Molecular identification of Bifidobacterium sp. from local yoghurt and evaluation of growth inhibition activity against pathogenic bacteria

Yoghurt is a potential source of probiotic bacteria including Bifidobacterium sp. In this context, sour yoghurt sample was collected from local market in Rajshahi for molecular identification and characterization of Bifidobacterium sp. with promising antagonistic activity against pathogenic bacteria. Isolation was done on Luria broth agar media for molecular identification and revealed that isolated bacterium showed 90% similarity with Bifidobacterium sp. Antibiotic sensitivity test result revealed that isolated Bifidobacterium sp. was sensitive to erythromycin, kanamycin, gentamycin, tetracycline, ciprofloxacin, doxycycline out of eleven commercially used antibiotics. Moreover, antagonistic activity of Bifidobacterium sp. was evaluated in our present study against four pathogenic bacteriathrough disc diffusion method. Bifidobacterium sp. had relatively strong antagonistic effect (inhibition zone ≥15 mm) against Salmonella sp. with 16mm and 19mm zones of inhibition at doses of 150 and 200 μg/disc, respectively. Similarly, the isolate showed strong growth inhibitory activity against Acinetobacter sp. and E. coli with inhibition zone of 17 mm and 16 mm at dose of 200 μg/disc while moderate growth inhibitory activity was observed against Aeromonas sp. at applied four doses. Furthermore, present investigation showed that the isolated Bifidobacterium sp. had the utmost effect against Salmonella sp. and exhibited growth inhibition of understudy pathogens in such pattern Salmonella sp.>Acinetobacter sp.> E. coli> Aeromonas sp. Bangladesh J. Sci. Ind. Res.56(3), 147-154, 2021