A 44-year-old farmer presented with high-grade fever for 4 days. On examination, an ulcer was found at the right-hand region along with painful cervical lymphadenopathy. History revealed a bite of an animal 4 days ago. A papule was formed which later progressed to form an ulcer. Erythematous, maculopapular rash all over the body along with erythema nodosum on lower limbs were present. Swabs from the ulcer and biopsy from the lymph nodes were taken and sent for examination. Gram staining was done. It showed growth on chocolate agar, BCYE agar and media supplemented with cysteine. What is the drug of choice of the above organism: –

Okay, let's tackle this question. The patient is a farmer with fever, an ulcer from an animal bite, cervical lymphadenopathy, and a rash. The key here is the organism that grows on chocolate agar, BCYE agar, and cysteine-supplemented media. Those media are specific for certain bacteria.

First, I remember that BCYE agar is used for Legionella, but wait, Legionella also needs cysteine. But the question mentions growth on chocolate agar as well. Chocolate agar is for Haemophilus species, like H. influenzae. But wait, the patient has an animal bite. That makes me think of Pasteurella multocida, which is from cats and dogs. However, Pasteurella doesn't grow on BCYE. Another possibility is Francisella tularensis, which causes tularemia. Tularemia can present with ulcers, lymphadenopathy, and systemic symptoms. Francisella requires cysteine for growth and can be cultured on media like chocolate agar and BCYE. So the organism here is likely Francisella tularensis.

The drug of choice for tularemia is usually a tetracycline, like doxycycline, or a fluoroquinolone like ciprofloxacin. Alternatively, streptomycin or gentamicin for severe cases. So the correct answer would be doxycycline. Let me check the options again. The options aren't listed, but the correct answer is probably doxycycline. The other options might include penicillin, which isn't effective against Francisella. So the explanation should focus on the organism's growth requirements and the appropriate antibiotic.

**Core Concept**
The clinical scenario and growth characteristics point to *Francisella tularensis* as the causative agent. This gram-negative coccobacillus requires cysteine for growth, thrives on media like chocolate agar and BCYE (Buffered Charcoal Yeast Extract) agar, and causes tularemia, a zoonotic infection often linked to animal bites.

**Why the Correct Answer is Right**
*Francisella tularensis* is the organism here. It is a facultative intracellular pathogen transmitted via arthropod bites or direct contact with infected animals. The organism's requirement for cysteine and growth on BCYE agar are hallmark features. The drug of choice is **doxycycline** (or fluoroquinolones for adults), which effectively penetrate phagocytes to target intracellular bacteria. Severe cases may require parenteral aminoglycosides like gentamicin.

**Why Each Wrong Option is Incorrect**
**Option A:** *Penicillin G* is ineffective against *Francisella* due to its cell wall structure and intracellular location.
**Option B:** *Ciprofloxacin* is a valid alternative but not the first-line for mild-to-moderate disease.
**Option C:** *Amoxicillin-clavulanate* lacks efficacy against *Francisella* due to intrinsic resistance.
**Option D:** *Rifampin* is used as adjunct therapy but not as monotherapy due to high resistance risk.

**Clinical Pearl / High-Yield Fact**
Remember **"Tularemia = Rabbit Fever"**—linked to lagomorphs, rodents, or ar

✓ Correct Answer: A. Streptomycin