Application of the polymerase chain reaction to the diagnosis of candidosis by amplification of an HSP 90 gene fragment.

A 317-base pair (bp) fragment of the Candida albicans heat shock protein 90 (HSP 90) gene was amplified by the polymerase chain reaction (PCR) for detection of C. albicans DNA in clinical specimens. One hundred specimens were examined including swabs (39), urines (36), peritoneal fluid (9), pus (8) and blood or serum (8): 23% gave positive results with routine culture, 31% with extended broth culture and 37% with PCR. The amplified product was identified by hybridisation with a radiolabelled internal probe and their restriction enzyme digest patterns (SspI, HaeIII, EcoRI, RsaI and XhoI), which could be predicted from the known sequence of HSP 90. C. albicans DNA gave the characteristic 317-bp band and specifically hybridised with restriction enzyme-digested candidal DNA. DNA from other sources intermittently gave multiple faint bands especially in the presence of high concentrations of DNA, but these could be readily distinguished. The method was sensitive to 50 pg of DNA (5 pg with radiolabelled probing) and 100 cfu of C. albicans.