What organism produces catalase and has been shown to protect S. mutans from hydrogen peroxide oxidative stress with adherence required?

• A. Streptococcus mutans
• B. Candida albicans
• C. Lactobacillus acidophilus
• D. Escherichia coli

Answer: (B)

Protecting S. mutans from hydrogen peroxide in the dental biofilm relies on detoxifying hydrogen peroxide via catalase. Candida albicans is catalase-positive, meaning it can break down H2O2. When C. albicans adheres to S. mutans in a biofilm, its catalase activity creates a localized environment with lower hydrogen peroxide, shielding S. mutans from oxidative stress. The adherence requirement indicates this is a close, cell-to-cell interaction within the biofilm, not a distant effect. Among the options, Candida albicans best fits as the organism that both produces catalase and can protect S. mutans through this adherent interaction.