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

Bulletin of the National Research Centre

Table 1 Minimum inhibitory concentration of the natural and organic antimicrobials against L. monocytogenes, E. coli O157:H7, and S. enteritidis at pH 4.5

Tested compound	Tested range	Minimum inhibitory concentration in ppm
		*L. monocytogenes*	*E. coli* O157:H7	*S. enteritidis*
		pH 4.5	pH 4.5	pH 4.5
Thymol	0–300	25 ppm	25 ppm	25 ppm
Salicylic acid	0–500	200 ppm	200 ppm	200 ppm
Acetylsalicylic acid	0–500	200 ppm	500 ppm	500 ppm
Benzoic acid	0–300	50 ppm	300 ppm	150 ppm
Sodium benzoate	0–300	50 ppm	300 ppm	200 ppm
3-t-butyl-4-Hydroxyanisole	0–300	200 ppm	300 ppm	300 ppm
Ibuprofin	0–300	50 ppm	50 ppm	NA
4-Acetamidophenol	0–300	NA	NA	300 ppm

Different concentrations of each antimicrobial were each added to 10-ml tryptone soya broth tubes and then inoculated (50 μl) of an overnight culture of the bacterial suspension. Tubes were incubated at 37 °C for 24 h. Negative and positive controls were performed. The optical density of each tube was measured using a spectrophotometer. Minimum inhibitory concentration is the lowest concentration of the assayed antimicrobial agent that inhibits the visible growth
NA not applicable