micro Enterobaceriaceae
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GENERAL CHARACTERISTICS OF ENTEROBA CTERIA CEAE
A. Morphology; 5 things
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1. Gram-negative bacilli
2. Large organisms with parallel sides and rounded ends
3. Motile strains have peritrichous flagella
4. Many strains have surface pili
5. Some species are encapsulated - B. Growth
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1. Grow readily on simple media after 12 to 18 hours incubation
2. Rapid growth occurs under aerobic and anaerobic conditions - C. Antigenic structure and related to heat
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1. O antigen (somatic) - cell wall lipopolysaccharide (causes disease), LPS (heat stable)
2. K antigens - cell surface polysaccharide antigens (heat labile)
3. H antigens - flagellar proteins (heat labile)
4. Serotyping systems for classification of these organisms have been
Established based upon these antigens, (eg. E. coli 0157:H7) -
Criteria for classification to species level
3 types -
identified on the basis of 1.growth requirements and 2.biochemical characteristics together with
3. DNA homology data - All Enterobacteriaceae share the following biochemical characteristics 3
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a. Ferment glucose
b. Reduce nitrates to nitrites
c. Oxidase negative - fermenting lactose makes
- pink colonies on MacConkey agar used for screening
- ferment lactose (pink)
- a. E. coll, Klebsiella, Enterobacter
- rarely lactose positive
- Salmonella, Shigella, Yersinia
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Toxins
1. Released when
-Specific effects during infection include
2.pathogenesis of -
Endotoxins
a. Synthesized by all Enterobacteriaceae
-cell wall is disrupted (cell dies
-fever, leukopenia, activation of blood coagulation factors
. Enterotoxins
are produced by some species and are important in the pathogenesis of diarrheal disease (travellers diarrhea) -
Habitat
survive in
Increased colonization -
1. Inhabitants of the lower gastrointestinal tract of humans and animals
2. Survive readily in nature - free living where water and minimal energy sources are available
3. of hospitalized patients observed -
6 Diseases caused by Enterobacteriaceae
a liitle like what bacteria -
1.Urinary tract infections most common
2. Diarrhea (gastrointestinal)
3. Meningitis (elderly, neonates, neurosurgical patients)
4. Bacteremia (sepsis)
5. Pneumonia (especially hospital acquired)
6. Wounds and abscesses
-staff - III. SPECIFIC GENERA AND 8 DISEASES OTHER THAN THOSE ASSOCIATED WITH DIARRHEA
- escherichia coli, klebsiella, enterobacter, serratia, citrobacter, proteus, proviencia, morganella
- 3 most common associated with disease
- e. coli, klebsiella, proteus
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e. coli
found in
leading cause of -
a. Most commonly encountered enteric rod in the colon
b. Leading cause of opportunistic infections - identify e. coli 2 things
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) lactose fermenter (pink colonies on MacConkey)
3) beta-hemolytic -
. E. coli Infections
E. coli sp. are one of the most common cause -
a. Most common cause of urinary tract infections (35-90%)
b. Intestinal infections
c. Meningitis
1) E. coli sp. are one of the most common causes of neonatal meningitis
2) 75% of strains possess Kl capsular polysaccharide
d. Nosocomial and opportunistic infections
1) wounds / abscesses
2) bacteremia
3) pneumonia - -are the most important species of klebsiella
- (K. pneumoniae and K. oxytoca are the most important species
- 1. 3 Klebsiella Bacteriology
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a. Non-motile
b. Lactose fermenter
c. Possesses mucoid capsule important for virulence - 3 Klebsiella Infections
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a. Second most common urinary pathogen
b. Pneumonia (Friedlander's pneumonia (red jelly phlem))
c. Nosocomial (hospital) infections - multiple drug resistance a problem in this setting -
C. Enterobacter
Bacteriology
-common cause of ..
-more or less virulent than kelvsiella?
-Associated with hospital outbreaks related to
-what else is a problem? -
15 species, 11 clinically significant)
a. Motile
b. bactose fermenter
nosocomial infections
a. Less virulent than Klebsiella
b.contaminated intravenous solutions
c.Multiple drug resistance is a problem -
Serratia (10 species or groups)
3 things to know -
1. Some strains may have red pigment
2. Truly an opportunistic pathogen (S. marcescens)
4. Multiresistant -
E. Citrobacter
most important types
Biochemically, serologically similar
2. Causes -
11 species or groups C.freundii, C. koseri are most important
-to Salmonella
-neonatal meningitis and bacteremia -
Proteus (4 species
which ones swarm
which one is most important
-what does it cause -
P. mirabilis, P. vulgaris "swarm" over agar surface
2. P. mirabilis is the most important; causes urinary, wound and bloodstream infections -
G. Providencia, Morganella
Frequently associated with
-often... -
nosocomial spread, especially among patients with indwelling urinary catheters
H. Often very resistant to antimicrobials