Chikramane S G, Matthews P R, Noble W C, Stewart P R, Dubin D T
Department of Molecular Genetics and Microbiology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854.
J Gen Microbiol. 1991 Jun;137(6):1303-11. doi: 10.1099/00221287-137-6-1303.
We have compared methicillin-resistant (Mcr) Staphylococcus aureus isolates from Australia, the UK and the USA with regard to chromosomal inserts of the macrolides-lincosamides-streptogramin B (MLS)-resistance transposon Tn554. The American isolates were known to have a distinctive Tn554 insert, designated insert 6, which was closely associated epidemiologically with the methicillin-resistance phenotype. Southern blots of DNA from Australian and London, UK Mcr isolates were hybridized with a range of probes related to Tn554. The isolates had similar or identical Tn554 inserts, and we consider them to be a single group, designated 'Australondon'. Australondon isolates were compared in detail with a deletion mutant, ANS62, that had lost the methicillin-resistance determinant mec, plus other resistance determinants resident in the mec region of the chromosome, and with an American Mcr isolate containing Tn554 insert 6. The Australondon isolates had three Tn554 inserts. Sequence analysis with the polymerase chain reaction showed that all of these inserts differed from classical Tn554 in that the 3'-terminal residues of the transposons were reverse complements of the usual GATGTA. One of the Australondon inserts, designated 6B, closely resembled Tn554 insert 6 in the sequence of its left flanking chromosomal DNA. This insert was found to abut the deletion from the mec region which results in strain ANS62. We infer that Tn554 insert 6B is part of the mec region of the chromosome in Australondon isolates, supporting the idea that insert 6 of the American isolates is also part of this chromosomal region.
我们比较了来自澳大利亚、英国和美国的耐甲氧西林金黄色葡萄球菌（Mcr）分离株中，大环内酯类-林可酰胺类-链阳菌素B（MLS）抗性转座子Tn554的染色体插入情况。已知美国的分离株有一个独特的Tn554插入片段，命名为插入片段6，在流行病学上它与甲氧西林抗性表型密切相关。用一系列与Tn554相关的探针，对来自澳大利亚和英国伦敦的Mcr分离株的DNA进行Southern杂交。这些分离株具有相似或相同的Tn554插入片段，我们认为它们是一个单一的群体，命名为“澳英群体”。将澳英群体的分离株与一个缺失突变体ANS62进行了详细比较，该突变体失去了甲氧西林抗性决定簇mec，以及位于染色体mec区域的其他抗性决定簇，还与一个含有Tn554插入片段6的美国Mcr分离株进行了比较。澳英群体的分离株有三个Tn554插入片段。用聚合酶链反应进行序列分析表明，所有这些插入片段都与经典的Tn554不同，因为转座子的3'末端残基是通常的GATGTA的反向互补序列。澳英群体的一个插入片段，命名为6B，其左侧侧翼染色体DNA序列与Tn554插入片段6非常相似。发现这个插入片段与导致菌株ANS62的mec区域缺失相邻。我们推断，Tn554插入片段6B是澳英群体分离株染色体mec区域的一部分，这支持了美国分离株的插入片段6也是该染色体区域一部分的观点。
