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Aim: This study aims to evaluate the antagonistic activities of Brevibacillus brevis and Pseudomonas chlororaphis isolated from Rattus norvegicus (Brown rat) nest against Staphylococcus aureus and Pseudomonas aeruginosa isolated from the brown rat’s foot-path soil sample and also on Trichophyton mentagrophytes (interdigitale) ATCC 9533 as a test organism in order to ascertain their antagonistic activities.
Place and Duration of Study: This research was carried out in the Department of Microbiology, The Federal University of Technology, Akure, Ondo State, Nigeria between November 2015 and May 2016.
Methodology: The isolates B. brevis and P. chlororaphis were isolated and characterized from Rattus norvegicus (Brown rat) nests using standard microbiological techniques. The pure cultures of the isolates were screened for antagonism against the following test organisms: S. aureus, P. aeruginosa obtained from foot-path soil samples and Trichophyton mentagrophytes (interdigitale) ATCC 9533 using in vitro antagonistic assay co-culture technique. Physicochemical analyses of R. norvegicus nest and soil samples were accomplished according to standard analytical methods. Analysis of variance (anova) was performed followed by Duncan multiple range post hoc tests, considered the value p =.05.
Results: The isolate B. brevis exhibited strong antagonism against S. aureus and P. aeruginosa with inhibition zones of 22.13±0.32 mm and 18.20±0.10 mm but had no antagonistic effect on Trichophyton mentagrophytes (interdigitale) ATCC 9533. However, P. chlororaphis showed antagonism against S. aureus and T. mentagrophytes (interdigitale) ATCC 9533 with inhibition zones of 17.50±0.17 mm and 15.13±0.20 mm but had no inhibition against P. aeruginosa. The results of this study revealed the antagonistic activities of B. brevis and P. chlororaphis on the test organisms and the findings from the physicochemical assay showed that the temperature and pH of the Brown rat nest supports optimum growth of microorganisms.
Conclusion: Findings from this research revealed the antagonistic potentials of B. brevis and P. chlororaphis against the test organisms and that Brown rat nests from which these organisms were isolated serve as good reservoirs for microorganisms.