沙门菌中第一类整合子的鉴定及特性分析

目的　基于整合子在细菌耐药机制中的重要作用 ,对来自正常人体内耐药沙门菌的整合子分布及其结构特征进行分析。方法　应用PCR方法 ,设计第一类整合酶基因intI1和耐药基因盒的特异性引物 ,用PCR方法检测整合子阳性菌株并对其整合的耐药基因进行测序和序列分析。结果　发现 1株S .hadar和 3株S .tshiongwe为第一类整合酶阳性菌株。耐药基因盒进行扩增的结果 ,从 2株中分别得到 10 0 9bp的扩增产物。 1株得到 16 6 4bp的扩增产物。 1株菌得到 10 0 9bp和 16 6 4bp的扩增产物。序列分析结果表明 ,10 0 9bp的扩增产物为携带aadA2 ,对氨基糖苷类抗生素药物壮观霉素、链霉素产生耐药的基因盒 ;16 6 4bp为携带aadA5和dfr17,对氨基糖苷类抗生素药物壮观霉素、链霉素和磺胺类药物甲氧氨苄嘧啶产生耐药的基因盒。结论　首次揭示了健康人携带由整合子介导的耐药菌这一现象 ,提示我们要从基因水平上监测细菌的耐药情况

Identification and characterization of class 1 integron-mediated antibiotic resistance among Salmonella strains

Objective Since integrons play an important role in the spread of antibiotic resistance genes in bacteria, the distribution and characterization of the class 1 integron among Salmonella strains from healthy was investigated. Methods 23 strains of Salmonella spp isolated from healthy humans in Guangdong, China were examined for their sensitivity to ten common antimicrobials. The presence and genetic content of class 1 integron were examined with specific primers of intI1 and genes cassettes by PCR and sequencing. Results Four strains, one isolate of S.hadar and three isolates of S.tshiongwe were positive for intI1 gene. Furthermore strains yielding a PCR product of intI1 gene were amplified by primers of in F and in B which were set for amplifying the region of antibiotics resistance genes. Among four intI1 positive strains, an amplicon of 1009bp was yielded in 2 isolates; an amplicon of 1664bp was yielded in 1 isolate; 1 isolate presented two amplicons of 1009bp and 1664bp. Sequencing analysis revealed that amplicon 1009bp harbored gene cassette aadA2 conferring resistant to spectinomycin and streptomycin, and another amplicon of 1664 harbored gene aadA5 and dfr17, conferring resistant to spectimomycin, streptomycin and trimethoprim respectively. Conclution Class 1 integron harboring multidrug resistance genes has been identified among Salmonella strains isolated from healthy humans. The result stressed the need for continued surveillance of bacteria from the asymptomatic carriers.