Empyema caused by trichomonas – selected reports

Kevin L. Lewis

Empyema is one of the potential complications of lower respiratory tract infections. Very rarely, in predisposed individuals, empyema can be caused by Trichomonas species, of which Trichomonas tenax appears to be the most common cause. Here, we present a case of trichomonal empyema in a 56-year-old man and review the available literature of this rare occurrence.

Key words: empyema; pleural effusion; protozoa; Trichomonas


The development of an infection within the pleural space, or empyema, is a well-known complication of pneumonia. Infections of the pleural space are usually bacterial in origin; however, in predisposed individuals empyema can be the result of microorganisms other than bacteria. Here, we present a rare case of empyema caused by Trichomonas tenax.


A 56-year-old white, male smoker with a history of type II diabetes mellitus presented to the hospital for elective resection of a subependymoma of the fourth ventricle of the brain. On the second postoperative day, a duodenal feeding tube was inadvertently placed into the right lung causing a pneumothorax, which was then treated with tube thoracostomy. On the fifth postoperative day, fever developed, along with tachypnea, purulent endotracheal aspirate, increasing fraction of inspired oxygen requirements, and left lower lung alveolar infiltrates on chest radiography. The patient was treated with levofloxacin, 750 mg/d, and his tracheal aspirate eventually grew Klebsiella oxytoca. He underwent a tracheostomy, was gradually weaned from the ventilator, and had his thoracostomy tube removed.

Two weeks after the surgery, a new fever developed with tachypnea, leukocytosis, purulent sputum, and increased fraction of inspired oxygen requirements. The chest radiograph revealed bibasilar alveolar infiltrates and a loculated right pleural effusion, which was confirmed on CT of the chest (Fig 1). Empiric treatment with piperacillin/tazobactam and tobramycin was started, and a tube thoracostomy was inserted into the right chest under CT guidance. A tracheal aspirate subsequently grew Pseudomonas aeruginosa sensitive to both antimicrobial agents, while blood culture findings were negative.


Pleural fluid analysis revealed a cloudy appearance with a glucose level of 24 mg/dL, lactate dehydrogenase level of 13,420 U/L, total protein of 2.6 g/dL, and pH 7.2. The Gram stain of the pleural fluid showed no organisms. Direct microscopic examination of a wet mount of the pleural fluid showed many neutrophils and a moderate number of flagellated organisms demonstrating tumbling motility. A Wright’s Giemsa and trichrome stains of a cytocentrifuged preparation of the pleural fluid demonstrated small, pale staining, flagellated organisms consistent with a diagnosis of Trichomonas species with size and morphology most consistent with T tenax. (Fig 2). The examination of multiple specimens of urine, sputum, and oral secretions revealed no trichomonads, while bacterial cultures of the pleural fluid grew Streptococcus constellatus. Metronidazole, 500 mg qid, was added to the other antibiotics. The empyema fluid cleared with antibiotics and drainage, and the patient was eventually discharged on the 25th postoperative day.



Trichomonas species are flagellated protozoa with undulating membranes. Three distinct trichomonad species can parasitize humans. Trichomonas vaginalis is found in the genitourinary tract, Pentatrichomonas hominis is found in the intestines, and T tenax is found as a commensal of the human oral cavity in those with poor oral hygiene. The discovery of trichomonal organisms in the lower respiratory tract is a rare occurrence. As far as we know, this is the 12th reported case of trichomonal empyema. (1-8) In all of the reported cases, cancer, chronic lung disease, or immunosuppression was present.

T tenax is the most common cause of trichomonal pleuropulmonary infection. (1) These organisms are believed to gain entry to the lower respiratory tract by aspiration from the contaminated oropharynx. Their proliferation appears to be dependent on the presence of bacterial species, which T tenax is thought to feed on. For this reason, it is believed that T tenax would be unable to cause an empyema as the lone microorganism. Indeed, most case reports have isolated anaerobic and/or aerobic bacteria in addition to the trichomonads. (1,4,6-8) In all cases that were treated with metronidazole, a rapid improvement was observed. P hominis and T vaginalis are much less common causes of pleuropulmonary infection.

Differentiation between the species of trichomonads can be difficult in the clinical setting. Morphologic characteristics on stained specimens are helpful but not definitive in many cases, owing to the presence of many leukocytes in stained specimens. Parasite culture has been the most reliable way to identify a particular species if the culture is successful; more recently, polymerase chain reaction techniques have made more accurate speciation possible. (2) The absolute necessity of accurately identifying trichomonal species in clinical practice is unclear since metronidazole is very effective in eradicating all trichomonal species in humans.

We believe that our patient was infected with T tenax that likely gained entry to the pleural space from the feeding tube that punctured the right visceral pleura. The presence of S constellatus serving as a possible food source in the pleural space may explain why the trichomonads were able to proliferate. Like other investigators, (7) we were unable to find trichomonads in other examined sites in our patient. Our patient had a dramatic response to the addition of metronidazole to his antibiotic regimen. Despite its rarity, pleural infection with Trichomonas should be considered in high-risk patients such as those with cancer, chronic lung disease, immunosuppression, or poor oral hygiene, and can be easily screened for by wet preparation evaluation of empyema fluid.


(1) Hersh SM. Pulmonary trichomoniasis and Trichomonas tenax. J Med Microbiol 1985; 20:1-10

(2) Jongwutiwes S, Silachamroon U, Putaporntip C. Pentatrichomonas hominis in empyema thoracis. Trans R Soc Trop Med Hyg 2000; 94:185-186

(3) Memik F. Trichomonads in pleural effusion. JAMA 1968; 204:1145-1146

(4) Miller MJ, Leith DE, Brooks JR, et al. Trichomonas empyema. Thorax 1982; 37:384-385

(5) Osborne PT, Giltman LI, Uthman EO. Trichomonads in the respiratory tract: a case report and literature review. Acta Cytol 1984; 28:136-138

(6) Radosavljevic-Asic G, Jovanovic D, Radovanovic D, et al. Trichomonas in pleural effusion. Eur Respir J 1994; 7:1906-1908

(7) Shiota T, Arizono N, Morimoto T, et al. Trichomonas tenax empyema in an immunocompromised patient with advanced cancer. Parasite 1998; 5:375-377

(8) Walzer PD, Rutherford I, East R. Empyema with Trichomonas species. Am Rev Respir Dis 1978; 118:415-418

* From the Divisions of Pulmonary and Critical Care Medicine (Drs. Lewis, Doherty, and Bensadoun) and Pathology and Microbiology (Drs. Ribes and Seabolt), The University of Kentucky Chandler Medical Center, Lexington, KY.

Manuscript received May 2, 2002; revision accepted June 26, 2002.

Correspondence to: Eric S. Bensadoun, MD, FCCP, Division of Pulmonary and Critical Care Medicine, University of Kentucky Medical Center, 800 Rose St, MN 614, Lexington, KY 40536; e-mail: ebens0@pop.uky.edu

COPYRIGHT 2003 American College of Chest Physicians

COPYRIGHT 2003 Gale Group

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