Fluoroquinolone resistance in atypical pneumococci and oral streptococci:: Evidence of horizontal gene transfer of fluoroquinolone resistance determinants from Streptococcus pneumoniae
Fluoroquinolone resistance in atypical pneumococci and oral streptococci:: Evidence of horizontal gene transfer of fluoroquinolone resistance determinants from Streptococcus pneumoniae
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DOI：
10.1128/aac.00258-07
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发表时间：
2007-08-01
影响因子：
4.9
通讯作者：
Chan, Paul K.
中科院分区：
文献类型：
--
作者：
Ip, Margaret;Chau, Shirley S. L.;Chan, Paul K.
对非典型菌株进行了检测，假定为肺炎球菌，与肺炎链球菌R6菌株相比，环丙沙星MIC>= 4.0 μ g/ml，并且在回旋酶和拓扑异构酶基因的喹诺酮耐药决定区（QRDRs）内存在独特的序列变异。使用表型方法和基因型方法重新鉴定这些菌株，表型方法包括检测optochin敏感性、胆汁溶解度和凝集，基因型方法包括通过PCR、16 S rRNA测序和多位点序列分型（MLST）检测肺炎球菌溶血素和自溶素基因。基于MLST基因连锁序列的分析将“非典型”菌株与肺炎球菌区分开来，这些菌株与S.缓解。然而，所有这些菌株和来自草绿色链球菌群的9株菌株中的5株具有1至3个gyrA、gyrB、parC和帕雷基因，其QRDR序列与S. pneumoniae，提供了螺旋酶和拓扑异构酶基因的QRDR从肺炎球菌水平转移到草绿色链球菌的证据。这些基因也赋予氟喹诺酮耐药草绿色链球菌。此外，还比较了来自菌血症患者的32株特征良好的缓症链球菌和口腔链球菌菌株的氟喹诺酮耐药决定簇。这些菌株在GyrA和ParC中具有独特的氨基酸取代，可与氟喹诺酮耐药肺炎球菌和“非典型”分离株中的氨基酸取代区分开。重组事件和从头突变在氟喹诺酮类药物耐药的发展中起重要作用。
Atypical strains, presumed to be pneumococcus, with ciprofloxacin MICs of >= 4.0 mu g/ml and unique sequence variations within the quinolone resistance-determining regions (QRDRs) of the gyrase and topoisomerase genes in comparison with the Streptococcus pneumoniae R6 strain, were examined. These strains were reidentified using phenotypic methods, including detection of optochin susceptibility, bile solubility, and agglutination by serotype-specific antisera, and genotypic methods, including detection of pneumolysin and autolysin genes by PCR, 16S rRNA sequencing, and multilocus sequence typing (MLST). The analysis based on concatenated sequences of the six MLST loci distinguished the "atypical" strains from pneumococci, and these strains clustered closely with S. mitis. However, all these strains and five of nine strains from the viridans streptococcal group possessed one to three gyrA, gyrB, parC, and parE genes whose QRDR sequences clustered with those of S. pneumoniae, providing evidence of horizontal transfer of the QRDRs of the gyrase and topoisomerase genes from pneumococci into viridans streptococei. These genes also conferred fluoroquinolone resistance to viridans streptococci. In addition, the fluoroquinolone resistance determinants of 32 well-characterized Streptococcus mitis and Streptococcus oralis strains from bacteremic patients were also compared. These strains have unique amino acid substitutions in GyrA and ParC that were distinguishable from those in fluoroquinolone-resistant pneumococci and the "atypical" isolates. Both recombinational events and de novo mutations play an important role in the development of fluoroquinolone resistance.