宋内志贺菌中ESBLs的检测

Detection of extended-spectrum β-lactamases in Shigella sonnei isolates

目的了解宋内志贺菌中ESBLs的基因型别。方法琼脂稀释法测定3株宋内志贺菌对β内酰胺类等抗菌药物的耐药性,改良三维试验进行产ESBLs菌株的表型鉴定,并进行转移接合试验;采用TEM、SHV、CTX-M-1组、CTX-M-2组、CTX-M-13组β内酰胺酶基因通用引物以及TEM、CTX-M-13组全编码基因引物进行PCR检测和DNA序列分析;同时对这些菌株进行指纹分析脉冲场电泳(PFGE)检测。结果3株宋内志贺菌对青霉素类、第一、二代头孢菌素以及庆大霉素、四环素、复方磺胺甲噁唑显著耐药,对第三代头孢菌素中头孢曲松、头孢噻肟中度敏感,对亚胺培南、头孢美唑、氟喹诺酮类、头孢噻肟-克拉维酸、头孢他啶-克拉维酸显示敏感。这些菌株均为产ESBLs菌株,ESBLs基因型别为CTX-M-14,并同时产生TEM-1型广谱β内酰胺酶;CTX-M-14编码基因可以接合方式发生水平转移;3株菌株的PFGE谱型相同。结论3株宋内志贺菌产生CTX-M-14型ESBLs,引起对多种β内酰胺类抗生素耐药,并存在克隆传播,应加强监测。

Objective To detect ESBLs gene in 3 Shigella sonnei isolates. Methods Antimicrobial susceptibility was determined by standard agar dilution procedure on Mueller-Hinton agar and ESBLs producing strains were confirmed by modified three-dimensional test. Conjugation experiment was performed to detcrmine whether the resistance was transferable. The partial blagene of ESBLs producing isolates were detected by PCR using universal primers for TEM, SHV, CTX-M-1 group, CTX-M-2 group, CTX-M-13 group, respectively. The entire blaCTS- M -13group, blaTEM were amplified by PCR using primers outside the Open Reading Frame （ORF） of these β-lactamases. The PCR products were also directly sequenced and analyzed. The 3 isolates were also analyzed by PFGE. Results Three S. sonnei isolates were ESBLs producers and produced CTX-M-14 ESBLs and TEM-1 β- lactamases. ESBL producers were resistant to most β-lactams such as ampicillin, the first and second generation cephalosporins, and non β-lactam antibiotics such as gentamicin, tetracycline and SMZ-TMP. Such strains were also intermediate to cefotaxime and ceftriaxone, but susceptible to ceftazidime, imipenem, cefmetazole, the third generation cephalosporins ＋ clavulanic acid, and fluoroquinolones. ESBLs phenotype CTX-M-14 could be transferred to the transconjugant. PFGE patterns of the 3 isolates were identical. Conclusions 3 Shigella sonnei isolates produce CTX-M-14 ESBLs, which results in their resistance to most β-lactams. Clone spread is evident in these isolates. More attention should be paid to survey such strains.