Intracellular parasites are those which spend most of their lives within host cells. The
fluoroquinolones demonstrate favourable intracellular pharmacokinetics for the treatment of intracellular
infections; these agents diffuse and accumulate in the phagocytes, mainly in the cytosol, and do not associate with cellular organelles. The
fluoroquinolones are generally active against Salmonella spp. in vitro, and have been used successfully in the treatment of
typhoid fever, Salmonella bacteraemia in patients with
AIDS, and chronic enteric carriage.
Fluoroquinolone monotherapy has also been found satisfactory in the treatment of tularaemia and
Mediterranean spotted fever.
Quinolones, alone or in combination with other agents, have also shown promise in animal models of
legionellosis and in limited clinical studies.
Quinolones, particularly
ciprofloxacin and
ofloxacin, have notable antimycobacterial activity. Both agents have been used in combination with other antimycobacterial drugs in the treatment of
infections caused by Mycobacterium tuberculosis, M. avium-intracellulare complex, rapidly growing mycobacteria and M. leprae, and deserve consideration as part of a multi-drug regimen in otherwise untreatable mycobacterial
infections. Clinical data regarding
fluoroquinolone monotherapy in
brucellosis indicate unacceptable failure rates which preclude the use of these agents in this indication. The
quinolones have some efficacy in genital chlamydial
infections, but may have limitations in this indication also. In conclusion, as a result of the in vitro activity of the
quinolones and their favourable pharmacokinetics, these agents are now an important part of the armamentarium against intracellular
infections.