Unanticipated global emergence and evolution of Pneumocystis jirovecii mutations and resistance driven by a human-targeted drug.

Six novel mutations in Pneumocystis jirovecii's IMPDH enzyme confer resistance to mycophenolic acid, emerging globally between 2005 and 2019 under human drug pressure.

• Why it matters: This reveals that microbial resistance can develop outside traditional antimicrobial use, highlighting a gap in understanding how human-targeted drugs influence pathogen evolution and transmission.
• What they did: Genetic analysis of 163 P. jirovecii samples from six countries identified six impdh mutations associated with prior MPA exposure, with structural modeling and enzyme assays confirming reduced drug binding and increased resistance.
• The result: The emergence of these mutations suggests ongoing adaptive evolution driven by human immunosuppressants, prompting a need to reassess immunosuppressive strategies and infection control to prevent resistant pathogen spread.