Performance of a molecular viability assay for the diagnosis of Pneumocystis pneumonia in HIV-infected patients.

Pneumocystis pneumonia (PCP), caused by infection with Pneumocystis jirovecii, remains an important opportunistic infection in humans. A reverse transcriptase polymerase chain reaction assay has been shown to specifically detect viable P. jirovecii organisms. In the current study, we evaluated this assay on different types of respiratory samples. The assay had a diagnostic sensitivity of 100% and a specificity of 86% when applied to bronchoalveolar lavage samples. The assay's performance declined when applied to less invasive induced sputum and oropharyngeal wash (OPW) samples. The sensitivity, when applied to OPWs, was improved by examining multiple sequential OPW samples and was affected by clinical sampling parameters that could increase or decrease the number of potential organisms in the oropharynx. When used in conjunction with an optimized clinical sampling protocol, this assay may become a useful tool for detecting and monitoring P. jirovecii in minimally invasive clinical samples.

Severity and outcome of HIV-associated Pneumocystis pneumonia containing Pneumocystis jirovecii dihydropteroate synthase gene mutations.

BACKGROUND: The impact of Pneumocystis jirovecii (formerly P. carinii) dihydropteroate synthase (DHPS) gene mutations on morbidity and mortality of Pneumocystis pneumonia (PCP) in HIV-positive patients is unclear. OBJECTIVE: To determine whether severity and outcome of HIV-associated PCP differs according to DHPS genotype. SETTING: A prospective, observational study in a university-affiliated county hospital. PATIENTS: The study included 197 patients with 215 microscopically confirmed PCP episodes and successfully sequenced DHPS genotypes; 175 (81%) episodes displayed mutant genotypes. MAIN OUTCOME MEASURE: All-cause mortality within 60 days. RESULTS: The majority of patients (86%) with PCP containing Pneumocystis DHPS mutations survived. Although severity of PCP was comparable, there was a trend for more patients with mutant genotypes than patients with wild-type to require mechanical ventilation (14.3% versus 2.5%; P = 0.056) and to die (14.3% versus 7.5%, P = 0.31). Independent predictors of mortality at baseline were low serum albumin levels [odds ratio (OR), 4.62; 95% confidence interval (CI), 1.63-13.1; P = 0.004] and requiring intensive care within 72 h of hospitalization (OR, 5.06; 95% CI, 1.43-18.0; P = 0.012). CONCLUSION: The majority of HIV-infected patients with PCP containing mutant Pneumocystis DHPS genotypes survived. Mortality was related primarily to the underlying severity of illness. However, a trend towards increased mortality in episodes of PCP containing mutant DHPS genotypes was observed and this warrants further study.

Antibody response to Pneumocystis jirovecii major surface glycoprotein.

We conducted a prospective pilot study of the serologic responses to overlapping recombinant fragments of the Pneumocystis jirovecii major surface glycoprotein (Msg) in HIV-infected patients with pneumonia due to P. jirovecii and other causes. Similar baseline geometric mean antibody levels to the fragments measured by an ELISA were found in both groups. Serum antibodies to MsgC in P. jirovecii patients rose to a peak level 3-4 weeks (p<0.001) after recovery from pneumocystosis; baseline CD4+ count > or =50 cells/microL and first episode of pneumocystosis were the principal host factors associated with this rise (both p<0.001). Thus, MsgC shows promise as a serologic reagent and should be tested further in clinical and epidemiologic studies.