Aggregatibacter aphrophilus, formerly known as Haemophilus aphrophilus, is a facultative anaerobic Gram-negative coccobacillus that forms part of the oropharyngeal flora. Although it is not highly pathogenic, it has been associated with infections, such as endocarditis, cerebral abscesses, bone and joint infections, and endophthalmitis.1,2 Pleuropulmonary involvement, however, remains exceptional.3 Another common commensal of the oropharyngeal cavity is Parvimonas micra, formerly Peptostreptococcus micros, a strictly anaerobic Gram-positive coccus that has been associated with polymicrobial infections (intracranial abscesses, paranasal sinus infections, periodontitis and septic embolism4,5). Reports of P. micra as a pathogen in lung infections are exceedingly rare. We report the first case of pleural empyema due to A. aphrophilus and P. micra coinfection.

A 49-year-old man was admitted with a 4-day history of dyspnea, cough with purulent expectoration and fever. In the previous 3 months, he had suffered asthenia and anorexia and had lost 12kg in weight. He was a habitual smoker (1 pack-year) and his alcohol intake was 80g ethanol/day. He had no other comorbidities. On physical examination, temperature was 37.4°C, hypoventilation in the lower half of the right hemithorax on lung auscultation, and poor oral hygiene, with extensive caries and evidence of periodontitis. Clinical laboratory results revealed a white blood cell count of 13.6×109/l (normal values [NV]: 4–11.5×109/l) with neutrophilia, hemoglobin 10.4g/dl (NV: 13–18g/dl) and hematocrit 32.8% (NV: 41%–50%), 959×109/l (NV: 130–450×109/l) platelets and erythrocyte sedimentation rate (ESR) 110mm/h (NV: <20mm). Chest X-ray on admission showed parenchymal infiltrations in the posterior segment of the right upper lobe and apical region of the right lower lobe, with loss of volume and right pleural effusion (Fig. 1a). Thoracocentesis was performed, and purulent fluid was obtained that was sent for culture. Wide-spectrum antibiotic treatment with linezolid and imipenem began and a chest tube was placed, to which fibrinolytics were added: 1500cc of purulent fluid was drained. Chest computed tomography (CT) was performed (Fig. 1b), showing pulmonary infiltrate, pleural and atelectasis of the lung. Mixed flora were identified on a direct Gram stain of the specimen. Culture of the pleural fluid was positive for A. aphrophilus and P. micra, as identified by mass spectronomy (MALDI-TOF). On the basis of these results, the antibiotic treatment was scaled down to amoxicillin–clavulanate, which continued for 4 weeks. The patient's progress was satisfactory with clear improvement of the clinical picture.

Fig. 1.

(a) Upper and lower right lobe infiltrates and pleural effusion; (b) right lower lobe atelectasis with pleural effusion.

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Pleuropulmonary infections by A. aphrophilus are uncommon; indeed, since 1965 only 3 cases have been reported.2,3,6 Our case is particularly unusual, due to the concomitant isolation of P. micra: an extensive search of the literature revealed only 1 case in which this microorganism was described as a causative agent of empyema.7 This is the first report of such a case in Spain.

The initial presentation, radiological pattern and clinical course of our case are indistinguishable from infections caused by other microorganisms. The patient had a history of general decline over several months, along with predisposing factors, such as alcohol abuse and periodontal disease. He responded to standard antibiotic treatment, chest drainage and fibrinolytics.

To conclude, although A. aphrophilus and P. micra may be exceptional, they should be considered as causative agents of pleural infection, particularly in patients with risk factors. The presentation, clinical management and clinical course were no different from empyema caused by more common microorganisms.