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PCR Fluorescent Probe-based Detection of Aspergillus Spp., Cryptococcus neoformans, and Pneumocystis jirovecii
Wenbi Zou1, Meiyan Liao1, Siqin Liao1
1Clinical Laboratory, Foshan Sanshui District People's Hospital.
Abstract:
This protocol describes a standardized procedure for the qualitative detection of Aspergillus spp., Cryptococcus neoformans, and Pneumocystis jirovecii in clinical sputum samples using a PCR fluorescent probe-based nucleic acid detection kit. The procedure involves clinical sample collection, alkaline liquefaction pretreatment, automated nucleic acid extraction, and multiplex real‑time PCR detection. Aspergillus spp., C. neoformans, and P. jirovecii are detected using target‑specific fluorescent probes (FAM, VIC, and CY5 channels, respectively), with an internal control (ROX channel) integrated for quality assurance. Assay validity and sample result interpretation are based on defined cycle threshold (Ct) cut-off values. A positive control must exhibit S-shaped amplification curves with Ct ≤ 33.7 in all channels, while the negative control must show no amplification. For clinical samples, a Ct value ≤ 33.7 in the FAM channel indicates positivity for Aspergillus spp., and a Ct value ≤ 36 in the VIC or CY5 channel indicates positivity for C. neoformans or P. jirovecii, respectively.
Insights
This study presents a standardized PCR method for detecting Aspergillus, Cryptococcus neoformans, and Pneumocystis jirovecii in sputum. The assay uses fluorescent probes for accurate and reliable qualitative detection of these fungal and yeast pathogens.
Area of Science:
- Medical Microbiology
- Molecular Diagnostics
Background:
- Invasive fungal infections caused by Aspergillus spp., Cryptococcus neoformans, and Pneumocystis jirovecii pose significant clinical challenges.
- Accurate and rapid detection of these pathogens in respiratory samples is crucial for timely diagnosis and treatment.
Purpose of the Study:
- To describe a standardized protocol for the qualitative detection of Aspergillus spp., C. neoformans, and P. jirovecii in clinical sputum samples.
- To validate a multiplex real-time PCR assay utilizing fluorescent probe-based detection.
Main Methods:
- The protocol involves sputum sample collection, alkaline liquefaction pretreatment, and automated nucleic acid extraction.
- Multiplex real-time PCR with target-specific fluorescent probes (FAM, VIC, CY5) and an internal control (ROX) was employed.
- Assay validity and interpretation relied on defined cycle threshold (Ct) cut-off values for positive and negative controls and clinical samples.
Main Results:
- Positive controls showed S-shaped amplification curves with Ct ≤ 33.7 in all channels.
- Negative controls demonstrated no amplification, confirming assay specificity.
- Clinical samples with Ct values ≤ 33.7 (FAM), ≤ 36 (VIC), or ≤ 36 (CY5) were interpreted as positive for Aspergillus spp., C. neoformans, and P. jirovecii, respectively.
Conclusions:
- The described protocol provides a standardized and reliable method for the qualitative detection of Aspergillus spp., C. neoformans, and P. jirovecii in sputum.
- This multiplex real-time PCR assay offers an efficient tool for diagnosing infections caused by these opportunistic pathogens.
