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Parabasalids in Respiratory Secretions and Lung DiseasesParabasalids in Respiratory Secretions FREE TO VIEW

Rafael Martínez-Girón, MD, PhD
Author and Funding Information

From the Protozoal Respiratory Pathology Research Unit, INCLÍNICA Foundation.

CORRESPONDENCE TO: Rafael Martínez-Girón, MD, PhD, INCLÍNICA Foundation, Calvo Sotelo, 16. 33007-Oviedo, Spain; e-mail: rmartinezgiron@hotmail.com


FINANCIAL/NONFINANCIAL DISCLOSURES: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(3):e111-e112. doi:10.1378/chest.14-2465
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To the Editor:

I read with great interest in a recent issue of CHEST (April 2014) the article by Khemasuwan et al,1 who provided a comprehensive review of helminthic and protozoal infestations of the respiratory system. Regarding the protozoal infestations, however, I think the authors have omitted a group of flagellated protists, the parabasalids, some of which are well-known protozoa and others of which are considered as uncommon emerging pathogens.2

Parabasalids, which belong to the Excavata supergroup and the Metamonada phylum, are a group of anaerobic multiflagellated protozoa. Parabasalids exhibit a number of unique morphologic features such as the parabasal apparatus (similar to the Golgi apparatus) and the hydrogenosomes, a membrane-enclosed organelle adapted to the anaerobic environment.3 Phylogenetically, the parabasalids can be classified into six genetic groups. Only a number of families and/or species have been associated with respiratory diseases, such as Trichomonadidae (Trichomonas vaginalis and Trichomonas tenax), Tritrichomonadidae (Tritrichomonas foetus), Lophomonadidae (Lophomonas blattarum), and Holomastigotoididae (Spirotrichonympha).

Some protozoa such as L blattarum and Spirotrichonympha live in anaerobic environments. While they are mainly endosymbionts living in the hindgut of certain insects such as termites and cockroaches, L blattarum and Spirotrichonympha have also been observed in human respiratory secretions under light microscopy.4 An interesting question is whether these parabasalids inhabiting in the intestines of termites and cockroaches are associated with lung diseases. Through their feces, termites and cockroaches can eject the parabasalids into unfavorable environmental conditions, in which the parabasalids can form protective cysts. The protozoal cysts may be easily spread through the air or by soil, and inhalation of protozoal cysts by humans is possible. Under favorable conditions in the respiratory system, especially anaerobic status caused by hypoxic inspissated mucopurulent secretions, flagellate protozoa may be released from the cysts through excystation (Fig 1). Based on the interaction between certain protozoal proteases and the respiratory epithelial cells, a number of mechanisms for how protozoa cause lung diseases have been proposed. Proteolytic enzymes secreted by protozoa can destroy bonds such as the tight junctions between bronchial epithelial cells, causing structural damage of the respiratory epithelium. In addition, synthesis of protozoal proteases may activate the protease-activated receptors, causing airway inflammation through a number of inflammatory mediators such as IL-6 and IL-8. More interestingly, these uncommon multiflagellated protozoa were identified in respiratory secretions and were associated with unusual inflammatory responses characterized by a marked increase of monocytes rather than other types of leukocytes.5 In summary, the role of pathogenic parabasalids in respiratory infections should be recognized and highlighted.

Figure Jump LinkFigure 1 –  Microphotographs obtained from a sputum smear of a patient with asthma. A, Two cystic forms can be observed where a tuft of thin and irregular flagella are protruding outward (black arrow). At the bottom (right corner) it is possible to observe a ciliated bronchial cell. B, The black arrow points to a multiflagellated protozoon. Note the irregular flagella and the absence of a terminal bar (Wheatley trichrome; scale bar = 20 μm).Grahic Jump Location

References

Khemasuwan D, Farver CF, Mehta AC. Parasites of the air passages. Chest. 2014;145(4):883-895. [CrossRef] [PubMed]
 
Martínez-Girón R. Protozoal infections.. In:Barrios R, Haque AK., eds. Parasitic Diseases of the Lungs. Heilderberg, NY: Springer-Verlag; 2013:47-68.
 
Cepicka I, Hampl V, Kulda J. Critical taxonomic revision of parabasalids with description of one new genus and three new species. Protist. 2010;161(3):400-433. [CrossRef] [PubMed]
 
Martinez-Girón R, van Woerden HC. Lophomonas blattarum and bronchopulmonary disease. J Med Microbiol. 2013;62(pt 11):1641-1648. [CrossRef] [PubMed]
 
Martínez-Girón R, van Woerden HC. Clinical and immunological characteristics associated with the presence of protozoa in sputum smears. Diagn Cytopathol. 2013;41(1):22-27. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  Microphotographs obtained from a sputum smear of a patient with asthma. A, Two cystic forms can be observed where a tuft of thin and irregular flagella are protruding outward (black arrow). At the bottom (right corner) it is possible to observe a ciliated bronchial cell. B, The black arrow points to a multiflagellated protozoon. Note the irregular flagella and the absence of a terminal bar (Wheatley trichrome; scale bar = 20 μm).Grahic Jump Location

Tables

References

Khemasuwan D, Farver CF, Mehta AC. Parasites of the air passages. Chest. 2014;145(4):883-895. [CrossRef] [PubMed]
 
Martínez-Girón R. Protozoal infections.. In:Barrios R, Haque AK., eds. Parasitic Diseases of the Lungs. Heilderberg, NY: Springer-Verlag; 2013:47-68.
 
Cepicka I, Hampl V, Kulda J. Critical taxonomic revision of parabasalids with description of one new genus and three new species. Protist. 2010;161(3):400-433. [CrossRef] [PubMed]
 
Martinez-Girón R, van Woerden HC. Lophomonas blattarum and bronchopulmonary disease. J Med Microbiol. 2013;62(pt 11):1641-1648. [CrossRef] [PubMed]
 
Martínez-Girón R, van Woerden HC. Clinical and immunological characteristics associated with the presence of protozoa in sputum smears. Diagn Cytopathol. 2013;41(1):22-27. [CrossRef] [PubMed]
 
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