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Appl Environ Microbiol. 1965 September; 13(5): 766-770
Copyright © 1965 American Society for Microbiology. All Rights Reserved.

Factors Affecting the Antimicrobial Activity of Vitamin K₅¹

Department of Food Science and Technology, Oregon State University, Corvallis, Oregon

ABSTRACT

Pure cultures of Escherichia coli, Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus, and Pseudomonas fluorescens were used in this investigation. The bactericidal concentrations of vitamin K₅ required for E. coli, B. subtilis, P. vulgaris, S. aureus, and P. fluorescens; the effect of an absence of oxygen; the effect of contact time with E. coli and S. aureus; and the effect of initial counts per milliliter of E. coli were studied. The bactericidal concentrations ranged from 60 ppm of K₅ for S. aureus to 220 ppm for E. coli, with an initial count of 160,000 to 200,000 cells per milliliter and a contact time of 12 hr in nutrient broth. The gram-positive bacteria tested were more susceptible to the antimicrobial activity of vitamin K₅ than the gram-negative bacteria. In the studies conducted under nitrogen atmosphere, the per cent inhibition showed an inverse relationship to the bactericidal concentrations required for complete inhibition in studies conducted under air atmosphere. This finding suggested that there might be different factors responsible for inhibition depending on the species of bacteria being tested, and it also might help explain the difference in concentrations necessary for inhibition. Cells of E. coli and S. aureus were not inhibited immediately on coming into contact with vitamin K₅; 50% inhibition occurred after 25 and 32 min, respectively. A rapid inhibition rate was maintained until approximately 90% inhibition occurred, after whch a rapid decrease in the rate was noted.

² Present address: Coca-Cola Export Corp., New York, N.Y.

¹ Technical Paper no. 1936, Oregon Agricultural Experiment Station. This paper is based on a thesis submitted by Larry S. Merrifield in partial fulfillment of the requirements for the M.S. degree.