A 63 year old male with a 75 pack year history of smoking and marked chronic obstructive pulmonary disease (COPD) develops fevers and a persistent cough frequently tinged with blood. Chest x-ray reveals a complex cavitary lesion in the right upper lobe. Bronchoscopic examination identifies a large lung abscess from which pure Fusobacterium nucleatum is cultured. What is the most likely source of the Fusobacterium?
Correct Answer: Oral cavity
Description: Anaerobic lung abscesses commonly arise from aspirated oral secretions in patients with compromised neurological status (e.g., anesthesia, coma, intoxication), or in individuals with a depressed cough reflex. The most common anaerobic organisms isolated from lung abscesses include Bacteroides, Fusobacterium, and Peptococcus species, all of which are typical oral flora. Bloodborne pathogens producing lung abscesses probably originate as emboli from vegetations on the right hea. The most likely pathogens in endocarditis are Staphylococcus and Streptococcus species; Fusobacterium would be very unusual. Fusobacterium usually is not pathogenic and lives in a commensal relationship with the host. Infective aerosols generally contain organisms that are intrinsically pathogenic (e.g., mycobacteria, influenza virus). It is the acidity of the gastric aspirate that most seriously injures the lung, not the gastric bacteria. Fusobacterium do inhabit the gastrointestinal tract, but ble bacteria are much more likely to be transmitted from the oral secretions than from the stomach . Ref: Brooks G.F. (2013). Chapter 21. Infections Caused by Anaerobic Bacteria. In G.F. Brooks (Ed), Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.
Category:
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