HALOPHILIC VIBRIOSDr Vishal KulkarniMBBS MD (Microbiology)

Definition

•Vibrios that need high concentration of

NaCl and can not grow in absence of it

are called halophilic vibrios

•Natural Habitat-

▫Sea water

▫Marine life

•Some of halophilic vibrios have been

known to cause human disease

▫V. parahaemolyticus

▫V. alginolyticus

▫V. vulnificus

Vibrio parahaemolyticus

• Enteropathogenic vibrio isolated in Japan in 1951

• Occurred as a outbreak of food poisoning caused by sea

fish

• Gastroenteritis has been reported from several countries.

• Inhabits in costal areas.

• Fish, arthropods, shrimps,

crabs, molluscs

• Kolkata- small pond fish.

• Morphology-

▫ Gram negative bacilli

▫ Short, comma shaped, motile

▫ Fish in stream appearance

▫ Capsulated

▫ Shows bipolar staining

▫ Pleomorphism

▫ Peritrichous flagella on solid media

▫ Polar flagella formed in liquid culture

Cultural characteristics-

- Grows on media containing NaCl

- Can tolerate conc. up to 8 % (but not 10%)

- Optimum conc.- 2-4%

- On TCBS- colonies are green

with opaque, raised center and

flat translucent periphery

- String test is positive

•Biochemical characteristics-

▫Oxidase, catalase, nitrate, indole and citrate

positive.

▫Glucose, maltose, mannitol, mannose and

arabinose are fermented with producing acid only.

▫3 antigens- O, K and H

▫Serotyping is based on O & K Ag.

•Resistance-

▫Killed at 60˚C in 15 minutes.

▫Drying destroys it

▫Does not grows at 4˚C but can survive

refrigeration and freezing.

▫Dies in distilled water & vinegar in few

minutes.

• Pathogenicity-

▫All strains are not pathogenic

▫Kanagawa phenomenon-

When grown on high salt blood agar, produce haemolysis

Strains from human patients are almost always

haemolytic

▫No enterotoxin is produced

▫Causes enteritis due to invasion of intestinal epithelial

cells.

•Clinical features-

▫Food poisoning associated with marine food.

▫Acute diarrhea, abdominal pain, vomiting, fever

▫Feces generally contain cellular exudate often also blood.

▫Dehydration is of moderate degree.

▫Recovery- within 1-3 days.

Epidemiological features-

▫Cases are common in adults than in

children.

▫Occurs mostly in summer.

▫In Kolkata, V. parahaemolyticus could be

isolated from 5-10% of diarrheal cases.

• Lab diagnosis-- Microscopy- dark ground/ Phase contrast, IF- Culture- NA, BA,Mac Conkey- TCBS- Green colonies ( sucrose non fermentation)- Wagatsuma agar- Kanagawa phenomenon- Biochemical reactions

- Catalase, oxidase-positive- Nitrate, indole, citrate- positive

- Ferments- glu, malt, mannitol, mannose, arabinose with acid

- String test positive

V. alginolyticus

Morphology-

- Resembles V.parahaemolyticus in many

respects.

- Can tolerate higher salt concentration (10%)

- Has been associated with infections of the

eyes, ears, wounds in human beings exposed

to sea water.

Tests V. Parahaemolyticus

V. alginolyticus

Indole + +

VP - +Nitrate reduction + +

Urease - -

Sucrose fermentation

- +

Swarming - +Growth on 0% NaCl

- -

7 % NaCl + +

10 % NaCl - +

Vibrio vulnificus

• Previously known as L+ vibrios or Beneckea vulnifica

• Marine vibrio

• Morphology- resembles V. parahaemolyticus.

• Biochemicals and cultural characteristics-

▫ VP negative.

▫ Ferments lactose but not sucrose

▫ Can tolerate up to 8% NaCl.

• Clinical features-

• Two types of infections-

1. Wound infection (contact with sea water)

2. Septicemia in person with pre-existing hepatic disease

following consumption of raw oysters.

• Penetrate gut mucosa without GI manifestations

and then blood stream leading to septicemia

• High Mortality

•Other clinically important spp.

▫V. damsela

▫V. fluvialis

▫V. furnisii

▫V. hollisae

▫V. metschnikovii

▫V. mimicus