Isolation and identification of a Bacillus paranthracis strain from Chinese giant salamander

Abstract:

[Objective] A bacterial strain likely affiliated with the Bacillus cereus group was isolated from the ascites of Chinese giant salamander from a giant salamander farm in Shaanxi Province and was investigated for the biological characteristics.[Methods]The diseased giant salamander was aseptically dissected,and the samples taken from intestine,ascites,skin and other parts were homogeneously diluted,separated and purified.A pure strain of suspected B.cereus group bacteria was obtained from the ascites,which was named SHOU-BC01.The strain was identified for morphological and staining characteristics,culture and biochemical characteristics,biofilm formation ability,spore formation,drug susceptibility,and whole genome sequencing.Based on the sequencing results,average nucleotide identity (ANI),digital DNA-DNA hybridization (dDDH),multilocus sequence typing (MLST),whole-genome SNP based clustering and virulence factor analysis were performed.[Results] Strain SHOU-BC01 is a Gram-positive bacillus with rough surface,with protease,lecithinase and fibrinolysin activities.It can ferment L-arabinose,D-ribose,D-xylose and other carbohydrates,and can utilize tryptophan and pyruvate,with strong biofilm formation ability.Its spore formation rate reached 70.60% in 120 h.The strain was resistant to 15 antibiotics including penicillin G,cephalothin and vancomycin,and sensitive to 25 antibiotics including piperacillin,cefazolin and gentamicin.According to biological characteristics combined with ANI,dDDH and whole-genome SNP based clustering analysis,strain SHOU-BC01 was identified as B.paranthracis,and the MLST typing showed that the strain belonged to ST205 sequence type.It contains virulence factors such as sphingomyelinase,CytK and NheC toxin genes,polysaccharide capsular,PlcR-PapR quorum-sensing system and type Ⅶ secretion system.[Conclusion] B.paranthracis was successfully isolated from the ascites of Chinese giant salamander,which enriched the data of B.paranthracis.

Key words:Chinese giant salamander;Bacillus paranthracis;isolation;identification