The intracellular location of certain strains of Staphylococcus aureus serves as a reservoir of bacteria which is thought to be important in
therapy of
recurrent infections in humans and in chronic staphylococcal
mastitis in dairy cows. This overview summarizes data pertaining to the intracellular survival of Staphylococcus aureus within polymorphonuclear neutrophils (PMNs) both in vitro and in vivo in the face of
antibiotic treatment. While compounds such as
rifampin,
clindamycin,
erythromycin, and
ciprofloxacin have been shown to be rapidly taken up by PMNs, the ability of
antibiotics to concentrate within PMNs did not strictly correlate with their ability to kill intracellular Staphylococcus aureus.
Rifampin and
ciprofloxacin have been shown to be the most effective intraphagocytic killing agents, while
clindamycin and
erythromycin were inactive in these in vitro assays. In vivo, in
therapy of Staphylococcus aureus
arthritis and
peritonitis in humans and in certain mouse models
rifampin has generally been shown to be more effective than comparator
antibiotics. In a staphylococcal subcutaneous
abscess model, however,
clindamycin was very effective in curing the Staphylococcus aureus
abscesses in this system where PMNs were the primary inflammatory cells involved. The intracellular bacterial counts decreased as rapidly as the extracellular bacteria.
Rifampin was also effective in the
abscess model but
ciprofloxacin was ineffective at the highest doses tested. The relevance of in vitro and in vivo models and the importance of PMNs as a reservoir of
infection in staphylococcal diseases in humans and the dairy cow are discussed.