CHOLERAE : CHOLERAE Dr.T.V.Rao MD Cholera affects Millions : Cholera affects Millions CHOLERA AFFECTS millions, in endemic areas and causes thousands of deaths especially during seasonal epidemics. Robert Koch, the famous microbiologist of Germany, discovered Vibrio cholerae, the causative organism. Because of its characteristic shape he originally referred to it as comma bacilli. Nearly 7-8 epidemics caused by the pathogen `Vibrio cholerae affected different parts of the world. Discovery of Cholera Organisms : Discovery of Cholera Organisms Cholera came to Florence in 1854 during the Asiatic Cholera Pandemic of 1846-63. Pacini became very interested in the disease. Immediately following the death of cholera patients, he performed an autopsy and with his microscope, conducted histological examinations of the intestinal mucosa. During such studies, Pacini first discovered a comma-shaped bacillus which he described as a Vibrio. He published a paper in 1854 entitled, "Microscopical observations and pathological deductions on cholera" in which he described the organism and its relation to the disease. His microscopic slides of the organism were clearly labeled, identifying the date and nature of his investigations. Spread of Cholera Pandemics : Spread of Cholera Pandemics Filippo Pacini - 1854 : Filippo Pacini - 1854 Filippo Pacini, would gain prominence for his discovery of Vibrio cholera, but not until 82 years after his death, when the international committee on nomenclature in 1965 adopted Vibrio cholerae Pacini 1854 as the correct name of the cholera-causing organism. Until then, many credited Robert Koch (1843-1910) with this seminal discovery. Robert Koch Isolates V.cholerae1883 : Robert Koch Isolates V.cholerae1883 The German physician Robert Koch, like most of the scientific community, was unaware of Pacini's work at the University of Florence. Yet both independently came to a similar conclusion. Since Koch's findings eventually became accepted by his scientific peers, and were widely know in the popular press, he became the acknowledged discoverer of the cholera organism. Recent Cholerae Outbreaks : Recent Cholerae Outbreaks Vibrios in Nature : Vibrios in Nature Vibrios are among the most common bacteria in surface water worldwide.
They appear curved aerobic rods and are motile,possesing a polar flagellum
V.cholerae serogroups O1 and O139 casue cholera in humans, while other vibrios may cause sepsis or enteritis Vibrio cholerae : Vibrio cholerae Epidemiology and spread of Cholera closely parallels the recognition of V.cholerae transmission in water and the development of sanitary system Morphology and Identification : Morphology and Identification V.cholerae is a comma shaped curved rod 2 – 4 µm long’
It is actively motile by means of polar flagellum.
On prolonged cultivation, vibrios may become straight rods that resemble the gram-negative enteric bacteria. Enrichment Medium : Enrichment Medium Enrichment of the fecal specimens are done on Alkaline peptone water
Venktraman Ramakrishan Meidum is simple medium can be used as transport medium Culture : Culture V.cholerae produces convex, smooth,round colonies that are opaque and granular in transmitted light;
Grow well at 370c on many defined media.
Vibrios grow at a very high pH ( 8-5 – 9-5 ) and are rapidly killed by acid
In resource poor laboratories MacConkey’s agar can be used. Selective Medium - TCBS : Selective Medium - TCBS V.cholerae grows well on Thiosulphate citrate bile sucrose (TCBS ) agar, on which it produces yellow colonies that are readily visible against the dark green background of the agar. Growth Characteristics : Growth Characteristics V.cholerae ferments sucrose and mannose but not arabinose
A positve Oxidase test is key step in preliminary identification of V.cholerae and other Vibrios
Vibrio species are susceptible to compound 0/129 and differentiates from Aeromonas
Vibrios usually grow on medium containing 6% NaCl
Halophilic vibrios need and grow in the presence of > 6% Nacl
On Blood agar Vibrios show hemodigesion Antigenic Structure and Biological Classification : Antigenic Structure and Biological Classification Many Vibrios share a single heatlaible H antigen. Antibodies to H antigen are probably not involved in the protection of susceptible hosts.
V.cholerae has O lipopolysachhrade that confer serologic specificity
There are at least 139 O antigen groups
V.cholerae strains of O group 1 and O group 139 cause classic cholera.
Occasionally non 01/non 0139 V.cholerae cause Cholera like disease V.cholerae - typing : V.cholerae - typing V.cholerae 01 has determinants that make possible futher typing
Ogawa, Inaba and
Epidemic V.cholerae is biotyped into
2 El Tor El Tor Vibrios : El Tor Vibrios The El Tor vibrios produce a Hemolysin and positive results with Voges- Proskauer test
Resistant to Polymyxin B
Molecular techniques can also be used to type V.chlorae
Tests can be done reference laboratories and technically demanding New Epidemic of V.cholrae 0139 : New Epidemic of V.cholrae 0139 The epidemic of cholera caused by V cholerae 0139 has affected at least 1 1 countries in southern Asia. 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. 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. V.cholerae- 0-139 : V.cholerae- 0-139 V.cholerae 0139 is very similar to V.cholerae 01 El Tor biotype
V.cholerae 0139 donot produce 01 type lipopolysachhrade and does not have all the genes necessary to make this antigen
V.cholerae 0139 make a polysachhrdie capsule like other non 01 V.cholerae strains while V.cholerae 01 does not make a capsule V.cholerae 0139 : V.cholerae 0139 V.cholrae 0139 Epidemic : V.cholrae 0139 Epidemic The epidemic of cholera caused by V cholerae 0139 has affected at least 1 1 countries in southern Asia. 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. Vibrio cholerae - Enterotoxin : Vibrio cholerae - Enterotoxin V.cholerae produce heat labile enterotxoin with a Mol wt of about 84,000 consisting of sub units A ( MW 28,000 ) and B
Ganglioside GM1 serves as a mucosal receptor for subunit B, which promotes entry of subunit A into the cell
Activation of subunit A1 yields increased levels of intracellular cAMP and results in prolonged hyper secretion of water and electrolytes
There is increased sodium dependent chloride secretion, and absorption of sodium and chloride is inhibited
The genes for V.cholerae Enterotoxin are on the bacterial chromosome
Cholerae Enterotoxin is antigenically related to LT of Escherichia How Enterotoxin acts : How Enterotoxin acts Pathology and pathogenesis : Pathology and pathogenesis V.cholerae is pathogenic to humans.
When bacteria are consumed with food few organism as much as 102 – 104 organisms are adequate to cause an attack because of the buffering capacity of the food
Any medication or conditions that decreases stomach acidity makes a person more susceptible to infection with V.cholrae
But a person with normal normal gastric acidity has to consume 1010 or more V.cholerae are when ingested with water Clinical events in Cholera : Clinical events in Cholera Pathology : Pathology Cholera is not an invasive infection
Organisms do not reach blood, only act locally
Virulent V.cholerae organism attach to the microvillus of the brush border of epithelial cells
They multiply and liberate cholera toxin and perhaps Mucinase and Endotoxin. Clinical manifestations : Clinical manifestations Diarrhea occurs as much as 20 – 30 Liters/Day fluids are lost.
Results in dehydration
Can lead to death.
About 60% of infections are caused with classic V.cholerae and are asymptomatic, about 75% of infections are caused by El Tor biotype Clinical features : Clinical features The incubation period is 1 – 4 days for person who develop symptoms, depends on the size of the inoculums ingested
Nausea , vomiting,
profuse diarrhea, and abdominal cramps
Rice water stool characteristic of cholera
loss of fluid leads to profound dehydration
Circulatory collapse and anuria. Stool Examination : Stool Examination Stool specimen appear as Rice water
On Microscopy contain Mucus, epithelial cells and large number of Vibrios.
Milder cases difficult to differentiate from other diarrheal diseases.
El Tor vibrios cause milder disease than classic biotypes. Specimen Collections : Specimen Collections Stool specimens are collected in acute stage of the disease. before the antibiotics are administered.
Simple collection of stool in a wide Mouthed container is safe and hygienic.
Specimens should not be collected from bed pans.
Vomitus not advised. Laboratory Diagnosis : Laboratory Diagnosis Mucus flecks from stool are cultured.
Smears are not useful for diagnosis.
Dark field microscopy shows rapidly motile vibrios. Laboratory DiagnosisCulture : Laboratory DiagnosisCulture Grwoth is rapid on Blood agar,
On TCBS medium typical colonies can be picked in 18 hours.
The stool specimens can be transported in Venkatraman Ramakrishnan medium
Alkaline peptone water is ideal enrichment medium Bio Chemical Reactions : Bio Chemical Reactions V.cholerae( Classical )
Voges-proskauer test -ve
Polymyxin sensitivity +ve
Group IV phage
Agglutination -ve V.cholerae (El Tor)
+ve Confirmatory Tests for V.cholerae : Confirmatory Tests for V.cholerae V.chlorae organisms are further identified by slide agglutination tests using anti -0 group 1 or group 139 Antisera and by Biochemical reactions Immunity in Cholerae : Immunity in Cholerae Gastric acid produces some protection against cholera vibrios.
An attack of cholera if followed by immunity to reinfection but the duration and degree of immunity are not known.
In experimental animals specific IgA antibodies occur in the lumen of intestine
Vibriocidal antibodies in the serum titer > 1:20 have been associated with protection against colonization and disease
The presence of antitoxin antibodies have not been asociated with protection When you suspect Cholera : When you suspect Cholera The diagnosis of cholera should be considered in patients with watery diarrhea who have recently (i.e., within 7 days) returned from cholera-affected countries. Patients with suspected cholera should be reported immediately to local and state health departments. Treatment : Treatment The most important part of therapy consists of correction water and electrolyte imbalance to correct severe dehydration and salt depletion.
Oral Tetracycline tends to reduce stool output in cholera and shortens the period of excretion of vibrios
In some endemic areas tetracycline resistance has emerged the genes are carried by transmissible plasmids Vaccines for Cholera : Vaccines for Cholera The licensed parenteral cholera vaccine provides only limited and brief protection against V cholerae 01, may not provide any protection against V cholerae 0139, and has a high cost-benefit ratio; therefore, the vaccine is not recommended for travelers. New oral cholera vaccines are being developed. Newer Vaccines : Newer Vaccines New oral cholera vaccines are being developed and provide more reliable protection, although still at a high cost per case averted. None of these vaccines have attained the combination of high efficacy, long duration of protection, simplicity of administration, and low cost necessary to make mass vaccination feasible in cholera-affected countries. CDC – On Vaccination for Cholerae : CDC – On Vaccination for Cholerae Cholera vaccine is no longer required, nor recommended for the vast majority of travelers by the Centers for Disease Control and Prevention (CDC). Epidemiology of Cholerae : Epidemiology of Cholerae Six Pandemics of Cholera occurred between 1817 – 1923.
Most likely V.cholerae 01 of Classical type contributed to pandemics.
All pandemics originated in Indian continent.
The seventh pandemic originated in Celebes Islands in Indonesia on 1961.
Spread far and wide 8th Pandemic ?Spread of 0-139 : 8th Pandemic ?Spread of 0-139 Several identify that onset of 0-139 is considered as 8th pandmeic started in India.
Cholerae is spread by contact with persons in early or even mild illness.
By contaminated water, food, flies
Only 1 -5% of exposed will get effected
Carrier stage seldom exceeds 3- 4 weeks. Control of Cholerae : Control of Cholerae Needs improvement of Sanitation associated with water treatment and food.
Patients infected preferably isolated .
All contacts to be followed up Use of Vaccine and Chemoprophylaxis : Use of Vaccine and Chemoprophylaxis Chemoprophylaxis with antibiotics is effective.
Repated injection of vaccine containing either Lipopolysaccharides extracted from Vibrios or dense Vibrios suspension can offer limited prevention to heavely exposed persons.
Vaccines not useful in Epidemic controls Prevention of Cholera : Prevention of Cholera Although cholera can be life-threatening, it is easily prevented and treated. In the United States, because of advanced water and sanitation systems, cholera is not a major threat; however, everyone, especially travelers, should be aware of how the disease is transmitted and what can be done to prevent it.
Several regions in the Devloping countries continue to be endemic locations. Created for Health awarness in Developing countries : Created for Health awarness in Developing countries Dr.T.V.Rao MD