Comparison of PrestoBlue ® and plating method to evaluate antimicrobial activity of ascorbic acid, boric acid and curcumin in an in vitro gastrointestinal model.

AIMS: To compare the conventional plating method vs a fluorometric method using PrestoBlue® as a dye by determining the antimicrobial activity of two organic acids and curcumin (CUR) against Salmonella Enteritidis in an avian in vitro digestion model that simulates the crop, proventriculus and intestine.

METHODS AND RESULTS: A concentration of 108  CFU per ml of S. Enteritidis was exposed to groups with different rates of ascorbic acid (AA), boric acid (BA) and CUR. Significant differences were observed when the means of the treatments were compared with the controls in the compartments that simulate the crop and intestine (P < 0·05). Ascorbic acid alone and high rates of AA in the mixtures were the most efficient treatments in the crop compartment. However, in the intestinal compartment BA alone and at different rates in the mixture BA-CUR (1 : 1) were the best treatments to decrease the concentration of S. Enteritidis.

CONCLUSIONS: The results of this study suggest that there could be an antagonistic bactericidal effect between AA and CUR and AA and BA as well as a synergistic bactericidal effect between BA and CUR.

SIGNIFICANCE AND IMPACT OF THE STUDY: These findings may contribute to the development of a formulation with microencapsulated compounds to liberate them in different compartments to combat S. Enteritidis infections in broiler chickens.