**Core Concept**
Streptococcal vaginitis, also known as streptococcal vaginosis, is a rare but serious infection caused by Group A beta-hemolytic Streptococcus (GABHS). This condition is often seen in newborn girls, particularly those born to mothers with streptococcal vaginosis. The infection can cause severe symptoms, including vaginal discharge, inflammation, and potentially life-threatening complications.

**Why the Correct Answer is Right**
The treatment of choice for streptococcal vaginitis is penicillin, specifically ampicillin or penicillin G. This is because Group A beta-hemolytic Streptococcus is sensitive to penicillin. The recommended dose and duration of treatment are typically 10-14 days. The goal of treatment is to eradicate the infection and prevent potential complications, such as sepsis or meningitis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because erythromycin is a macrolide antibiotic that may not be effective against Group A beta-hemolytic Streptococcus.
**Option B:** This option is incorrect because clindamycin is a lincosamide antibiotic that may not be the first-line treatment for streptococcal vaginitis.
**Option C:** This option is incorrect because fluconazole is an antifungal medication that is not indicated for the treatment of streptococcal vaginitis.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that Group A beta-hemolytic Streptococcus is a common cause of postpartum endometritis and sepsis, particularly in women who have undergone cesarean delivery. Therefore, it is essential to consider this organism in the differential diagnosis of postpartum infections.

**Correct Answer: D. Penicillin G**