**Core Concept**
Leptospirosis, a zoonotic infection caused by *Leptospira* bacteria, is a common occupational hazard for sewage workers. The infection can lead to a wide range of symptoms, including fever, jaundice, and renal failure.

**Why the Correct Answer is Right**
In leptospirosis, the bacteria can invade the kidneys, causing interstitial nephritis and acute renal failure. The recommended antibiotic, penicillin, is effective against *Leptospira* species and can help prevent the progression of the disease. Penicillin works by inhibiting cell wall synthesis in the bacteria, ultimately leading to their death.

**Why Each Wrong Option is Incorrect**
**Option A:** Doxycycline is not the first-line treatment for leptospirosis, although it may be used as an alternative in penicillin-allergic patients.

**Option B:** Ciprofloxacin is a fluoroquinolone antibiotic with broad-spectrum activity, but it is not the preferred choice for treating leptospirosis.

**Option C:** Amoxicillin-clavulanate is a broad-spectrum antibiotic combination, but it is not effective against *Leptospira* species.

**Clinical Pearl / High-Yield Fact**
Leptospirosis is a vaccine-preventable disease, and sewage workers, especially those in tropical or subtropical regions, should be vaccinated against it to prevent occupational exposure.

**Correct Answer:** C. Penicillin.