Abstract

Examination of pathogenic bacteria, isolated from Rana temporaria chensinensis, was conducted including morphological characteristics, physiological and biochemical characteristics, as well as the detection of the 16S rRNA gene sequence of the isolates. Phylogenetic tree based on the two sequences (HQ070610A-1, HQ070610B-1) and homologous sequences from GenBank was constructed by neighbor-joining method. Meanwhile, the pathogenic effect of the representative strains to healthy R. temporaria chensinensis was determined, the susceptibility to antimicrobial agents was conducted with agar diffusion method (Kirby-Bauer, K-B) and the haemolysin A gene was detected by PCR amplification. The isolated strains were identified as Aeromonas hydrophila. The length of 16S rRNA gene of strain HQ070610A-1(GenBank accession No.GQ470995) was 1444 bp, and the length of 16S rRNA gene of strain HQ070610B-1(GenBank accession No.GQ470996) was 1445 bp. The high pathogenicity of the representative isolated strain to healthy R. temporaria chensinensis could be confirmed by challenge test. All strains were sensitive or highly sensitive to 28 agents including cefotaxime, cefotaxime etc., and they were slightly sensitive to cefazolin, resistant to 8 agents including penicillin G, vancomycin,  etc. The eleven isolated strains all carried haemolysin A gene.

Key words: Rana temporaria chensinensis, red-leg disease, Aeromonas hydrophila.