Efficacy assessment of various natural and organic antimicrobials against Escherichia coli O157:H7, Salmonella enteritidis and Listeria monocytogenes

Abstract

The bactericidal effect of eight compounds and their concentrations were evaluated by the tube dilution assay against the tested bacterial strains. Thymol was found to be superior to all tested compounds. Antimicrobial activities found to be highly influenced by varying pH values. Low pH 4.5 found to report higher inhibition when compared with pH 7.1. For instance, minimum inhibitory concentration (MIC) occurred at pH 7.1 with 25 ppm of thymol against Escherichia coli O157:H7 and Salmonella enteritidis, while 200 ppm against Listeria monocytogenes. However, MIC occurred at pH 4.5 with 25 ppm of thymol against all tested bacterial strains.