天津地区气单胞菌分离株的鉴定与多位点序列分型

Characterization and multilocus sequence typing of Aeromonas strains isolated in Tianjin area

【目的】研究气单胞菌菌株分类情况,并分析其致病性。【方法】采集环境样品和鱼类标本,分离并鉴定气单胞菌菌株,并运用多位点序列分型(Multilocus sequence typing,MLST)方法进行分类研究,利用PCR和测序方法分析毒力基因Aera、Hly、Aha1、GCAT和Nuc的分布。【结果】通过对分离菌株的16S rRNA基因进行分析,确认属于4种不同气单胞菌的7个分离株。发现所有菌株至少有1种毒力基因阳性,其中3株具有4种毒力基因。药物敏感实验显示,6株分离株对3种或3种以上抗菌素具有多重耐药性。最后,对看家基因gyrB、groL、gltA、metG、ppsA和recA进行分析,与MLST数据库中的等位基因序列比对,发现7株分离株均为新的不同的序列型(Sequence type,ST)。【结论】气单胞菌具有较高的遗传多样性。

[Objective] To study the classification of Aeromonas genus and its pathogenicity. [Methods] Various environmental samples were collected, Aeromonas strains were isolated and characterized, and multilocus sequence typing （MLST） method was adopted to classify the isolates. [Results] Among the isolates 7 Aeromonas strains were identified, belonging to 4 dif- ferent species of the genus Aeromonas based on 16S rRNA sequence analysis. Furthermore, 5 major virulence genes including Aera, Hly, Ahal, GACT and Nuc were detected in the isolates by PCR and sequencing methods. All strains contained at least one virulence gene, and 3 of them contained 4 virulence genes, respectively. Antibiotic susceptibility test showed that 6 strains exhibited multiple drug resistances to at least 3 antibiotics. Finally, 6 housekeeping genes （gyrB, groL, gltA, metG, ppsA, and recA） were chosen for the MLST analysis by PCR and sequencing. Allele sequences were aligned by searching the MLST database. All 7 Aeromonas strains were assigned a new ST number. [Conclusion] High genetic diversity existed in Aeromonas strains.