Distribution and molecular analysis of mef(A)-containing elements in tetracycline-susceptible and -resistant Streptococcus pyogenes clinical isolates with efflux-mediated erythromycin resistance
Distribution and molecular analysis of mef(A)-containing elements in tetracycline-susceptible and -resistant Streptococcus pyogenes clinical isolates with efflux-mediated erythromycin resistance
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DOI：
10.1093/jac/dkh481
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发表时间：
2004-12-01
影响因子：
5.2
通讯作者：
Giovanetti, E
中科院分区：
文献类型：
--
作者：
Brenciani, A;Ojo, KK;Giovanetti, E
目的：分析大量具有外流介导的红霉素耐药性的不同化脓性链球菌临床分离株中含有 mef(A) 的元件的分布和分子特征。为了进一步表征 tet(O)-mef(A) 元件。方法：使用根据已建立的序列或本研究中的序列设计的引物，通过 PCR 进行基因检测。从 tet(O)-mef(A) 元件（类似于 60 kb），对包括 tet(O) 和 mef(A) 基因的 11 972 bp 区域进行了测序。结果：在四环素敏感分离株（n = 28）中，mef（A）基因包含在常规 Tn1207.1 转座子（7.2 kb）中，该转座子被插入到先前描述的两个转座子之一中Tn1207.3（类似于 52 kb）或 58.8 kb 嵌合元件，两侧都是 comEC 基因。在所有携带 tet(O) 基因的四环素抗性分离株 (n = 61) 中，mef(A) 基因是可变 Tn1207.1 相关转座子的一部分，插入独特元件中，该元件包含与 mef(A) 基因上游 2.3 至 5.5 kb 相似的 tet(O) 基因，并且两侧没有 comEC 基因。在这些 tet(O)-mef(A) 元件的 Tn1207.1 样转座子中，除了 mef(A) 之外，在所有测试的分离株中仅通过 PCR 检测到 msr(D) (orf5) 和修饰的 orf6；虽然 orf1 和 orf2 始终检测不到，但 orf3、orf7 和 orf8 的百分比有所不同。在orf3阳性元件中，测序鉴定出tet(O)基因下游的四个新的开放阅读框，随后是与肺炎球菌mega元件序列同源的三个短序列。结论：mef(A)基因携带在不同的染色体遗传元件上，具体取决于分离株是否对四环素敏感或耐药。
Objectives: To analyse the distribution and molecular features of mef(A)-containing elements in a large collection of different Streptococcus pyogenes clinical isolates with efflux-mediated erythromycin resistance. To further characterize a tet(O)-mef(A) element.Methods: Gene detection was carried out by PCR using primers designed from established sequences or from sequences in this study. From a tet(O)-mef(A) element (similar to60 kb), an 11 972 bp region including the tet(O) and mef(A) genes was sequenced.Results: In the tetracycline-susceptible isolates (n =28), the mef(A) gene was contained in a regular Tn1207.1 transposon (7.2 kb), which was inserted into one of two previously described elements, Tn1207.3 (similar to52 kb) or a 58.8 kb chimeric element, both flanked by the comEC gene. In the tetracycline-resistant isolates (n =61), all of which carried the tet(O) gene, the mef(A) gene was part of a variable Tn1207.1-related transposon inserted into unique elements which contained the tet(O) gene similar to2.3 to 5.5 kb upstream of the mef(A) gene and were not flanked by the comEC gene. In the Tn1207.1-like transposon of these tet(O)-mef(A) elements, only msr(D) (orf5) and a modified orf6, in addition to mef(A), were detected by PCR in all isolates tested; while orf1 and orf2 were always undetectable, orf3, orf7 and orf8 were found in variable percentages. In an orf3-positive element, sequencing identified four new open reading frames downstream of the tet(O) gene, followed by three short sequences with homology to sequences of the pneumococcal mega element.Conclusions: The mef(A) gene is carried on different chromosomal genetic elements depending on whether the isolates are susceptible or resistant to tetracycline.