Two Distinct Genetic Elements Are Responsible for erm(TR)-Mediated Erythromycin Resistance in Tetracycline-Susceptible and Tetracycline-Resistant Strains of Streptococcus pyogenes
Two Distinct Genetic Elements Are Responsible for erm(TR)-Mediated Erythromycin Resistance in Tetracycline-Susceptible and Tetracycline-Resistant Strains of Streptococcus pyogenes
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DOI：
10.1128/aac.01378-10
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发表时间：
2011-05-01
影响因子：
4.9
通讯作者：
Giovanetti, Eleonora
中科院分区：
文献类型：
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作者：
Brenciani, Andrea;Tiberi, Erika;Giovanetti, Eleonora
在化脓性链球菌中，诱导型红霉素 (ERY) 耐药性是由于 23S rRNA 中腺嘌呤残基的转录后甲基化所致，该残基可由 erm(B) 基因或最近描述的 erm(TR) 基因编码。两个携带 erm(TR) 的遗传元件显示出广泛的 DNA 特性，迄今为止已被测序：ICE10750-RD。 2（类似于 49 kb）和 Tn1806（类似于 54 kb），分别来自化脓性链球菌和肺炎链球菌的四环素 (TET) 敏感菌株。然而，通常由 tet(O) 基因介导的 TET 抗性在 erm(TR) 阳性化脓性链球菌中广泛存在。在这项研究中，研究了 23 种具有 erm(TR) 介导的 ERY 抗性的化脓性链球菌临床菌株，其中 3 株对 TET 敏感，20 株对 TET 耐药。两个 erm(TR) 携带元件仅共享一个短的、高同一性的包含 erm(TR) 的核心序列，并进行了全面表征：来自 TET 敏感菌株 C1 的 ICESp1108（45,456 bp）和来自 TET 抗性菌株 iB21 的 ICESp2905（65,575 bp）。而 ICESp1108 与 ICE10750-RD 表现出广泛的相似性。与图2和Tn1806相比，ICESp2905显示了先前未报道的遗传组织，这是由于在梭菌起源的支架中插入了单独的包含erm(TR)和tet(O)的片段而产生的。早期的研究已经证明了本研究中使用的相同菌株的 erm(TR) 元件通过缀合的可转移性。与 ICE10750-RD 不同。 ICESp1108 和 ICESp2905 均整合到 hsdM 染色体基因中，而 ICESp1108 和 ICESp2905 均在保守的 rum 基因 3' 端共享染色体整合位点，该位点是多个移动链球菌元件的整合热点。通过使用 PCR 作图分析，在其他 TET 敏感和 TET 抗性测试菌株中分别显示了与 ICESp1108 和 ICESp2905 非常相似的 erm(TR) 携带元件。
In Streptococcus pyogenes, inducible erythromycin (ERY) resistance is due to posttranscriptional methylation of an adenine residue in 23S rRNA that can be encoded either by the erm(B) gene or by the more recently described erm(TR) gene. Two erm(TR)-carrying genetic elements, showing extensive DNA identities, have thus far been sequenced: ICE10750-RD. 2 (similar to 49 kb) and Tn1806 (similar to 54 kb), from tetracycline (TET)-susceptible strains of S. pyogenes and Streptococcus pneumoniae, respectively. However, TET resistance, commonly mediated by the tet(O) gene, is widespread in erm(TR)-positive S. pyogenes. In this study, 23 S. pyogenes clinical strains with erm(TR)-mediated ERY resistance-3 TET susceptible and 20 TET resistant-were investigated. Two erm(TR)-carrying elements sharing only a short, high-identity erm(TR)-containing core sequence were comprehensively characterized: ICESp1108 (45,456 bp) from the TET-susceptible strain C1 and ICESp2905 (65,575 bp) from the TET-resistant strain iB21. While ICESp1108 exhibited extensive identities to ICE10750-RD. 2 and Tn1806, ICESp2905 showed a previously unreported genetic organization resulting from the insertion of separate erm(TR)- and tet(O)-containing fragments in a scaffold of clostridial origin. Transferability by conjugation of the erm(TR) elements from the same strains used in this study had been demonstrated in earlier investigations. Unlike ICE10750-RD. 2 and Tn1806, which are integrated into an hsdM chromosomal gene, both ICESp1108 and ICESp2905 shared the chromosomal integration site at the 3' end of the conserved rum gene, which is an integration hot spot for several mobile streptococcal elements. By using PCR-mapping assays, erm(TR)-carrying elements closely resembling ICESp1108 and ICESp2905 were shown in the other TET-susceptible and TET-resistant test strains, respectively.