Rare infection diagnosed by cytology in a bronchoalveolar lavage specimen in a patient with massive pulmonary hemorrhage

A 62-year-old male presented with hemoptysis. At bronchoscopy, the pulmonologist could not visualize the bronchial tree due to massive pulmonary hemorrhage. Bronchial alveolar lavage fluid was sent to the microbiology laboratory for examination. Wet prep revealed numerous, large ciliated organisms with rapid spiraling movement. Multiple videos captured from the wet prep show a large organism with continuous movement rotating around itself and moving rapidly. Various sizes of organisms are noted, some quite large in size.

Q1. On reviewing the video (Video 1), what is your interpretation?

1. Entamoeba histolytica

2. Trophozoite of lung fluke

3. Cyst of Balantidium coli

4. Trophozoite of Balantidium coli.

The correct answer is

Q1-D. Trophozoite of Balantidium coli.

Balantidium coli infection occurs throughout the world,^[1] but is most common in tropical countries. It is a zoonotic infection,^[1] with pigs being the most common cause of human infection. Humans, like pigs, are often asymptomatic.^[2] The most common manifestation in symptomatic patients is diarrhea. The infection can mimic acute colitis,^[2] with abdominal pain, nausea, vomiting, diarrhea, and weight loss. Extracolonic manifestations with pulmonary hemorrhage^[3,4] and involvement of the urinary system are rare.^[2] The infection is easy to treat with tetracycline or metronidazole. Doxycycline has also been employed.^[5] Drug resistance has not been reported.^[1]

B. coli is the largest protozoan ciliate parasite that infects humans.^[1] Humans get infected when B. coli cysts from the pig feces contaminate water and food.^[5] Once ingested, the cysts form trophozoites which are ciliated protozoans. The trophozoites, in turn, form cysts that are excreted through the stool, and the disease is thus transmitted. Organic farmers who use aerosolized pig manure can get infected, and inhalation of the cysts can result in pulmonary cavities and hemorrhage.^[5] Pulmonary disease can occur without an enteric infection. The trophozoites can be of varying sizes, with some trophozoites as large as 200 microns.^[1] B. coli does not stain well on permanent smears,^[6] and the diagnosis is best made by examining wet preps.^[6] On unstained wet preps, the trophozoite is recognized by its large size, cilia, and spiraling motility [See Video 1].^[6] B. coli is often a neglected organism, and as such, it has not been widely researched.^[1]

The organism was first recognized by Malmsten^[1] in 1857, in two Swedish patients who presented with dysentery. Malstem thought it was a Paramecium,and since it was from the colon, coined the name Paramecium coli. This name was short-lived. Soon after in 1861, Leuckart^[1] discovered the organism in pigs. Later, Stein discovered that Leuckart’s organism from the pigs, and Malmsten’s organism from the humans was the same, and called it B. c oli (Greek Balanto = bag).

Although B. coli is most known for causing diarrhea and infecting the colon, extraintestinal manifestations^[7] are possible. Because of the rarity of B. coli in Western countries, the infection may go undiagnosed, especially in an extracolonic location. B. coli infections have been reported to cause necrotizing cavities in the lung,^[5] infections in immunocompromised hosts,^[2,7] serious infections in transplant patients, and even infections in the bone causing vertebral osteomyelitis.^[2] Infections of the peritoneal cavity, genitourinary tract, and appendix have been reported.^[2] Occasionally, B. coli infections can be seen in immunocompetent hosts without exposure to pigs. With the advent of the internet, and the use of Google, timely, immediate diagnosis of B. coli is possible in an unusual clinical setting. YouTube videos can be used as important learning tools, to demonstrate the motility of the organism, so that they are easily recognized in unusual clinical settings.

The patient recovered completely after treatment with antibiotics.