Isolation and Characterization of Haemolytic Bacillus cereus from Black Rats (Research Article)

Author(s): Manohar B. Vadela, Satyanagalakshmi Karri, Daveedu Thathapudi and Vijay A.K.B. Gundi

Abstract: Bacillus cereus is a Gram-positive spore-forming bacteria belonging to B. cereus group in the genus Bacillus. The organism was reported as major food poisoning pathogen and responsible to cause diarrhoea and septicaemia. B. cereus was ubiquitous and frequently isolated from soil and environmental surfaces. Animals and insects were also reported to carry the pathogen. However, B. cereus was not isolated from rodents until now. In this study, we have isolated B. cereus from black rats (Rattua rattus) for the first time. A total of 13 (20.31%) out of 64 animals were positive for B. cereus. Sixteen isolates were recovered from both blood (4) and faecal (12) samples. All isolates were detected as B. cereus by VITECK 2 compact automated system. Gram staining revealed all isolates are Gram-positive rods and β-haemolysis was observed on blood agar. Molecular identification with 16S rRNA sequences revealed that all isolates have shared 99.67 to 99.78% similarity with B. cereus. In the phylogenetic tree, all isolates were formed as four groups and branched with B. cereus group. The study indicating that B. cereus may be a new zoonotic risk to humans associated with rodents.

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