A 55-year-old woman comes to the office due to a cough producing thick, yellowish sputum for the past 2 weeks. She has also had night sweats and increased fatigue over this time. Temperature is 38.3 C (101 F), blood pressure is 110/70 mm Hg, pulse is 88/min, and respirations are 20/min. There are crackles on lung auscultation. Chest imaging reveals a nonspecific pulmonary lesion. A transthoracic needle aspiration is performed. The specimen is cultured and grows several bacterial species, including Peptostreptococcus and Fusobacterium. Which of the following predisposing factors is most likely responsible for this patient's condition?

Question

A 55-year-old woman comes to the office due to a cough producing thick, yellowish sputum for the past 2 weeks.  She has also had night sweats and increased fatigue over this time.  Temperature is 38.3 C (101 F), blood pressure is 110/70 mm Hg, pulse is 88/min, and respirations are 20/min.  There are crackles on lung auscultation.  Chest imaging reveals a nonspecific pulmonary lesion.  A transthoracic needle aspiration is performed.  The specimen is cultured and grows several bacterial species, including Peptostreptococcus and Fusobacterium.  Which of the following predisposing factors is most likely responsible for this patient's condition?

Quizplus · Accepted Answer

Peptostreptococcus and Fusobacterium are anaerobic bacteria that are part of normal mouth flora. The presence of these organisms in this patient's lung lesion is highly suggestive of a developing lung abscess. As an abscess evolves, it typically forms a cavitary lesion with an identifiable air-fluid level on imaging. Symptoms are often indolent and include fever, night sweats, weight loss, and a cough producing foul-smelling sputum (indicating anaerobes). Lung abscesses are usually caused by one of the following: Aspiration of oral bacteria into the lower airways (most common) - These abscesses are usually composed of a combination of anaerobic oral flora (eg, Peptostreptococcus, Prevotella, Bacteroides, Fusobacterium) and aerobic organisms (eg, Streptococcus). Risk is greatest in those who have conditions associated with loss of consciousness or impaired swallowing, such as alcoholism, drug abuse, neurologic disease (eg, seizures, stroke), or anatomic abnormalities (eg, esophageal strictures or diverticula). Bacterial pneumonia - Lung abscess can occur in the setting of certain bacterial pneumonias such as those due to Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, or Pseudomonas aeruginosa. Most cases arise in the hospital setting and occur in patients with immunosuppression, older age, or underlying lung disease. Bacteremia and/or infectious endocarditis - Hematogenous spread of an infection to the lung usually causes multiple, monomicrobial lung abscesses. The most common causative agents are Staphylococcus and Streptococcus species. (Choice A) Mitral valve prolapse is a risk factor for development of subacute bacterial endocarditis (with Streptococcus species). Left-sided endocarditis could cause septic embolization to downstream organs (eg, spleen, brain) but would not send septic emboli to the lungs. (Choice B) Bronchogenic carcinoma can cause bronchial obstruction and postobstructive pneumonia, which may lead to secondary abscess formation. However, these lung abscesses would be less likely to contain oral anaerobic flora. (Choice C) Lung abscess may be associated with a prior penetrating trauma. Staphylococcus and Streptococcus species (introduced from the skin) are usually responsible. (Choice E) Tobacco smoking compromises pulmonary defenses and predisposes patients to developing community-acquired pneumonia due to common pathogens such as Streptococcus pneumoniae and Mycoplasma pneumoniae. These organisms are less likely to cause lung abscess. (Choice F) Urinary infections can be associated with bacteremia, particularly in those with diabetes mellitus, advanced age, or structural urinary abnormalities. However, most urinary infections are caused by coliform bacteria (eg, E coli) from the lower gastrointestinal tract. Lung abscess is not a common complication of urinary infection, and Peptostreptococcus and Fusobacterium would be unusual urinary organisms. Educational objective: Lung abscess is most often due to aspiration of anaerobic oral bacteria such as Peptostreptococcus, Prevotella, Bacteroides, and Fusobacterium species. Risk factors for lung abscess include conditions that increase aspiration risk, such as alcoholism, drug abuse, seizure disorders, previous stroke, and dementia.

A 55-Year-Old Woman Comes to the Office Due to a Cough