Dihydropteroate synthase polymorphisms in Pneumocystis carinii

Area of Science:

• Microbiology
• Molecular Biology
• Pharmacology

Background:

• Sulfa drugs are essential for treating and preventing Pneumocystis carinii pneumonia (PCP).
• Pneumocystis carinii is an opportunistic pathogen causing pneumonia, particularly in immunocompromised individuals.
• Dihydropteroate synthase (DHPS) is the molecular target of sulfa drugs in the folate synthesis pathway.

Purpose of the Study:

• To investigate sequence variations in the dihydropteroate synthase (DHPS) gene of Pneumocystis carinii from different hosts.
• To analyze sequence differences in DHPS among human-derived P. carinii isolates.
• To determine if observed genetic variations correlate with potential sulfa drug resistance.

Main Methods:

• Nucleotide sequencing of the dihydropteroate synthase (DHPS) gene.
• Comparative sequence analysis of DHPS from human, rat, and mouse isolates of P. carinii.
• Identification of nucleotide and amino acid changes within the DHPS gene.

Main Results:

• Significant nucleotide sequence differences were observed in the DHPS gene across human, rat, and mouse P. carinii.
• Multiple nucleotide variations, all resulting in amino acid changes, were identified in DHPS from human isolates.
• Several identified amino acid substitutions occurred in highly conserved regions of DHPS, mirroring known resistance mutations in other organisms.

Conclusions:

• The genetic diversity in P. carinii DHPS suggests host-specific adaptations.
• Sequence variations in human-derived P. carinii DHPS may confer reduced susceptibility to sulfa drugs.
• These findings indicate that P. carinii DHPS in humans might be evolving under positive selective pressure from sulfa drug use.