What is used for preventing the growth of yeast and molds from vaginal specimens in culture?

Nystatin is an antifungal medication effective in preventing the growth of yeast and molds, particularly Candida species, which are commonly encountered in vaginal specimens. It works by binding to sterols in the fungal cell membrane, leading to increased permeability and ultimately cell death. This property makes nystatin particularly useful in clinical settings where contamination from yeast and molds can interfere with the accurate culture and identification of pathogenic organisms.

While other options listed may have antifungal properties or functions in inhibiting bacterial growth, they are not specifically tailored for preventing fungal growth in vaginal specimens. For instance, colistin is primarily used against Gram-negative bacterial infections and does not have antifungal activity. Trimethoprim is an antibiotic that acts on bacterial folic acid synthesis and would not affect fungal organisms. Amphotericin B, while it is an antifungal medication used to treat serious fungal infections, is typically not employed for routine prevention of yeast and mold growth in culture settings due to its toxicity and side effects at higher doses. Thus, nystatin is the most appropriate choice for this specific scenario in microbiological culture practices.