Which mechanism best explains thrush developing after antibiotics?

• A. Antibiotics stimulate candida growth directly
• B. Antibiotics prevent candida overgrowth
• C. Antibiotics disrupt vaginal flora by reducing normal bacteria, allowing candida overgrowth
• D. Antibiotics have no effect on vaginal flora

Answer: (C)

The main idea is that antibiotics can disrupt the vaginal microbiome, creating a dysbiosis that allows Candida to overgrow. Normally, beneficial bacteria, especially lactobacilli, dominate the vaginal flora and keep the environment acidic and hostile to fungi. They also compete with Candida for space and nutrients and produce substances that inhibit fungal growth. When antibiotics reduce these normal bacteria, the protective balance is lost, giving Candida the opportunity to multiply and cause thrush. Antibiotics don’t directly stimulate Candida, and they don’t prevent its growth; they do affect vaginal flora, so the mechanism described—disruption of normal bacteria permitting Candida overgrowth—is the best explanation.