Determination of the inhibitory effect on Toxoplasma growth in the serum of AIDS patients during acute therapy for toxoplasmic encephalitis.

In 26 AIDS patients treated for toxoplasmic encephalitis, the inhibitory effect on Toxoxplasma growth of sequential sera taken before and after initiation of therapy was determined using a culture-based immunoassay and compared with pyrimethamine blood levels. A marked inhibition of Toxoplasma growth was observed 1 day after initiation of therapy with pyrimethamine plus sulfadiazine and was maintained between 67% and 93% throughout the 15-day follow-up period. The degree of inhibition was not correlated to pyrimethamine blood levels and seemed highly potentiated when sulfadiazine rather than macrolides was given in combination with pyrimethamine.