Antimicrobial activities of medium-chain fatty acids and monoacylglycerols on Cronobacter sakazakii DBM 3157T and Cronobacter malonaticus DBM

Abstract

Cronobacter sakazakii and Cronobacter malonaticus are pathogens causing infections in children that are primarily linked to the consumption of contaminated infant milk formula and food. Both Cronobacter strains examined were susceptible to caprylic acid, monocaprylin and, to a lesser extent, sorbic acid. Capric acid, lauric acid, monosorbin, monocaprin, monolaurin, and sucrose caprate exhibited no inhibitory activity. Caprylic acid and monocaprylin treatment (2 mg/ml) of C. sakazakii DBM 3157^T reduced the number of viable cells by five orders of magnitude. In the case of C. malonaticus DBM 3148, both caprylic acid and monocaprylin (2 mg/ml) decreased the viable cell counts below the limits of detection. The bactericidal activity of monocaprylin increased as a function of concentration (0.5–2.0 mg/ml) and temperature (40–55°C). The exposure of each Cronobacter strain to monocaprylin resulted in the release of cellular proteins and nucleic acids. Electron microscopy revealed that the antimicrobial treatment damaged cytoplasmic structures and resulted in cell aggregation. The combination of monocaprylin at 0.5 mg/ml and increased temperature (50°C) appears to be a suitable treatment against C. sakazakii and C. malonaticus.