Scientific Publications - Work Done by Microbiology Reader Bioscreen C

A. Hinton, Jr. and J. A. Dickens, Ability  of formulations of the commercial herbal extract, Protecta,  to inhibit Listeria monocytogenes growth in vitro, abstracts of papers from Concurrent Meeting of The Southern Poultry Science Society, 22nd Annual Meeting The Southern Conference on Avian Diseases, 42nd Annual Meeting January 15 & 16, 2001

ABSTRACT

Di.erences in the in vitro inhibition of Listeria monocytogenes growth by 4 formulations of the herbal extract,Prote cta, were determined. Cultures of L. monocytogenes ATCC #13932 were grown in Brain Heart Infusion (BHI) for 18-24 h at 37^oC. Bacterial cells were harvested by centrifugation, and cell pellets were rinsed in peptone water. The rinsed cells were centrifuged, and the final cell pellet was suspended in fresh peptone water. A portion of the cell suspension was added to a Nephelo culture flask, and a spectrophotometer was used to determine the optical density (OD) of the suspension. Peptone water was added to the flask to adjust the OD of the suspension to a value equivalent to a population of 10⁹ cfu of L. monocytogenes/ml. Separate solutions of Protectas 1,2,3a, or 3b were prepared by dissolving the extracts in distilled water. The Protecta solutions were filter sterilized and added to sterile BHI to produce final concentrations of 0, 0.005, 0.010, 0.015, or 0.020% (w/v) of each Protecta in the medium. The L. monocytogenes suspension was serially diluted and added to BHI-Protecta mixtures in test tubes to yield a final concentration of 103 cfu/ml. Aliquots of 0.1 ml of the inoculated BHI-Protecta mixtures were added to separate wells of a Bioscreen honeycomb plate. The filled honeycomb plates were placed in a Bioscreen C Microbiology Reader, and the reader was programmed to monitor changes in the OD of the cultures during a 48 h incubation period at 37^oC. Analysis of results indicated that during incubation, there was a significant increase in the OD of L. monocytogenes cultures grown in BHI not supplemented with Protecta and in BHI supplemented with 0.005% of Protectas 1, 2, 3a, or 3b; 0.010% of Protectas 2, 3a,or 3b; or 0.015% of Protecta 3b. There was no significant change in the OD of cultures grown in BHI supplemented with concentrations >0.010% of Protecta 1, >0.015% of Protectas 2 or 3a,or 0.020% of Protecta 3b. Findings of this study indicate that when used at appropriate concentrations, each Protecta formulation can inhibit L. monocytogenes growth in vitro. The relationship between the inhibitory activities of the Protectas can be expressed as: Protecta 1>Protecta 2 and Protecta 3a>Protecta 3b.

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