Study in vitro of essential oil of Cymbopogon citratus (EOCC) on Listeria monocytogenes NCTC 11994 control

Abstract

Listeria monocytogenes has great resistance to adverse environments. Under refrigeration conditions it can survive long periods of time. In addition, the consumption of foods contaminated with Listeria monocytogenes can cause listeriosis. The genus Listeria spp. are facultative anaerobic bacilli that do not form spores, do not contain a capsule and are ubiquitous, that is, they are widely distributed in the environment. Some studies mention mechanisms of physiological resistance, e.g. to thermal and acid stress. The control of this pathogenic microorganism can be carried out with natural preservatives such as the essential oil of Cymbopogon citratus; which has a citral content > 70%. Citral is a monoterpene composed of two isomers, neral and geranial. It has antimicrobial activity against Enterobacter zakazakii and Echerichia coli. In this study was evaluated the effect of the concentration (PICs, PBCs, MICs and MBCs) of the essential oil of Cymbopogon citratus on control of Listeria monocytogenes NCTC11994 in a model system. A statistical analysis was performed, with a multiple comparison test of Duncan means (SAS System, WindowsTM Versión 6.12, USA). Inhibition (%) and growth (%) was evaluated during study time: 1 and 60 min showed. In some treatments its were significant effect (P> 0.05) on variable respons. It was inhibition between 45-50% for concentrations of EOCC, 10,000 mg/L , 2000 mg/L and 500 mg/L. Significant growth was observed, specifically in the treatments of 50 mg/L and 100 mg/L. The experimental results were adjusted to a linear model for both study systems, the first related to inhibition (%) and the second to the growth (%) of Listeria monocytogenes NCTC 11994. In this study it was observed at  EOCC concentration of 10000 mg/L a significant control of the growth of Listeria monocytogenes,