Staphylococcus
The staphylococcal organisms of clinical interest include S. aureus, S. epidermidis, S. saprophyticus, and S. lugdunensis.
S. aureus is distinguished from the other staphylococcal organisms mainly by its ability to produce coagulase, an enzyme that converts fibrinogen to fibrin in citrated plasma; S. aureusis referred to as coagulase positive.
The other staphylococcal organisms usually do not produce this coagulase enzyme and are termed coagulase negative.
The two main coagulase-negative staphylococcal species are distinguished by susceptibility to the antibiotic novobiocin:S. epidermidis is novobiocin susceptible and S. saprophyticus is novobiocin resistant.
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. The catalase enzyme helps bacteria convert hydrogen peroxide (H2O2) into oxygen and water. The catalase test involves adding H2O2 to a culture sample; if the bacteria in question produce catalase, they will cause conversion of the H2O2 to oxygen gas and bubbles will form.
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Staphylococcal species are usually found in grape-like clusters, whereas the streptococci tend to form pairs and chains.
Alphabetical List of Bacterial Agents