Cellular antibiotic pharmacology.

Many perinatal pathogens are able to survive and in some cases replicate intracellularly. With the exception of viruses and toxoplasma, these pathogens principally infect phagocytic cells of the reticuloendothelial system. Such intracellular organisms, by evading the effects of antibiotics that act only extracellularly, may respond poorly to conventional therapy. Of currently available antibiotics, rifampin, chloramphenicol and trimethoprim are the most active intracellularly. Other antibiotics are either taken up by cells but appear to be inactive intracellularly (lincomycin) or are excluded from cells (penicillins, cephalosporins, aminoglycosides). The clinical role of antibiotics that are active intracellularly is not clear; anecdotal human experience and limited controlled animal experience suggests that they may be useful in the treatment of some infections. Because of the decreased microbicidal activity of newborn phagocytes, intracellular activity of antibiotics may be of greater importance than in older patients. Further study is needed to answer these questions. Methods of enhancing intracellular activity of antibiotics are available should this property prove to be desirable.