What characteristic is most definitive for identifying Staphylococcus aureus?

Coagulase production is a key characteristic used to definitively identify Staphylococcus aureus. This bacterium is unique among staphylococci in that it produces the enzyme coagulase, which causes the coagulation of plasma. This reaction can be observed in laboratory settings, where a positive coagulase test indicates the presence of S. aureus, distinguishing it from other staphylococci, such as Staphylococcus epidermidis, which do not produce this enzyme. The ability to coagulase plasma is a significant virulence factor for S. aureus as it helps the organism evade immune responses by forming protective barriers around itself.

Other factors, such as the oxidase test, lactose fermentation, and novobiocin sensitivity, do not provide definitive identification for S. aureus specifically. The oxidase test is primarily used to differentiate between oxidase-positive and oxidase-negative bacteria, while lactose fermentation is more relevant to enteric bacteria like Escherichia coli. The novobiocin sensitivity test is helpful in differentiating Staphylococcus saprophyticus, which is resistant, from other staphylococci, but does not uniquely identify S. aureus. Therefore, coagulase production stands out as the most definitive feature for