In an introductory microbiology lab, if the only test that turned out positive was for catalase activity, which of the following organisms was most likely present?

Identify the catalase activity of each organism listed: Streptococcus pyogenes is catalase-negative, Staphylococcus aureus is catalase-positive, Clostridium botulinum is catalase-negative (anaerobic), and Escherichia coli is catalase-positive but less commonly tested in this context.

Since the only positive test was for catalase activity, focus on organisms known to be catalase-positive and commonly identified by this test in introductory labs.