The importance of penetration of antimicrobial agents into cells.

Phagocytes may shelter intracellular pathogens from the otherwise lethal effects of many antibiotics. Research in conditions such as chronic granulomatous disease, tuberculosis, legionellosis, and experimental staphylococcal infection underscores the principle that an antibiotic must enter the cell in order to be active against an intracellular microorganism. Demonstrating entry does not guarantee activity, however. The microenvironment and intracellular distribution of the pathogen and antimicrobial agent, and interactions between agent, pathogen, and host cell all contribute to determining the treatment result.