Relationship between growth rate and phagocytosis susceptibility in Streptococcus mutans

Streptococcus mutans strain GS-5 was grown in a variety of carbon sources in order to achieve different balanced growth rates, ranging from 61 to 383 minutes. The influence of the S. mutans growth rate on mouse phagocyte activity against these bacteria has been evaluated. The percentages of bacteria phagocytized and intracellularly killed by macrophages rose to 60-80% and 85-95% respectively when the doubling time was longer, showing that S. mutans is particularly sensitive to nonspecific immune defence mechanisms when cultured under conditions similar to those of its natural ecosystem.