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Background:  Mutations in the Pneumocystis jiroveci dihydropteroate synthase (DHPS) gene have been associated with prophylaxis failure. However, it is controversial whether these mutations are associated with poor outcome. We investigated, in Spanish HIV-1-infected Pneumocystis carinii pneumonia (PCP) patients, if DHPS mutations are associated with a poor outcome and whether the prevalence of mutations changed after the introduction of HAART.

Methods:  We studied consecutive PCP episodes in HIV-1-infected patients from  a single institution in Spain during the pre-HAART (1989-1995) and HAART (2001-2004) periods. Diagnosis of P. jiroveci was made by Gomori, Giemsa, or Papanicolaou stains in respiratory samples either from bronchoalveolar lavage or induced sputum. The P. jiroveci DHPS locus was amplified by nested PCR and sequenced. Clinicians were blinded to laboratory results. We compared the presence of mutations at the DHPS gene with survival, relapses and response to anti-PCP drugs.

Results:  We successfully genotyped the P. jiroveci DHPS gene from 43 of 110 (39%) pre-HAART patients and from 60 of 63 (95%) HAART patients, of which 17 (16.5%) had mutations in the P. jiroveci DHPS gene (14 [33%] in the pre-HAART period vs 3 [6%] in the HAART period; p = 0.001). The pre-HAART group had 5 single (3 T55A, 2 P57S) and 9 double mutations; the HAART group, 2 single and 1 double mutations. Patients with DHPS mutations had similar median age (40 years vs 36), gender (male 76% vs 79%) and median CD4 cell counts (13 cells/mm³ vs 25) than those with a wild type genotype. Patients with mutations were more likely to be homosexual (47% vs 17%, p = 0.03), to have previous AIDS criteria (53% vs 25%, p = 0.02), previous PCP episodes (24% vs 6%, p = 0.03), to be ART-experienced (71% vs 34%, p = 0.006) and to be on TMP-SMZ or dapsone/pyrimethamine prophylaxis (59% vs 23%, p = 0.005). Overall, 95% of patients were treated with TMP-SMZ. In-hospital mortality (6% vs 10%, p = 0.57) and 3-month (13% vs 10%, p = 0.80) and 6-month (19% vs 16%, p = 0.75) mortality ratios were low and similar in both groups. There were only 3 relapses (6%) at 6 months in the group of patients with wild type genotypes (p = 0.37).

Conclusions:  Mutations in the DHPS gene were higher in the pre-HAART period and were associated with previous exposure to sulfa drugs. However, their presence did not worsen the prognosis of PCP. Response to TMP-SMZ was successful in most cases.

Keywords: P. jiroveci Pneumonia; DHPS mutations; outcome