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. 2022 Dec 20;66(12):e0099022.
doi: 10.1128/aac.00990-22. Epub 2022 Nov 1.

Apparent Absence of Selective Pressure on Pneumocystis jirovecii Organisms in Patients with Prior Methotrexate Exposure

Pierre L Bonnet  1   2 , Solène Le Gal  1   2 , Chloé Gautier  2 , Claire V Hoffmann  1   2 , Nathan Le Nan  1   2 , André Happe  3 , Rozenn Le Berre  4   5 , Alain Saraux  6   7 , Gilles Nevez  1   2
Affiliations

Apparent Absence of Selective Pressure on Pneumocystis jirovecii Organisms in Patients with Prior Methotrexate Exposure

Pierre L Bonnet et al. Antimicrob Agents Chemother. .

Abstract

Pneumocystis jirovecii infections occur in patients treated with methotrexate (MTX) because of immunosuppressive effects of this highly potent dihydrofolate reductase (DHFR) inhibitor. Conversely, MTX may act as an anti-P. jirovecii drug and consequently may exert a selective pressure on this fungus. In this context, we compared the sequences of the dhfr gene of P. jirovecii isolates obtained from two groups of patients with P. jirovecii infections. The first group, with systemic diseases or malignancies, had prior exposure to MTX (21 patients), whereas the second group (22 patients), the control group, did not. Three single nucleotide polymorphisms (SNPs) were observed at positions 278, 312, and 381. The first one was located in the intronic region and the two others were synonymous. Based on these SNPs, three P. jirovecii dhfr alleles, named A, B, and C, were specified. Allele A was the most frequent, as it was observed in 18 patients (85.7%) and in 16 patients (72.7%) of the first and second groups, respectively. No significant difference in P. jirovecii dhfr gene diversity in the two patient groups was observed. In conclusion, these original results suggest that MTX does not exert an overt selective pressure on P. jirovecii organisms.

Keywords: Pneumocystis jirovecii; dhfr; dihydrofolate reductase; genetic diversity; methotrexate.

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Conflict of interest statement

The authors declare no conflict of interest.

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