Catalase function: Breaks down hydrogen peroxide (H₂O₂ → H₂O + O₂) before it can be converted by myeloperoxidase into microbicidal products.
Clinical relevance: Patients with chronic granulomatous disease (CGD) (NADPH oxidase deficiency) cannot generate sufficient reactive oxygen species.
They are especially susceptible to infections with catalase-positive organisms, because these microbes degrade the small amounts of H₂O₂ that host cells could otherwise use to kill them.
Examples of catalase-positive organisms:
- Candida
- Pseudomonas
- Nocardia
- Bordetella pertussis
- Burkholderia cepacia
- Helicobacter pylori
- Aspergillus
- Staphylococcus
- Serratia
- Listeria
- Escherichia coli
- Nocardia
- Burkholderia cepacia / Bordetella pertussis
- Bubbling (Catalase reaction)
- Helicobacter pylori
- Aspergillus
- Staphylococcus
- Serratia
- Listeria
- E. coli
Learning Objective (USMLE Step 1): Identify catalase-positive organisms and understand why patients with chronic granulomatous disease are predisposed to recurrent infections with these microbes.
