The effect of phenolic compounds (benzoic acid) on the susceptibility of gram-positive and gram-negative bacteria exposed to antibiotics.

Benzoic acid is a common phenolic phytochemical found in the natural environment. This phenol has been found to increase the susceptibility of resistant microbes, making it more feasible to kill the microbials by antibiotics. The experiment modeled the effects of phenolic acids by placing them into an agar medium and exposing them to gram-positive and gram-negative bacteria. The antibiotics [Bactrim and Ciprofloxacin] discs were placed on the top of the agar medium and then the inhibition zone was measured after 24 hours to determine the antimicrobial effects of the phenols. It was hypothesized that higher concentrations of phenols would increase the susceptibility of the microbe, allowing the antibiotics to inhibit the gram-positive and gram-negative bacteria. The groups consisting solely of the antibiotic and bacteria served as a controls for the experiment. The concentrations of the phenols in the experimental group increased at similar levels for each phenol, from 0 µg/ml- 800 µg/ml. The hypothesis was partially supported. The gram-positive microbe Staphylococcus aureus was sensitized to both CIP and SXT when exposed to benzoic acid concentrations yielding a p \u3c 0.01 at an α=0.05. Similarly, the gram-negative microbe Pseudomonas aeruginosa was sensitized significantly to CIP when exposed to phenol, having a p \u3c 0.01 at an α=0.05. In comparison, gram-negative microbe Escherichia Coli, proved no statistical significance with a p \u3e 0.01 at an α=0.05. Conclusions were not drawn in comparison to both strains of bacteria, but evidence suggests that bacteria can be sensitized with benzoic acid, as indicated by the successes with antibiotic application