Date of Completion

Spring 5-1-2026

Thesis Advisor(s)

Angela LaRue

Honors Major

Diagnostic Genetic Sciences

Disciplines

Bacterial Infections and Mycoses | Diagnosis | Fungi | Infectious Disease | Laboratory Medicine | Medical Microbiology | Medical Molecular Biology | Molecular Genetics | Pathogenic Microbiology | Pathology

Abstract

Pneumocystis jirovecii is an opportunistic, host-obligate fungal pathogen responsible for causing P. jirovecii pneumonia (PJP) in humans. PJP is treated with trimethoprim-sulfamethoxazole (TMP-SMX), a strong broad-spectrum antibiotic that carries risk of renal and hepatotoxicity. Therefore, rapid diagnosis or exclusion of PJP is crucial to ensure PJP-positive patients receive effective treatment and PJP-negative patients avoid unnecessary antibiotics. Unlike most microorganisms, P. jirovecii cannot be cultured, presenting complications for the typical methods of diagnosing fungal pathogens. Historically, the gold standard for diagnosis was direct microscopic examination with stains such as methenamine silver and calcofluor white, but this diagnostic technique requires highly skilled laboratory professionals and lacks high sensitivity. Recently, PJP testing has shifted toward molecular assays, namely real-time polymerase chain reaction (PCR) due to its higher sensitivity and definitive results. Currently, all PJP testing at Dartmouth Health (DH) is performed by an external reference laboratory, lengthening the turn-around-time of these critical results. The DiaSorin LIAISON MDX is a real-time PCR system that supports the use of analyte specific reagents (ASRs) for the detection of a specific organism, such as P. jirovecii, using a targeted primer pair for the mitochondrial large subunit ribosomal RNA gene (mtLSU rRNA). In this study, this laboratory developed test (LDT) was validated, confirming its high sensitivity, specificity, and reproducibility across samples of varying quality. The validation of this assay will allow PJP testing to be performed in-house, providing quality results and a quick turn-around time for DH patients.

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