What bacterium is known to cause abscesses or boils?

Streptococcus aureus is a bacterium commonly associated with the formation of abscesses and boils. This organism is a significant pathogen that can invade tissues and lead to localized infections characterized by accumulation of pus, which forms an abscess. It is known for its ability to produce various enzymes and toxins that contribute to tissue damage and the inflammatory response, allowing it to thrive in various environments within the body.

Infections caused by Streptococcus aureus can occur in several forms, including skin infections such as boils, which are swollen, painful lumps filled with pus that typically arise from hair follicles or oil glands. The bacterium can also lead to more serious infections if it enters the bloodstream or deeper tissues.

Other bacteria listed, while important in their own right, do not primarily cause abscesses or boils. For instance, Streptococcus mutans is mainly involved in dental caries; Lactobacillus functions primarily in the gut and dental health but is not an aggressive pathogen; and Porphyromonas gingivalis is more associated with periodontal disease rather than causing abscesses. Thus, the association of Streptococcus aureus with skin and soft tissue infections makes it the correct choice for this question.