Which of the following statements are true?

B. Anaerobic bacteria are commonly present in pyogenic lung abscess. 

D. Penicillin is the treatment of choice for lung abscess. 

DISCUSSION: Pyogenic lung abscess is the result of aspiration of debris from the oropharynx. Since most patients are unconscious and supine when this occurs, the aspirated material usually finds its way into the most dependent bronchi. These are the superior division of the right lower lobe and the posterior segment of the right upper lobe. The organisms most commonly responsible for pyogenic lung abscess are the same anaerobic bacteria found in the mouths of patients with poor oral hygiene. In addition to anaerobic organisms alpha- and beta-hemolytic streptococci, staphylococci, nonhemolytic streptococci, and Escherichia coli may be present. Gram-negative rods and staphylococci are particularly common in hospital-acquired infections. These organisms are almost always penicillin sensitive. Surgical therapy is rarely necessary to eradicate a pyogenic lung abscess. Penicillin, alone or in combination with metronidazole, is the drug of choice. Metronidazole alone probably lacks sufficient activity against anaerobic and microaerophilic streptococci. Clindamycin is also effective against most anaerobic bacteria present in pyogenic lung abscesses.