Title

Investigating the antimicrobial potential of trans-cinnamaldehyde for controlling Cronobacter sakazakii infections

Date of Completion

January 2010

Keywords

Biology, Microbiology|Agriculture, Animal Culture and Nutrition|Biology, Virology

Degree

Ph.D.

Abstract

Cronobacter sakazakii is an emerging pathogen, which causes a life-threatening form of meningitis, necrotizing colitis and meningoencephalitis in neonates and children. Epidemiological studies implicate dried infant formula as the principal source of the pathogen. In this dissertation, the efficacy of trans-cinnamaldehyde (TC), an ingredient in cinnamon, was investigated for inactivating C. sakazakii in infant formula, decreasing its stress resistance to environmental stresses, inhibiting and inactivating biofilm formation and reducing virulence in vitro. In addition, proteomics was used to elucidate the antimicrobial mechanism of action of TC at the molecular level. TC significantly (P≤0.05) reduced C. sakazakii populations in reconstituted infant formula compared to control. Resistance to acid, heat, osmotic and desiccation in C. sakazakii was significantly reduced by exposure to TC. Additionally TC at sub-inhibitory concentrations reduced the ability of C. sakazakii to form biofilms while higher concentrations of TC inactivated fully formed mature biofilms. TC reduced virulence in C. sakazakii by decreasing its motility, invasion of intestinal epithelial and brain cells, survival within macrophages, induction of nitric oxide synthesis and endotoxin production. Real time qPCR results revealed that TC downregulated the expression of genes essential for stress resistance, biofilm formation and virulence in C. sakazakii. The proteomics data revealed that TC exerts antimicrobial effects by multiple mechanisms, including disruption of carbohydrate, amino acid and lipid metabolism. The efficacy of TC in attenuating stress tolerance, biofilm formation and major virulence factors in C. sakazakii underscores its potential use in the prevention and/or control of human diseases caused by this pathogen. Additionally the proteomics study provides us with novel targets for controlling C. sakazakii infections. ^