Gram negative Rods - Lactose fermenters

Question 1

Which gram negative rods are lactose fermenters?

Answer 1

Those that grow in maConKEES.

Question 2

Which gram negative rods are slow fermenters?

Answer 2

Citrobacter, Serratia, others.

Question 3

Which gram negative rods are fast fermenters?

Answer 3

Klebsiella, E. coli, Enterobacter.

Question 4

Where is Klebsiella a normal inhabitant?

Answer 4

GI tract

Question 5

When does Klebsiella cause disease?

Answer 5

When aspirated.

Question 6

What populations are at risk for Klebsiella pnuemonia?

Answer 6

Alcoholics, diAbetics get Aspiration pneumo w/ Abscess in lungs and liver

Question 7

What is the quality of the sputum of Klebsiella pneumonia?

Answer 7

currant jelly - blood/mucus. Caused by abundant polysaccaride capsules.

Question 8

What other organ system does Klebsiella cause disease in?

Answer 8

nosocomial UTIs.

Question 9

Where is E. coli found?

Answer 9

GI and urinary tract

Question 10

What are the modes of E. coli transmission?

Answer 10

Fecal oral, migration up urethra, colonization of catheters, aspiration of oral E. coli

Question 11

In addition to fermenting lactose, what are E. coli’s notable metabolic capabilities?

Answer 11

Beta hemolytic, indole positive (makes indole from tryptophan).

Question 12

What is the significance of E. coli fimbrae?

Answer 12

E. coli fimbrae/pili = colonization factor, significant in cystitis and pyelonephritis.

Question 13

What is the significance of E. coli’s capsule??

Answer 13

Has K antigen. Identifiable in pneumonia, neonatal meningitis.

Question 14

What is the significance of the E. coli LPS?

Answer 14

It is an endotoxin - Lipid A can cause septic shock.

Question 15

What does ETEC stand for, and how does it present?

Answer 15

EnteroTOXIGENIC Escherichia coli. Causes travelers diarrhea.

Question 16

How does ETEC cause diarrhea?

Answer 16

1. Cholera-like heat labile toxin
   (Gs –> cAMP –> secretion of NaCl)
2. Heat stable toxin.
   Binds to receptor on brush border, activates GUANYlate cyclase, produces GMP.–> inhibits resorption of NaCl.

Question 17

What characterizes the diarrhea of ETEC?

Answer 17

Rice-water like diarrhea – like Cholera. No inflammation of invasion.

Question 18

What does EIEC stand for and how does it present?

Answer 18

EnteroINVASIVE e. coli. Bloody diarrhea with WBCs, inflammation/fever.

Question 19

How does EIEC cause symptoms?

Answer 19

Virulence factor from Shigella on plasmid, gives to EIEC.
(5B subunits bind and allow entry.
Asubunit invades and inactivates 60S ribosome, killing intestinal epithelial cell.)
EIEC actually invades intestinal mucosa, and causes necrosis and inflammation.

Question 20

What does EHEC stand for and what does it cause?

Answer 20

Enterohemorrhagic e. coli. Dysentery - bloody diarrhea.

Question 21

What does EHEC secrete?

Answer 21

Shiga-like toxin (inhibits 60S). Also called STEC - shiga-toxin producing E. coli.

Question 22

What distinguishes EHEC from other e. coli?

Answer 22

Does not ferment sorbitol

Question 23

What else can shiga-like toxin create?

Answer 23

Hemolytic-uremic syndrome

Question 24

What is the presentation of HUS?

Answer 24

Anemia, thrombocytopenia, acute renal failure due to microthrombi forming on damaged endothelium –> mechanical hemolysis –> schistocytes –> platelet consumption, decreased renal blood flow.

Question 25

What does EPEC cause?

Answer 25

Diarrhea in children (P for Peds).

Question 26

What distinguishes EPEC from other E. coli?

Answer 26

No toxin produced. Adheres to apical surface, flattens villi, prevents absorption.