| Abstract
| - The in-vitro activity of rifabutin and albendazole alone and in combination withclarithromycin, etoposide, minocycline and pyrimethamine was investigated against four clinicalisolatesof Pneumocystis carinii. The susceptibility tests were performed by inoculation of theisolateson to cell monolayers and by determining the parasite count after 72 h incubation at 37°C.Theculture medium was supplemented with serial dilutions of each agent. Albendazole tested alonewasmore active than rifabutin. Albendazole suppressed the growth of cysts and trophozoites by>50% at 4mg/L. Rifabutin, at the same concentration, produced about 40% reduction in the mean cyst andtrophozoite counts. Albendazole (4 mg/L) combined with etoposide 4 mg/L showed the highestanti-P. carinii activity, with a decrease of 86.3% and 90.1% in cyst and trophozoitecounts,respectively. The greatest synergic interaction was detected when rifabutin (4 mg/L) wascombined withclarithromycin (4 mg/L). Our study suggests that clinically used antimicrobial agents may beeffective ininhibiting P. carinii growth in vitro and that, above all, some of these agentspossess apositive interaction upon combination with other clinically used compounds. These findings maybeuseful in the establishment of a prophylaxis regimen for multiple opportunistic pathogens.
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