Detection of Aspergillus fumigatus by quantitative polymerase chain reaction in air samples impacted on low-melt agar.
BACKGROUND
The standard procedure for routine environmental sampling for the prevention of invasive aspergillosis outbreaks is culturing of Aspergillus fumigatus after impaction of air. Time to results is usually 7 days. A preliminary study was carried out to compare the time to results and sensitivity of culturing and quantitative polymerase chain reaction (QPCR) in the detection of airborne A fumigatus.


METHODS
Fungal DNA was extracted from 43 samples of impacted low-melt agar by a 3-step extraction method and amplified by QPCR. Identification was made using a specific A fumigatus probe.


RESULTS
With QPCR, 19 of the 43 samples were positive for A fumigatus; with culturing, 7 of these 19 samples were positive, and 12 were negative. The cycle threshold (Ct) values for the 12 culture-negative samples were between 39 and 43 cycles, and the Ct values for 6 of the 7 culture-positive samples were <38 cycles, suggesting that the amount of DNA detected by QPCR was higher in the presence of viable conidia.


CONCLUSIONS
QPCR detection of airborne A fumigatus in impacted low-melt agar significantly reduces the period of time between sample collection and results (48 hours), suggesting that this new approach can be beneficial for routine environmental sampling.
Bellanger
Anne-Pauline
AP
Department of Parasitology-Mycology, University Hospital Jean Minjoz, Besançon, France. apbellanger@chu-besancon.fr
Reboux
Gabriel
G
Murat
Jean-Benjamin
JB
Bex
Valerie
V
Millon
Laurence
L
D000362:Agar; D000391:Air Microbiology; D001232:Aspergillus fumigatus / Q000302:isolation & purification*; D001431:Bacteriological Techniques / Q000379:methods*; D003470:Culture Media / Q000737:chemistry*; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013997:Time Factors
D003470:Culture Media; D000362:Agar