儿童A族链球菌emm分型变迁与大环内酯类耐药的关系

Macrolide resistance in group A beta haemolytic streptococcus isolated from children in China ermB is related to Tn916 transposons family

目的通过对1993-1994年和2005-2008年456株儿童A族β溶血性链球菌（GAS）分离株抗生素敏感性、耐药基因及转座子Tn916的emm分型检测,探讨GAS对抗菌药物敏感性的变化与转座子Tn916的关系。方法采用琼脂稀释法检测临床分离株对8种抗生素敏感性;PCR检测大环内酯类耐药基因ermB、ermTR、mefA,四环素耐药基因tetM和Tn916家族转座子基因int、xis;PCR扩增及测序对菌株进行emm分型;对每种emm型的代表菌株进行PFGE分型。结果与1993-1994年比较,2005-2008年GAS菌株,红霉素、克林霉素、泰利霉素的耐药率增加（79.7%vs 94.0%,75.4%vs 96.9%,20.37%vs 87.93%）;大环内酯类抗生素耐药菌株int、xis、tetM和ermB基因的携带率增加（P〈0.05）;emm1型和emm12型菌株ermB基因携带率增加（65.20%vs 86.23%,7.7%vs 91.8%）。结论我国儿童GAS大环内酯耐药性在16年间增加,可能与emm型变化及大环内酯类抗生素耐药机制的变化有关,分离菌株的Tn916族变化可能与耐药性增加相关。

【Objective】To explore the relationship between changes in the antimicrobial susceptibility of Streptococcus pyogenes and Tn916 family in different periods（1993-1994, 2005-2006） in children through testing the emm types, resistance genes and susceptibilities to antibiotics of 456 group Astreptococal isolates（GSA）.【Methods】Susceptibilities to antibiotics were performed using agar dilution methods. The macrolide resistance genes, ermTR,mefA, and tetracycline-resistant gene tetM and the int and xis genes of Tn916 family were detected by polymerase chain reaction. All 456 strains were analyzed by emm typing. Selected strains representing eachemmtype were further characterized by pulsed-field gel electrophoresis. 【Results】Comparing the results in the 2 sample periods, the resistance rates of erythromycin and clindamycin both significantly increased（79.7% versus 94% for erythromycin and 75.4% versus 96.9% for clindamycin）. Telithromycin resistance rate increased from 20.37% to 87.93%. Among the macrolide resistance strains, the rate of strains with the genes int, xis, tetM, and ermB increased with time（P〈0.05）. The emm1 and emm12 isolates had high rates of ermB gene, which increased after 16 years（65.2% versus86.23% for emm1 and 7.7% versus 91.8% for emm12）.【Conclusions】 This study demonstrates the increase in macrolide resistance in S. pyogenes in Chinese children over a 16-year period. The phenomenon may be related not only with the shift in the emmtypes but also with the change of macrolide-resistant mechanisms. The change of Tn916 family among the isolates may be related with the increased resistance.