Antibiotic Effects on Coliform Enumeration

The inhibitory effects of Bacillus polymyxa on Escherichia coli were studied. Significant coliform inhibition was observed. The inhibitory agent (presumably polymyxin) was active against coliforms after a one hour holding time. Different suspending menstrua were analyzed for their effects on coliform inhibition. It was observed that Peptone water provided the highest recovery of coliforms while phosphate buffer provided less protection. Two methods of enumeration were also studied as to their ability to quantify coliforms inhibited by B. polymyxa. Comparable inhibition was shown using both methods. No significant differences exist between the Standard Plate Count and Membrane Filter techniques. Overall, wide variations in coliform inhibition independent of the experimental conditions were observed