GENETIC-VARIABILITY IN DIFFERENT PNEUMOCYSTIS ISOLATES FROM MAN AND RATS

To gain further insight into the genetic variability between different isolates of Pneumocystis carinii of rat and human origin, we sequence d three DNA regions from the mitochondrial rRNA gene, the 5S rRNA gene and the dihydrofolate reductase gene (DHFR) of microrganisms isolated from three different immunosuppressed rat sources and from one HIV+ p atient with P. carinii pneumonia. Some point mutations and deletions w ere found among rat isolates in two regions (mitochondrial rRNA gene a nd 5S rRNA gene). Nucleotide sequence variations in these conserved re gions support the hypothesis of the existence of several Pneumocystis strains infecting the same host species.