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
P. jirovecii gsc1
gene diversity are still scarce, compared to the homologous
fks1
gene of
Candida
spp. In this study, we analyzed
P. jirovecii gsc1
gene diversity and the putative selection pressure of echinocandins on
P. jirovecii. Gsc1
gene sequences of
P. jirovecii
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
P. jirovecii
infection diagnoses. Two portions of
P. jirovecii gsc1
gene, HS1 and HS2, homologous to hot spots described in
Candida
spp., were sequenced. Three 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
gsc1
HS1 alleles, A, B, and C, and two
gsc1
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 (
p
= 0.57). Considering the identical diversity of
P. jirovecii gsc1
gene and the detection of synonymous mutations in both patient groups, no selection pressure of echinocandins among
P. jirovecii
microorganisms can be pointed out so far.