Antimicrobial Activities of Acetic Acid, Citric Acid and Lactic Acid against S higella Species

This study determined the antimicrobial activities of acetic acid, citric acid and lactic acid against four S higella species: S . sonnei , S . flexneri , S . boydii and S . dysenteriae . Minimal inhibitory concentrations of acetic acid and citric acid against S higella were 200 and 300 ppm, respectively. But S . sonnei was 400 ppm. Lactic acid (0.5%) in tryptic soya broth inhibited the growth of all S higella species. Citric acid weakly inhibited the growth of S . flexneri , but it strongly inhibited the growth of S . dysenteriae , resulting in a 5‐log reduction. Acetic acid exhibited the weakest antimicrobial activity among the tested organic acids but produced the highest ratios of injured cells. When artificially inoculated lettuce was dipped in 1% organic acid solutions, the growth of S . flexneri, S . dysenteriae and S . boydii were reduced by 2 logs. And the growth was further reduced by lactic acid as the dipping time increased. The antimicrobial activities of organic acids against S higella species differed. Acetic acid exhibited the greatest antimicrobial activity in the paper disk diffusion experiment, but lactic acid was the most effective antimicrobial agent against S higella species artificially inoculated on lettuce. Practical Applications Shigellosis induced by S higella species results in at least 600,000 deaths worldwide each year. And in the U.S.A. , it is a major bacteria involved in food poisoning, reported in 10,000–20,000 patients. In the present study, organic acids were used as basic materials for controlling S higella species, and there are potential for organic acids, which are natural antimicrobials, to be used in the development of eco‐friendly reduction technology on S higella species.