American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the key criteria for adding vancomycin or linezolid to beta-lactam therapy in CAP?

1. Pending laboratory results

2. Presence of cavitary infiltrates

3. Age of the patient

4. Allergy history

The correct answer is: Presence of cavitary infiltrates

The inclusion of vancomycin or linezolid in the treatment regimen for community-acquired pneumonia (CAP) is primarily based on the presence of cavitary infiltrates on imaging studies. This is because cavitary lesions often suggest a more severe or atypical pneumonia, which may be caused by organisms such as Methicillin-resistant Staphylococcus aureus (MRSA) or other pathogens not adequately covered by beta-lactams alone. Patients with cavitary lung lesions are at higher risk of having infections caused by these resistant organisms, necessitating the use of agents like vancomycin or linezolid that provide coverage against MRSA. Therefore, the development of a treatment plan that includes these medications effectively addresses the potential for more complicated lung infections, therefore improving patient outcomes. While pending laboratory results, the age of the patient, and allergy history are important considerations in the overall management of pneumonia, they do not serve as primary indicators for the addition of these specific antibiotics in the context of CAP. The presence of cavitary infiltrates is a clear and significant marker that guides clinicians toward a more aggressive and effective treatment strategy.