Shigellosis Shigellosis

CholeraCholera

Shigella sonneiShigella sonnei

Properties of Properties of ShigellaeShigellae

Gram-negative rodsGram-negative rodsNonmotile (do not have flagella)Nonmotile (do not have flagella)Nonencapsulated Nonencapsulated Not fastidious to laboratory medium Not fastidious to laboratory medium Do not ferment lactose (during first 48 hours)Do not ferment lactose (during first 48 hours)

Do not form HDo not form H22SSThey produce no gas from the fermentation of They produce no gas from the fermentation of sugars sugars They are human parasites They are human parasites Low infectious dose (<Low infectious dose (<100100 bacteria) bacteria)Reproduce in the enterocytes of colonReproduce in the enterocytes of colon

Antigenic structure of Antigenic structure of ShigellaShigella

O antigen. It used to divide the genus into 4 O antigen. It used to divide the genus into 4 serogroup: serogroup: A, B, C, DA, B, C, D

K antigen. According it shigellae are divided into K antigen. According it shigellae are divided into serotypesserotypes

Modern classification of Modern classification of ShigellaShigella

FamilyFamily – – EnterobacteriaceaeEnterobacteriaceae GenusGenus – – ShigellaShigella

SpeciesSpecies:: Sh. disenteriaeSh. disenteriae – 12 serotypes – 12 serotypes Sh. flexneriSh. flexneri – 9 – 9 serotypesserotypes Sh. boydiiSh. boydii – 18 – 18 serotypesserotypes Sh. sonneiSh. sonnei – 1 – 1 serotypeserotype

Biochemical activity of Biochemical activity of shigellaeshigellae

Species Biochemical feature

Glucose Manitol Lactose Sucrose H2S Indole

Sh. dysenteriae + - - - - +

Sh. flexneri + + - - - +

Sh. boydii + + - - - +

Sh. sonnei + + + (after 48 hours)

+ (after 72 hours)

- -

Virulence factors of shigellaeVirulence factors of shigellae

Adherence Adherence by piliby pili Invasion.Invasion. Ipa-BCD antigen. Ensures entering of Ipa-BCD antigen. Ensures entering of

bacteria to the M-cells of large intestine, spreading to bacteria to the M-cells of large intestine, spreading to the underlying tissue, and apoptosis of phagocytesthe underlying tissue, and apoptosis of phagocytes

Endotoxin Endotoxin that causesthat causes fever, general intoxication fever, general intoxication Exotoxin Exotoxin ((Shiga toxinShiga toxin)) that has a number that has a number

activities:activities: Enterotoxic effect Enterotoxic effect - inflammation of the underlying - inflammation of the underlying

gut wall layer, degeneration of the villi, and local gut wall layer, degeneration of the villi, and local erosion that causes bleeding and heavy mucous erosion that causes bleeding and heavy mucous secretion. secretion.

Cytotoxic effectCytotoxic effect - damage to the intestine, injury to - damage to the intestine, injury to the nerve cells, capillary endothelium, myocardial the nerve cells, capillary endothelium, myocardial and kidney cells. and kidney cells.

Pathogenesis of shigellosisPathogenesis of shigellosis Reservoir of shigellae are ill humans onlyReservoir of shigellae are ill humans only (not (not animals)animals)Mechanism of transmission is fecal-oralMechanism of transmission is fecal-oral. . The 4 F’s – fingers, flies, food, and feces – are the The 4 F’s – fingers, flies, food, and feces – are the principal factors in transmission.principal factors in transmission.Infectious doseInfectious dose is small and depend on virulence of is small and depend on virulence of Shigella, for Sh.disenteriae ID is 10 cells, for Sh.sonnei – Shigella, for Sh.disenteriae ID is 10 cells, for Sh.sonnei – at least 10at least 1044 cells. cells.Incubation periodIncubation period is 1 to 4 days. is 1 to 4 days.Sh.dysenteriae (the most virulent among shigellae) Sh.dysenteriae (the most virulent among shigellae) causes the most severe disease, Sh.sonnei (the least causes the most severe disease, Sh.sonnei (the least virulent among shigellae) causes mild disease.virulent among shigellae) causes mild disease.Manifestations Manifestations of dysentery are fever, vomiting, frequent of dysentery are fever, vomiting, frequent liquid stools containing blood and pus, abdominal cramps, liquid stools containing blood and pus, abdominal cramps, and intestinal pain but unproductive urge to defecate. and intestinal pain but unproductive urge to defecate. Less common symptoms are headache, stiff neck, Less common symptoms are headache, stiff neck, convulsions.convulsions.

ShigellosisShigellosis

within 2-3 dayswithin 2-3 days epithelial cell damageepithelial cell damage

Destructive effect of shigellae resembles effect of enteroinvasive E. coli

The appearance of large The appearance of large intestinal mucosa in intestinal mucosa in Shigella Shigella

(bacillary) dysentery(bacillary) dysentery

Diagnosis of bacillary Diagnosis of bacillary dysenterydysentery

Bacteriologic methodBacteriologic method – isolation of pure – isolation of pure culture from feces and identification:culture from feces and identification:

Morphology properties, Gram-stainingMorphology properties, Gram-stainingBiochemical propertiesBiochemical propertiesAntigenic properties (serological identification)Antigenic properties (serological identification)

Gen diagnosisGen diagnosis - PCR - PCRSerological methodSerological method - revealing of antibody - revealing of antibody titer increasing in pair serum or specific titer increasing in pair serum or specific IgM exposureIgM exposureBacterioscopy method Bacterioscopy method can not be usedcan not be used

TreatmentTreatment

Fluid and electrolyte replacementFluid and electrolyte replacement. .

In severe cases In severe cases antibiotics antibiotics are indicated, in are indicated, in mild cases, non antibiotics are used. Due to mild cases, non antibiotics are used. Due to multiple drug resistance (connected with multiple drug resistance (connected with plasmids) antibiotics sensitivity tests must be plasmids) antibiotics sensitivity tests must be performed.performed.

Antiperistaltic drugs Antiperistaltic drugs are contraindicatedare contraindicated in in shigellosis, because they prolong the fever, shigellosis, because they prolong the fever, diarrhea, excretion of the microorganisms, diarrhea, excretion of the microorganisms, and can provoke ulcers formation. and can provoke ulcers formation.

Vibrio choleraeVibrio cholerae

Properties of VibrioProperties of Vibrio choleraecholerae

Gram negativeGram negative motile rodmotile rod

comma shapedcomma shaped

facultative anaerobefacultative anaerobe

oxidase positiveoxidase positive

it has one flagellum at one endit has one flagellum at one end

it is able to tolerate strong alkaline it is able to tolerate strong alkaline conditions and high salt concentrationsconditions and high salt concentrations

readily cultivatedreadily cultivated

Vibrio cholerae. Vibrio cholerae. Micrograph of bacteria in tissueMicrograph of bacteria in tissue

Curved shape and single polar flagellum

Genuses ofGenuses of Vibrionaceae that Vibrionaceae that are medically importantare medically important

Vibrionaceae

Vibrio Aeromonas Plesiomonas

V. cholerae causes cholera

V. parahaemolyticus is primarily marine organism (halophilic). It causes diarrhea associated with eating raw or improperly cooked seafood

V. vulnificus is found in seawater (halophilic). It causes severe skin and soft tissue infections, can cause a rapidly fatal septicemia in immunocompromised people

Antigenic structure of Antigenic structure of vibriosvibrios

O (somatic) antigen. There are 150 O (somatic) antigen. There are 150 serogroup of vibriosserogroup of vibrios

H (flagella) antigen. It is common H (flagella) antigen. It is common antigen for all vibriosantigen for all vibrios

Electron micrograph of Vibrio Electron micrograph of Vibrio cholerae cholerae

Classification of Vibrio Classification of Vibrio choleraecholerae

Family Family VibrionaceaeVibrionaceae

GenusGenus VibrioVibrio

Species Species ВидВид choleraecholerae

Serogroup Serogroup Agents of cholera belong to O1 Agents of cholera belong to O1 serogroup and O139 serogroup (serogroup and O139 serogroup (a a new strain of V.cholerae that appeared new strain of V.cholerae that appeared in India in late 1992in India in late 1992))

BiotypesBiotypes Classic and El TorClassic and El Tor

Serotypes Serotypes OgawaOgawa, , InabaInaba, , HikojimaHikojima

Chemogroups of vibrios according Chemogroups of vibrios according to Heiberg classificationto Heiberg classification (1935) (1935)

Chemogroup Fermentation of carbohydrates

Mannose Arabinose Sucrose

І + - +

ІІ - - +

ІІІ + + +

IV - + +

V + - -

VI - - -

V. cholerae belongs to I chemogroup

Differentiation of biotypes V. Differentiation of biotypes V. cholera classic and El Torcholera classic and El Tor

Feature V. cholerae classic

V. cholerae El Tor

Susceptibility to group IV (C) bacteriophage

+ -

Susceptibility to group II (El Tor) bacteriophage

- +

Sensitivity to polymyxin + -

Agglutination of chicken erythrocytes

- +

Hemolysis - +

Hemolysis testHemolysis test

Classic El Tor

V. cholerae classic and El Tor V. cholerae classic and El Tor growth on the blood agar growth on the blood agar

Classic El Tor

Virulence factors of Virulence factors of V.choleraeV.cholerae

AdherenceAdherence to mucosa layer of small intestine by pili to mucosa layer of small intestine by piliEnzyme of virulenceEnzyme of virulence – mucinase, hyaluronidase. – mucinase, hyaluronidase.ExotoxinExotoxin (cholerogen). The heat labile enterotoxin (cholerogen). The heat labile enterotoxin that consist of an A (active) and a B (binding) that consist of an A (active) and a B (binding) subunits. The B subunit binds to a ganglioside subunits. The B subunit binds to a ganglioside receptor on the surface of the enterosyte. The A receptor on the surface of the enterosyte. The A subunit is inserted into the cytosol, where cause subunit is inserted into the cytosol, where cause activation of the enzyme adenylate cyclase. The activation of the enzyme adenylate cyclase. The resulting overproduction of cAMP (cyclic adenosine resulting overproduction of cAMP (cyclic adenosine monophosphate) stimulates secretion of chloride monophosphate) stimulates secretion of chloride ions and water, leading to a massive watery diarrhea ions and water, leading to a massive watery diarrhea without inflammatory cells. without inflammatory cells. EndotoxinEndotoxin cause inhibition of phagocytosis, decrease cause inhibition of phagocytosis, decrease of blood pressure, general intoxication of blood pressure, general intoxication

Pathogenesis of choleraPathogenesis of cholera

Sours of infectionSours of infection are ill humans of carries. are ill humans of carries.

The main animal reservoirs are marine shellfish, such The main animal reservoirs are marine shellfish, such as shrimp and oysters.as shrimp and oysters.

TransmissionTransmission fecal-oral, with feces contaminated fecal-oral, with feces contaminated water or food. water or food.

Infectious doseInfectious dose is approximately 1 billion of is approximately 1 billion of bacteria. bacteria.

Incubation periodIncubation period is a few hours to a few days. is a few hours to a few days.

Pathogenesis of choleraPathogenesis of cholera

ColonizationColonization of small of small intestine. Vibrio penetrate intestine. Vibrio penetrate the mucous barrier of the mucous barrier of duodenum using their duodenum using their flagellum, flagellum, adhereadhere to the to the microvilli of the epithelial microvilli of the epithelial cells and multiply there. cells and multiply there.

Adherence is related to Adherence is related to secretion of the bacterial secretion of the bacterial enzyme mucinaseenzyme mucinase, which , which dissolves the protective dissolves the protective glycoprotein coating over glycoprotein coating over the intestinal cells.the intestinal cells.

Visible damage intestinal Visible damage intestinal epithelial cells is absence. epithelial cells is absence.

Vibrios Villus surface

Cholera - attachmentCholera - attachment

V. cholerae bacteria, unlike the shigellae, do not penetrate into the intestinal cells

Mechanism of infectious Mechanism of infectious diarrheadiarrheaIntestinal epithelium

Secretion of fluids

Bacteria

Non-Non-blooding blooding diarrhea diarrhea

BloodinBlooding g diarrhea diarrhea

Pathogenesis of cholera.Pathogenesis of cholera.Symptoms of choleraSymptoms of cholera

Due to cholerogen symptoms of disease occur. Vomiting, secretory diarrhea, dehydration lead to muscle, circulatory, and neurological symptoms and death. Watery diarrheal fluid contains flecks of mucus and therefore has been described as “rice-watery stool”.

Fluid losses of nearly one liter per hour (to 20 liters a day) have been reported in severe cases, and an untreated patient can lose up to 50% of body weight during the course of the disease.

The diarrhea causes loss of blood volume, acidosis from bicarbonate loss, and potassium depletion that predispose the patient to muscle cramps, and, in young children, coma and convulsions.

The loss of fluid and electrolytes leads to cardiac and renal failure.

Secondary circulatory consequences can include hypotension, tachycardia, cyanosis, and collapse from shock within 18 to 24 hours.

Mortality rate from cholera approaches 55%.

DiagnosisDiagnosis

Material from patient – Material from patient – stool samplesstool samples

Methods of diagnosis:Methods of diagnosis:

Bacterioscopy.Bacterioscopy. Direct dark-field microscopic observation. Curved cells Direct dark-field microscopic observation. Curved cells with darting motility. with darting motility.

Gram stained swab of feces. Gram negative curved Gram stained swab of feces. Gram negative curved rodsrods

Indication of specific antigenIndication of specific antigen of the V. cholerae of the V. cholerae with immunofluorescence test.with immunofluorescence test.

Bacteriological method.Bacteriological method. Isolation and Isolation and identification of pure culture. identification of pure culture.

Serological methodSerological method.. Detection of rising antitoxin Detection of rising antitoxin titer in the serumtiter in the serum

TherapyTherapy

Replacement of water and Replacement of water and electrolyteselectrolytes

Antimicrobial therapy – antibioticsAntimicrobial therapy – antibiotics

PreventionPrevention

Vaccines are available, butVaccines are available, but partially effective not generally used used only for international travelers and people, living in endemic regions

Types of vaccines:

Killed cholera vibrios. But it protect for only 6 months or less.

Oral attenuated vaccine containing live vibrios. It is more effective.