Lab method
DNase test
Clearing on DNA agar = S. aureus positive
DEE-en-ays
High-yield clue
A clear zone on DNase agar helps flag Staphylococcus aureus among the staphylococci.
Overview
A biochemical concept detecting deoxyribonuclease, an enzyme that hydrolyzes DNA in the medium; positives clear the surrounding methyl-green (or acid-precipitated) DNA agar.
Classification
- Enzyme-detection concept
- DNA agar medium
- Clearing-zone readout
Lab & identification clues
- Clearing around growth = DNase positive
- S. aureus is DNase positive
- S. epidermidis is DNase negative
- Serratia marcescens is also DNase positive
Associations
- S. aureus vs coagulase-negative staph differentiation
- Study pairing with coagulase test
- Gram-positive cocci identification
Commonly confused with
- Coagulase test
- Catalase test
Your notes
Original concept summary for coursework. Sources checked: OpenStax Microbiology 2e and NCBI Bookshelf Medical Microbiology; reviewed 2026-06. Describes vocabulary and interpretation concepts only; not a lab protocol and not for handling specimens or identifying patient isolates.