Halophilic vibrios are bacteria that require high salt concentrations and cannot grow without it. They naturally inhabit sea water and marine life. Some halophilic vibrios, such as V. parahaemolyticus, V. alginolyticus, and V. vulnificus can cause human disease. V. parahaemolyticus was first isolated in 1951 in Japan during a food poisoning outbreak linked to seafood. It causes gastroenteritis and inhabits coastal areas and seafood. V. alginolyticus resembles V. parahaemolyticus and has been associated with infections from exposure to sea water. V. vulnificus can cause wound infections or septicemia in people with

1. HALOPHILIC VIBRIOS
Dr Vishal Kulkarni
MBBS MD (Microbiology)

2. 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

3. • Some of halophilic vibrios have been known to
cause human disease
▫ V. parahaemolyticus
▫ V. alginolyticus
▫ V. vulnificus

4. 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.

5. • 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

6. 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

7. • 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.

8. • 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.

9. • 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.

10. • 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.

11. 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.

12. • 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

13. 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.

14. Tests V.
Parahaemolyticus
V. alginolyticus
Indole + +
VP - +
Nitrate reduction + +
Urease - -
Sucrose
fermentation
- +
Swarming - +
Growth on 0%
NaCl
- -
7 % NaCl + +
10 % NaCl - +

15. 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.

16. • 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

17. • Other clinically important spp.
▫ V. damsela
▫ V. fluvialis
▫ V. furnisii
▫ V. hollisae
▫ V. metschnikovii
▫ V. mimicus