PetriKey

Bacterium

Aeromonas hydrophila

Freshwater rod, wound and gut infection

air-oh-MOH-nas hy-DROF-ih-luh

Gram negativegram-negativerodaquaticoxidase-positivewoundfoodborne

High-yield clue

Oxidase-positive freshwater rod causing wound infection after freshwater exposure and classically linked to medicinal leech therapy.

Overview

An oxidase-positive Gram-negative rod found in fresh and brackish water, studied as a cause of gastroenteritis and of wound infection after freshwater exposure.

Classification

  • Gram-negative
  • Rod
  • Aeromonadaceae
  • Facultative anaerobe
  • Oxidase positive

Lab & identification clues

  • Oxidase positive (distinguishes from Enterobacterales)
  • Beta-hemolytic on blood agar vocabulary
  • Freshwater/aquatic origin concept
  • Resistant to ampicillin vocabulary

Associations

  • Freshwater wound exposure transmission vocabulary
  • Watery gastroenteritis presentation vocabulary
  • Medicinal leech therapy association

Commonly confused with

  • Vibrio vulnificus
  • Pseudomonas aeruginosa

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.

OpenStax: Microbiology 2e organism classification foundationssourceNCBI Bookshelf: Medical Microbiology organism chapterssourceCDC: CDC disease and public-health topic pagessource