Invasion of HeLa cells by beta-hemolytic group G streptococci

The invasion of HeLa cells by beta-hemolytic Lancefield group G streptococci was studied by measuring the number of bacterial cells that survive exposure to gentamicin. Approximately 50% of bacteria introduced to the HeLa cell monolayer survived gentamicin treatment, suggesting that they were intracellular. Electron microscopy of these preparations showed intracellular bacteria in the cytoplasm, not surrounded by host cell membranes. Trypsinized bacteria incubated with HeLa cells were all killed by gentamicin. It appears that the beta-hemolytic group G streptococci have mechanisms for entry into human epithelial cells which may have importance in the virulence of the organisms.