In vitro study demonstrates that coagulase reverses human serum bacteriostasis against Micrococcus pyogenes, indicating an essential protective mechanism during host infection.
Key Points
To determine whether bacterial coagulase protects Micrococcus pyogenes against the natural antibacterial and bacteriostatic properties of normal human serum.
Monitored the 24-hour growth of coagulase-positive (virulent) and coagulase-negative (avirulent) strains of M. pyogenes in undiluted normal human serum.
Treated bacteriostatic human serum with partially purified, cell-free coagulase preparations to assess growth restoration in susceptible coagulase-negative strains, while assessing the potential roles of alpha and beta toxins.
Coagulase-positive strains grew robustly in undiluted human serum over 24 hours, whereas coagulase-negative strains underwent complete growth inhibition.
Addition of cell-free, heat-stable coagulase reversed serum bacteriostasis and permitted the growth of coagulase-negative strains, an effect independent of alpha and beta toxins.