Morphologic and molecular characterization of Isospora belli oocysts from patients in Thailand.

To investigate the extent of genetic heterogeneity in the genus Isospora infecting patients in Thailand, a total of 38 fecal samples containing Isospora oocysts from human immunodeficiency virus/acquired immunodeficiency syndrome patients (n = 30), corticosteroid-treated patients (n = 3) and immunocompetent individuals (n = 5) were recruited for analysis. Remarkable variation in the maximum width and length of oocysts both within and between isolates was observed. However, the average length-width ratio of oocysts was within the range for I.