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12-13_True Pathogens of the Enterobacteriaceae. Salmonella, Shigella &

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True Pathogens of the Enterobacteriaceae:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Salmonella, Shigella & Yersinia

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Слайд 1

Слайд 2True Pathogens
of the Enterobacteriaceae:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Salmonella, Shigella & Yersinia

True Pathogens of the Enterobacteriaceae:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Salmonella, Shigella & Yersinia

Слайд 3Digestive tract is a “tube” (from mouth to anus); technically

“outside” of the body
Lumen = space within tubular or hollow

organ such as an artery, vein, or intestine
Intestinal lumen = the inside of the intestine
Mesentery = membrane attaching organ (e.g., intestine) to body wall; often has lymphoid tissue
Food is moved down tract via peristalsis
Entire length of digestive tract epithelium is covered by mucosal membrane (mucosa) with mucus that is secreted from specialized glands
Surface area of intestine increased by presence of villi (finger-like projections) and microvilli that absorb nutrients and other products of digestion

Anatomy of Digestive Tract

Digestive tract is a “tube” (from mouth to anus); technically “outside” of the bodyLumen = space within

Слайд 4 Mouth, pharynx, esophagus & esophageal sphincter
Stomach and pyloric

valve (sphincter)
Small intestine (about 23 feet in length)
Duodenum (~10”

in length) (bile & pancreatic ducts carry digestive juices secreted by gall bladder, liver & pancreas)
Jejunum (~8 feet in length)
Ileum (final 3/5 of length) and ileocecal valve
Absorbs bile salts & nutrients, including vitamin B12
Large intestine
Cecum(caecum) (blind pouch where appendix also enters)
Colon (ascending, transverse, descending, sigmoid)
Rectum and anus (with internal and external sphincters)

Anatomy of Digestive Tract (cont.)

Mouth, pharynx, esophagus & esophageal sphincter Stomach and pyloric valve (sphincter) Small intestine (about 23 feet

Слайд 5 Coliform bacilli (enteric rods)

Motile gram-negative facultative anaerobes

Non-lactose

fermenting

Resistant to bile salts

H2S producing
General Characteristics of

Salmonella
Coliform bacilli (enteric rods) Motile gram-negative facultative anaerobes Non-lactose fermenting Resistant to bile salts H2S producingGeneral

Слайд 6Classification and Taxonomy of Salmonella (Confused)
Old: Serotyping & biochemical assays

used to name individual species within genus (e.g., Salmonella enteritidis,

S. choleraesuis, S. typhi)
Over 2400 O-serotypes (referred to as species) (Kauffman-White antigenic schema)
Bioserotyping (e.g., S. typhimurium)
New: DNA homology shows only two species Salmonella enterica (six subspecies) and S. bongori
Most pathogens in S. enterica ssp. enterica
Classification and Taxonomy of Salmonella (Confused)Old: Serotyping & biochemical assays used to name individual species within genus

Слайд 7Epidemiology of Salmonella Infection

Epidemiology of Salmonella Infection

Слайд 8Annual Reported Incidence of Salmonella

Infection (excluding typhoid

fever)
Annual Reported Incidence of Salmonella Infection

Слайд 9Clinical Syndromes of Salmonella
Salmonellosis = Generic term for disease

Clinical

Syndromes

Enteritis (acute gastroenteritis)

Enteric fever (prototype is typhoid fever and less

severe paratyphoid fever)

Septicemia (particularly S. choleraesuis, S. typhi, and S. paratyphi)

Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi)
Clinical Syndromes of Salmonella Salmonellosis = Generic term for diseaseClinical SyndromesEnteritis (acute gastroenteritis)Enteric fever (prototype is typhoid

Слайд 10Epidemiology and Clinical Syndromes of Salmonella (cont.)
Enteritis

Most common

form of salmonellosis with major foodborne outbreaks and sporadic disease
High

infectious dose (108 CFU)
Poultry, eggs, etc. are sources of infection
6-48h incubation period
Nausea, vomiting, nonbloody diarrhea, fever, cramps, myalgia and headache common
S. enteritidis bioserotypes (e.g., S. typhimurium)

Epidemiology and Clinical Syndromes of Salmonella (cont.) Enteritis Most common form of salmonellosis with major foodborne outbreaks

Слайд 11Virulence attributable to:
Invasiveness
Intracellular survival & multiplication
Endotoxin
Exotoxins:

Effects in host have not been identified
Several Salmonella serotypes

produce enterotoxins similar to both the heat-labile (LT) and heat-stable enterotoxins (ST), but their effect has not been identified
A distinct cytotoxin is also produced and may be involved in invasion and cell destruction

Pathogenesis of Salmonella
Enteritis (cont.)

Virulence attributable to: Invasiveness Intracellular survival & multiplication Endotoxin Exotoxins: Effects in host have not been identified

Слайд 12Invasiveness in Enteritis (cont.)
Penetrate mucus, adhere to and invade into

epithelial layer (enterocytes) of terminal small intestine and further into

subepithelial tissue
Bacterial cells are internalized in endocytic vacuoles (intracellular) and the organisms multiply
PMN’s confine infection to gastrointestinal (GI) tract, but organisms may spread hematogenously (through blood, i.e., septicemia) to other body sites
Inflammatory response mediates release of prostaglandins, stimulating cAMP and active fluid secretion with loose diarrheal stools; epithelial destruction occurs during late stage of disease

Pathogenesis of Salmonella (cont.)

Invasiveness in Enteritis (cont.)Penetrate mucus, adhere to and invade into epithelial layer (enterocytes) of terminal small intestine

Слайд 13Clinical Progression of Salmonella Enteritis
Lamina propria = thin membrane between

epithelium & basement layer
Hyperplasia = abnormal increase in # of

normal cells
Hypertrophy = abnormal increase in normal tissue/organ size
Prostaglandins = potent mediators of diverse set of physiologic processes
Clinical Progression of Salmonella EnteritisLamina propria = thin membrane between epithelium & basement layerHyperplasia = abnormal increase

Слайд 14Epidemiology & Clinical Syndromes (cont.)
Enteric Fevers

S. typhi

causes typhoid fever S. paratyphi A, B (S. schottmuelleri) and C

(S. hirschfeldii) cause milder form of enteric fever
Infectious dose = 106 CFU
Fecal-oral route of transmission
Person-to-person spread by chronic carrier
Fecally-contaminated food or water
10-14 day incubation period
Initially signs of sepsis/bacteremia with sustained fever (delirium) for > one week before abdominal pain and gastrointestinal symptoms
Epidemiology & Clinical Syndromes (cont.) Enteric Fevers S. typhi causes typhoid fever S. paratyphi A, B (S. schottmuelleri)

Слайд 15Pathogenesis of Salmonella (cont.) Enteric Fevers (cont.)
Virulence attributable to:

Invasiveness
Pass through intestinal epithelial cells in ileocecal region, infect

the regional lymphatic system, invade the bloodstream, and infect other parts of the reticuloendothelial system
Organisms are phagocytosed by macrophages and monocytes, but survive, multiply and are transported to the liver, spleen, and bone marrow where they continue to replicate
Second week: organisms reenter bloodstream and cause prolonged bacteremia; biliary tree and other organs are infected; gradually increasing sustained fever likely from endotoxemia
Second to third week: bacteria colonize gallbladder, reinfect intestinal tract with diarrheal symptoms and possible necrosis of the Peyer’s patches
Pathogenesis of Salmonella (cont.) Enteric Fevers (cont.) Virulence attributable to: Invasiveness Pass through intestinal epithelial cells in

Слайд 16Clinical Progression of Enteric Fever (Typhoid fever)
Lumen

(intraluminal); ileocecal area = see above - Anatomy of Digestive

Tract
RES = sum total of strongly phagocytic cells; primarily found in lymph nodes, blood, liver, spleen and bone marrow
Hyperplastic changes = see hyperplasia above - Clinical Progression of Enteritis
Clinical Progression of Enteric Fever (Typhoid fever)Lumen (intraluminal); ileocecal area = see above -

Слайд 17Microbial Defenses Against Host Immunological Clearance
ENCAPSULATION and
ANTIGENIC MIMICRY, MASKING

or SHIFT

CAPSULE, GLYCOCALYX or SLIME LAYER
Polysachharide capsules Streptococcus pneumoniae, Neisseria

meningitidis, Haemophilus influenzae, etc.
Polypeptide capsule of Bacillus anthracis

EVASION or INCAPACITATION of PHAGOCYTOSIS and/or IMMUNE CLEARANCE
PHAGOCYTOSIS INHIBITORS: mechanisms enabling an invading microorganism to resist being engulfed, ingested, and or lysed by phagocytes/ phagolysosomes
RESISTANCE to HUMORAL FACTORS
RESISTANCE to CELLULAR FACTORS

See Chpt. 19

Microbial Defenses Against Host Immunological ClearanceENCAPSULATION and ANTIGENIC MIMICRY, MASKING or SHIFTCAPSULE, GLYCOCALYX or SLIME LAYERPolysachharide capsules

Слайд 18Methods That Circumvent Phagocytic Killing
See Chpt. 19
, Salmonella typhi

Methods That Circumvent Phagocytic KillingSee Chpt. 19, Salmonella typhi

Слайд 19Septicemia

Can be caused by all species, but more commonly

associated with S. choleraesuis, S. paratyphi, S. typhi, and S.

dublin

Old, young and immunocompromised (e.g., AIDS patients) at increased risk

Epidemiology & Clinical Syndromes (cont.)

Septicemia Can be caused by all species, but more commonly associated with S. choleraesuis, S. paratyphi, S.

Слайд 20Asymptomatic Carriage

Chronic carriage in 1-5% of cases following S.

typhi or S. paratyphi infection

Gall bladder usually the reservoir

Chronic carriage

with other Salmonella spp. occurs in <<1% of cases and does not play a role in human disease transmission

Epidemiology & Clinical Syndromes (cont.)

Asymptomatic Carriage Chronic carriage in 1-5% of cases following S. typhi or S. paratyphi infectionGall bladder usually

Слайд 21Treatment, Prevention and Control of Salmonella Infections
Enteritis:
Antibiotics not recommended for

enteritis because prolong duration
Control by proper preparation of poultry &

eggs
Enteric fever:
Antibiotics to avoid carrier state
Identify & treat carriers of S. typhi & S. paratyphi
Vaccination can reduce risk of disease for travellers in endemic areas
Treatment, Prevention and Control of Salmonella InfectionsEnteritis:Antibiotics not recommended for enteritis because prolong durationControl by proper preparation

Слайд 23 Coliform bacilli (enteric rods)

Nonmotile gram-negative facultative anaerobes

Four species
Shigella sonnei (most common in industrial world)
Shigella flexneri (most

common in developing countries)
Shigella boydii
Shigella dysenteriae

Non-lactose fermenting

Resistant to bile salts

General Characteristics of Shigella

Coliform bacilli (enteric rods) Nonmotile gram-negative facultative anaerobes Four speciesShigella sonnei (most common in industrial world)Shigella

Слайд 24
Shigellosis = Generic term for disease

Low infectious dose (102-104 CFU)
Humans

are only reservoir
Transmission by fecal-oral route
Incubation period = 1-3 days
Watery

diarrhea with fever; changing to dysentery
Major cause of bacillary dysentery (severe 2nd stage) in pediatric age group (1-10 yrs) via fecal-oral route
Outbreaks in daycare centers, nurseries, institutions
Estimated 15% of pediatric diarrhea in U.S.
Leading cause of infant diarrhea and mortality (death) in developing countries

Epidemiology and Clinical Syndromes of Shigella

Shigellosis = Generic term for diseaseLow infectious dose (102-104 CFU)Humans are only reservoirTransmission by fecal-oral routeIncubation period

Слайд 25DEFINITIONS

Enterotoxin = an exotoxin with enteric activity, i.e., affects the

intestinal tract

Dysentery = inflammation of intestines (especially the colon (colitis)

of the large intestine) with accompanying severe abdominal cramps, tenesmus (straining to defecate), and frequent, low-volume stools containing blood, mucus, and fecal leukocytes (PMN’s)

Bacillary dysentery = dysentery caused by bacterial infection with invasion of host cells/tissues and/or production of exotoxins
DEFINITIONSEnterotoxin = an exotoxin with enteric activity, i.e., affects the intestinal tractDysentery = inflammation of intestines (especially

Слайд 26Epidemiology of Shigella Infection

Epidemiology of Shigella Infection

Слайд 27Shigellosis

Two-stage disease:
Early stage:
Watery diarrhea attributed to the enterotoxic

activity of Shiga toxin following ingestion and noninvasive colonization, multiplication,

and production of enterotoxin in the small intestine
Fever attributed to neurotoxic activity of toxin

Second stage:
Adherence to and tissue invasion of large intestine with typical symptoms of dysentery
Cytotoxic activity of Shiga toxin increases severity

Pathogenesis of Shigella

ShigellosisTwo-stage disease: Early stage: Watery diarrhea attributed to the enterotoxic activity of Shiga toxin following ingestion and

Слайд 28Pathogenesis and Virulence Factors (cont.)
Virulence attributable to:

Invasiveness
Attachment (adherence)

and internalization with complex genetic control
Large multi-gene virulence plasmid regulated

by multiple chromosomal genes

Exotoxin (Shiga toxin)

Intracellular survival & multiplication
Pathogenesis and Virulence Factors (cont.) Virulence attributable to: InvasivenessAttachment (adherence) and internalization with complex genetic controlLarge multi-gene

Слайд 29Penetrate through mucosal surface of colon (colonic mucosa) and invade

and multiply in the colonic epithelium but do not typically

invade beyond the epithelium into the lamina propria (thin layer of fibrous connective tissue immediately beneath the surface epithelium of mucous membranes)

Preferentially attach to and invade into M cells in Peyer’s patches (lymphoid tissue, i.e., lymphatic system) of small intestine

Invasiveness in Shigella-Associated Dysentery

Pathogenesis and Virulence Factors (cont.)

Penetrate through mucosal surface of colon (colonic mucosa) and invade and multiply in the colonic epithelium but

Слайд 30M cells typically transport foreign antigens from the intestine to

underlying macrophages, but Shigella can lyse the phagocytic vacuole (phagosome)

and replicate in the cytoplasm
Note: This contrasts with Salmonella which multiplies in the phagocytic vacuole
Actin filaments propel the bacteria through the cytoplasm and into adjacent epithelial cells with cell-to-cell passage, thereby effectively avoiding antibody-mediated humoral immunity (similar to Listeria monocytogenes)

Pathogenesis and Virulence Factors (cont.)

Invasiveness in Shigella-Associated Dysentery(cont.)

M cells typically transport foreign antigens from the intestine to underlying macrophages, but Shigella can lyse the

Слайд 32Methods That Circumvent Phagocytic Killing
See Chpt. 19
, Shigella spp.
Shigella spp.
,

Methods That Circumvent Phagocytic KillingSee Chpt. 19, Shigella spp.Shigella spp.,

Слайд 33Enterotoxic, neurotoxic and cytotoxic

Encoded by chromosomal genes

Two domain (A-5B) structure

Similar

to the Shiga-like toxin of enterohemorrhagic E. coli (EHEC)

NOTE: except

that Shiga-like toxin is encoded by lysogenic bacteriophage

Pathogenesis and Virulence Factors (cont.)

Characteristics of Shiga Toxin

Enterotoxic, neurotoxic and cytotoxicEncoded by chromosomal genesTwo domain (A-5B) structureSimilar to the Shiga-like toxin of enterohemorrhagic E.

Слайд 34Shiga Toxin Effects in Shigellosis
Enterotoxic Effect:
Adheres to small intestine

receptors
Blocks absorption (uptake) of electrolytes, glucose, and amino acids from

the intestinal lumen
Note: This contrasts with the effects of cholera toxin (Vibrio cholerae) and labile toxin (LT) of enterotoxigenic E. coli (ETEC) which act by blocking absorption of Na+, but also cause hypersecretion of water and ions of Cl-, K+ (low potassium = hypokalemia), and HCO3- (loss of bicarbonate buffering capacity leads to metabolic acidosis) out of the intestine and into the lumen

Pathogenesis and Virulence Factors (cont.)

Shiga Toxin Effects in ShigellosisEnterotoxic Effect: Adheres to small intestine receptorsBlocks absorption (uptake) of electrolytes, glucose, and

Слайд 35Cytotoxic Effect:
B subunit of Shiga toxin binds host cell

glycolipid
A domain is internalized via receptor-mediated endocytosis (coated pits)
Causes

irreversible inactivation of the 60S ribosomal subunit, thereby causing:
Inhibition of protein synthesis
Cell death
Microvasculature damage to the intestine
Hemorrhage (blood & fecal leukocytes in stool)

Neurotoxic Effect: Fever, abdominal cramping are
considered signs of neurotoxicity

Shiga Toxin Effects in Shigellosis (cont.)

Pathogenesis and Virulence Factors (cont.)

Cytotoxic Effect: B subunit of Shiga toxin binds host cell glycolipidA domain is internalized via receptor-mediated endocytosis

Слайд 38Yersinia pestis

Clinical Forms of Plague (a.k.a., Black Death):
Bubonic plague with

swollen and painful axillary (arm pit) & inguinal (groin) lymph

nodes (buboes)
Transmitted from mammalian reservoirs by flea (arthropod) bites or contact with contaminated animal tissues
Pneumonic plaque
Person-to-person spread


Yersinia enterocolitica
Enterocolitis
Transfusion-related septicemia

Summary of Yersinia Infections

Yersinia pestisClinical Forms of Plague (a.k.a., Black Death):Bubonic plague with swollen and painful axillary (arm pit) &

Слайд 39Epidemiology and History of Plague
Zoonotic infection; Humans are accidental hosts
Outbreaks

are cyclical corresponding to rodent reservoir and arthropod vector populations
Plague

recorded more than 2000 years ago
Three pandemics
1st 542AD; 100million dead in 60 years; from N.Africa
2nd 14th century; Black Death; 25million dead in Europe alone (>1/4 of entire population); from central Asia; disease became endemic in urban rat population and smaller epidemics occurred through 17th century
3rd ended in 1990s; Burma to China (1894) & Hong Kong to other continents including N. America via rat-infected ships; 20million dead in India alone; foci of infection firmly established in wild rodents in rural areas
Folk stories & nursery rhymes: Pied Piper of Hamelin (Ring Around the Rosie is “urban myth”??)
Epidemiology and History of PlagueZoonotic infection; Humans are accidental hostsOutbreaks are cyclical corresponding to rodent reservoir and

Слайд 40Epidemiology of Yersinia Infection

Epidemiology of Yersinia Infection

Слайд 41Epidemiological Cycles of Plague
Sylvatic (wild) Cycle of Plague
Reservoir (foci) =

wild rodents (prairie dogs, rabbits, mice, dogs)
Vector = wild rodent

flea

Urban (domestic) Cycle of Plague
Reservoir = domestic (urban) black rat
Over 8 million in NYC = human population
Vector = oriental rat flea (Xenopsylla cheopis)

Human Cycle of Plague
Bubonic plague acquired from contact with either sylvatic or urban reservoirs or arthropod vector bite and further transmitted in human population by spread of pneumonic plague
Epidemiological Cycles of PlagueSylvatic (wild) Cycle of PlagueReservoir (foci) = wild rodents (prairie dogs, rabbits, mice, dogs)Vector

Слайд 42Epidemiological Cycles of Plague

Epidemiological Cycles of Plague

Слайд 43Annual Incidence of Plague in U.S.

Annual Incidence of Plague in U.S.

Слайд 44Annual Incidence of Plague in U.S.

Annual Incidence of Plague in U.S.

Слайд 45Arthropod-Borne Transmission of Plague
Fleas required for perpetuation of plague vary

greatly in vector efficiency and host range

Organisms ingested during blood

meal from bacteremic host

Coagulase of flea may cause fibrin clot of organism in stomach which fixes to spines of proventriculus (throat parts of flea)

Organisms multiply causing blockage

Flea regurgitates infectious material into new host during subsequent attempts at blood meal

Flea remains hungry & feeds more aggressively

Sudden eradication of rats could lead to outbreak
Arthropod-Borne Transmission of PlagueFleas required for perpetuation of plague vary greatly in vector efficiency and host rangeOrganisms

Слайд 46Yersinia Summary Table

Yersinia Summary Table

Слайд 47Yersinia Summary Table (cont.)

Yersinia Summary Table (cont.)

Слайд 50See Handouts
REVIEW

See HandoutsREVIEW

Слайд 51Salmonella Summary Table
REVIEW

Salmonella Summary TableREVIEW

Слайд 52Salmonella Summary Table (cont.)
REVIEW

Salmonella Summary Table (cont.)REVIEW

Слайд 53Clinical Syndromes of Salmonella
Salmonellosis = Generic term for disease

Clinical

Syndromes

Enteritis (acute gastroenteritis)

Enteric fever (prototype is typhoid fever and less

severe paratyphoid fever)

Septicemia (particularly S. choleraesuis, S. typhi, and S. paratyphi)

Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi)

REVIEW

Clinical Syndromes of Salmonella Salmonellosis = Generic term for diseaseClinical SyndromesEnteritis (acute gastroenteritis)Enteric fever (prototype is typhoid

Слайд 54Epidemiology and Clinical Syndromes of Salmonella (cont.)
Enteritis

Most common

form of salmonellosis with major foodborne outbreaks and sporadic disease
High

infectious dose (108 CFU)
Poultry, eggs, etc. are sources of infection
6-48h incubation period
Nausea, vomiting, nonbloody diarrhea, fever, cramps, myalgia and headache common
S. enteritidis bioserotypes (e.g., S. typhimurium)

REVIEW

Epidemiology and Clinical Syndromes of Salmonella (cont.) Enteritis Most common form of salmonellosis with major foodborne outbreaks

Слайд 55Virulence attributable to:
Invasiveness
Intracellular survival & multiplication
Endotoxin
Exotoxins:

Effects in host have not been identified
Several Salmonella serotypes

produce enterotoxins similar to both the heat-labile (LT) and heat-stable enterotoxins (ST), but their effect has not been identified
A distinct cytotoxin is also produced and may be involved in invasion and cell destruction

Pathogenesis of Salmonella
Enteritis (cont.)

REVIEW

Virulence attributable to: Invasiveness Intracellular survival & multiplication Endotoxin Exotoxins: Effects in host have not been identified

Слайд 56Clinical Progression of Salmonella Enteritis
Lamina propria = thin membrane between

epithelium & basement layer
Hyperplasia = abnormal increase in # of

normal cells
Hypertrophy = abnormal increase in normal tissue/organ size
Prostaglandins = potent mediators of diverse set of physiologic processes

REVIEW

Clinical Progression of Salmonella EnteritisLamina propria = thin membrane between epithelium & basement layerHyperplasia = abnormal increase

Слайд 57Clinical Progression of Enteric Fever (Typhoid fever)
Lumen

(intraluminal); ileocecal area = see above - Anatomy of Digestive

Tract
RES = sum total of strongly phagocytic cells; primarily found in lymph nodes, blood, liver, spleen and bone marrow
Hyperplastic changes = see hyperplasia above - Clinical Progression of Enteritis

REVIEW

Clinical Progression of Enteric Fever (Typhoid fever)Lumen (intraluminal); ileocecal area = see above -

Слайд 59Shigella Summary Table
REVIEW

Shigella Summary TableREVIEW

Слайд 60Shigella Summary Table (cont.)
REVIEW

Shigella Summary Table (cont.)REVIEW

Слайд 61
Shigellosis = Generic term for disease

Low infectious dose (102-104 CFU)
Humans

are only reservoir
Transmission by fecal-oral route
Incubation period = 1-3 days
Watery

diarrhea with fever; changing to dysentery
Major cause of bacillary dysentery (severe 2nd stage) in pediatric age group (1-10 yrs) via fecal-oral route
Outbreaks in daycare centers, nurseries, institutions
Estimated 15% of pediatric diarrhea in U.S.
Leading cause of infant diarrhea and mortality (death) in developing countries

Epidemiology and Clinical Syndromes of Shigella

REVIEW

Shigellosis = Generic term for diseaseLow infectious dose (102-104 CFU)Humans are only reservoirTransmission by fecal-oral routeIncubation period

Слайд 62DEFINITIONS

Enterotoxin = an exotoxin with enteric activity, i.e., affects the

intestinal tract

Dysentery = inflammation of intestines (especially the colon (colitis)

of the large intestine) with accompanying severe abdominal cramps, tenesmus (straining to defecate), and frequent, low-volume stools containing blood, mucus, and fecal leukocytes (PMN’s)

Bacillary dysentery = dysentery caused by bacterial infection with invasion of host cells/tissues and/or production of exotoxins

REVIEW

DEFINITIONSEnterotoxin = an exotoxin with enteric activity, i.e., affects the intestinal tractDysentery = inflammation of intestines (especially

Слайд 63Shigellosis

Two-stage disease:
Early stage:
Watery diarrhea attributed to the enterotoxic

activity of Shiga toxin following ingestion and noninvasive colonization, multiplication,

and production of enterotoxin in the small intestine
Fever attributed to neurotoxic activity of toxin

Second stage:
Adherence to and tissue invasion of large intestine with typical symptoms of dysentery
Cytotoxic activity of Shiga toxin increases severity

Pathogenesis of Shigella

REVIEW

ShigellosisTwo-stage disease: Early stage: Watery diarrhea attributed to the enterotoxic activity of Shiga toxin following ingestion and

Слайд 64Pathogenesis and Virulence Factors (cont.)
Virulence attributable to:

Invasiveness
Attachment (adherence)

and internalization with complex genetic control
Large multi-gene virulence plasmid regulated

by multiple chromosomal genes

Exotoxin (Shiga toxin)

Intracellular survival & multiplication

REVIEW

Pathogenesis and Virulence Factors (cont.) Virulence attributable to: InvasivenessAttachment (adherence) and internalization with complex genetic controlLarge multi-gene

Слайд 65Enterotoxic, neurotoxic and cytotoxic

Encoded by chromosomal genes

Two domain (A-5B) structure

Similar

to the Shiga-like toxin of enterohemorrhagic E. coli (EHEC)

NOTE: except

that Shiga-like toxin is encoded by lysogenic bacteriophage

Pathogenesis and Virulence Factors (cont.)

Characteristics of Shiga Toxin

REVIEW

Enterotoxic, neurotoxic and cytotoxicEncoded by chromosomal genesTwo domain (A-5B) structureSimilar to the Shiga-like toxin of enterohemorrhagic E.

Слайд 67Yersinia Summary Table
REVIEW

Yersinia Summary TableREVIEW

Слайд 68Yersinia Summary Table (cont.)
REVIEW

Yersinia Summary Table (cont.)REVIEW

Слайд 69Yersinia pestis

Clinical Forms of Plague (a.k.a., Black Death):
Bubonic plague with

swollen and painful axillary (arm pit) & inguinal (groin) lymph

nodes (buboes)
Transmitted from mammalian reservoirs by flea (arthropod) bites or contact with contaminated animal tissues
Pneumonic plaque
Person-to-person spread


Yersinia enterocolitica
Enterocolitis
Transfusion-related septicemia

Summary of Yersinia Infections

REVIEW

Yersinia pestisClinical Forms of Plague (a.k.a., Black Death):Bubonic plague with swollen and painful axillary (arm pit) &

Слайд 70Epidemiology and History of Plague
Zoonotic infection; Humans are accidental hosts
Outbreaks

are cyclical corresponding to rodent reservoir and arthropod vector populations
Plague

recorded more than 2000 years ago
Three pandemics
1st 542AD; 100million dead in 60 years; from N.Africa
2nd 14th century; Black Death; 25million dead in Europe alone (>1/4 of entire population); from central Asia; disease became endemic in urban rat population and smaller epidemics occurred through 17th century
3rd ended in 1990s; Burma to China (1894) & Hong Kong to other continents including N. America via rat-infected ships; 20million dead in India alone; foci of infection firmly established in wild rodents in rural areas
Folk stories & nursery rhymes: Pied Piper of Hamelin (Ring Around the Rosie is “urban myth”??)

REVIEW

Epidemiology and History of PlagueZoonotic infection; Humans are accidental hostsOutbreaks are cyclical corresponding to rodent reservoir and

Слайд 71Epidemiological Cycles of Plague
Sylvatic (wild) Cycle of Plague
Reservoir (foci) =

wild rodents (prairie dogs, rabbits, mice, dogs)
Vector = wild rodent

flea

Urban (domestic) Cycle of Plague
Reservoir = domestic (urban) black rat
Over 8 million in NYC = human population
Vector = oriental rat flea (Xenopsylla cheopis)

Human Cycle of Plague
Bubonic plague acquired from contact with either sylvatic or urban reservoirs or arthropod vector bite and further transmitted in human population by spread of pneumonic plague

REVIEW

Epidemiological Cycles of PlagueSylvatic (wild) Cycle of PlagueReservoir (foci) = wild rodents (prairie dogs, rabbits, mice, dogs)Vector

Слайд 72Epidemiological Cycles of Plague
REVIEW

Epidemiological Cycles of PlagueREVIEW

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