252. Development and Evaluation of a Novel MultiCode Real-Time PCR Assay for the Detection of Pneumocystis jirovecii in Bronchoalveolar Lavage Fluid and Induced Sputum

BACKGROUND: Pneumocystis jirovecii is a medically important fungal pathogen responsible for opportunistic infections in immunocompromised hosts with high morbidity and mortality. Compared with standard microscopy based assays, home-brew nucleic acid amplification tests (NAAT) have emerged as sensitive tools for the diagnosis of P. jirovecii pneumonia, but their sensitivities vary depending upon selected genetic targets. Recent studies suggest that the mitochondrial small subunit (mtSSU) is a better NAAT target given its higher copy number and stable expression in the disease process. We aimed to develop and evaluate a mtSSU-targeted MultiCode real-time PCR assay that incorporates a sample processing control (SPC) and enables detection of P. jirovecii in bronchoalveolar lavage fluid (BALF) and induced sputum. METHODS: Firstly, we compared manual DNA extraction using Zymo Quick DNA kit with automated extraction using the NucliSENS easyMAG system after sample pretreatment with either FastPrep mechanical grinding or vortex-based bead beating. We then determined the mouse hepatitis virus SPC (Luminex) spike-in amount, and optimized the PCR conditions on the ABI 7500 PCR system. A new Pneumocystis mtSSU run control was generated by cloning and transforming mtSSU gene into a genetically engineered E. coli strain, and quantified with a home-brew quantitative TaqMan PCR. Lastly, the performance characteristics of the MultiCode PCR assay were determined. RESULTS: Mechanical grinding of BALF or sputum before the easyMAG based extraction was better than the other extraction protocols as evidenced by lower C(T) of mtSSU or SPC. Diluted SPC added to samples before DNA extraction made its C(T) within 31–34. With the mtSSU run control, the limit of detection of the new assay was 80 copies/mL. No cross-reactivity was found with 9 respiratory viruses, 8 bacteria or 11 fungi. The assay has high reproducibility for three-day detection of the same sample aliquots for mtSSU (C(T): 30.0–30.3; CV%: 0.5–1.6) and SPC (C(T): 32.1–32.2; CV%: 0.8–2.4). CONCLUSION: We developed a novel MultiCode real-time PCR assay for detection of P. jirovecii in BALF and sputum, which demonstrated high analytical sensitivity, specificity and reproducibility and warrants further clinical validation. DISCLOSURES: All authors: No reported disclosures.