Dihydropteroate synthase (DHPS) mutations may be associated with trimethoprim-sulfamethoxazole resistance in Pneumocystis jirovecii pneumonia (PCP) and worse clinical outcomes. However, the clinical significances of DHPS mutations in PCP among non-human immunodeficiency virus (HIV)-infected patients remains unclear.
Between 2016 and 2020, PCP patients in three tertiary referral hospitals in Taiwan were retrospectively enrolled. Two point mutations, Thr55Ala and Pro57Ser, in the DHPS protein, were analyzed. Patients with invalid DHPS mutations in the respiratory specimen, chronic respiratory failure, receiving endotracheal intubation for surgical intervention, HIV infection, Pneumocystis jirovecii colonization, and no lactate dehydrogenase (LDH) data were excluded. The primary outcome was 30-day survival.
In total, 215 patients were analyzed, mutants inside DHPS were found in 78 (36.3 %) patients, and 68 (31.6 %) patients died within 30 days. A total of 214 (99.5%) patients received trimethoprim-sulfamethoxazole as the first line treatment. The rates of mechanical ventilation, 30-day, and in-hospital mortality rates were similar between wild-type and mutant DHPS PCP. After adjusting for important confounders, LDH >500 U/L (adjusted hazard ratio [aHR] =2.448, p =0.001), pneumonia severity index >135 mg/dL (aHR =1.689, p =0.049), and having solid tumors (aHR =1.832, p =0.034) were independently associated with higher mortality. In subgroup analysis, mutant DHPS PCP patients had less 30-day mortality among patients older than 65 years (p =0.049), with lymphopenia (p =0.040) and those without solid tumor (p =0.045).
In non-HIV-infected PCP, point mutants inside DHPS may not associate with trimethoprim-sulfamethoxazole treatment outcomes. Further prospective large-scale studies are warranted.

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