- Lung abscess typically results from aspiration of oral flora.
- Polymicrobial infections are common and involve oral anaerobes (Prevotella spp., Peptostreptococcus, Fusobacterium, Bacteroides spp., and Actinomyces spp.). Microaerophilic streptococci (Streptococcus milleri), enteric gram-negative bacilli (Klebsiella pneumoniae), and S. aureus, including community-acquired MRSA, are less frequent causes.
- Risk factors include periodontal disease and conditions that predispose patients to aspiration of oropharyngeal contents (alcohol intoxication, sedative use, seizures, stroke, and neuromuscular disease).
Infections are indolent and may be reminiscent of pulmonary tuberculosis, with fever, chills, night sweats, weight loss, dyspnea, and cough productive of putrid or blood-streaked sputum for several weeks.
- Chest radiography is sensitive and typically reveals infiltrates with cavitation and air–fluid levels in dependent areas of the lung, such as the lower lobes or the posterior segments of the upper lobes. Chest CT can provide additional anatomic detail.
- Respiratory isolation and sputum testing for tuberculosis should be performed on all patients with cavitary lung lesions.
- Antibiotic therapy should consist of clindamycin or a β-lactam/β-lactamase inhibitor (ampicillin-sulbactam, piperacillin-tazobactam, amoxicillin-clavulanate) or a carbapenem (ertapenem). For MRSA cavitary lung lesions, linezolid or vancomycin should be used. Metronidazole monotherapy is ineffective due to the presence of microaerophilic nonculturable organisms in the oral microbiota, thus, it should be combined with penicillin.
- Percutaneous drainage or surgical resection is rarely necessary and should be reserved for antibiotic-refractory disease, usually involving large abscesses (>6 cm) or infections with resistant organisms.
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