Phenotypic and Molecular Characterizations of Haemolytic and Penicillin-Resistant Bacillus cereusand its Control by Plant Extracts

Bacillus cereusis a spore-forming bacterial species that has some pathogenic strains responsible for several human diseases. The present study was aimed to characterize a pathogenic strain of B. cereusWBI3 isolated from pond water of rural Tinna village area of West Bengal and its control by plant products. Out of the four screened bacterial isolates, WBI3 was found to possess haemolytic character. The bacterial strain WBI3 was gram-positive, spore forming, rod-shaped, motile bacterium, positive for catalase, oxidase, methyl red and nitrate reduction test and negative for indole, urease, citrate and Voges–Proskauer test. Bacterial isolate WBI3 was capable of producing amylase, lipase and gelatinase enzymes and was able to ferment trehalose, dextrose, fructose and salicin. Among twenty standard antibiotics, the bacterium was sensitive to seventeen antibiotics but resistant to three antibiotics. Morphological, biochemical and molecular analyses of the bacterial strain WBI3 indicated that it was a haemolytic and penicillin-resistant strain of B. cereus. Among six tested plant extracts, aqueous and alcoholic (methanolic and ethanolic) extracts of Acacia niloticashowed significant antibacterial activity against B. cereusWBI3 and inhibition zone diameters were 21.66 ± 1.52 mm, 25.33 ± 0.57 mm and 22.33 ± 1.52 mm, respectively. Further studies are needed to identify the bioactive compounds which have an antagonistic role against this pathogenic strain, so that a formulation can be made which would help to control the bacterial strain in the water bodies and spreading of diseases caused by this strain.