儿科产超广谱β-内酰胺酶志贺菌的基因型和耐药性研究

目的 探讨儿科临床分离志贺菌产超广谱β-内酰胺酶(ESBLs)的基因型及其耐药特点.方法 收集2004年1月至2008年12月北京儿童医院细菌性痢疾住院患儿粪便标本中分离出志贺菌共59株,按照美国临床和实验室标准协会推荐的表型确证试验检测ESBLs,用琼脂稀释法进行最低抑菌浓度(MIC)测定,对产ESBLs菌株进行PCR扩增明确其基因型,对扩增产物进行DNA序列分析确定基因亚型.结果 59株志贺菌中共检出产ESBLs者21株,占35.6%.21株产ESBLs志贺菌PCR均扩增到CTX-M型ESBLs,包括CTX-M-1型6株,CTX-M-9型15株,其中有4株同时伴有TEM型酶,6株伴有OXA型酶.DNA序列分析证实6株CTX-M-1型分别为CTX-M-3亚型(1株)、CTX-M-15亚型(2株)、CTX-M-57亚型(3株),15株CTX-M-9型均为CTX-M-14亚型,伴随存在的TEM型及OXA型耐药基因分别为TEM-1型广谱酶、OXA-1型广谱酶.药敏结果显示对产ESBLs菌株敏感性较好的抗生素有亚胺培南、美罗培南、哌拉西林/他唑巴坦、头孢哌酮/舒巴坦和头孢西丁,其耐药率均小于15%.产不同CTX-M基因亚型的菌株对头孢他啶的耐药性不同.结论 本地区儿科分离志贺菌产ESBLs阳性率高,均为CTX-M型,其中以CTX-M-14亚型为主,少部分为CTX-M-3、CTX-M-15和CTX-M-57亚型.大部分产ESBLs菌株呈多重耐药,碳青霉烯类抗生素应作为治疗产ESBLs志贺菌的首选.

Genotype and drug resistance analysis of extended-spectrum beta-lactamases-producing Shigella in pediatric patients

Objective To investigate the genotype and drug resistance of extended-spectrum beta-lac-tamases(ESBLs) -producing Shigella in pediatric patients.Methods A total of 59 strains of Shigella were isolated from stool specimens of hospitalized children with shigellosis in Beijing Children's Hospital from January 2004 to December 2008.Phenotypic confirmatory test,which is based on Clinical and Laboratory Standards Institute(CLSI),was used to detect the ESBLs-producing strains.Agar dilution method was used to determine the minimal inhibitory concentration (MIC).PCR amplification was performed for ESBLs producers to determine the genotype.PCR product was sequenced and then analyzed to confirm the subtype of ESBLs.Results Of the 59 isolates,21 (35.6%) strains were identified as ESBLs producers.The 21 strains of ESBLs-producing Shigella all carried the genes of CTX-M as shown by PCR,and CTX-M-1,CTX-M-9 accounted for 6,15,respectively.Among the 21 CTX-M producers,there were 4 strains accompanied by TEM-type and 6 strains accompanied by OXA-type.Nucleotide sequence analysis showed that there were CTX-M-3 (n = 1),CTX-M-15 (n = 2),CTX-M-57(n =3) of the 6 CTX-M-1-producing isolates.The subtypes of CTX-M-9,TEM,OXA were all CTX-M-14,TEM-1,OXA-1,respectively.The sensitive drugs to ESBLs producers were imipenem,meropenem,piperacillin/tazobactam,cefoperazone/sulbactam and cefoxitin,with resistance rate all less than 15%.The resistance to ceftazidime was remarkably variable among different CTX-M producers.Conclusion The prevalence of ESBLsproducing Shigella is in a high level in pediatric patients in this area.The genotypes of ESBLs are all CTX-M.Most of them are CTX-M-14,but some are CTX-M-3,CTX-M-15 and CTX-M-57.Most ESBLs-producing strains are multidrug resistant.Carbopenems should be the first choice for ESBLs producers.