**Question:** 30 year old man has mitral valve vegetation. Patient is an intravenous drug abuser. Culture media used to isolate the organism responsible for this is

A. Blood agar
B. Chocolate agar
C. MacConkey agar
D. Sabouraud dextrose agar

**Correct Answer:** .

**Core Concept:**
Mitral valve vegetation is an abnormal growth on the surface of the mitral valve, commonly caused by bacterial endocarditis. In intravenous drug abusers, the risk of acquiring endocarditis is significantly increased due to the direct injection of contaminated blood into the circulatory system.

**Why the Correct Answer is Right:**
The correct answer is **B. Chocolate agar**, a culture medium that supports the growth of fastidious anaerobic bacteria, including those responsible for causing endocarditis in intravenous drug abusers. Chocolate agar is rich in iron and has a blood agar base, which provides an optimal environment for the growth of fastidious bacteria like Streptococcus viridans, Streptococcus milleri, and other anaerobes that commonly cause endocarditis in such patients.

**Why Each Wrong Option is Incorrect:**

A. **Blood agar (A. Blood agar)** is a culture medium suitable for the growth of aerobic and facultatively anaerobic bacteria. It is not specific for anaerobic bacteria, which makes it an incorrect choice.

C. **MacConkey agar (C. MacConkey agar)** is a medium used to differentiate lactose-fermenting and non-lactose fermenting bacteria. It is not specific for the growth of anaerobic bacteria, making it an incorrect choice.

D. **Sabouraud dextrose agar (D. Sabouraud dextrose agar)** is a culture medium designed for the isolation and identification of fungi, particularly yeasts. It is not suitable for the growth of anaerobic bacteria, making it an incorrect choice.

**Clinical Pearl:**

In intravenous drug abusers with mitral valve vegetation, the isolation of anaerobic bacteria like fastidious streptococci and anaerobic bacilli is crucial for appropriate antibiotic therapy and appropriate management of the patient. Early recognition and targeted therapy can prevent complications and reduce morbidity and mortality associated with endocarditis in this high-risk patient population.