American Board of Internal Medicine (ABIM) Certification Practice Exam

Which organism is primarily responsible for infection after contact with cats?

1. Capnocytophaga canimorsus

2. Bacillus anthracis

3. Pasteurella multocida

4. Aeromonas hydrophila

The correct answer is: Pasteurella multocida

The organism primarily responsible for infections following contact with cats is Pasteurella multocida. This bacterium is commonly found in the mouths of domestic cats and can be introduced into the human body through bites, scratches, or even close contact with cat saliva. Infections caused by Pasteurella multocida typically manifest as localized cellulitis or more severe systemic infections, especially in individuals with compromised immune systems or underlying health conditions. In contrast, the other organisms listed are associated with different types of infections or sources. Capnocytophaga canimorsus is more commonly linked with dog bites than cat exposure, while Bacillus anthracis is the causative agent of anthrax and is primarily associated with exposure to infected animals or contaminated animal products. Aeromonas hydrophila is primarily associated with freshwater environments and is typically linked to infections arising from exposure to aquatic environments rather than close contact with cats. Thus, Pasteurella multocida stands out as the key pathogen related to cat contact, reinforcing its significance in veterinary and human medicine contexts.