Genetic diversity of Pneumocystis jirovecii in Thailand.

A fungus Pneumocystis jirovecii, which causes a diffuse bilateral pneumonia called Pneumocystis pneumonia (PcP) is one of the most common opportunistic infections in HIV-infected patients in Thailand. Molecular techniques have demonstrated diversity among isolates of P. jirovecii by comparison of DNA-sequence variation at the internal transcribed spacer region 1 (ITS1) and region 2 (ITS2) of the nuclear ribosomal RNA genes. The studies confirm that a high diversity of P. jirovecii ITS types exists in different populations from different geographical areas. Type Eg is found globally from represent countries in Europe, North America, South Africa and Asia. Among the 23 types of P. jirovecii observed in Thailand, type Ir is present at the highest frequency (28.6 %), followed by type Eb (21.4%) and types Eg and Rp (14.3 %), respectively. Ir and Rp are unique types observed in Thailand. Mixed infections of more than one types of P. jirovecii are commonly observed in all studies with prevalence of 25-82 %. Moreover, unique types of P. jirovecii can be found in a specific group of populations. These types may be used as genetic markers to study the evolution of the organism in each geographical area.