152株沙门菌临床分离株的耐药性及同源性分析

目的研究本地区沙门菌临床分离株的的耐药状况、分子流行病学特征及对头孢菌素类药物的耐药机制。方法采用琼脂稀释法测定临床常用抗菌药物对沙门菌的最低抑菌浓度（MIC）值,使用 PCR 法和DNA测序法检测头孢菌素耐药基因,脉冲场凝胶电泳（PFGE）法对沙门菌进行同源性分析。结果本地区肠炎沙门菌为主要血清型,占59.9%（91/152）。所有被测菌株均对亚胺培南敏感,对萘啶酸的耐药率最高（86.2%）,其次是氨苄西林（59.9%）、氯霉素（36.2%）和四环素（34.9%）。46.1%（70/152）的沙门菌对3种及以上抗菌药物耐药,其中鼠伤寒沙门菌的多重耐药率比肠炎沙门菌高（85.2% ＞31.9%）。对头孢菌素耐药的14株沙门菌进行PCR扩增并测序均为blaCTX-M型,其中7株为blaCTX-M-55,4株为blaCTX-M-14,2株blaCTX-M-3和1株 blaCTX-M-15。91株肠炎沙门菌分成23个PFGE型,27株鼠伤寒沙门菌分成15个 PFGE 型。PFGE 型别存在多个克隆系。结论本地区沙门菌多重耐药现象严重,产 blaCTX-M型超广谱β-内酰胺酶（ESBLs）是沙门菌对头孢菌素耐药的重要机制。本研究中沙门菌的 ESBLs 基因以 blaCTX-M-55型为主。沙门菌 PFGE 型别多样,存在明显的遗传多样性。

Analysis of Antimicrobial Susceptibility and Genetic Homogeny of 1 5 2 Clinical Isolates of Sal-monella

Obj ective]To study the antimicrobial resistance situation,molecular epidemiology and cepha-losporins-resistance mechanism of Salmonella spp .isolated from clinical cases in local region.[Methods]Minimal inhibitory concentrations（MICs）of common antibiotics to Salmonella spp .were measured by agar dilution method.PCR and DNA sequencing method were used to detect cephalosporins-resistance gene.Pulsed field electrophoresis（PFGE）method was performed for determining the homogeneity of Salmonella spp .[Re-sults]Salmonella enteritidis isolates in local region was the main serotype,and accounted for 59.9%（91/152）. All the strains were sensitive to imipenem and the resistance to nalidixic acid was the highest（86.2%）,fol-lowed by ampicillin（59.9%）,chloramphenicol（36.2%）and tetracycline（34.9%）.About 46.1%（70/152）i-solates of Salmonella spp .were multiple resistant to 3 and more antimicrobials,and multiple resistance of Salmonella typhimurium isolates was higher than Salmonella enteritidis isolates（85.2% vs.31.9%）.Fourteen Salmonella spp .isolates were resistant to cephalosporin and positive for blaCTX-M （7 for blaCTX-M-55 ,4 for blaCTX-M-14 ,2 for blaCTX-M-3 and 1 for blaCTX-M-15 ）amplified by PCR.The 91 strains of Salmonella enteritidis were divided into 23 PFGE types and 27 strains of Salmonella typhimurium were divided into 15 PFGE types.PFGE types had multiple clones.[Conclusion]The situation of multiple antimicrobial resistance of Salmonella spp . in local region is serious.Production of CTX-M-type extended-spectrumβ-lactamases（ESBLs）is the prevalent mechanism responsible for the resistance to cephalosporins in Salmonella spp .In our study,ESBLs gene is dominated by blaCTX-M-55 .The PFGE types of Salmonella spp .come from different clones and have significant genetic diversity.