Growth and Airborne Transmission of Cell-Sorted Life Cycle Stages of Pneumocystis carinii

Anna Martinez,El Moukhtar Aliouat,Emilie Fréalle,Marie C M Halliez,Nausicaa Gantois,Cécile-Marie Aliouat-Denis,Annie Standaert-Vitse,Eduardo Dei-Cas,Magali Chabé,Muriel Pottier,Anthony Pinon,Friedrich Frischknecht

doi:10.1371/journal.pone.0079958

Abstract

Pneumocystis organisms are airborne opportunistic pathogens that cannot be continuously grown in culture. Consequently, the follow-up of Pneumocystis stage-to-stage differentiation, the sequence of their multiplication processes as well as formal identification of the transmitted form have remained elusive. The successful high-speed cell sorting of trophic and cystic forms is paving the way for the elucidation of the complex Pneumocystis life cycle. The growth of each sorted Pneumocystis stage population was followed up independently both in nude rats and in vitro. In addition, by setting up a novel nude rat model, we attempted to delineate which cystic and/or trophic forms can be naturally aerially transmitted from host to host. The results showed that in axenic culture, cystic forms can differentiate into trophic forms, whereas trophic forms are unable to evolve into cystic forms. In contrast, nude rats inoculated with pure trophic forms are able to produce cystic forms and vice versa. Transmission experiments indicated that 12 h of contact between seeder and recipient nude rats was sufficient for cystic forms to be aerially transmitted. In conclusion, trophic- to cystic-form transition is a key step in the proliferation of Pneumocystis microfungi because the cystic forms (but not the trophic forms) can be transmitted by aerial route from host to host.

Highlights

Opportunistic fungal organisms, belonging to the Pneumocystis jirovecii species, are responsible for a severe interstitial lung disease, called Pneumocystis pneumonia (PcP), that can occur in immunocompromised patients and is fatal without effective treatment [1,2]
An attempt to further elucidate its complex life cycle was to physically separate P. carinii life cycle stages with a thin cell wall from those with a thick cell wall
Cultivation of pure trophic forms did not lead to a detectable de novo production of cystic forms, while a significant increase in the number of trophic forms occurring at day 2 attested to their dividing capacity (Figure 1B)

Summary

Introduction

Opportunistic fungal organisms, belonging to the Pneumocystis jirovecii species, are responsible for a severe interstitial lung disease, called Pneumocystis pneumonia (PcP), that can occur in immunocompromised patients and is fatal without effective treatment [1,2]. Studies of PcP in murine models have led to a better understanding of the pathogenesis and transmission of Pneumocystis organisms [4,5,6,7]. The life cycle of P. carinii is further dissected by independently following the growth kinetics of trophic and cystic forms both in axenic culture and in vivo after endotracheal infection of nude rats. To further determine the transmission form of PcP, a novel nude rat model of natural infection was established

Methods

Results

Conclusion