Droplet Digital PCR and PCR-free BIOSensors for the Detection of Resistance-associated SNPs in Pneumocystis Jirovecii

Pneumocystis jirovecii (P. jirovecii) is an opportunistic pathogenic fungus responsible for pulmonary infection or Pneumocystis pneumonia (PCP) in immunocompromised patients. There is currently no system for its in vitro culture. The diagnostic methods used are mainly based on molecular biology techniques which also allow the detection and analysis of single nucleotide polymorphisms (SNPs), particularly at the level of genes coding for the targets of molecules widely used in the prevention and treatment of PCP. These SNPs may represent missense mutations potentially associated with treatment resistance. They may result from exposure of patients to these treatments before the development of P. jirovecii infection. However, data concerning the prevalence of these mutations remains scarce, particularly in France. Methods for detecting these mutations based on PCR followed by DNA sequencing have limitations in terms of sensitivity. The evaluation of new, more sensitive and rapid tools for the detection and characterization of pathogens in this context is necessary.

The main objective of the proposed research is to identify P. jirovecii mutant strains on 4 genes encoding therapeutic targets such as dihydropteroate synthase (DHPS), dihydrofolate reductase (DHFR), cytochrome b (CYB), inosine-5'-monophosphate dehydrogenase (IMPDH) and therefore to assess the prevalence of potentially resistant strains in patients infected with P. jirovecii.

The secondary objectives are:

• to determine the factors associated (e.g. exposure to treatments) with mutant P. jirovecii strains
• to determine the impact of mutations on the effectiveness of anti-Pneumocystis treatment (e.g. favorable vs. unfavorable evolution of the infection)
• to evaluate two methods - digital droplet PCR and biosensors without PCR - for the detection and characterization of mutations associated with resistance in Pneumocystis jirovecii