Comparison of galactomannan detection, PCR-enzyme-linked immunosorbent assay, and real-time PCR for diagnosis of invasive aspergillosis in a neutropenic rat model and effect of caspofungin acetate.
The performance of different in vitro diagnostic tests for the diagnosis of invasive aspergillosis (IA) was investigated in a transiently neutropenic rat model. Rats were immunosuppressed with cyclophosphamide and then inoculated intravenously with 1.5 x 10(4) CFU Aspergillus fumigatus spores. Animals were then either treated with caspofungin acetate, 1 mg/kg/day for 7 days, or not treated. PCR-enzyme-linked immunosorbent assay (ELISA), real-time PCR, and galactomannan (GM) detection were performed on postmortem blood samples, along with culture of liver, lung, and kidney homogenate. Caspofungin-treated animals showed a decrease in residual tissue burden of A. fumigatus from organ homogenate compared to untreated animals (P < 0.002). PCR-ELISA returned positive results for 11/17 animals treated with antifungal agents and for 10/17 untreated animals. Galactomannan was positive in 8/17 caspofungin-treated animals and 4/17 untreated animals. Real-time PCR was positive in 2/17 treated and 3/17 untreated animals. This study demonstrates that PCR-ELISA is a more sensitive test than either GM detection (P = 0.052) or real-time PCR (P < 0.01) for diagnosis of IA but that any of the three tests may return false-negative results in cases of histologically proven disease. Galactomannan indices from animals treated with antifungal agents showed a trend (P = 0.1) towards higher levels than those of untreated animals, but no effect was observed with PCR-ELISA indices (P = 0.29). GM detection, as previously described, may be enhanced by the administration of caspofungin, but PCR-ELISA appears not to be affected in the same way. We conclude that PCR-ELISA is a more sensitive and reliable method for laboratory diagnosis of IA.
Scotter
Jennifer M
JM
Microbiology Unit, Canterbury Health Laboratories, Christchurch, New Zealand.
Chambers
Stephen T
ST
D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D001228:Aspergillosis / Q000175:diagnosis* / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D000077336:Caspofungin; D004195:Disease Models, Animal; D054714:Echinocandins; D004797:Enzyme-Linked Immunosorbent Assay; D005690:Galactose / Q000031:analogs & derivatives; D055666:Lipopeptides; D008107:Liver Diseases / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008351:Mannans; D009503:Neutropenia / Q000175:diagnosis* / Q000382:microbiology; D010456:Peptides, Cyclic / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D008351:Mannans; D010456:Peptides, Cyclic; C012990:galactomannan; D000077336:Caspofungin; D005690:Galactose