Abstract:

Objective To confirm an acute death case of Pavo cristatus at Anyang zoo， this study carried out clinical diagnosis and laboratory tests. Method The clinical symptoms and pathological changes of dead peacocks were observed. The pathogenic bacteria were isolated and identified by methods such as identification medium， Gram staining， biochemical identification， 16S rRNA gene PCR amplification， phylogenetic tree construction and animal experiments. The biofilm-forming ability of the isolated bacteria was detected by crystal violet staining method， and the drug sensitivity test was conducted by K-B disk method. Drug resistance genes were detected by PCR. Result There was no obvious symptoms on the body surface of dead peacocks. The results of the peafowl necropsy showed that there was an increase and turbidity in pericardial effusion， and the liver was enlarged. There was urate deposition in the kidneys， and bleeding in the intestines. The liver tissues of dead peacocks were aseptically collected and streaked and inoculated on MacConkey medium， and red colonies were isolated. Microscopic examination revealed that the pathogenic bacteria were pink short rods， scattered singly or in pairs， and suspected to be bacteria of the Enterobacteriaceae family. The results of biochemical identification indicated positive reactions for indole， MR， pentose， sorbitol， and so on， and negative reactions for Simonsons citrate， V-P， urea， hydrogen sulfide， and so on. 16S rRNA gene PCR amplified fragment was sequenced to obtain a sequence of about 1 500 bp in length （GenBase accession No.： C_AA110994.1）. The phylogenetic tree indicated that the isolated strain had the highest similarity （100%） to Escherichia coli （E. coli）， confirming that the isolated bacterium was E. coli. The isolated bacteria had stronger biofilm-forming ability than standard strain and could cause liver and spleen enlargement， lung congestion， intestinal wall thinning， intestinal bleeding， and villus shedding in BALB/c mice， eventually leading to death. The isolated bacteria were sensitive to levofloxacin， norfloxacin and so on， but resistant to tetracycline， streptomycin and other drugs， and carried six resistance genes tetA， ampC， bla_TEM， Sul1， Sul2 and strA-strB. Conclusion In this study， the pathogenic E. coli srtain was isolated and identified form Pavo cristatus. The results of drug sensitivity test showed that this E. coli strain was sensitive to levofloxacin， norfloxacin， and so on， but resistant to tetracycline， streptomycin， and so on. This study provided a valuable reference for the diagnosis and clinical medication of E. coli-related diseases in Pavo cristatus.

Key words: Pavo cristatus; Escherichia coli; isolation and identification; drug resistance