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目的研究导致对氟喹诺酮类药物耐药的金葡菌norA基因的介导机制。方法 K-B纸片扩散法测定细菌敏感性(Kirby-Bauer法),研究两种FQNS在菌体内的蓄积量,通过Real-time PCR方法检测金黄色葡萄球菌norA基因的表达。结果两种药物在敏感菌菌体内的稳态蓄积浓度明显高于耐药菌,所有实验菌株中均检测到norA基因的存在,经RealTime PCR扩增后,检测到高度耐药菌株的norA基因表达量较敏感菌菌株平均norA基因表达量高0～8倍;中度耐药菌株的norA基因表达量较敏感菌株高5～17倍。结论推测norA基因表达增加是菌体内药物蓄积量减少的主要原因之一;部分菌株的耐药可能没有norA基因参与,即使有norA基因参与,起作用也不相同;可能有其他外排泵共同参与金葡菌的耐药。
Objective To study the mechanism of norA gene in S. aureus which is resistant to fluoroquinolones. Methods K-B disk diffusion method was used to determine the bacterial sensitivity (Kirby-Bauer method). The accumulation of two FQNS in the bacterial cells was studied. The expression of norA gene in Staphylococcus aureus was detected by Real-time PCR. Results The steady-state accumulation concentration of the two drugs in the sensitive bacteria was significantly higher than that in the resistant bacteria. The norA gene was detected in all the experimental strains. After RealTime PCR amplification, the norA gene expression in the highly resistant strains was detected The average amount of norA gene expressed in the sensitive strains was 0 ~ 8 times higher than that of the sensitive strains. The norA gene expression in moderately resistant strains was 5 ~ 17 times higher than that of the sensitive strains. Conclusion It is inferred that the increase of norA gene expression is one of the main reasons for the decrease of drug accumulation in the bacteria. Some of the strains may not have the norA gene involved in the drug resistance, and may play a role not even if norA gene is involved. Other efflux pumps may be involved Staphylococcus aureus resistance.