Significance of Aspergillus fumigatus rDNA detected by polymerase chain reaction in diagnosis of pulmonary aspergillosis

Abstract

We have studied the clinical significance of Aspergillus fumigatus rDNA detected by polymerase chain reaction (PCR) for diagnosing aspergillosis. For this purpose, a specific and sensitive PCR assay was developed to amplify the 26S rDNA/intergenic spacer region of A. fumigatus. Control experiments showed that the set of primers used was capable of amplifying A. fumigatus DNA specifically and that the DNA amount of detection limit was 1 pg. Eighteen samples from 13 patients with aspergillosis and 36 samples from 24 patients without aspergillosis were tested by means of PCR, culture, latex agglutination test for galactomannan antigen and double gel diffusion assay for precipitation of antibodies to A. fumigatus. PCR showed positive test in 8 among 13 patients with pulmonary aspergillosis. On the other hand, culture of samples detected A. fumigatus in 6 patients. Galactomannan antigen and antibodies specific to A. fumigatus were positive in 2 and 6 patients respectively. These results indicated that PCR is the most sensitive among these 4 methods. Five patients showed negative PCR test despite of having pulmonary aspergillosis. Two of these patients were proved to have aspergillosis caused by A. flavus and A. niger. On the other hand, galactomannan antigen and A. fumigatus antibody were positive in one and 2 patients, respectively. PCR was positive in 2 out of 24 patients diagnosed as not having aspergillosis: one patient had diagnosis of acute bronchitis, but she showed positive culture of A. fumigatus. The other patient had diagnosis of lobar pneumonia, because any pathogens were not detected before PCR assay. The PCR assay we developed is a useful method for diagnosing aspergillosis caused by A. fumigatus as compared with other conventional methods.