萘啶酸抗性甲型副伤寒病原菌的克隆扩散和遗传多样性

目的 认识肠沙门菌甲型副伤寒血清型(SPA)的克隆扩散和遗传多样性,建立并确定病原菌流行克隆的分型方法.方法 采用有对照的K-B纸片扩散技术对分离的3980株SPA进行抗微生物药物敏感性试验;经PCR扩增和基因测序检测15个萘啶酸抗性菌株喹诺酮抗性决定区的gyrA、gyrB、syrC和syrE基因;采用Spe Ⅰ和Xba Ⅰ消化染色体DNA脉冲场凝胶电泳(PFGE)对来自7个县的121个分离株进行分型和聚类分析.结果 萘啶酸敏感菌株在1999年占有优势,但2000年以后被萘啶酸抗性菌株替代;15个萘啶酸抗性菌株的PCR扩增和基因测序显示抗性机制是由gyrA基因的单点突变引起;121个菌株spe Ⅰ和Xba Ⅰ消化产物分别得出以Spe Ⅰ 01、spe Ⅰ 02或Xba Ⅰ 01型占优势的5种和4种PFGE型,Spe Ⅰ 01和Spe Ⅰ 02分别占37.2%和57.9%,或Xhn Ⅰ 01占95.0%.结论 在研究期间SPA分离株萘啶酸抗性率上升;PFGE型的SpeⅠ01和SpeⅠ 02或XbaⅠ01是玉溪流行的主要克隆;采用Spe Ⅰ和Xba Ⅰ的PFGE是鉴别SPA的一项有用技术.

Clonal expansion and genetic diversity of nalidixic acid-resistant Salmonella enterica serotype Paratyphi A in Yuxi city, China

Objective To understand the elonal expansion and genetic diversity of Salmonella en-terica semtype Paratyphi A (SPA) and to construct a typing method to determine the epidemic clones of the isolates. Methods Antimicrobial susceptibility testing was performed with 3980 SPA isolates by the cen-trolled Kirby-Bauer disc diffusion technique on Muller-Hinton agar plates. A total of 15 SPA with nalidixie acid resistance for mutations in gyrA, gyrB, gyrC and gyrE genes within the quinolone-resistant determina-tion region (QRDR) were examined. Subtyping of 121 isolates of SPA from seven counties in Yuxi were studied using pulsed-field gel eleetrophoresis (PFGE) analysis following digestion of chromosomal DNA with restriction endanucleases Spe Ⅰ and Xba Ⅰ. PFGE patterns were analyzed by duster analysis. Results The nalidixic acid-susceptible isolates predominated in 1999 but was replaced by nalidixic acid -resistant (NAR) isolates after 2000. Amplification by PCR and sequencing of the genes with subsets of 15 NAR strains re-vealed that the resistance mechanisms had resulted from single point mutations in the gyrA gene. Spe Ⅰ and Xba Ⅰ digestion of 121 isolates gave five and four different PFGE patterns with the predominance of the Spe Ⅰ 01 and Spe Ⅰ 02 (or the Xba Ⅰ 01) epidemic patterns, respectively. Spe Ⅰ 01 and Spe Ⅰ 02 consisted of 37.2% and 57.9% of isolates, respectively, or Xba Ⅰ 01 consisted of 95.0% of isolates. Conclusion The incidence of resistance to nalidixic acid of the isolates increased during the study period. PFGE patterns Spe Ⅰ 01 and Spe Ⅰ 02 (or Xba Ⅰ 01), the main clones of the epidemics, are highly prevalent in Yuxi. PFGE with Spe Ⅰ and Xba Ⅰ is a useful technique to differentiate SPA.