南阳地区手术感染大肠埃希菌gyrA基因突变的耐药研究及抗生素合理选用

A study of the correlation between surgical infections with Escherichia coli and gyrA gene mutations and antibiotic resistance and the rational selection of antibiotics

目的研究手术感染大肠埃希菌gyrA基因突变及耐药性,以指导临床治疗中抗生素的合理选用。方法分离提取40株大肠埃希菌gyrA基因,进行PCR扩增及基因测序,分析突变位点,并进行细菌药敏试验。结果药敏试验显示,40株手术感染大肠埃希菌分离株(诺氟沙星耐药)对萘啶酸、诺氟沙星、培氟沙星的耐药率均为100.0%,对氧氟沙星、左氧氟沙星、环丙沙星、依诺沙星的耐药率分别为90.0%、75.0%、75.0%和70.0%,对加替沙星和莫西沙星耐药率为15.0%和10.0%。PCR扩增gyrA基因,大小为285bp。对其进行测序分析,此基因的突变多数发生在密码子编码氨基酸的第83位和第87位,主要有:83位丝氨酸(Ser)突变为亮氨酸(Leu)或色氨酸(Trp)或丙氨酸(Ala)或缬氨酸(Val),87位天冬氨酸(Asp)突变为天冬酰胺(Asn)或甘氨酸(Gly)或酪氨酸(Tyr)或组氨酸(His)或缬氨酸(Val)。结论47株手术感染大肠埃希菌分离株为诺氟沙星耐药株,该细菌对多数抗菌药物产生了耐药性,gyrA基因突变是导致手术感染大肠埃希菌对抗菌药物产生耐药性的主要原因之一。因此,在治疗手术感染大肠埃希菌时应根据药敏试验结果选用抗生素。

Objective To study the correlation between gyrA mutations in surgical infections due to Escherichia coli and the drug resistance of E.coli in order to facilitate the rational selection of antibiotics in clinical treatment. MethodsThe gyrA gene was extracted from 40 isolates of E.coli.The gene was amplified with PCR and then sequenced and its mutations were analyzed. Results A drug sensitivity test was performed on 40 strains of E.coli causing surgical infections.Test results indicated that resistance to nalidixic acid,norfloxacin,and pefloxacin was 100.0%.The isolates had90.0% resistance to ofloxacin,75.0% resistance to levofloxacin,75.0% resistance to ciprofloxacin,and 70.0% resistance to enoxacin.The isolates also had 15%resistance to gatifloxacin and 10%resistance to moxifloxacin.PCR amplification of strains with the gyrA gene yielded a product that was 285 bp in length.Sequencing indicated that most of the gene mutations occurred in codons encoding amino acids 83 and 87.Principal mutations at amino acid 83 were replacement of serine（Ser）with leucine（Leu）,tryptophan（Trp）,alanine（Ala）,or valine（Val）.Principal mutations at amino acid 87 were replacement of aspartic acid（Asp）with asparagine（Asn）,glycine（Gly）,tyrosine（Tyr）,histidine（His）,or valine（Val）. Conclusion The strains of E.coli that caused surgical infections were norfloxacin-resistant.These E.coli isolates were resistant to most antimicrobials due to mutations in the gyrA gene.Thus,caution should be exercised when selecting antibiotics for clinical treatment of surgical infections.