临床产ESBLs细菌耐药特性及其基因分型的研究

Resistance and initial gene typing of clinical ESBLs-producing bacteria

目的 了解并研究产超广谱 β-内酰胺酶 (ESBL s)细菌流行及耐药特点 ,应用聚合酶链反应(PCR)对产 ESBL s细菌进行初步分型。方法 先后用 nitrocefin及纸片扩散初筛法、纸片扩散确认法从临床分离的肺炎克雷伯氏菌及大肠埃希氏菌中检测产 ESBL s菌株 ,用微量稀释法测定不同类抗生素对产 ESBL s菌株的 MIC值 ,并用聚合酶链反应对 ESBL s基因进行初步分型。结果 我院临床分离肺炎克雷伯氏菌产ESBL s率为 16 .7%、大肠埃希氏菌产 ESBL s率为 12 .4%。产 ESBL s细菌对青霉素类及第三代头孢菌素类耐药率约为 70 %～ 10 0 % ,加用酶抑制剂后它们的耐药率降为 2 %～ 6 0 %。它们对磺胺甲口恶唑 /甲氧苄氨嘧啶、环丙沙星及头孢吡肟的耐药率分别为 6 9.2 3%、5 6 .41%和 2 0 .5 1% ,但它们对阿米卡星的耐药率为 12 .82 %。而非典型 β-内酰胺类抗生素头孢西丁、头孢美唑及拉氧头孢对产 ESBL s菌株的敏感率分别为 94.88%、92 .32 %和 97.44 %。碳青霉烯类的亚胺培南和美罗培南表现了最高的敏感率未发现耐药菌株。 ESBL s对单独头孢哌酮的水解率为 43.93% ,而当结合了舒巴坦、克拉维酸及三唑巴坦时对头孢哌酮的水解率分别下降为2 0 .91%、18.13%及 15 .2 7%。产 ESBL s肺炎克雷伯氏菌中产 SHV型、TEM型、SHV和

Objective To study the prevalence of extended spectrum β-lactamases (ESBLs) and the resistance of ESBLs-producing bacteria. The polymerase chain reaction (PCR) was used to establish an effective method for the initial typing of ESBLs. Mehods β-lactamases-producing strains among clinical isolates of Escherichia coli and Klebsiella pnumoniae were detected by nitrocefin and were screened by K-B method, and confirmed by a disc dilution confirmatory test. Then microdilution broth method was used to analyze the minimal inhibitory concentration (MIC) of different antibiotics against these strains. In further test,the initial typing of ESBLs was conducted by PCR. Results In our hospital, the positive rate of ESBLs producing isolates in Escherichia coli and Klebsilla pnumoniae were 12.4% and 16.7% respectively. The resistant rates of ESBLs-producing isolates against penicillins and the third generation cephalosporins were about 70%~100%. When combined with the β-lactamase inhibitors, the resistant rates were about 2%~60%. The resistant rate to sulfamethoxazole/trimethoprim, ciprofloxacin and cefepime were 69.23%, 56.41% and 20.51% respectively. Whereas the resistant rate to amikacin was 12.82%. Susceptibility rate of atypical β-lactams such as cefoxitin, cefmetazole and latamoxef were: 94.88%, 92.32%, and 97.44% respectively. Imipenem and meropenem showed the highest susceptibility and all ESBLs-producing isolates in our study were susceptible to them. The hydrolysis rate of cefoperazone by ESBLs was 43.93%. When combined with sulbactam, clavulanic acid and tazobactam, the hydrolysis rate of cefoperazone was reduced to 20.91%, 18.13% and 15.27% respectively. The result of PCR showed that the rates of TEM type, SHV type and TEM, SHV type in Escherichia coli were 41.66%, 8.33% and 50% respectively; and the resistant rates in Klebsilla pnumoniae were 96.3%, 0% and 3.7% respectively. Conclusion The ESBLs-producing isolates had high resistance to penicillins, cephalo-sporins and had multi-resistance. These isolates showed high susceptibility rates to the cefomycin. The carbapenems were most effective against the ESBLs-producing isolates. Using cefoperazone as common substrate, the inhibitory potency against ESBLs of tazobactam was more higher than sulbactam and had significant difference, clavulanic acid was also better than sulbactam but had no significant difference. Most of the ESBLs-producing Escherichia coli carried TEM related genes and Klebsilla pnumoniae carried more SHV related genes.