Synergistic activity of clarithromycin and minocycline in an animal model of acute experimental toxoplasmosis

Abstract

The efficacy of clarithromycin in a murine model of acute toxoplasmosis was studied. Clarithromycin was administered alone and concurrently with minocycline, and eficacy was assessed by survival rates and sequential determination of parasite burden in blood, brains, and lungs. ILmited protection resulted from administration of each drug alone, whereas a remarkable synergistic effect followed concurrent administration.Survival of mice treated with 200 mg of clarithromycin plus 20 mg of minocycline per kg of body weight dalfy was 95%; that of mice treated with 50 mg of clarithromycin plus 50 mg of minocycline per kg daily was 93%.The parasite burden in the blood and organ tissues of these mice was markedly reduced compared with that in mice treated with a single agent. In mice treated with 200 mg of carithromycin plus 50 mg of minocyline per kg per day, survival was 100%o during the 30-day experliment; no parasites were found in blood and tissues.The combination of pyrimethamine and sulfadiazine is the standard therapy for toxoplasmic encephalitis. However, the incidence of side effects is high; skin reaction due to the sulfonamide and hematologic toxicity due to pyrimethamine have been reported with high frequency (8). Alternative regimens involving the replacement of one of the two components by another drug are currently being investigated. The combination of pyrimethamine plus clindamycin and the combination of pyrimethamine plus clarithromycin proved efficient for treatment of patients with toxoplasmic encephalitis (5, 7); other drug combinations using a macrolide have also been effective in an experimental model of acute toxoplasmosis (6). We designed a study to identify a combination of drugs that might make the use of folate inhibitors unnecessary. Since clarithromycin and minocycline are individually active against Toxoplasma gondii (3, The treatment regimens associated with at least 50% survival by day 30 were then reevaluated by using larger groups of mice. Both survival rate and the kinetics of blood and tissue infection were evaluated. In these larger-sample experiments, mice were randomly allocated to separate groups: 30 mice served as controls (no treatment), and each treatment group consisted of 40 mice. The regimens con- Mice were studied for 30 days after infection. Monitoring of infection involved the estimation of survival rates by using the Kaplan Meier product limit method and sequential examination of parasite burden in blood, brains, and lungs on days 4, 7, 10, 14, 22, and 30 after infection; on day 30, liver and spleen tissues were also examined. At each time point, five mice from each group were sacrificed and blood and organ homogenates were cultured as described previously (12). Briefly, serial fourfold dilutions of each blood or organ suspension were prepared in the culture medium, and then 40 ,ul of each dilution was inoculated into duplicate wells of tissue culture plates.

Clarithromycin-minocycline combination as salvage therapy for toxoplasmosis in patients infected with human immunodeficiency virus

“…The rate of treatment-limiting adverse events related to this combination appears to be moderate. These data support the favorable results reported for the murine model (1,3). They warrant further studies to assess this combination along with other alternative regimens, such as atovaquone (5), which might benefit the patients unable to tolerate conventional therapies.…”

“…They were six men and two women with a mean age of 28 to 38 years and a mean CD4 count of 18 Ϯ 15 cells/mm 3 . All patients had toxoplasmosis diagnosed after suggestive contrast-enhancing lesions were found at the initial CT scan (n ϭ 7), before any anti Toxoplasma gondii treatment was started, or after detection of T. gondii in broncho-alveolar lavage (patient 8).…”

In vitro and in vivo activities of the hydroxynaphthoquinone atovaquone alone or combined with pyrimethamine, sulfadiazine, clarithromycin, or minocycline against Toxoplasma gondii

“…With the combinations of dihydrofolate reductase inhibitors and sulfonamides, strong synergistic activity has been observed both in vitro and in vivo, because of the sequential activity of the drugs on the folate metabolism of the parasite (5,8,20). With some other combinations, marked in vivo synergy can be obtained in the absence of an in vitro interaction, possibly because of the complementary effects of the compounds on different sites of Toxoplasma infection (4,6,7). In the present study, no synergistic interaction either in vivo or in vitro could be clearly demonstrated.…”

“…Combination studies were performed in two separate experiments, with atovaquone administered at 50 mg/kg/day in combination with pyrimethamine or sulfadiazine (experiment 1) and clarithromycin or minocycline (experiment 2). For each drug combination, we selected a dose that was previously found to be noncurative, i.e., clarithromycin at 50 mg/kg, sulfadiazine at 200 mg/kg, pyrimethamine at 12.5 mg/kg, and minocycline at 50 mg/kg (6,7,20). Drug suspensions were prepared daily in a solution of methyl cellulose-carboxymethyl cellulose-0.1% Tween 20, briefly sonicated, and administered orally to mice via tube feeding.…”

In Vitro Susceptibility of Pythium insidiosum to Macrolides and Tetracycline Antibiotics

“…Tetracyclines and macrolides have antimicrobial activity, alone and in combination with other drugs, against other eukaryotic organisms, including algae (10), fungi (11,14,22), and protozoa (6,12). Although the mechanism of action of these drugs on eukaryotic organisms is not completely understood, the main mechanisms described include the inhibition of protein synthesis (14,17) and selective inhibition of both mitochondrial and plastid activity (12) and intracellular calcium release (22).…”