耐甲氧西林金葡菌对抗菌药物的耐药表型和基因型分析

目的 了解来自汕头和北京地区的67株耐甲氧西林金葡菌(MRSA)的耐药情况及耐药机制,并分析耐药表型与基因型的一致情况.方法 以琼脂稀释法测定24种抗菌药物对MRSA的体外抗菌活性,PCR扩增MRSA的耐药基因,nitrocefin测定细菌产β-内酰胺酶的情况.结果 67株MRSA除了对氯霉素和多西环素的耐药率较低,分别为3%和7.5%,对万古霉素、米诺环素和利凡诺100%敏感外,对利福平的耐药率为52.2%,对四环素的耐药率为77.6%,而对于其它包括青霉素、第1～4代头孢菌素、单环β-内酰胺类、碳青霉烯类、氨基糖苷类和磺胺类的耐药率均在80%～90%以上,氨苄西林加酶抑制剂以后则耐药程度有所降低.qacA/B、mecA、tetM、NorA、gyrA、aac(6')/aph(2")、aph(3')Ⅲ和β-内酰胺酶检出率分别为11.9%、95.5%、70.1%、4.5%、10.4%、82.1%、73.1%和92.5%,未检出qacC、ant(6)-I、ant(2")-I、VanA和VanB耐药基因.67株MRSA均携带有多种耐药基因:同时携带2种耐药基因的有7株,3种的有10K,4种的有11株,5种的29株,6种的10株.结论 67株MRSA耐药情况严重,并同时携带多种耐药基因.

Analysis of resistant phenotype and genotype of MRSA

Objective To investigate resistance to antibiotics and its mechanism of sixty-seven methicillin resistant Staphylococcus aureus(MRSA)strains from Shantou and Beijing,and to analyze the coherence between resistant phenotype and genotype.Methods The antimicrobial activities of twenty-four kinds of antibiotics against MRSA in vitro were performed by agar dilution method.Gene encoding resistance were detected by PCR and the production of β-latamases were determined with nitrocefin.Results All isolates remained 100%sensitive to vancocin,minocycline and rivanol.Resistance rate to chloromycetin and doxycycline(3%and 7.5%respectively)was also low.Except for that,resistance rate to rifampicin and tetracycline were 52.2%and 77.6%respectively.As for resistance rate to other antibiotics such as penicillin,the first to fourth generation cephalosporin,monobactams,carbopenems,aminoglycosides,and sulfamido were all above 80%to 90%.Resistance to ampicillin decreased when β-1actamse inhibitor was added.The prevalence of qacA/B,mecA,tetM,NorA,gyrA,aac(6')/aph(2"),aph(3')Ⅲ and β-lactamasewere 11.9%,95.5%,70.1%,4.5%,10.4%,82.1%,73.1%and 92.5%respectively.The gene of qacC,ant(6)-Ⅰ,ant(2")-Ⅰ,VanA and VanB were not detected.All isolates carried more than one resistance genes:seven strains for two resistance genes,ten strains for three resistance genes,eleven strains for four resistance genes,twentynine strains for five resistance genes,and ten strains for six resistance genes were deteced.Conclusions Drug resistance were serious in sixty-seven MRSA strains,and at the same time they all carried multiple resistance genes.