Malbruny Brigitte, Canu Annie, Bozdogan Bülent, Fantin Bruno, Zarrouk Virginie, Dutka-Malen Sylvie, Feger Celine, Leclercq Roland
Service de Microbiologie, CHU de Caen, Caen, France.
Antimicrob Agents Chemother. 2002 Jul;46(7):2200-7. doi: 10.1128/AAC.46.7.2200-2207.2002.
The mechanism of resistance to the streptogramin antibiotics quinupristin and dalfopristin was studied in a Staphylococcus aureus clinical isolate selected under quinupristin-dalfopristin therapy, in four derivatives of S. aureus RN4220 selected in vitro, and in a mutant selected in a model of rabbit aortic endocarditis. For all strains the MICs of erythromycin, quinupristin, and quinupristin-dalfopristin were higher than those for the parental strains but the MICs of dalfopristin and lincomycin were similar. Portions of genes for domains II and V of 23S rRNA and the genes for ribosomal proteins L4 and L22 were amplified and sequenced. All mutants contained insertions or deletions in a protruding beta hairpin that is part of the conserved C terminus of the L22 protein and that interacts with 23S rRNA. Susceptible S. aureus RN4220 was transformed with plasmid DNA encoding the L22 alteration, resulting in transformants that were erythromycin and quinupristin resistant. Synergistic ribosomal binding of streptogramins A and B, studied by analyzing the fluorescence kinetics of pristinamycin I(A)-ribosome complexes, was abolished in the mutant strain, providing an explanation for quinupristin-dalfopristin resistance.
在一株经奎奴普丁-达福普汀治疗后筛选出的金黄色葡萄球菌临床分离株、四株体外筛选出的金黄色葡萄球菌RN4220衍生物以及一株在兔主动脉心内膜炎模型中筛选出的突变株中，研究了对链阳性菌素类抗生素奎奴普丁和达福普汀的耐药机制。对于所有菌株，红霉素、奎奴普丁和奎奴普丁-达福普汀的最低抑菌浓度（MIC）均高于亲本菌株，但达福普汀和林可霉素的MIC相似。对23S rRNA的结构域II和V的基因片段以及核糖体蛋白L4和L22的基因进行了扩增和测序。所有突变株在L22蛋白保守C末端的一个突出β发夹结构中存在插入或缺失，该结构与23S rRNA相互作用。用编码L22改变的质粒DNA转化敏感的金黄色葡萄球菌RN4220，产生了对红霉素和奎奴普丁耐药的转化子。通过分析普那霉素I(A)-核糖体复合物的荧光动力学研究发现，突变株中链阳性菌素A和B的协同核糖体结合被消除，这为奎奴普丁-达福普汀耐药提供了解释。
