On cilia, flagella, and pulmonary pseudoprotozoa.

Dear Editor,

We have read with interest the article published in your journal by Xue et al. [1] regarding a case report of bronchopulmonary infection by the multiflagellated protozoon Lophomonas blattarum (LB). After observing carefully the images showed by authors, we think that there may be a misidentification of detached ciliated bronchial cells as true LB. The figures for the fresh samples may reflect a ciliated cell as there is a clear terminal bar and short, regular unidirectional cilia inserted on the apical end (Fig. 1A). In the top right panel (Fig. 1B), a small cluster (2 or 3 elements) of ciliated bronchial cells may represent a “Creola body”, as there is irregularity of the cytoplasm contours and a round nucleus. This irregular cytoplasmic contour could resemble an ameboid movement, which is different from the flagellar-related motility of LB. Moreover, short regular and unidirectional cilia can be also observed.

In the Wright-Giemsa stained images, some cells in the center (Fig. 1C) have a columnar shape with a visible short tail behind the nucleus and short, unidirectional cilia at the apical end. Finally, in Fig. 1D, which may represent a pseudoparasite, the cytoplasmic projections are irregular and very thick, resembling detached ciliary tufts which we would argue are different to those observed in LB.

Although cilia and flagella, at an ultrastructural level, are virtually indistinguishable, they differ principally in their length (cilia are much shorter than flagella), mode of beat, and function [2]. In the respiratory epithelium, cilia are responsible for the displacement of the mucus to the throat. In protozoa, flagella are responsible for its locomotion and for the capture of particles for ingestion.

LB is a Parabasalid that has been recognized under light microscopy in respiratory secretions [3,4] and considered as a bronchopulmonary pathogen [5]. Nevertheless, the possibility of misinterpretation between bronchial ciliated cells and true multiflagellated protozoa [6] is a possibility in this case.