C18 gram-negative rods enteric tract
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Pili: adherence Enterotoxins: cause diarrhea act on the cells of the jejunum and ileum LT: stimulate adenylate cyclase, cause outpouring of fluid, potassium, chloride ST: stimulate guanylate cyclase
Pathogens both within and outside the enteric tract
Escherichia coli
Diseases
urinary tract infection gram-negative rod sepsis neonatal meningitis traveler’s diarrhea----the most common bloody diarrhea
Diarrhea
Enterotoxigenic E coli: watery, nonbloody, self-limited and short duration. Traveler’s diarrhea Enteropathogenic E coli: dysenterylike syndrome----bloody diarrhea, abdominal cramping, and fever O157:H7: bloody diarrhea hemolytic-uremic symdrom
Laboratory diagnosis
Gram-stained smear and culture green sheen on EMB agar
Important features
Produce indole from tryptophan Decarboxylates lysine Uses acetate as its only source of carbon motile
antigens
O antigen: subdivide groups A-I H antigen: phases 1 and 2 Vi antigen: typhoid fever
pathogenesis
three types of infections: enterocolitis enteric fevers septicemia
pathogenesis
All contain endotoxin Secrete several exotoxins (enterotoxins)
antigபைடு நூலகம்ns
Used for identification
1.O antigen: the cell wall antigen, the outer polysaccharide portion of the LPS, is the basis for the serologic typing
characteristics
facultative anaerobe G- rods ferment lactose three antigens: O antigen H antigen K antigen
Habitat and transmission
habitat: human colon neonatal meningitis: during transmission birth diarrhea: fecal-oral route
septicemia
Patient with an underlying chronic disease Cancer Child with enterocolitis Seeding of many organs osteomyelitis
epidemiology
Ingestion of food and water contaminated by human an animal wastes S typhi transmitted only by humans The most frequent animal source is poultry and eggs
septicemia
Begin with fever Little or no enterocolitis Focal symptoms associated with the affected organ
pathogenesis
endotoxin: septic shock enterotoxins: LT: diarrhea ST: diarrhea virulence factors: pili and capsule verotoxin: bloody diarrhea
A. Intestinal tract infection
Enterobacteriaceae &related organisms
large family of G- rods Primarily in the colon of humans and other animals many as part of the normal flora cause a variety of diseases with different pathogenetic mechanisms
G- rods related to the enteric tract
Pathogens both within and outside the enteric tract Pathogens primarily within the enteric tract Pathogens outside the enteric tract
Enterohemorrhagic strains Cause bloody diarrhea Do not cause inflammation No neutrophils in the stool Produce verotoxin Have a life threatening complication: hemolytic-uremic syndroms O157:H7
B. Systemic infection
Capsule: interfere with phagocytosis
Endotoxin: cause several features of Gram-negative sepsis
Clinical findings
The leading cause of community-acquired urinary tract infections Major cause of neonatal meningitis
Lactose fermentation: the most important nonlactose fermenters: colorless colonies Lactose fermenters: colored colonis
Coliforms & public health
Coliforms: E coli and other inhabitants of the colon the presence of coliforms in water: Indicate contamination of the public water supply system criterion: not above 4/dL in municipal drinking water
Common features
All facultative anaerobes Ferment glucose None have cytochrome oxidase Reduce nitrates to nitrites as part of their energy-generating processes
Clinical findings
Enterocolitis nausea and vomitting abdominal pain nonbloody diarrhea self-limited
Typhoid fever
Slowly onset with fever and constipation Bacteremia: high fever, delirium, tender abdomen and enlarged spleen “rose spots” Begin to resolve by the third week Intestinal hemorrhage and perforation Chronic carrier
typhoid
Begin in the small intestine, few gastrointestinal symptoms Bacteremia----endotoxin Survive and grow within phagosomes in phagocytic cells Carrier state
enterocolitis
Invasion of the epithelial and subepithelial tissue of intestines Penetrate through and between the mucosal cells Inflammation and diarrhea Bacteremia is infrequent
2. H antigen: on the flagellar protein 3. K polycaccharide antigen: the capsule antigen, identified by the qurllung reaction.
Laboratory diagnosis Usually inoculated onto two media: blood agar plate selective differential medium EMB based on lactose fermentation suppress unwanted G+ organisms
Salmonella disease
enterocolitis enteric fever---- typhoid fever septicemia with metastatic abscesses
characteristics
facultative G- rods non-lactose-fermenting produces H2S-----identification
chapter 18 gram-negative rods related to the Enteric Tract
overview
Gram-negative rods
related primarily to
the enteric tract the respiratory tract animal sources
Enterotoxin-producing strains Do not cause inflammation Do not invade the intestinal mucosa Cause a watery, nonbloody diarrhea
Enteroinvasive strains Not by enterotoxin formation By invasion of the epithelium of the large intestine Cause bloody diarrhea accompanied by inflammatory cells in the stool
Pathogens both within and outside the enteric tract
Escherichia coli
Diseases
urinary tract infection gram-negative rod sepsis neonatal meningitis traveler’s diarrhea----the most common bloody diarrhea
Diarrhea
Enterotoxigenic E coli: watery, nonbloody, self-limited and short duration. Traveler’s diarrhea Enteropathogenic E coli: dysenterylike syndrome----bloody diarrhea, abdominal cramping, and fever O157:H7: bloody diarrhea hemolytic-uremic symdrom
Laboratory diagnosis
Gram-stained smear and culture green sheen on EMB agar
Important features
Produce indole from tryptophan Decarboxylates lysine Uses acetate as its only source of carbon motile
antigens
O antigen: subdivide groups A-I H antigen: phases 1 and 2 Vi antigen: typhoid fever
pathogenesis
three types of infections: enterocolitis enteric fevers septicemia
pathogenesis
All contain endotoxin Secrete several exotoxins (enterotoxins)
antigபைடு நூலகம்ns
Used for identification
1.O antigen: the cell wall antigen, the outer polysaccharide portion of the LPS, is the basis for the serologic typing
characteristics
facultative anaerobe G- rods ferment lactose three antigens: O antigen H antigen K antigen
Habitat and transmission
habitat: human colon neonatal meningitis: during transmission birth diarrhea: fecal-oral route
septicemia
Patient with an underlying chronic disease Cancer Child with enterocolitis Seeding of many organs osteomyelitis
epidemiology
Ingestion of food and water contaminated by human an animal wastes S typhi transmitted only by humans The most frequent animal source is poultry and eggs
septicemia
Begin with fever Little or no enterocolitis Focal symptoms associated with the affected organ
pathogenesis
endotoxin: septic shock enterotoxins: LT: diarrhea ST: diarrhea virulence factors: pili and capsule verotoxin: bloody diarrhea
A. Intestinal tract infection
Enterobacteriaceae &related organisms
large family of G- rods Primarily in the colon of humans and other animals many as part of the normal flora cause a variety of diseases with different pathogenetic mechanisms
G- rods related to the enteric tract
Pathogens both within and outside the enteric tract Pathogens primarily within the enteric tract Pathogens outside the enteric tract
Enterohemorrhagic strains Cause bloody diarrhea Do not cause inflammation No neutrophils in the stool Produce verotoxin Have a life threatening complication: hemolytic-uremic syndroms O157:H7
B. Systemic infection
Capsule: interfere with phagocytosis
Endotoxin: cause several features of Gram-negative sepsis
Clinical findings
The leading cause of community-acquired urinary tract infections Major cause of neonatal meningitis
Lactose fermentation: the most important nonlactose fermenters: colorless colonies Lactose fermenters: colored colonis
Coliforms & public health
Coliforms: E coli and other inhabitants of the colon the presence of coliforms in water: Indicate contamination of the public water supply system criterion: not above 4/dL in municipal drinking water
Common features
All facultative anaerobes Ferment glucose None have cytochrome oxidase Reduce nitrates to nitrites as part of their energy-generating processes
Clinical findings
Enterocolitis nausea and vomitting abdominal pain nonbloody diarrhea self-limited
Typhoid fever
Slowly onset with fever and constipation Bacteremia: high fever, delirium, tender abdomen and enlarged spleen “rose spots” Begin to resolve by the third week Intestinal hemorrhage and perforation Chronic carrier
typhoid
Begin in the small intestine, few gastrointestinal symptoms Bacteremia----endotoxin Survive and grow within phagosomes in phagocytic cells Carrier state
enterocolitis
Invasion of the epithelial and subepithelial tissue of intestines Penetrate through and between the mucosal cells Inflammation and diarrhea Bacteremia is infrequent
2. H antigen: on the flagellar protein 3. K polycaccharide antigen: the capsule antigen, identified by the qurllung reaction.
Laboratory diagnosis Usually inoculated onto two media: blood agar plate selective differential medium EMB based on lactose fermentation suppress unwanted G+ organisms
Salmonella disease
enterocolitis enteric fever---- typhoid fever septicemia with metastatic abscesses
characteristics
facultative G- rods non-lactose-fermenting produces H2S-----identification
chapter 18 gram-negative rods related to the Enteric Tract
overview
Gram-negative rods
related primarily to
the enteric tract the respiratory tract animal sources
Enterotoxin-producing strains Do not cause inflammation Do not invade the intestinal mucosa Cause a watery, nonbloody diarrhea
Enteroinvasive strains Not by enterotoxin formation By invasion of the epithelium of the large intestine Cause bloody diarrhea accompanied by inflammatory cells in the stool