Detection of Tn917-Like Sequences within a Tn916-like Conjugative Transposon (Tn3872) in Erythromycin-Resistant Isolates of Streptococcus pneumoniae

A series of macrolide-lincosamide-streptogramin B (MLS)-resistant pneumococcal isolates of a variety of serotypes was examined and was found to contain Tn917-like elements by DNA-DNA hybridization. Like Tn1545, Tn917 also encodes an ermAM gene but does not mediate resistance to other antimicrobial agents. Furthermore, nucleotide sequence analyses of the DNAs flanking three of the Tn917-like elements revealed that they were inserted into orf9 of a Tn916-like element in a composite transposon-like structure (Tn3872). Other MLS-resistant strains appeared to contain Tn1545-like elements that had suffered a deletion of sequences including the aphA-3 sequences responsible for kanamycin resistance. Thus, the MLS resistance phenotype in pneumococci appears to be mediated by the ermAM present on a much wider variety of genetic elements than was previously appreciated.

本研究对一系列不同血清型的大环内酯类-林可酰胺类-链阳菌素B（macrolide-lincosamide-streptogramin B, MLS）耐药肺炎球菌分离株开展检测，通过DNA-DNA杂交技术证实其携带类Tn917转座子元件。与Tn1545类似，Tn917同样编码ermAM基因，但无法介导其他抗菌剂的耐药性。此外，对3个类Tn917转座子元件侧翼DNA的核苷酸序列分析显示，这些元件以复合转座子样结构（Tn3872）的形式插入至类Tn916转座子的orf9位点。其余MLS耐药菌株则携带类Tn1545转座子元件，该类元件发生了包含负责卡那霉素耐药的aphA-3序列在内的片段缺失。综上，肺炎球菌的MLS耐药表型似乎由分布于更多样化遗传元件上的ermAM基因介导，这一遗传多样性范围远超此前的认知。