Pathogenicity and drug resistance of Bacillus paranthracis strain BC006 from bluntnose black bream(Megalobrama amblycephala)based on whole genome analysis
In order to understand the pathogenicity and drug resistance of Bacillus paranthracis from a genetic per-spective,whole genome sequencing,in vivo bacterial virulence testing,and antibiotic sensitivity testing were con-ducted in the pathogenic bacterium B.paranthracis designated as strain BC006 isolated from viscera of diseased bluntnose black bream(Megalobrama amblycephala).The results showed that,the genome of B.paranthracis strain BC006 consisted of 5 457 931 bp,including 1 chromosome(GenBank ID CP119629)and 7 plasmids(GenBank ID CP119630～CP119636),containing 5 539 coding genes,with the maximal degree of collinearity with B.paran-thracis strain 1710 from bovine.The LD50 induced by intraperitoneal injection of BC006 was found to be 4.68×10 5 CFU/g in bluntnose black bream and 4.22×105 CFU/g in mice.The B.paranthracis strain BC006 carried 43 viru-lence genes,including alo encoding the hemolysin Ⅰ component,hly Ⅲ encoding the hemolysin Ⅲ component,nheA/B/C encoding the non hemolytic enterotoxin(Nhe),and sph encoding sphingomyelinase(SMase),whose virulence genes were associated with β-hemolysis and enteritis by BC006.BC006 carried 16 resistance genes.Tet(45)and tetB(P)were shown to be involved in the resistance to tetracycline and doxycycline,and MPhL was in-volved in the resistance to erythromycin.Both Bc Ⅰ and Bc Ⅱ were involved in the resistance to cefotaxime and penicillin G.QacJ was involved in the resistance to metronidazole,trimethoprim,rifampicin,norfloxacin,enroflox-acin,ciprofloxacin,ofloxacin,and compound sulfamethoxazole.The findings indicate that Bacillus subtilis BC006 is a multidrug-resistant bacterium carrying multiple virulence factors,and a newly discovered pathogenic bacterium to bluntnose black bream.It is recommended to use fluophenicol and neomycin sulfate sensitive to this bacterium in national standard fishing medicines.
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