性发生转化。在其他实验中，对上述四株菌株以及四株质粒阴性的三重耐药菌株进行了检测，以评估它们通过接合将tet或ery耐药性转移到tet和ery敏感受体的能力。在每次交配中，ery耐药性转移频率平均为2.4×10^(-6)重组体/受体，tet耐药性转移频率平均为3.4×10^(-6)重组体/受体。用tn916对每个临床标本以及上述重组体的DNA进行探针杂交。放射自显影片显示，一些临床分离株和重组体与探针结合。得出结论，这些临床菌株中抗生素耐药性的接合可能由类似于tn916的转座子介导。
