katalasenegativ

Katalasenegativ, or catalase-negative, describes microorganisms that do not produce the enzyme catalase. Catalase breaks down hydrogen peroxide into water and oxygen, a reaction that is easy to test for in the laboratory.

In practice, the catalase test is performed by applying a small amount of hydrogen peroxide to a bacterial colony. If bubbles appear, the result is catalase-positive; if there is no effervescence, the result is catalase-negative. The test is commonly used to differentiate major groups of Gram-positive cocci, helping to separate Staphylococcus species (usually catalase-positive) from Streptococcus and Enterococcus species (usually catalase-negative).

Catalase-negative organisms include most species of Streptococcus and Enterococcus. Streptococcus pneumoniae (pneumococcus) is also catalase-negative, while Staphylococcus aureus and most coagulase-positive staphylococci are catalase-positive. Some anaerobic bacteria may be catalase-negative as well. While catalase status provides a useful initial clue for identification, it is not sufficient on its own to determine a species. Additional tests—such as Gram stain characteristics, hemolysis patterns, Lancefield grouping, and molecular methods—are typically required.

Limitations and caveats include the possibility of false results due to factors such as sample handling, age of the culture, concentration of hydrogen peroxide, or the presence of weakly reactive species. Therefore, catalase testing is most informative when interpreted within a broader set of microbiological tests.