Department of Medical Biotechnologies, University of Siena, Siena, Italy.
BMC Res Notes. 2021 Nov 25;14(1):432. doi: 10.1186/s13104-021-05856-6.
In streptococci, the type M resistance to macrolides is due to the mef(A)-msr(D) efflux transport system of the ATP-Binding cassette (ABC) superfamily, where it is proposed that mef(A) codes for the transmembrane channel and msr(D) for the two ATP-binding domains. Phage ϕ1207.3 of Streptococcus pyogenes, carrying the mef(A)-msr(D) gene pair, is able to transfer the macrolide efflux phenotype to Streptococcus pneumoniae. Deletion of mef(A) in pneumococcal ϕ1207.3-carrying strains did not affect erythromycin efflux. In order to identify candidate genes likely involved in complementation of mef(A) deletion, the Mef(A) amino acid sequence was used as probe for database searching.
In silico analysis identified 3 putative candidates in the S. pneumoniae R6 genome, namely spr0971, spr1023 and spr1932. Isogenic deletion mutants of each candidate gene were constructed and used in erythromycin sensitivity assays to investigate their contribution to mef(A) complementation. Since no change in erythromycin sensitivity was observed compared to the parental strain, we produced double and triple mutants to assess the potential synergic activity of the selected genes. Also these mutants did not complement the mef(A) function.
在链球菌中，对大环内酯类药物的 M 型耐药性是由于 ABC 超家族的 mef(A)-msr(D)外排转运系统所致，其中 m ef(A)被认为编码跨膜通道，msr(D)编码两个 ATP 结合结构域。携带 mef(A)-msr(D)基因对的化脓性链球菌噬菌体ϕ1207.3 能够将大环内酯类药物外排表型转移至肺炎链球菌。肺炎链球菌ϕ1207.3 携带株中 m ef(A)的缺失并不影响红霉素外排。为了鉴定可能参与 m ef(A)缺失互补的候选基因，使用 Mef(A)氨基酸序列作为探针进行数据库搜索。
在 S. pneumoniae R6 基因组中，通过计算机分析鉴定了 3 个可能的候选基因，即 spr0971、spr1023 和 spr1932。每个候选基因的同源缺失突变体均构建，并用于红霉素敏感性测定，以研究它们对 m ef(A)互补的贡献。与亲本菌株相比，红霉素敏感性没有变化，因此我们产生了双突变体和三突变体，以评估所选基因的潜在协同活性。这些突变体也不能补充 m ef(A)的功能。
