大肠埃希菌氨基糖苷酰基转移酶基因型研究

目的：了解大肠埃希菌的耐药谱、氨基糖苷酰基转移酶基因（aac）的分布规律及其与氨基糖苷类抗生素耐药的相关性。方法：琼脂稀释法测定无菌体液分离的44株大肠埃希菌对阿米卡星等12种抗生素的耐药性，聚合酶联反应（PCR）法测定酰基转移酶基因型aac（3）-Ⅰ、Ⅱ和aac（6’）-Ⅰ。结果：大肠埃希菌超广谱β-内酰胺酶（ESBLs）的发生率为45．45％（20／44），对亚胺培南（IPM）、关罗培南（MEM）的耐药率为0，对哌拉西林／他唑巴坦、头孢他啶的耐药率较低（〈20％），对左氟沙星、环丙沙星的耐药率较高（〉60％），对氨基糖苷类阿米卡星、庆大霉素、妥布霉素的耐药率分别为18．18％、56．82％、61．36％。氨基糖苷类耐药模式TG（妥布霉素、庆大霉素）〉TGA（妥布霉素、庆大霉素、阿米卡星）〉T（妥布霉素）〉G（庆大霉素），分别占36．36％、18．189／5、6．82％、2．27％。氨基糖苷酰基转移酶基因检出以aac（3）-Ⅱ最高，占52．27％（23／44），aac（6＇）-Ⅰ次之，占29．55％（13／44），aac（3）-Ⅱ和aac（6’）-Ⅰ同时检出者占15．91％（7／44），未检出aac（3）-Ⅰ。ESBLs阳性株的aac（3）-Ⅱ、aac（6’）-Ⅰ检出率分别为60％、50％，高于ESBLs阴性株的45．81％、12．51％。TG模式与其耐药基因aac（3）-Ⅱ符合率较高为93．75％（15／16）。结论：本地分离大肠埃希菌氨基糖苷类耐药模式以TG为主，酰基转移酶基因以aac（3）-Ⅱ为主，aac（6’）-Ⅰ次之，aac（3）-Ⅰ罕见。

Evaluation of aminoglycoside resistance phenotypes and genotyping of acetyltransferase in Escherichia coli

OBJECTIVE: To investigate the prevalence of aminoglycoside resistance and genotyping of acetyltransferase in Escherichia coli. METHODS: Resistance phenotypes to 12 antibiotics of 44 Escherichia coli isolates were analyzed using agar dilution method and 3 aminoglycoside resistance genes aac(3)-I, II and aac(6')-I were determined by PCR method. RESULTS: In 44 clinical isolates, the occurrence of ESBLs was 45.45%, resistance rates were discrepant for amikacin (18.18%), gentamicin (56.82%) and tobramycin (61.36%), the prevalence of phenotype TG (tobramycin and gentamicin) indicative of aac(3)-II production and TGA (tobramycin, gentamicin and amikacin) indicative of aac(6')-I production were 36.36% and 18.18%, respectively. The most common aminoglycoside resistance genotype of acetyltransferase was aac(3)-II (52.27%) and aac(6')-I was lower (29.55%), but no aac(3)-I was detected. CONCLUSION: At least 2 acetyltransferase genes exist in this area i.e. aac(3)-II and aac(6')-I.