Dogan Belgin, Schukken Y H, Santisteban C, Boor Kathryn J
Department of Food Science, 413 Stocking Hall, Cornell University, Ithaca, NY 14853, USA.
J Clin Microbiol. 2005 Dec;43(12):5899-906. doi: 10.1128/JCM.43.12.5899-5906.2005.
To better understand the emergence and transmission of antibiotic-resistant Streptococcus agalactiae, we compared phenotypic and genotypic characteristics of 52 human and 83 bovine S. agalactiae isolates. Serotypes found among isolates from human hosts included V (48.1%), III (19.2%), Ia and Ib (13.5% each), and II (5.8%). Among isolates from bovine hosts, molecular serotypes III and II were predominant (53 and 14.5%, respectively). Four and 21 different ribotypes were found among human and bovine isolates, respectively. A combination of ribotyping and serotyping showed that two bovine isolates were indistinguishable from human isolates. Resistance to tetracycline and erythromycin was more common among human (84.6% and 26.9%, respectively) than bovine (14.5% and 3.6%, respectively) isolates. tetM was found in all tetracycline-resistant human isolates, while tetO was the predominant resistance gene among bovine isolates. tet genes were found among various ribotypes. ermB, ermTR, and mefA were detected among erythromycin-resistant human isolates, while ermB was the only erythromycin resistance determinant among isolates from bovine hosts. For isolates from human hosts, erythromycin resistance genes appeared to be associated with specific ribotypes. We conclude that (i) human and bovine S. agalactiae isolates represent distinct populations; (ii) human host-associated S. agalactiae subtypes may occasionally be transmitted to bovines; (iii) while emergence of erythromycin and tetracycline resistance appears to largely occur independently among human and bovine isolates, occasional cross-species transfer of resistant strains or transmission of resistance genes between human- and bovine-associated subtypes may occur; and (iv) dissemination of antibiotic-resistant S. agalactiae appears to include both clonal spread of resistant strains as well as horizontal gene transfer.
为了更好地理解耐抗生素无乳链球菌的出现和传播情况，我们比较了52株人源和83株牛源无乳链球菌分离株的表型和基因型特征。在人源宿主分离株中发现的血清型包括V型（48.1%）、III型（19.2%）、Ia型和Ib型（各占13.5%）以及II型（5.8%）。在牛源宿主分离株中，分子血清型III型和II型占主导地位（分别为53%和14.5%）。在人源和牛源分离株中分别发现了4种和21种不同的核糖体分型。核糖体分型和血清分型相结合显示，有两株牛源分离株与人源分离株无法区分。人源分离株对四环素和红霉素的耐药性比牛源分离株更常见（分别为84.6%和26.9%，而牛源分离株分别为14.5%和3.6%）。在所有耐四环素的人源分离株中均发现tetM，而tetO是牛源分离株中主要的耐药基因。在各种核糖体分型中均发现了tet基因。在耐红霉素的人源分离株中检测到ermB、ermTR和mefA，而ermB是牛源宿主分离株中唯一的红霉素耐药决定因素。对于人源宿主分离株，红霉素耐药基因似乎与特定的核糖体分型相关。我们得出以下结论：（i）人源和牛源无乳链球菌分离株代表不同的群体；（ii）与人源宿主相关的无乳链球菌亚型偶尔可能传播给牛；（iii）虽然红霉素和四环素耐药性的出现似乎在很大程度上在人源和牛源分离株中独立发生，但耐药菌株偶尔可能发生跨物种转移，或者耐药基因可能在人源和牛源相关亚型之间传播；（iv）耐抗生素无乳链球菌的传播似乎包括耐药菌株的克隆传播以及水平基因转移。
