Dihydropteroate synthase (DHPS) gene mutation study in HIV-Infected Indian patients with Pneumocystis jirovecii pneumonia

Abstract

Introduction: Pneumocystis jirovecii dihydropteroate synthase (DHPS) gene mutations' (55^th and 57^th codon) association with prior sulfa prophylaxis failure has been reported from both developed and developing countries. We conducted a prospective study to determine the prevalence of P. jirovecii DHPS mutations from 2006 to 2009 on P. jirovecii isolates obtained from HIV-infected patients with a clinical diagnosis of Pneumocystis carinii pneumonia (PCP) admitted to our tertiary care reference health center in New Delhi, India.

Methodology: Detection of P. jirovecii cysts was performed by direct fluorescent antibody (DFA) staining and by Grocott's-Gomori methenamine silver staining (GMS). DNA detection was performed by polymerase chain reaction (PCR) using primers for the major surface glycoprotein (MSG) gene. P. jirovecii DHPS gene was amplified by nested PCR protocol and sequenced for detecting mutations at the 55^th and 57^th codons.

Results: Out of 147 HIV-positive patients with suspected Pneumocystis pneumonia (PCP), 16 (10.8%) PCP positive cases were detected. Of 16 cases, nine (56.2%) were positive by DFA staining, four (25%) were positive by Grocott's-Gomori methenamine silver staining, and all 16 were positive by MSG PCR. DHPS mutations at the 55^th and 57^th codons were observed in 6.2% of HIV patients studied, which was relatively low compared to reports from developed nations.

Conclusions:  Prevalence of Pneumocystis jirovecii DHPS mutations associated with cotrimoxazole treatment failure may be low in the Indian subpopulation of HIV-positive patients and warrants larger studies to elucidate the true picture of Pneumocystis jirovecii sulfa drug resistance in India.