Which bacterium is commonly found in decayed teeth?

The bacterium commonly associated with decayed teeth is Streptococcus mutans. This organism plays a significant role in the development of dental caries (tooth decay). It is primarily responsible for initiating the decay process by metabolizing sugars to produce acid, which demineralizes the tooth enamel, leading to cavities. Streptococcus mutans thrives in the oral environment, particularly in the presence of fermentable carbohydrates often found in sugary foods and drinks.

In contrast, while Lactobacillus does contribute to the progression of dental caries, particularly in deeper stages, it is not the primary bacterium involved in the initial decay process. Bacillus fusiformis and Streptococcus aureus are not typically associated with dental decay and do not play a significant role in the oral cavity in the context of caries formation. Therefore, understanding that Streptococcus mutans is a key player in the pathogenesis of carious lesions is crucial for dental professionals and students in the field.