Highly Conserved Gene of Pneumocystis jirovecii in Patients with or without Prior Exposure to Echinocandins.

Echinocandins are noncompetitive inhibitors of the GSC1 subunit of the enzymatic complex involved in synthesis of 1,3-beta-d-glucan, a cell wall component of most fungi, including Pneumocystis spp. Echinocandins are widely used for treating systemic candidiasis and rarely used for treating Pneumocystis pneumonia. Consequently, data on gene diversity are still scarce compared to that for the homologous gene of spp. In this study, we analyzed gene diversity and the putative selection pressure of echinocandins on gene sequences of specimens from two patient groups were compared. One group of 27 patients had prior exposure to echinocandins, whereas the second group of 24 patients did not, at the time of infection diagnoses. Two portions of the gene, HS1 and HS2, homologous to hot spots described in spp., were sequenced. Three single-nucleotide polymorphisms (SNPs) at positions 2204, 2243, and 2303 close to the HS1 region and another SNP at position 4540 more distant from the HS2 region were identified. These SNPs represent synonymous mutations. Three HS1 alleles, A, B, and C, and two HS2 alleles, a and b, and four haplotypes, Ca, Cb, Aa, and Ba, were defined, without significant difference in haplotype distribution in both patient groups (0.57). Considering the identical diversity of gene and the detection of synonymous mutations in both patient groups, no selection pressure of echinocandins among microorganisms can be pointed out so far.