Wan Tsai-Wen, Hung Wei-Chun, Tsai Jui-Chang, Lin Yu-Tzu, Lee Hao, Hsueh Po-Ren, Lee Tai-Fen, Teng Lee-Jene
Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei, Taiwan.
Department of Microbiology and Immunology, Kaohsiung Medical University, Kaohsiung, Taiwan.
Antimicrob Agents Chemother. 2016 Sep 23;60(10):6108-14. doi: 10.1128/AAC.01096-16. Print 2016 Oct.
We determined the resistance determinants in 274 erythromycin-resistant methicillin-susceptible Staphylococcus aureus (MSSA) isolates during a 13-year period, 2000 to 2012. The resistance phenotypes, inducible macrolide-lincosamide-streptogramin (iMLS), constitutive MLS (cMLS), and macrolide-streptogramin (MS) resistance phenotypes, were examined by a double-disk diffusion D test. The ermB gene was more frequent (35%; 97/274) than ermC (27%; 75/274) or ermA (21%; 58/274). All 97 ermB-positive isolates harbored Tn551 and IS1216V The majority (89/97) of ermB-positive isolates displayed the cMLS phenotype and carried mobile element structure (MES)-like structures, which has been previously reported in sequence type 59 (ST59) methicillin-resistant S. aureus (MRSA). The remaining 8 ermB-carrying isolates, belonging to ST7 (n = 4), ST5 (n = 3), and ST59 (n = 1), were sasK intact and did not carry MES-like structures. Unlike a MES-like structure that was located on the chromosome, the ermB elements on sasK-intact isolates were located on plasmids by S1 nuclease pulsed-field gel electrophoresis (PFGE) analysis and conjugation tests. Sequence data for the ermB-containing region (14,566 bp) from ST59 NTUH_3874 revealed that the best match was a Tn1546-like element in plasmid pMCCL2 DNA (GenBank accession number AP009486) of Macrococcus caseolyticus Tn1546 is recognized as an enterococcal transposon and was known from the vancomycin resistance gene cluster in vancomycin-resistant Enterococcus (VRE). So far, acquisitions of Tn1546 in S. aureus have occurred in clonal complex 5 (CC5) MRSA, but not in MSSA. This is the first report that MSSA harbors an Enterococcus faecium-originated ermB-positive Tn1546-like element located on a plasmid.
在2000年至2012年的13年期间，我们对274株耐红霉素、对甲氧西林敏感的金黄色葡萄球菌（MSSA）分离株进行了耐药决定因素分析。通过双纸片扩散D试验检测了耐药表型，即诱导型大环内酯-林可酰胺-链阳菌素（iMLS）、组成型MLS（cMLS）和大环内酯-链阳菌素（MS）耐药表型。ermB基因比ermC（27%；75/274）或ermA（21%；58/274）更常见（35%；97/274）。所有97株ermB阳性分离株均携带Tn551和IS1216V。大多数（89/97）ermB阳性分离株表现出cMLS表型，并携带移动元件结构（MES）样结构，此前已在序列类型59（ST59）耐甲氧西林金黄色葡萄球菌（MRSA）中报道过。其余8株携带ermB的分离株，分别属于ST7（n = 4）、ST5（n = 3）和ST59（n = 1），sasK完整，不携带MES样结构。与位于染色体上的MES样结构不同，通过S1核酸酶脉冲场凝胶电泳（PFGE）分析和接合试验，sasK完整的分离株上的ermB元件位于质粒上。来自ST59 NTUH_3874的含ermB区域（14,566 bp）的序列数据显示，最佳匹配是解酪大球菌质粒pMCCL2 DNA（GenBank登录号AP009486）中的Tn1546样元件。Tn1546被认为是一种肠球菌转座子，已知存在于耐万古霉素肠球菌（VRE）的万古霉素耐药基因簇中。到目前为止，金黄色葡萄球菌中Tn1546的获得发生在克隆复合体5（CC5）MRSA中，但在MSSA中未发现。这是首次报道MSSA携带位于质粒上的源自粪肠球菌的ermB阳性Tn1546样元件。
