ABSTRACT
Diagnosis of invasive pulmonary aspergillosis (IPA) remains a major challenge to clinical microbiology laboratories. We developed rapid and sensitive quantitative PCR (qPCR) assays for genus- and species-specific identification of Aspergillus infections by use of TaqMan technology. In order to validate these assays and understand their potential diagnostic utility, we then performed a blinded study of bronchoalveolar lavage (BAL) fluid specimens from well-characterized models of IPA with the four medically important species. A set of real-time qPCR primers and probes was developed by utilizing unique ITS1 regions for genus- and species-specific detection of the four most common medically important Aspergillus species (Aspergillus fumigatus, A. flavus, A. niger, and A. terreus). Pan-Aspergillus and species-specific qPCRs with BAL fluid were more sensitive than culture for detection of IPA caused by A. fumigatus in untreated (P < 0.0007) and treated (P ≤ 0.008) animals, respectively. For infections caused by A. terreus and A. niger, culture and PCR amplification from BAL fluid yielded similar sensitivities for untreated and treated animals. Pan-Aspergillus PCR was more sensitive than culture for detection of A. flavus in treated animals (P = 0.002). BAL fluid pan-Aspergillus and species-specific PCRs were comparable in sensitivity to BAL fluid galactomannan (GM) assay. The copy numbers from the qPCR assays correlated with quantitative cultures to determine the pulmonary residual fungal burdens in lung tissue. Pan-Aspergillus and species-specific qPCR assays may improve the rapid and accurate identification of IPA in immunocompromised patients.
Subject(s)
Aspergillus/isolation & purification , Invasive Pulmonary Aspergillosis/diagnosis , Invasive Pulmonary Aspergillosis/microbiology , Molecular Diagnostic Techniques/methods , Mycology/methods , Real-Time Polymerase Chain Reaction/methods , Animals , Aspergillus/genetics , Bacterial Load , Bronchoalveolar Lavage Fluid/microbiology , DNA Primers/genetics , DNA, Ribosomal Spacer/genetics , Disease Models, Animal , Female , Oligonucleotide Probes/genetics , Rabbits , Sensitivity and Specificity , Time FactorsABSTRACT
BACKGROUND: Early diagnosis and treatment of invasive pulmonary aspergillosis (IPA) improves outcome. METHODS: We compared the performance of publicly available pan-Aspergillus, Aspergillus fumigatus-, and Aspergillus terreus-specific real-time polymerase chain reaction (PCR) assays with the Platelia galactomannan (GM) assay in 150 bronchoalveolar lavage (BAL) samples from lung transplant recipients (16 proven/probable IPA, 26 Aspergillus colonization, 11 non-Aspergillus mold colonization, and 97 negative controls). RESULTS: The sensitivity and specificity of pan-Aspergillus PCR (optimal quantification cycle [Cq], ≤35.0 by receiver operating characteristic analysis) and GM (≥.5) for diagnosing IPA were 100% (95% confidence interval, 79%-100%) and 88% (79%-92%), and 93% (68%-100%) and 89% (82%-93%), respectively. The sensitivity and specificity of A. fumigatus-specific PCR were 85% (55%-89%) and 96% (91%-98%), respectively. A. terreus-specific PCR was positive for the 1 patient with IPA due to this species; specificity was 99% (148 of 149 samples). Aspergillus PCR identified 1 patient with IPA not diagnosed by GM. For BAL samples associated with Aspergillus colonization, the specificity of GM (92%) was higher than that of pan-Aspergillus PCR (50%; P = .003). Among negative control samples, the specificity of pan-Aspergillus PCR (97%) was higher than that of BAL GM (88%; P = .03). Positive results for both BAL PCR and GM testing improved the specificity to 97% with minimal detriment to sensitivity (93%). CONCLUSIONS: A recently developed pan-Aspergillus PCR assay and GM testing of BAL fluid may facilitate the diagnosis of IPA after lung transplantation. A. fumigatus- and A. terreus-specific real-time PCR assays may be useful in rapidly identifying the most common cause of IPA and a species that is intrinsically resistant to amphotericin B, respectively.
