Vibrio cholerae

INTRODUCTION:
  • Pacini first discovered a comma-shaped bacillus which he described as a Vibrio. 
  • John Snow (1813-1858) found the link between cholera and contaminated drinking water in 1854, using spot map.
  • Robert Koch Isolated V.cholrae in 1883
  • Cholera is caused by Vibriocholera .01
  • Cholera belongs to category-B of bioterrorism 
  • Cholera is WHO notifiable disease
  • Father of public health is cholera
VIBRIO'S IN NATURE:
  • Vibrio cholerae can survive in extracellular environment.The natural habitat of vibrio cholerae is salt water in coastal areas, where they live for a long periods around planktons.
  • It is transported in Alkaline pH
  • Ingestion of water contaminated by human feces is the most common mode of contamination cholera.
  • Man is the only natural host in which blood group O+ve are more susceptible
MORPHOLOGY & IDENTIFICATION:
  • They appear curved gram negative aerobic rods and are motile,possesing a polar flagellum that shows Darting motility (shooting star)
  • V. cholera is able to stay in GIT because of motility
  • It is non halophilic 
  • V.cholrae is a comma shaped curved rod 2 – 4 ┬Ám long
  • It is actively motile by means of polar flagellum.
  • On prolonged cultivation, vibrio's may become straight rods that resemble the gram-negative enteric bacteria.
ANTIGENIC STRUCTURE & BIOLOGICAL CLASSIFICATION:
  • Many Vibrio's share a single healable H antigen. Antibodies to H antigen are probably not involved in the protection of susceptible hosts.
  • V.cholrae has O lipopolysaccharide that confer serologic specificity
  • Produces indole and reduces nitrates 
  • There are at least 139 O antigen groups
  • V.cholrae strains of O group 1 and O group 139 cause classic cholera.
  • Occasionally non .01/non 0139 V.cholrae cause Cholera like disease
V.cholrae - typing
  • V.cholrae .01 has determinants that make possible futher typing
  1. Vibrio cholerae .O1:
  • Infectious dose: 106 – 108
  • Varies with vehicle of transmission
  1. Gastric acidity
  2. Incubation period 1-3 days (½-5 days)
  3. Salt resistant, Heat and acid sensitive
  • Epidemic V.cholerae is biotyped into
  • Classic
  • El Tor
El Tor Vibrio's:
  • The El Tor biotype of vibrio cholerae was first isolated in Egypt
  • 7th Pandemic of cholera was caused by El Tor
  • The El Tor vibrios produce a Hemolysin and positive results with Voges- Proskauer test
  • Resistant to Polymyxin B
  • El Tor vibrios has three serotypes- Ogawa(found in India), Inaba, Hikojima 
  • Molecular techniques can also be used to type V.cholrae
  • Tests can be done reference laboratories and technically demanding
  • It is much harder than classical vibrios, capable of surviving in the environment much longer.
  • The severity of illness is much less, with a large proportion of mild and asymptomatic infections.
  • Mortality is low and the carrier rate is high.
  • Fewer secondary cases in affected families 
  • Asymptomatic infections common(75%) ,18% mild diarrhea, 1-5% severe-cholera gravis
  • Fast growing in food & Lengthy survival in environment
V.cholrae- 0-139:
  • V.cholrae 0139 is very similar to epidimologically & clinically V.cholrae .01 El Tor biotype
  • V.cholrae 0139 do not produce 01 type lipopolysaccharide and does not have all the genes necessary to make this antigen
  • V.cholrae 0139 make a polysaccharide capsule like other non 01 V.cholrae strains while V.cholrae.01 does not make a capsule
  • V.cholrae 0139 Epidemic:
  1. The epidemic of cholera caused by V cholerae 0139 was discovered in chennai & has affected at least 11 countries in southern Asia.
  2. Strain of V. cholerae in Bengal
  3. V cholerae 0139 produces severe watery diarrhea and dehydration that is indistinguishable from the illness caused by V cholerae 01, and appears to be closely related to V cholerae 01 biotype El Tor strains. 
  4. Specific totals for numbers of V cholerae 0139 cases are unknown because affected countries do not report infections caused by .01 and 0139 separately; however, >100,000 cases of cholera caused by V cholerae 0139 may have occurred. 
Classical cholera vibria:
  • Most severe diarrhea. Read the following statements.
  • The mortality rate of cholera, without treatment is between 25-50%.
  • The incidence of mild and asymptomatic infections is more with El Tor vibrios than with classical cholera vibrios.
  • Most cases of v.parahaemolyticus - associated gastro intestinal illness, regardless of the presentation, are self limited and required neither antimicrobial treatment nor hospitalization. 
  • Non-01 (NAG) strains of V cholerae cause mild, sometimes bloody diarrhea. Symptoms may occasionally be severe, in which case the disease resembles cholera
Exam Question
  • Cholera is caused by Vibriocholera .01 & 0139
  • V.cholrae 0139 is very similar epidimologically & clinically to V.cholrae .01 El Tor biotype
  • V cholerae 0139 was discovered in chennai
  • V cholerae is non halophilic & gram negative aerobic rods and are motile,possesing a polar flagellum
  • Man is the only natural host
  • V cholerae transported in Alkaline pH
  • The El Tor biotype of vibrio cholerae was first isolated in Egypt
  • Commonest serotype of El Tor V. cholerae found in India is Ogawa
  • Increased susceptibility to disease due to V. cholerae is seen in O+ve blood groups
  • Vibriocholera 0139 is the Strain of V. cholerae in Bengal
  • El Tor Vibrio's is much harder than classical vibrios, capable of surviving in the environment much longer.
  • V.cholrae Produces indole & neuraminidase and reduces nitrates 
  • V. cholera is able to stay in GIT because of motility
  • Darting motility (shooting star)occur in V.cholera
  • Vibrio cholera is was discovered by Robert Koch 
  • 7th Pandemic of cholera was caused by El Tor
  • In cholera the highest case fatality is observed in case of Classical cholera vibrio
  • Cholera belongs to category-B of bioterrorism 
  • Father of public health is cholera
  • John Snow found the link between cholera and contaminated drinking water
  • Cholera is WHO notifiable disease
  • Incubation period 1-3 days (½-5 days)

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