Detection of a molecular biomarker for zygomycetes by quantitative PCR assays of plasma, bronchoalveolar lavage, and lung tissue in a rabbit model of experimental pulmonary zygomycosis.
We developed two real-time quantitative PCR (qPCR) assays, targeting the 28S rRNA gene, for the diagnosis of zygomycosis caused by the most common, clinically significant Zygomycetes. The amplicons of the first qPCR assay (qPCR-1) from Rhizopus, Mucor, and Rhizomucor species were distinguished through melt curve analysis. The second qPCR assay (qPCR-2) detected Cunninghamella species using a different primer/probe set. For both assays, the analytic sensitivity for the detection of hyphal elements from germinating sporangiospores in bronchoalveolar lavage (BAL) fluid and lung tissue homogenates from rabbits was 1 to 10 sporangiospores/ml. Four unique and clinically applicable models of invasive pulmonary zygomycosis served as surrogates of human infections, facilitating the validation of these assays for potential diagnostic utility. For qPCR-1, 5 of 98 infarcted lung specimens were positive by qPCR and negative by quantitative culture (qCx). None were qCx positive only. Among 23 BAL fluid samples, all were positive by qPCR, while 22 were positive by qCx. qPCR-1 detected Rhizopus and Mucor DNA in 20 (39%) of 51 serial plasma samples as early as day 1 postinoculation. Similar properties were observed for qPCR-2, which showed greater sensitivity than qCx for BAL fluid (100% versus 67%; P = 0.04; n = 15). The assay detected Cunninghamella DNA in 18 (58%) of 31 serial plasma samples as early as day 1 postinoculation. These qPCR assays are sensitive and specific for the detection of Rhizopus, Mucor, Rhizomucor, and Cunninghamella species and can be used for the study and detection of infections caused by these life-threatening pathogens.
Kasai
Miki
M
Immunocompromised Host Section, Pediatric Oncology Branch, National Cancer Institute, Building 10-CRC, Room 1-5740, Bethesda, MD 20892, USA.
Harrington
Susan M
SM
Francesconi
Andrea
A
Petraitis
Vidmantas
V
Petraitiene
Ruta
R
Beveridge
Mara G
MG
Knudsen
Tena
T
Milanovich
Jeffery
J
Cotton
Margaret P
MP
Hughes
Johanna
J
Schaufele
Robert L
RL
Sein
Tin
T
Bacher
John
J
Murray
Patrick R
PR
Kontoyiannis
Dimitrios P
DP
Walsh
Thomas J
TJ
D000818:Animals; D015415:Biomarkers; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology*; D005260:Female; D005658:Fungi / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D008168:Lung / Q000382:microbiology*; D008172:Lung Diseases, Fungal / Q000175:diagnosis*; D010949:Plasma / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012331:RNA, Fungal / Q000235:genetics; D012339:RNA, Ribosomal, 28S / Q000235:genetics; D011817:Rabbits; D012680:Sensitivity and Specificity; D020096:Zygomycosis / Q000175:diagnosis*
D015415:Biomarkers; D012331:RNA, Fungal; D012339:RNA, Ribosomal, 28S