Bacterium
Moraxella catarrhalis
Oxidase-positive Gram-negative diplococcus
mor-ax-EL-uh kah-tar-AL-is
High-yield clue
Oxidase-positive diplococcus + respiratory tract comparison vocabulary.
Overview
A respiratory Gram-negative diplococcus used in coursework to avoid overcalling every Gram-negative diplococcus as Neisseria.
Classification
- Gram-negative
- Diplococcus
- Oxidase positive
Lab & identification clues
- Oxidase positive
- Diplococcus morphology
- Respiratory culture vocabulary
Associations
- Otitis media vocabulary
- Sinusitis vocabulary
- COPD exacerbation coursework association
Commonly confused with
- Neisseria meningitidis
- Neisseria gonorrhoeae
- Haemophilus influenzae
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.