Influence of Antimicrobial Agents on Replication and Stage Conversion of Toxoplasma gondii

Abstract

As yet, only a few drugs are available that are frequently used for the treatment of human toxoplasmosis. Pyrimethamine and sulfadiazine are regularly used in combination and are the first choice for most clinical conditions. However, due to severe side effects that are observed especially with sulfadiazine, other drugs, such as clindamycin, have successfully been used as alternative treatment. Since pyrimethamine might be teratogenic when used in the first weeks of pregnancy, spiramycin has been introduced as first-choice treatment during the first 16–20 weeks of pregnancy. In addition to these four well-established drugs, others such as tetracycline or cotrimoxazole have been studied as therapeutics against toxoplasmosis. Although their effectiveness has been demonstrated to some extent, they have not been accepted as general treatment (Joss 1992). None of these drugs has been shown to completely eliminate the parasite in the human host. Since persistent infection with cysts is the source of reactivated toxoplasmosis, new drugs have been developed that might even be more effective against the cyst stage. The hydroxynaphthoquinone atovaquone and macrolides such as azithromycin, clarithromycin, and roxithromycin are thought to inhibit the tachyzoite and the cyst stage as well, as has been shown in vitro or/and in vivo (Araujo et al. 1991,1992a,1992b; Blais et al. 1993a, Huskinson-Mark et al. 1991).