VIBRIO

• Vibrio


  Genus of gram-negative, facultatively anaerobic, fermentative rods
• Cholera reaches Florence, Italy

  1854
• Bacterium named Vibrio cholerae


  1965
• Vibrio and Aeromonas


  • At one time classified together in the family Vibrionaceae and separated from the Enterobacteriaceae
  • Basis of a positive oxidase reaction and the presence of polar flagella
  • Primarily found in water and able to cause gastrointestinal disease
• Commonly isolated species of Vibrio

  • Vibrio cholerae (O-1 and non-O-1)
  • Vibrio parahaemolyticus
  • Vibrio alginolyticus
  • Vibrio vulnificus
• All Vibrio species are found in water sources and are transmitted by contaminated food and water
• Vibrio cholerae


  Produces an enterotoxin that causes cholera, a profuse watery diarrhea that can rapidly lead to dehydration and death
• Vibrio cholerae


  Described as "curved" gram-negative rods, often only seen in the initial Gram stain of clinical specimen
• Vibrio isolates


  • Straight to pleomorphic gram-negative rods
  • Usually isolated from stool specimens
• Vibrio cholerae enrichment


  Alkaline peptone water (pH 8.4) suppresses the growth of other organisms
• All Vibrio species grow well on routine media
• Halophilic


  Salt-loving (exception of Vibrio cholerae and Vibrio mimicus)
• Vibrio cholerae


  • Cause of cholera, vast quantities of fluid and electrolytes are lost from the intestinal tract
  • Liquid stools are often referred to as "rice-water" stools because they are colorless and contain mucus flecks
  • Cholera causing isolates have a somatic antigen referred to as O-1
  • Non-O-1 isolates do not cause cholera but may cause other infections
  • Can be differentiated from other species by a positive "string test" when mixed with sodium deoxycholate
• Vibrio parahaemolyticus and Vibrio alginolyticus

  • Cause gastroenteritis following ingestion of raw or improperly handled seafood and wound infections following exposure to sea water
  • Both organisms require salt for growth (halophilic)
• Vibrio vulnificus

  • An extremely virulent organism, causes rapidly progressive wound infections after exposure to contaminated water and septicemia after eating raw oysters
• Vibrio general characteristics


  • Short, 2 x 0.5 μm, often curved gram-negative rods
  • Motile by means of a single polar, sheathed flagella
  • Producing acid from the fermentation of a range of carbohydrates
  • Oxidase positive (except Vibrio metschnikovii)
  • Reduce nitrate to nitrite (except Vibrio metschnikovii)
  • Growth stimulated by Na+, an absolute requirement for most species (except Vibrio cholerae & Vibrio mimicus)
  • Simple nutritional requirements
  • Produce a wide array of enzymes including proteases, nucleases, lipases & chitinase
  • Vibrio cholerae regularly ferments sucrose and mannose but not arabinose
  • Positive oxidase test, key step in preliminary identification
  • Susceptible to the compound O/129, differentiates them from Aeromonas species
  • Vibrios grow on media containing 6% NaCl, whereas Aeromonas does not
• Vibrio cultural characteristics


  • Peptone Water → Incubated at 37°C forms a fine surface pellicle in 6-9 hours
  • Nutrient Agar → Glistening and translucent colonies, 1-2 mm in diameter after 18-24 hours
  • Horse Blood Agar → Zones of hemolysis are produced
  • MacConkey's Agar → Most strains grow well giving non lactose fermenting colonies in 24-36 hours
  • Desoxycholate citrate Agar (DCA), Xylose Lysine Deoxycholate Agar (XLD) & Other enteric Selective Media → Growth is poor
  • Alkaline Peptone Water → pH 8.6 is useful for preliminary enrichment from feces or other contaminated materials
  • Thiosulphate Citrate Bile-salt Sucrose Agar (TCBS) → Most widely selective media, gives good growth of Vibrio cholerae, Vibrio parahaemolyticus and other Vibrios within 37°C, colonies of sucrose fermenting Vibrios are yellow, colonies of sucrose non-fermenting Vibrios are green, inhibits most enterobacteria and gram-positive bacteria
  • Monsur's Tellurite Taurocholate Gelatin Agar → Useful for isolation of cholera and other Vibrios from feces, rectal swabs & other contaminated materials, Vibrios at 24 hours show small (1-2 mm) translucent colonies with a grey-black center and a turbid halo, at 48 hours show larger (3-4 mm) colonies with a black center and a well-defined halo
  • Alkaline Salt Transport Medium → No nutritive fluid, helps maintain viability of Vibrio cholera & other Vibrio species
  • Taurocholate Peptone Transport and Enrichment Medium → Nutritive selective liquid medium, used either as Transport (holding) medium to maintain the viability of Vibrio cholerae and other Vibrio species or Enrichment medium to promote selective outgrowth of Vibrio cholerae from feces before plating on a selective agar medium
  • Cary Blair Medium → Stool specimens suspected of containing Vibrio species, should be collected and transported only in this medium
  • Buffered Glycerol Saline → Not acceptable, because glycerol is toxic for Vibrios
• Vibrio cholerae pathogenesis


  • Pathogenic only for humans under natural conditions
  • A person with normal gastric acidity may have to ingest as many as 1000 organism or more Vibrio cholerae to become infected when the vehicle is water, because the organisms are susceptible to acid
  • When the vehicle is food, as few as 102–104 organisms are necessary because of the buffering capacity of food
  • Any medication or condition that decreases stomach acidity makes a person more susceptible to infection with Vibrio cholerae
  • The organisms do not reach the bloodstream but remain within the intestinal tract
  • About 60% of infections with classic V cholerae are asymptomatic
  • Incubation period is 1–4 days
  • There is a sudden onset of nausea, vomiting and profuse diarrhea with abdominal cramps
  • Stools, which resemble rice water, contain mucus, epithelial cells, and large numbers of Vibrios
  • Rapid loss of fluid and electrolytes, which leads to profound dehydration, circulatory collapse, and anuria
  • Serotype O1 is responsible for major pandemics (worldwide epidemics) with significant mortality in developing countries, O139 can cause similar diseases and may cause a pandemic
  • Organism can multiply freely in water, Bacterial levels increase
• Vibrio cholerae


  Organisms that cause cholera
• As few as 102–104 organisms are necessary to cause cholera because of the buffering capacity of food
• Any medication or condition that decreases stomach acidity


  Makes a person more susceptible to infection with Vibrio cholerae
• The organisms do not reach the bloodstream but remain within the intestinal tract
• About 60% of infections with classic V cholerae are asymptomatic
• Incubation period


  1–4 days
• Symptoms of cholera


  1. Sudden onset of nausea

  2. Vomiting

  3. Profuse diarrhea with abdominal cramps
• Stools


  Resemble rice water, contain mucus, epithelial cells, and large numbers of Vibrios
• Cholera


  • Rapid loss of fluid and electrolytes
  • Leads to profound dehydration, circulatory collapse, and anuria
• Serotype O1


  Responsible for major pandemics (worldwide epidemics) with significant mortality in developing countries
• Serotype O139


  Can cause similar diseases and may cause a pandemic
• Organism can multiply freely in water

  Bacterial levels increase in contaminated waters during the warm months
• Spread by consumption of contaminated food or water
• Direct person-to-person spread is rare because the infectious dose is high; but most organisms are killed by stomach acids
• Microscopic examination of stool not effective because the organism is diluted in the large volume of watery diarrhea
• Diagnosis


  Culture should be performed early in course of disease with fresh stool specimens
• Treatment


  1. Fluid and electrolyte replacement are crucial

  2. Doxycycline (adults), trimethoprim-sulfamethoxazole (children), or furazolidone (pregnant women) is administered
• Improved hygiene is critical for control
• Campylobacter


  Most clinically relevant species are Campylobacter jejuni subsp. jejuni, Campylobacter coli, and Campylobacter fetus subsp. fetus
• Campylobacter jejuni


  Causes diarrhea, the primary disease caused by Campylobacter
• Campylobacter is often transmitted by means of contaminated water and animals, especially poultry and carcasses
• Campylobacter fetus


  Causative agent of bacteremia