REDUCTION OF AN ESCHERICHIA-COLI K12 POPULATION BY BDELLOVIBRIO-BACTERIOVORUS UNDER VARIOUS INVITRO CONDITIONS OF PARASITE - HOST RATIO, TEMPERATURE, OR PH

Intrinsic and extrinsic parameters of food products, as well as bacterial population, were evaluated for their effects on the ability of Bdellovibrio bacteriovorus, a bacterium parasitic upon gram-negative bacteria, to reduce an Escherichia coli population. High concentrations of both parasite and host were the most effective for reducing a specified E. coli population. B. bacteriovorus was able to reduce the E. coli count by 90% (1 log) in < 1 h at ratios of 5:1, 10:1, and 30:1 (parasite:host). Temperatures between 20 and 30-degrees-C were more conducive to bdellovibrio attack than temperatures less than 20-degrees-C. E. coli populations were reduced by more than 7-log values after 7 h of incubation at 30-degrees-C with parasite:host ratios of 2:1, 5:1, and 10:1. Greater than a 5-log reduction in the E. coli population was observed at the ratio of 30:1. B. bacteriovorus reduced the E. coli population by 1 log in approximately 24 min and 20 min at pH 7.2 and 6.8, respectively. At pH values < 6.8, the activity of B. bacteriovorus was diminished. These results define some of the conditions where the application of B. bacteriovorus may aid in the reduction/elimination of some gram-negative pathogens and spoilage flora that may be present in foods.