Detection of Pneumocystis DNA in samples from patients suspected of bacterial pneumonia--a case-control study.
BACKGROUND
Pneumocystis jiroveci (formerly known as P. carinii f.sp. hominis) is an opportunistic fungus that causes Pneumocystis pneumonia (PCP) in immunocompromised individuals. Pneumocystis jiroveci can be detected by polymerase chain reaction (PCR). To investigate the clinical importance of a positive Pneumocystis-PCR among HIV-uninfected patients suspected of bacterial pneumonia, a retrospective matched case-control study was conducted.


METHODS
Respiratory samples from 367 patients suspected of bacterial pneumonia were analysed by PCR amplification of Pneumocystis jiroveci. To compare clinical factors associated with carriage of P. jiroveci, a case-control study was done. For each PCR-positive case, four PCR-negative controls, randomly chosen from the PCR-negative patients, were matched on sex and date of birth.


RESULTS
Pneumocystis-DNA was detected in 16 (4.4%) of patients. The median age for PCR-positive patients was higher than PCR-negative patients (74 vs. 62 years, p = 0.011). PCR-positive cases had a higher rate of chronic or severe concomitant illness (15 (94%)) than controls (32 (50%)) (p = 0.004). Twelve (75%) of the 16 PCR positive patients had received corticosteroids, compared to 8 (13%) of the 64 PCR-negative controls (p < 0.001). Detection of Pneumocystis-DNA was associated with a worse prognosis: seven (44%) of patients with positive PCR died within one month compared to nine (14%) of the controls (p = 0.01). None of the nine PCR-positive patients who survived had developed PCP at one year of follow-up.


CONCLUSIONS
Our data suggest that carriage of Pneumocystis jiroveci is associated with old age, concurrent disease and steroid treatment. PCR detection of P. jiroveci has low specificity for diagnosing PCP among patients without established immunodeficiency. Whether overt infection is involved in the poorer prognosis or merely reflects sub-clinical carriage is not clear. Further studies of P. jiroveci in patients receiving systemic treatment with corticosteroids are warranted.
Helweg-Larsen
Jannik
J
Copenhagen HIV Programme, Department of Infectious Diseases, Copenhagen, Denmark. jhl@cphiv.dk
Jensen
Jørgen Skov
JS
Dohn
Birthe
B
Benfield
Thomas L
TL
Lundgren
Bettina
B
D000367:Age Factors; D000368:Aged; D001203:Ascomycota / Q000235:genetics / Q000302:isolation & purification*; D016022:Case-Control Studies; D004271:DNA, Fungal / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000382:microbiology*; D013256:Steroids / Q000009:adverse effects
D004271:DNA, Fungal; D013256:Steroids