Which of the following organisms is commonly beta-lactamase positive?

Escherichia coli is commonly known to produce beta-lactamase, an enzyme that provides resistance to beta-lactam antibiotics, such as penicillin and cephalosporins. The presence of beta-lactamase can lead to treatment challenges because it can render these antibiotics ineffective against E. coli infections, which is why this characteristic is clinically significant. Beta-lactamase production is a common mechanism of resistance among enteric bacteria, and various strains of E. coli, especially those associated with urinary tract infections and other healthcare-associated infections, frequently possess this trait.

In contrast, Staphylococcus aureus can also be beta-lactamase positive, particularly methicillin-resistant strains (MRSA), but it is not as universally associated with this resistance mechanism as E. coli. Streptococcus pyogenes is typically sensitive to beta-lactam antibiotics and does not produce this enzyme. Clostridium difficile primarily exhibits resistance through other mechanisms, not through beta-lactamase production, and is not a common beta-lactamase positive organism. Therefore, E. coli stands out as a key example of a beta-lactamase positive organism in clinical microbiology.