We read with interest the scientific letter from Pinos et al.1 on Lophomonas blattarum (LB) lung infection recently published in your journal.

In this study, the authors report 6 cases of lung infection allegedly caused by this multiflagellated protozoan that responded positively to treatment with metronidazole after unsuccessful empirical antibiotic therapy.

Bronchopulmonary infection by LB is quite rare and, although numerous cases have been described in the literature, it is unexpectedly common for this protozoan to be confused with bronchial epithelial cells or cell remains that retain only part of their cytoplasm and associated cilia and are capable of movement, a phenomenon known as ciliocytophthoria2.

Morphological criteria using various staining techniques have improved the identification of this protozoan3. Molecular biology methods have also recently contributed to deciphering their genetic sequence4.

LB are commensals found in their trophozoite form in the intestine of cockroaches5 and as cysts in the feces of these insects, making them resistant to adverse environmental conditions. It can be assumed that inhaling fecal particles containing protozoan cysts is the route of entry of the microorganism into the airways6. The favorable humidity and temperature conditions encountered in the respiratory tree allow the LB cysts to release their trophozoite forms.

LB infection often manifests as bronchopneumonia with productive cough, fever, and dyspnea that does not respond to standard antibiotic therapy and yields nonspecific radiological images.

Treatment with metronidazole appears to resolve most clinical syndromes, suggesting that a respiratory infection with consistent clinical symptoms that does not respond to conventional antibiotic therapy may be caused by LB. However, it is important to remember that metronidazole is effective against gram-negative and anaerobic germs, so cultures and sensitivity testing are essential.

The image from a left lower lobectomy specimen shared by the authors shows what they believe to be the presence of LB.

In our view, the image provided is more in line with a small row of ciliated epithelial cells. The criteria on which we base our premise are: a) the presence of a rounded nucleus in the basal position of the two cells on the left of the image; b) the existence of a clear terminal bar in the middle cell, and c) an arrangement of short, uniform, unidirectional cilia at the apical end.

We provide an image to help compare these morphological criteria (Fig. 1) in which the phenomenon of ciliocytophthoria can be seen on the left, with well preserved and oriented remains of cytoplasm and cilia anchored to the terminal bar. On the right of the cytoplasmic remains, we can see what could be the nucleus of the ciliated cell. The image on the right shows a pyriform LB with numerous flagellae, the longest in the center, in an irregular arrangement. No terminal bar is observed, but a small nucleus can be seen in the apical pole just below the flagellar insertion.

Fig. 1.

Cytological sputum smear. Left: Ciliocytophthoria phenomenon, and an accompanying polymorphonuclear leukocyte (Papanicolaou, 1000×). Right: Lophomonas blattarum. Bar scale 20 μm (Wheatley trichrome stain, 1000×).

(0.11MB).

Because this protozoan is easily confused with ciliated epithelial cells on direct microscopy of fresh samples, we recommend using specific staining techniques (Wheatley trichrome, Giemsa or Papanicolaou) to assist in identification. The current lack of an appropriate culture method for this parasite could be supplemented by molecular biology techniques.