Catalase Test Reaction Guide
An original slide-test bench reference for observing rapid oxygen bubble evolution to differentiate staphylococci from streptococci.
Bench card visual
Catalase spot tests A-B
Read first
Apply 3% hydrogen peroxide (H2O2) to colonies on a glass slide and check for immediate bubbling.
A
PositiveStaphylococcus aureusImmediate, copious elaboration of white oxygen bubbles forming a frothy foam.
B
NegativeStreptococcus pyogenesNo bubble production; colony smear remains suspended in clear liquid.
PositiveStaphylococcus aureus
Immediate, copious elaboration of white oxygen bubbles forming a frothy foam.
NegativeStreptococcus pyogenes
No bubble production; colony smear remains suspended in clear liquid.
What to look for
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Vigorous Bubbling | Catalase enzyme breaks down hydrogen peroxide into oxygen gas and water | Shorthand: Positive (+) |
| No Bubbles | Lack of catalase enzyme; hydrogen peroxide remains unhydrolyzed | Shorthand: Negative (-) |
| 3% H2O2 Reagent | Standard hydrogen peroxide solution applied directly to colony smear | Must use fresh reagent |
Catalase study readout
| Pattern | What to call it | How to think about it |
|---|---|---|
| Positive | Copious, immediate bubble production | Presumptive Staphylococci, Micrococci, Listeria, Bacillus, or Corynebacterium. |
| Negative | No bubble production (or trace delayed bubbles) | Presumptive Streptococci, Enterococci, or Lactobacilli. |
| Neisseria exception | 30% H2O2 (Superoxol) is positive for N. gonorrhoeae | Differentiation tool for fastidious Gram-negative diplococci. |
Key takeaways
- Core first-pass branch point for Gram-positive cocci.
- Differentiates Staphylococcaceae (positive) from Streptococcaceae (negative).
- Extremely rapid spot test giving results within seconds.
Remember
S. aureus is catalase positive and coagulase positive; S. pyogenes is catalase negative and PYR positive.