Download - Halophilic vibrios
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