Treatment of Rickettsioses

Treatment of Rickettsioses

Doxycycline is the drug of choice for the treatment of infections caused byRickettsia except in cases of pregnancy and tetracycline hypersensitivity. some studies have shown that doxycycline is superior to chloramphenicol for the treatment of Rocky Mountain spotted fever as it is associated with a lower case fatality rate and a lower hospitalization rate. Several fluoroquinolones, azithromycin, and clarithromycin, have been used successfully to treat boutonneuse fever but are not recommended for more pathogenic rickettsioses. It should be emphasized that rickettsiae are highly resistant to most antibiotics. Most fatal cases of Rocky Mountain spotted fever have received substantial courses of antimicrobial treatment, including beta lactams, aminoglycosides, and erythromycin. Sulfonamide antimicrobials actually appear to exacerbate the severity of rickettsial infections.

Immunity

Rickettsial infection stimulates an early innate immune response with activation of natural killer cells and production of gamma interferon (gamma IFN), which act in concert to dampen rickettsial growth. Acquired immunity develops with clonal expansion of CD4 and CD8 T lymphocytes as well as antibody-producing B cells. Clearance of intraendothelial rickettsiae is achieved by rickettsicidal effects due to cytokine activation of the infected endothelial cells themselves. Cell mediated immunity (CMI) plays an important role as expected in infection by an intracellular parasite, but antibodies (including those directed at epitopes of OmpA and OmpB) also play a role in protective immunity.