Snapshot A 52-year-old man presents to the emergency department with a cough, foul-smelling sputum, and a subjective fever. He is homeless and has a history of alcohol-use disorder. His temperature is 102.2°F (39°C). A radiograph of the chest demonstrates a thick-walled cavitary lesion. He is admitted to the hospital for empiric antibiotic treatment. Introduction Definition parenchymal necrosis of the lung caused by a microbial infection this leads to the development of a circumscribed collection of pus Epidemiology Incidence most common cause is aspiration Etiology Pathophysiology Aspiration leads to bacterail inoculation in the lung parenchyma → lung parenchyma necrosis (within 7-14 days) → abscess formation foul smelling sputum results if the abscess communicates with the airway Anaerobic bacteria is the most common cause Polymicrobial in cases of aspiration Monomicrobial causes include group A streptococci Staphylococcus aureus (including MRSA) Klebsiella pneumoniae Nocardia (in immunocompromised patients) Presentation Symptoms cough foul-smelling sputum Physical exam weight loss fever Imaging Chest radiography indication imaging of choice and diagnostic in patients with signs and symptoms concerning for abscess findings cavity with an air-fluid level Studies Microbiology testing from sputum or respiratory specimen Differential Empyema differentiating factor radiography typically demonstrates opacifying lesion Treatment Medical intravenous empiric antibiotics indication mainstay of treatment medications clindamycin be cautious for C. difficile infection carbapenem (e.g., imipenem or meropenem) ampicillin-sulbactam Complications Death Prognosis Morbidity and mortality improved with antibiotics