Microbiologie médicale et diagnostic

Diagnosis of Pneumocystis jirovecii Pneumonia by Real Time PCR: An Analysis of 10 Clinical Cases

Abstract

Baccouchi Nawel, Mtibaa Latifa, Souid Hana, Mehiri Emna, Slim Leila and Jemli Boutheina

Introduction: Pneumocystis jirovecii Pneumonia (PCP) is a life-threatening disease in immunocompromised patients. The aim of this work is to demonstrate the contribution of molecular biology in diagnosis compared to conventional methods and we propose an adapted cut-off value for differentiating Pneumocystis colonization from infection using real-time PCR.

Methodology: This was a prospective study enrolled from April 2015 to December 2018 at the Laboratory of parasitology of Military Hospital of Tunis. All pulmonary secretions samples were analyzed using: May-Grunwald-Giemsa (MGG) and Gomori Grocott Modified MUSTO Coloring Technology (GG). Optimization of conventional PCR and real-time PCR were accomplished.

Results: During the study period, we collected 200 samples. The prevalence of the disease was 5% (10/200). MGG coloring didn’t discern vegetative forms of Pneumocystis jirovecii for all samples. Cysts were visualized by GG coloring for seven samples. Conventional PCR and Realtime PCR were positives for 10 samples with quantity of DNA going from one copy to 10⁴ copies per milliliter.

Conclusion: Molecular biology is more sensitive than techniques of coloring. Currently real-time PCR gives at the same time a quantitative and qualitative approach with a threshold of detection very low which allows differentiating between a simple colonization and an infestation.