English

Abstract

Brucellosis, being a zoonotic disease, is difficult to control despite the availability of vaccines. Bovine brucellosis could be controlled effectively using brucellaphages. This study was conducted to isolate bacteriophages against Brucella abortus from cattle farms sewage/slurry samples (n=50). Isolation and propagation of brucellaphages was made through spot and plaque assay. Two samples (n=2) were found positive on the plates as circular, clear, and pinpoint plaques (0.3 to 0.5 mm) with 4.6×106 PFU/mL of brucellaphage titre against Brucella abortus RB51. One- step growth experiments revealed latent period of 120 min and burst size of 93 and 114 PFU for two isolated brucellaphages (ϕP1 and ϕP2) respectively. These phages were unable to lyse Staphylococcus aureus, Streptococcus spp., Salmonella spp., Escherichia coli, Bacillus subtilis and Pasteurella multocida. Isolated brucellaphages were stable up to 60°C and between 7 to 9 pH. No loss in phage titres were observed at 4°C but phage titres were reduced by one log at (-20°C) overnight. There was no effect of SM buffer, normal saline and EDTA on stability of brucellaphages and addition of divalent salts in medium showed significant increase in PFU. However, treatment with SDS and chloroform destroyed the phages in one hour exposure. The phages were found carrying double stranded DNA (~40 kb size) and two prominent protein bands of 45 kDa and 70 kDa. Biocontrol activity of brucellaphages showed average Brucella abortus count reduction to 4.5×103 from 5.0×108 CFU/ g of soil sample within 48 h when treated with maximum phage titre of 5.0×1011 PFU/ mL. Hence, this study revealed that brucellaphages are present in our environment and can potentially be consider for their cost-effective practical applications in inactivation of Brucella abortus after comprehensive experimental evaluations. © 2021 Friends Science Publishers