Genetic diversity of the tet(M) gene in tetracycline-resistant clonal lineages of Streptococcus pneumoniae
Genetic diversity of the tet(M) gene in tetracycline-resistant clonal lineages of Streptococcus pneumoniae
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DOI：
10.1128/aac.44.11.2979-2984.2000
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发表时间：
2000-11-01
影响因子：
4.9
通讯作者：
Dowson, CG
中科院分区：
文献类型：
--
作者：
Doherty, N;Trzcinski, K;Dowson, CG
本研究的目的是研究肺炎链球菌不同克隆谱系成员对四环素类药物tet(M)介导的耐药性的稳定性和进化。代表三个国家(西班牙14型、西班牙15型和波兰23F型)和一个国际(西班牙23F型)多药耐药流行克隆的32株四环素耐药分离株均为TER(M)阳性，而tet(O)、tet(K)和tet(L)均为阴性。这些分离株都携带整合酶基因int，该基因与Tn1545-Tn916家族的接合转座子相关。对tet(M)产物的高分辨限制性内切酶分析鉴定出6个等位基因，即在西班牙血清14型克隆中的tet(M)1至tet(M)6：Tet(M)1至tet(M)3和tet(M)5，在西班牙血清15和23F克隆中均为tet(M)4，在波兰23F克隆中为差异最大的等位基因tet(M)6。这表明Tet(M)变异可以发生在肺炎球菌的克隆间和克隆内水平。鉴定出INT的两个等位基因，除了携带INT2的国际西班牙23F克隆的成员外，所有分离株中都发现了INT1。对四环素、多西环素和米诺环素的敏感性进行了评估。在四环素的亚抑制浓度存在的情况下，所有克隆的菌株都可以诱导出对四环素的耐药性；然而，在携带tet(M)4的西班牙血清型15和23F克隆中观察到最强的诱导。四环素被发现是最强的抗性诱导剂，米诺环素被发现是最弱的诱导剂。
The aim of the present study was to examine the stability and evolution of tet(M)-mediated resistance to tetracyclines among members of different clonal lineages of Streptococcus pneumoniae. Thirty-two tetracycline-resistant isolates representing three national (Spanish serotype 14, Spanish serotype 15, and Polish serotype 23F) and one international (Spanish serotype 23F) multidrug-resistant epidemic clones were all found to be ter(M) positive and tet(O), tet(K), and tet(L) negative. These isolates all carried the integrase gene, int, which is associated with the Tn1545-Tn916 family of conjugative transposons. High-resolution restriction analysis of tet(M) products identified six alleles, tet(M)1 to tet(M)6: tet(M)1 to tet(M)3 and tet(M)5 in isolates of the Spanish serotype 14 clone, tet(M)4 in both the Spanish serotype 15 and 23F clones, and tet(M)6, the most divergent allele, in the Polish 23F clone. This indicates that tet(M) variation can occur at the inter- and intraclone levels in pneumococci. Two alleles of int were identified, with int1 being found in all isolates apart from members of the international Spanish 23F clone, which carried int2. Susceptibility to tetracycline, doxycycline, and minocycline was evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracyclines, Resistance to tetracyclines was found to be inducible in isolates of all clones; however, the strongest induction was observed in the Spanish serotype 15 and 23F clones carrying tet(M)4. Tetracycline was found to be the strongest inducer of resistance, and minocycline was found to be the weakest inducer of resistance.