Abstract: In order to develop a rapid PCR method to detect pathogenic Aeromonas hydrophila in Andrias davidianus, four pairs of primers were designed based on the conservative sequences of 16S rDNA, outer membrane protein（omp）, hemolysin（hly）and serine protease（ahp）genes. By optimizing of PCR conditions, a quadruple PCR assay was established. The assay had a highly specific detection on pathogenic strains of Aeromonas hydrophila without other irrelative bacteria. This assay had a high sensitivity with the detection limit as low as 100 fg DNA template. From quadruple PCR assay, there were 18 positive results in Aeromonas hydrophila（n = 20）. After artificial infection of Andrias davidianus and the extracellular products assay, the positive strains with more species of virulence genes showed a highly pathogenic activity. This method also was applied in other artificial samples（n = 33）isolated from Andrias davidianus and suspicious samples（n = 34）, resulting in 100% and 21/34 positive results, respectively. In conclusion, the quadruple PCR assay, which has a highly specific and sensitive characteristic, could be applied in rapid diagnosis for Aeromonas hydrophila in Andrias davidianus.

Key words: Andrias davidianus , Aeromonas hydrophila , Virulence factors , PCR