American Board of Internal Medicine (ABIM) Certification Practice Exam

What organism is most commonly associated with infections from contact with fresh water lakes?

1. Vibrio vulnificus

2. Aeromonas hydrophila

3. Pasteurella multocida

4. Capnocytophaga canimorsus

The correct answer is: Aeromonas hydrophila

The organism most commonly associated with infections from contact with fresh water lakes is Aeromonas hydrophila. This bacterium is frequently found in freshwater environments, such as lakes, rivers, and ponds. Infections can occur when individuals expose broken skin or mucous membranes to contaminated water, leading to various clinical conditions ranging from skin and soft tissue infections to more severe gastrointestinal and systemic illnesses. Aeromonas hydrophila is known for causing wound infections, particularly in individuals with compromised immune systems or those with pre-existing conditions like liver disease. The bacteria can enter the body through cuts, scrapes, or other forms of trauma while swimming or engaging in recreational activities in freshwater, making it particularly relevant in the context of fresh water exposure. In contrast, other organisms listed do not have the same association with freshwater environments. Vibrio vulnificus is more commonly linked to marine environments and seafood consumption. Pasteurella multocida is typically associated with animal bites or scratches, particularly from cats and dogs. Capnocytophaga canimorsus is also linked to dog bites and is not typically found in freshwater habitats. Thus, Aeromonas hydrophila stands out as the primary pathogen connected with fresh water infections.