Which organism is a likely cause of aspiration pneumonia among the choices?

• A. Lactobacillus sp.
• B. Mobiluncus sp.
• C. Porphyromonas sp.
• D. Clostridium sp.

Answer: (C)

Aspiration pneumonia typically arises from inhaling oropharyngeal contents, so the usual culprits are anaerobic bacteria that inhabit the mouth and upper airway. Porphyromonas species are anaerobic Gram-negative rods that reside in periodontal pockets and are well known as oral pathogens. When material from the oropharynx is aspirated, these anaerobes are frequently involved in the resulting infection, making Porphyromonas a classic etiologic candidate for aspiration pneumonia.

The other organisms listed are less likely culprits in this context. Lactobacillus species are common, mostly benign members of the oral and GI flora and are not a leading cause of aspiration pneumonia. Mobiluncus is associated with bacterial vaginosis rather than lung infection. Clostridium species can cause anaerobic infections in many sites, but they are not the typical agents linked to aspiration pneumonia from oral flora.