Isolation, Identification and Drug Sensitive Test of Aeromonas jandaei from Tilapia (Tilapia nilotica)

Abstract:

Tilapia is a very important freshwater aquacultural species in China; however, bacterial disease caused huge economic losses in recent years with the continous expansion of tilapia aquaculture. The aim of this research was to isolate, identify, and test drug sensitivity of bacteria pathogen found in diseased Tilapia nilotica. Six bacteria were isolated from diseased T. nilotica as suspected pathogenic bacteria. The bacteria (NL05) isolated from intestine of diseased T. nilotica was determined as pathogenic bacteria by infection experiment. The LD50 was 1×103 CFU/g. Bacteria NL05 was identified as Aeromonas jandaei. Morphology observation indicated that NL05 was gram-negative, rod-shaped. Thirteen physiological and biochemical indexes were positive including maltose, mannitol, glucose, salicin, and hydrogen sulfide. Ten indexes were negative including saccharum, arabinose, xylose, inositol, and dulcitol. There was 1442 bp in the sequence of 16S rRNA, which was submitted into GenBank (Accession number: KC916744). The phylogenetic tree based on 16S rRNA showed that NL05 was A. jandaei. Drug sensitivity test indicated that NL05 was sensitive to 13 antibiotics including ofloxacin, ciprofloxacin, amikacin, polymyxin B, norfloxacin, rifampicin, and lincomycin, and intermediate sensitive to 5 antibiotics including azithromycin, ceftriaxone, kanamycin, streptomycin and minocycline, and resistant to 13 antibiotics including ampicillin, amoxicillin, enrofloxacin, sulfamethoxazole, and trimethoprim. The results will provide references for the prevention and treatment of diseases caused by T. nilotica.