Hiding Behind Confusion: Pleural Empyema Caused by Parvimonas micra

P arvimonas micra is a facultative pathogenic, anaerobic gram-positive bacterium of the oral (gingival) human microflora [1]. Only a few cases of infection with a pure culture have been published. We recently saw a case of pleural empyema associated with P. micra. A 72-year old male was admitted for somnolence, confusion, loss of appetite, and fluctuating memory deficits. Symptoms had begun 2 wks before admission. The patient's medical history yielded Alzheimer disease, hypertension, New York Heart Association class 2 congestive heart failure, complete heart block with a pacemaker, atrial flutter, and generalized peripheral arterial disease. The white blood cell (WBC) count was 22.0×10⁹/L (93.0% neutrophils), temperature 37.8°C, and C-reactive protein 230.5 mg/L. Chest radiography showed a left-sided pulmonary infiltrate. Intravenous antibiotic therapy with amoxicillin-clavulanic acid (1 g/125 mg) tid and ofloxacin 200 mg bid was started. Blood cultures were sterile. A chest CT scan on the fourth day showed a large left-sided pleural empyema (Fig. 1), which was drained with a 14F pleural catheter. Microbiologic analysis of the evacuated pus yielded high colony counts of Parvimonas micra [1] sensitive to amoxicillin-clavulanic acid. No other microorganism was found, and gram staining (including for Mycobacterium) was negative. Isolation of the organism was achieved on an anaerobic blood agar plate with subsequent identification and susceptibility testing by an automated technique.

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FIG. 1.

Thoracic computed tomography scan before insertion of chest tube shows large left-sided pleural empyema.

Respiratory and neurologic functions deteriorated, and the patient was admitted to our intensive care unit for respiratory failure and deep somnolence. The initial thoracic drain was replaced by a 34F chest tube, enabling pleural irrigation with streptokinase 100,000 IU twice daily [2]. The initial antibiotic therapy was maintained at the same dosage for 16 days. Cranial and pan-oral computed tomography (CT) scans showed substantial loss of gingival substance, periodontitis, and tooth loss but no apical root abscess. Our patient left the hospital two months after admission, and his physical status and neurologic functions were restored 2 mos later.