TITLE:
Menaquinone (Vitamin K2) Enhancement of Staphylococcus aureus Biofilm Formation
AUTHORS:
Derek T. Kirby, Joyce M. Savage, Balbina J. Plotkin
KEYWORDS:
Quorum; S. aureus; Menaquinone; Fibronectin; Biofilm; Capsule; Plastic; Adherence; Carotenoid
JOURNAL NAME:
Journal of Biosciences and Medicines,
Vol.2 No.1,
March
19,
2014
ABSTRACT: During infection, Staphylococcus
aureus is exposed to exogenous menaquinone which is essential for the human
blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not
known. To test whether menaquinone affects expression of virulence-associated phenotypes, methicillin-sensitive
(MSSA) and -resistant (MRSA) S. aureus strains
(n = 8) were grown in the presence of menaquinone
(0.001 - 12 μg/ml). Capsule production, biofilm formation
(plastic and fibronectin-coated microtiter plates) and carotenoid levels were
determined spectrophotometrically after growth in Mueller Hinton broth (MH; 24-hr, 37°C). All experiments were, at minimum,
done in triplicate and repeated twice. Menaquinone at physiologic levels (0.01
μg/ml MH) significantly increased (p 0.05) biofilm formation
on plastic in a manner that was bacterial population size dependent. In
addition, menaquinone (0.05 - 4 μg/ml) significantly increased
(p 0.05) biofilm formation on fibronectin-coated
surfaces for four MSSA strains and one MRSA strain by two to six-fold as
compared to medium controls. However, menaquinone had no effect on capsule
production or cell-associated carotenoid levels. Menaquinone’s effect on
biofilm formation on fibronectin-coated surfaces appears to be regulated by sarA. These findings are the first to
demonstrate that a vitamin at concentrations reported in humans affects S. aureus virulence-associated phenotypes.