Aeromonas hydrophila: Pathogenic Mechanisms and PCR Detection

A. hydrophila is a short rod-shaped bacterium with rounded ends, exhibiting diverse morphologies including straight, slightly curved, coccobacillary, or filamentous forms.

It possesses a single polar flagellum, enabling motility, and does not form spores. Some strains may have a thin capsule.

This organism is facultatively anaerobic and grows within a wide pH range (5.5–9.0), with an optimal temperature of 25–35°C.

Colonies on nutrient agar after 24 hours at 28°C are smooth, convex, circular, and appear colorless to pale yellow, often producing a characteristic odor.

Biochemically, it is oxidase-positive and capable of fermenting glucose and arabinose.

1. Virulence Factors
Pathogenicity is associated with multiple extracellular toxins, including hemolysins, cytotoxins, enterotoxins, proteases, and necrotizing factors.

Adhesion factors enable strong attachment to intestinal epithelial cells, facilitating colonization and infection.

2. Infection Model
In aquatic organisms, the bacterium initially colonizes the intestine, then spreads systemically via circulation, leading to organ damage such as liver and kidney lesions.

3. Host Range
It infects a wide range of aquatic species (fish, amphibians, eels) and can also infect mammals, making it a zoonotic pathogen.

Human infection typically occurs through:

• Ingestion of contaminated water or food
• Exposure of open wounds to contaminated water
• Injuries caused by aquatic animals

Avoid consumption of raw or undercooked aquatic products.

Wash fruits and vegetables thoroughly before consumption.

Prevent open wounds from contacting untreated water sources.

After exposure, clean and disinfect wounds promptly.

Take precautions when swimming to avoid inhalation or ingestion of contaminated water.

A. hydrophila represents a critical intersection between environmental microbiology, aquaculture health, and zoonotic disease.

Understanding its virulence mechanisms and transmission pathways is essential for effective prevention and control.