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24 Cards in this Set

  • Front
  • Back
A. Morphology; 5 things
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
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
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
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

1. Released when
-Specific effects during infection include
2.pathogenesis of

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)
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

escherichia coli, klebsiella, enterobacter, serratia, citrobacter, proteus, proviencia, morganella
3 most common associated with disease
e. coli, klebsiella, proteus
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
) 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
a. Non-motile

b. Lactose fermenter
c. Possesses mucoid capsule important for virulence
3 Klebsiella Infections
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

-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

nosocomial spread, especially among patients with indwelling urinary catheters
H. Often very resistant to antimicrobials