02c: E. coli and P. aeruginosa

Question 1

Enterobacteriaceae family is gram (pos/neg) (cocci/bacilli) that are (aerobes/anaerobes) and ferment (glucose/maltose/lactose).

Answer 1

Gram-neg coccobacilli (rods);
Facultative anaerobes;
All ferment glucose (some ferment lactose)

Question 2

Enterobacteriaceae family: most strains have (flagella/pili) and are oxidase (pos/neg).

Answer 2

Both (motile);

Oxidase-negative

Question 3

Enterobacteriaceae family is classified on the basis of which 3 major groups of antigens?

Answer 3

1. Somatic O polysaccharide (part of LPS)
2. Capsular K Ag
3. Flagellar H proteins

Ex: E. coli O157:H7

Question 4

List virulence factors for Enterobacteriaceae family.

Answer 4

1. LPS
2. Capsule
3. Ag phase variation
4. Type III secretion systems
5. Nutrient competition (siderophores, hemolysins)
6. Antibiotic resistance

Question 5

T/F: E. coli is the most common facultative anaerobe in the human GI tract.

Answer 5

True

Question 6

E. coli strains that cause gastroenteritis are usually from (endogenous/exogenous) infection. And UTIs?

Answer 6

Exogenous;

Endogenous (move from colon to urethra and ascend to bladder (or further))

Question 7

Aside from the virulence factors found in Enterobacteriaceae family, list the additional factors in E. coli strains that cause UTI/gastroenteritis.

Answer 7

1. Adhesins (resist “washing away” by urine/peristalsis)

2. Exotoxins (enterotoxins)

Question 8

List the clinical diseases that E. coli can produce.

Answer 8

Acronym: GUNS

1. Gastroenteritis
2. UTIs
3. Neonatal meningitis
4. Septicemia

Question 9

List the most common cause of uncomplicated UTIs. And second most common?

Answer 9

1. E. coli

2. S. Saprophyticus

Question 10

Which two bacteria cause most of the CNS infections (neonatal meningitis) in babies under 1 month old?

Answer 10

E. coli and S. agalactiae

Question 11

(X) agar is used to ID E. coli because it is selective for (Y) and differential for (Z).

Answer 11

X = MacConkey 
Y = gram-neg rods (gram-pos bac growth inhibited)
Z = lactose fermenters (colonies appear red/hot pink)

Question 12

Typical treatment of gastroenteritis from E. coli infection.

Answer 12

Supportive care (fluids, electrolytes)

Question 13

Typical treatment of UTI, septicemia, neonatal meningitis from E. coli infection.

Answer 13

Antibiotic therapy

Question 14

List the 3 preventative steps to take to reduce E. coli infections.

Answer 14

1. Good hygiene
2. Infection control
3. Adequate cooking of meat products/washing of veggies

Question 15

(X) is the most common cause of “traveler’s diarrhea”, which involves watery (bloody/nonbloody) stools.

Answer 15

X = Enterotoxigenic E. coli (ETEC)

Nonbloody

Question 16

ETEC, aka (X) E. coli, acts at which site to cause (UTI/Gastroenteritis)?

Answer 16

X = Enterotoxigenic
Gastroenteritis (“traveler’s diarrhea”)

Small intestine (hypersecretion

Question 17

(X) is the most common cause of gastroenteritis in developed countries. How is infection typically acquired?

Answer 17

X = EHEC (Enterohemorrhagic E. coli) aka Shiga toxin E. coli

Via ingestion of undercooked meat (esp beef), unpast milk/juice, uncooked fruit/veggies

Question 18

E. coli O157:H7 is most common strain (in US) associated with (X) disease.

Answer 18

X = gastroenteritis (via shiga toxin E. coli, EHEC)

Question 19

EHEC, aka (X) E. coli, acts at which site to cause (UTI/Gastroenteritis)?

Answer 19

X = Shiga toxin (or enterohemorrhagic)
Gastroenteritis;
Large intestine (kills absorptive cells)

Question 20

Patient infected by Shiga toxin E. coli will present clinically with:

Answer 20

1. Watery, nonbloody diarrhea (that can then progress to bloody diarrhea)
2. Abdominal cramps
3. Hemolytic urea syndrome (if organism enters blood)

Question 21

P. aeruginosa is gram (pos/neg) (cocci/bacilli) that are (motile/non-motile), (aerobe/anaerobe), and oxidase (pos/neg).

Answer 21

Gram-neg coccobacilli (rods);
Motile (usually);
Aerobes;
Oxidase positive

Question 22

T/F: Like E. coli, P. aeruginosa is a lactose fermenter.

Answer 22

False

Question 23

(X) bacteria is so resistant to disinfectants, it can grow in some soaps!

Answer 23

X = P. aeruginosa

Question 24

T/F: Unlike E. coli, P. aeruginosa is not commonly found in normal flora of humans.

Answer 24

True

Question 25

(X) bacteria is a MAJOR problem in hospitals (sinks, faucets, respiratory therapy, etc).

Answer 25

X = P. aeruginosa

Question 26

P. aeruginosa is (strict/opportunistic) pathogen that commonly causes infections in which patient population(s)?

Answer 26

Opportunistic;

1. Extensive burns
2. Chronic resp diseases (ex: CF)
3. Indwelling catheters
4. Immunosuppressed

Question 27

T/F: MRSA is the most common pathogen isolated from patients who have been hospitalized for over 1 week.

Answer 27

False - P. aeruginosa is

Question 28

T/F: P. aeruginosa causes about 50% of all hospital-acquired infections.

Answer 28

False - 10%

Question 29

List the virulence factors of P. aeruginosa.

Answer 29

1. LPS, capsule, pili, flagellum
2. Exotoxin A (and others)
3. Elastase, protease
4. Pyocyanin (blue pigment)
5. Type III secretion system

Question 30

T/F: P. aeruginosa can infect and cause disease in almost all body sites.

Answer 30

True

Question 31

Hospitalized patients on broad-spectrum antibiotics are at increased risk of infection, for example by (X). Why?

Answer 31

X = P. aeruginosa

Antibiotics kill normal flora and selects for resistant bac strains

Question 32

(X) bacterial colonies smell like Kool-aid and are (alpha/beta/gamma)-hemolytic.

Answer 32

X = P. aeruginosa

Beta-hemolytic

Question 33

Treatment for P. aeruginosa.

Answer 33

Antibiotics (though resistance is a problem) - usually combination therapy

Question 34

T/F: Prevention of P. aeruginosa infection includes prophylactic antibiotics for close contacts, especially in hospital setting.

Answer 34

False!! Will promote emergence/selecting of resistant strains