ABSTRACT

The genus Bacillus produces various classes of antibiotics, among which is bacitracin. Bacitracin is a mixture of related cyclic peptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, first isolated in 1945. This study was carried out to screen and evaluate the antimicrobial activity of bacitracin produced by Bacillus subtilis at varying culture conditions. The crude bacitracin produced was tested at different dilutions against Escherichia coli and Staphylococcus aureus which are known to be susceptible to this antibiotic. The organism was isolated from the UGC farm of Michael Okpara University of Agriculture, Umudike and they were confirmed as Bacillus subtilis by using standard biochemical tests, gram and spore stains and other morphological characteristics. The efficiency of the bacitracin produced at different parameters were studied and determined by testing it against the test organisms through the agar well diffusion method. The susceptibility of the test organisms to the bacitracin extracts was determined by measuring the diameter of inhibition zones formed around agar wells in different agar plates prepared. From this analysis, the results showed that pH was the major contributing factor to increased activity of bacitracin, especially at pH 8, were it showed the highest inhibition of test organism. Glycerol and Calcium Carbonate also improved the effectiveness of the bacitracin produced, while Magnessium Sulphate greatly hindered its potency. Also, from the analysis, Staphylococcus aureus was more susceptible to the crude extracts of bacitracin compared to Escherichia coli which was less susceptible. From this work, it can be said that the effects of bacitracin produced by Bacillus subtilis cannot be optimized except with the variation of certain culture conditions. It can also be said that some cultural parameters decrease its effectiveness and thus should be avoided during industrial production of this antibiotic.