COMPARISON OF PNEUMOCYSTIS-CARINII DETECTION BY TOLUIDINE BLUE-O STAINING, DIRECT IMMUNOFLUORESCENCE AND DNA AMPLIFICATION IN SPUTUM SPECIMENS FROM HIV-POSITIVE PATIENTS

Pneumocystis carinii pneumonia (PCP) is the commonest opportunistic in fection in AIDS patients. By using the polymerase chain reaction (PCR) , specific DNA sequences can be amplified and used in diagnosis of inf ections such as PCP where the causative pathogen is both difficult to grow and present in low numbers.Twenty HIV positive patients were inve stigated for PCP. Twenty sputa (15 induced and 5 expectorated) had tol uidine blue O staining, direct immunofluorescence and PCR performed fo r Pneumocystis carinii in a blinded fashion. PCR was performed using p rimers pAZ102-E 5' GATGGCTGTTTCAAGCCCA 3' and pAZ102-H 5' GTGTACGTTGCA AAGTACTC 3' from the gene coding for Pneumocystis carinii mitochondria l ribosomal RNA with a specific 346 base-pair sequence being amplified from positive specimens. Ten of the patients had Pneumocystis carinii shown by conventional tests and PCR. Another 3 patients were positive only by PCR, all had evidence of infection with Pneumocystis carinii; the first was positive by subsequent conventional stains, the second was treated for bacterial bronchitis but had a non-resolving chest inf ection with PCP found on postmortem after 4 mths, the third had a typi cal interstitial infiltrate on CXR and responded to empiric PCP treatm ent. PCR is more sensitive than toluidine blue O staining and direct i mmunofluorescence in detecting Pneumocystis carinii in sputum for HIV patients and may become the diagnostic method of choice for PCP.