临床痢疾志贺菌整合子检测及耐药基因盒序列分析

目的 检测印度东部1988、1995和2002年部分临床分离痢疾志贺菌中细菌耐药关系密切的1、2、3类整合酶基因及整合子携带的耐药基因盒的分布,分析整合子系统对志贺菌耐药的影响.方法 纸片扩散法检测实验菌株对药物的敏感性;应用PCR方法对16株临床耐药菌株进行1、2、3类整合酶基因(intI)筛选,对阳性样本可变区基因盒序列进行鉴定分析.结果 所有16株菌均耐4种及4种以上药物,包括β-内酰胺类、氨基糖苷类、四环素类、磺胺类、氯霉素类和喹诺酮类.13株菌检出1类整合酶基因,全部菌株含2类整合酶基因,即发现同时存在两种整合子结构菌株,未检测到3类整合酶基因.1类整合酶插入基因盒以blaara30-aadAl基因家族为主,分别对β-内酰胺类抗生素、链霉素、壮观霉素耐药;2类整合酶插人基因盒以dfrAl-satl组合为主,分别对甲氧苄氨嘧啶、链丝菌素耐药,同时在4株菌中发现dfrAl-satl-aadAl基因盒组合.结论 2类整合子普遍存在于临床志贺菌中.整合子与志贺菌的多重耐药具有密切相关性.

Detection of integron structure and sequence of drug resistance gene cassette in clinical multidrug resistant Shigella dysenteriae strains

Objective Clinical strains of Shigella dysenteriae isolated from eastern parts of India in 1988, 1995 and 2002 were examined for the presence of class 1, 2 and 3 integrons which closely related with drug resistance and the distribution of resistance gene cassette in order to clarify the influence of integron system on drug resistance of Shigella dysenteriae. Methods Susceptibility to antimicrobial agents was tested by the disk agar diffusion method. Class 1, 2 and 3 integron genes (intI) were screened by polymerase chain reaction (PCR) in 16 clinical strains with drug resistance.The variable regions of gene cassette of positive strains were sequenced. Results All 16 isolates were resistant to at least 4 agents including β-lactams, aminoglycosides, tetracyclines, sulfonamides,chloramphenicols and quinolones. Class 1 integron gene was detected in 13 strains and all isolates carried class 2 integron which indicated that strains with two integron structures were detected simultaneously and class 3 integron was not detected. Class 1 integron inserted gene cassette was mainly blaara30 -aadA 1 family, conferring resistance to β-lactamase, spectinomycin and streptomycins isolates carried class 2 integron were mainly dfrAl-satl genes cassettes conferring resistance to methoxybenzyl aminopyrimidine and streptothricin, while dfrA\-sat\-aadA\ genes were present only in 4 isolates. Conclusions These data indicate that class 2 integrons are widespread in Shigella dysenteriae strains, and closely associated with multidrug resistance of Shigella.