• Vibrio is gram negative , rigid, curved rods, motile bacteria using flagellum
• Non capsulated
• Asporogenous
• Present in marine environment, surface water

Morphology

• Short
• Curved
• Cylindrical rod
• 1.5 micrometre X 0.2-0.4 micrometre
• Rounded or slightly pointed end

The cell is typically comma shaped but curvature often lost on subculture

S shaped or spiral shaped seen due to two or more cells lying end to end

It is actively motile, with single sheathed polar flagellum

Culture characteristics

• Strongly aerobic
• Scant growth
• Slow anaerobic
• Temperature 16-40 degree C
• Better growth in alkaline medium with 6.4-9.6 PH
• NAC is required for optimal growth

Nutrient agar :

• After overnight growth colonies are moist, round disc, 1-2 mm in diameter bluish tinge in transmitted light

Mckonkey agar :

• Colourless colony at first
• Reduction on prolonged incubation
• Due to late fermentation of lactose

Blood agar :

• Colonies are initially surrounded by zone of greening
• Which later becomes clear due to hemodigestion

Gelatin stab culture:

• Funnel shaped liquefaction occurs in 3 days at 22 degree C

Peptone water :

• Growth occurs in about six hours as a fine surface pellicle
• Which on shaking breaks up into membranous pieces

Biochemical reaction :

• Formative carbohydrate metabolism produces not gas but acid
• Ferments glucose, mannitol and maltose but no more lactose
• Nitrates are reduced to nitrites
• Indole is formed
• These two properties contributed to cholera red reaction
• Reddish pink colour is developed due to formation of nitroso-indole
• Positive catalase and oxidase test
• Negative methyl red and urease test
• Vibrio elaborate several enzymes like collagenase, elastase

Enterotoxins :

• V. cholerae produces heat labile enterotoxins consisting of subunit A and B
• Ganglioside GMI serves as mucosal receptor for subunit B which promotes entry of subunit A into cell
• Activation of subunit A yields increased level of intracellular cAMP and results in prolong hypersecretion of water and electrolytes

Mode of transmission :

• Person to person
• Water
• Food
• Drinking contaminated water
• Eating raw or undercooked shellfish

Signs and symptoms :

• Rice water diarrhoea
• Stomach pain
• Leg cramps
• Mild fever
• Vommitting

Lab diagnosis :