福建省鼠伤寒沙门菌β-内酰胺耐药表型及ESBLs耐药基因分析

目的 调查福建省鼠伤寒沙门菌β-内酰胺耐药状况及其与ESBLs耐药基因之间的关系。方法 利用微量肉汤稀释法测定83 株鼠伤寒沙门菌对β-内酰胺类及ESBLs菌株其他18种药物的最小抑菌浓度(MIC)并计算耐药率;同时用PCR方法检测菌株ESBLs相关基因bla_TEM、bla_CTX-M、bla_OXA及bla_SHV的携带情况,并对bla_CTX-M阳性基因进行测序分型。结果 两类不同来源菌株均对氨苄西林和氨苄西林-舒巴坦的耐药率较高,腹泻患者来源株对第三、四代头孢有不同程度的耐药。腹泻患者来源株中检出10株ESBLs阳性菌株,检出率16.39%(10/61),该类菌株全部为多重耐药。腹泻患者来源株bla_TEM、bla_CTX-M和bla_OXA基因检出率分别为55.74%(34/61)、16.39%(10/61)和19.67%(12/61);健康人员来源株bla_TEM和bla_OXA基因检出率分别为22.73%(5/22)和18.18%(4/22),未检出bla_CTX-M基因,两类菌株均未检出bla_SHV基因。10株bla_CTX-M基因阳性株测序表明bla_CTX-M-14基因型4株、bla_CTX-M-15和bla_CTX-M-55基因型各3株。相关性分析表明bla_TEM基因与氨苄西林耐药表型具有较好的一致性(P<0.001, Ka=0.546),bla_CTX-M基因与头孢噻肟和头孢吡肟耐药表型高度一致(P<0.001, Ka=1.000),与头孢他定(P<0.001, Ka=0.626)和氨曲南(P<0.001, Ka=0.668)一致性较好。结论 福建省鼠伤寒沙门菌对头孢菌素及ESBLs耐药主要由bla_CTX-M基因介导且ESBLs菌株多重耐药现象严重。

Analysis on the relationship between β-lactam resistance phenotype and ESBLs resistance gene of Salmonella typhimurium in Fujian,China

To investigate the prevalence of β-lactam resistance and relationship between resistance genotype of ESBLs and resistance phenotype in Salmonella typhimurium strains in Fujian. The minimal inhibitory concentration (MIC) of 83 strains of Salmonella typhimurium against β-lactam and ESBLs strains against other 18 drugs was determined by broth dilution and the drug resistance rate was calculated. The gene of bla_TEM, bla_CTX-M, bla_OXA and bla_SHV related to ESBLs in Salmonella typhimurium strains detected by PCR, then the bla_CTX-M genotype was further confirmed by sequenciny.The strains from healthy persons and diarrheal patients were shown in different resistant rate to lactam drugs,with higher rate in diarrheal patients than others. Different degrees of resistance to third-generation and fourth-generation cephalosporins were found in strains from various diarrheal patients. 10 ESBLs strains in Salmonella typhimurium were detected from diarrheal patients, the detection rate was 16.39% (10/61), and they’re all multi-drug resistance. The detection rate of bla_TEM, bla_CTX-M and bla_OXA gene of Salmonella typhimurium in diarrhea patients were 55.74%, 12.2% and 19.67% respectively. The detection rate of bla_TEM, bla_CTX-M and bla_OXA gene of Salmonella typhimurium in healthy persons were 55.74%, 12.2% and 0% respectively. No bla_SHV gene was detected in both healthy persons and diarrhea patients. Among bla_CTX-M genes positive strains, 4 belongs to bla_CTX-M-14 genotype, 3 belongs to bla_CTX-M-15 and bla_CTX-M-55 genotypes respectively. Correlation analysis indicated that bla_TEM genes was better consistency with ampicillin resistant phenotype(P<0.001, Ka=0.546). The bla_CTX-M gene was highly consistency with the cefotaxime and cefepime resistant phenotypes(P<0.001, Ka=1.000), and bla_CTX-M gene also was better consistency with ceftazidime(P<0.001, Ka=0.626) and aztreonam(P<0.001, Ka=0.668) resistant phenotypes. The resistance of Salmonella typhimurium to cephalosporins and ESBLs was mainly mediated by bla_CTX-M gene and the multi-drug resistance of ESBLs strains is serious in Fujian now.