An 83-year-old man with Parkinson's disease presents with low-grade fever and cough for several weeks. Lately, he has been experiencing more rigidity and difficulty with his walking. He is on a levodopa/carbidopa combination for treatment for the past 5 years. On examination, his gait is shuffling and slow. He has a tremor in his left hand at rest, and there is cogwheel rigidity of the forearm. There are crackles in the left lower lung field. CXR reveals a lung abscess in the left lower lobe. Which of the following is the most likely bacteriologic diagnosis for the lung abscess?
High-Yield Explanation
Most lung abscesses and all anaerobic abscesses involve the normal flora of the oropharynx. Septic embolic usually contain S. aureus. Factors that predispose to Gram-negative colonization of the oropharynx include hospitalization, debility, severe underlying diseases, alcoholism, diabetes, and advanced age. Impaired consciousness, neurologic disease, swallowing disorders, and nasogastric or endotracheal tubes all increase the likelihood of aspiration.