Gram negatives I

Question 1

What are some characteristics of G- rods?

Answer 1

Most are enterobacteriaceae

Resistant to Penicillin and Vancomycin

Inhabitants of normal GI flora

Ceftriaxone and Ciprofloaxin normally treatment of choice

Question 2

What are the characteristics of the enterobacteriaceae family?

Answer 2

Gram negative rods with LPS in the cell wall

Serological typing: O antigen, K antigen (capsule), H antigen

All ferment glucose and oxidase negative

Lactose fermentation varies

Question 3

What are some characteristics of Klebsiella?

Answer 3

Non-motile, capsular intestinal flora

Resistant to many antibiotics

Infects immunocompromised people (nosocomial), and aspiration of GI contents

Question 4

What is Klebsilla pneumonia?

Answer 4

Occurs in alcoholics or diabetics, often after aspiration

Classically results in red “currant jelly” sputum

Can also cause lung abscesses

Rare cause of UTIs

Question 5

What are the E. coli diseases?

Answer 5

Watery diarrhea

Bloody diarrhea (dysentery)

UTI/pyelonephritis

Neonatal meningitis

Septicemia

Question 6

Describe Enterotoxigenic E. coli (ETEC).

Answer 6

Plasmid-mediated strain

Produce heat labile (LT) and heat stable (ST) enterotoxins

Causes watery diarrhea in infants and traveler’s diarrhea

No inflammation and no fever

Question 7

Describe Enteropathogenic E. coli (EPEC).

Answer 7

No toxin, no inflammation, no fever

Blunt microvilli, preventing absorption

Causes infantile diarrhea, similar to ETEC

Common in underdeveloped countries

Question 8

Describe Enterohemorrhagic E. coli (EHEC).

Answer 8

Does not ferment sorbitol

Does not invade host cells

Produces Shiga-like toxin (aka verotoxin)

Usually from undercooked beef

Pediatric diarrhea, copious bloody discharge hemorrhagic colitis, intense inflammation and hemolytic uremia

Question 9

What are the effects of Shiga-like toxin?

Answer 9

Endothelium swells, detaches, vessel lumens narrow

Fibrin-platelets aggregation in microvasculature, ischemia and small vessel damage

Hemolysis

Question 10

What is hemolytic uremic syndrome (HUS)?

Answer 10

Occurs in about 10% of EHEC cases, common in children

Triad: hemolytic anemia, thrombocytopenia, acute renal failure (uremia)

HUS + fever, mental status change = TTP

Question 11

Describe Eneroinvasive E. coli (EIEC).

Answer 11

Invasive, enters M cells

Does not produce shiga toxin

Dysentery-like diarrhea, severe inflammation, fever

Very large plasmid

Question 12

What are the treatments for E. coli?

Answer 12

Most E.coli diarrhea is self-limited

Hydration

Antibiotics are rarely used because they may increase toxin release

Question 13

What are the characteristics of gram negative sepsis?

Answer 13

Fever, tachycardia, hypotension

Driven by endotoxin (LPS, Lipid A)

Common presentation: Elderly patient, UTI, + blood culture

Question 14

What diseases are caused by Salmonella spp.?

Answer 14

Gastroenteritis

Typhoid fever

Bacteremia

Localized infections in other sites

Question 15

What are the symptoms of Typhoid fever?

Answer 15

Fever, headache, malaise, and anorexia

Skin rash with rose-colored spots also possible

Question 16

How does typhoid fever spread through the body?

Answer 16

Starts in the small intestine through Peyer’s patches, then spreads to the phagocytes of the lvier, gallbladder, and spleen - causing bacteremia

Survives in the phagosomes in phagocytic cells

Can remain in gallbladder

Question 17

Describe enterocolitis.

Answer 17

Caused by non-typhoid Salmonella

Invasion of epithelia and subepithelial tissue of the small and large intestines

PMN response limits the infection to the gut and the adjacent mesenteric lymph node

Gastric acid important host defense

Question 18

What is septicemia?

Answer 18

Occurs on only about 5-10% of Salmonella infections

Underlying chronic disease: sickle cell or cancer

Bacteremia results in seeding of many organs, with osteomeylitits, pneumonia and meningitis as the most common sequelae

Question 19

What is the treatment for gastroenteritis?

Answer 19

Fluids, electrolytes

Antibiotics not helpful due to resistance

Question 20

What is the treatment for typhoid fever?

Answer 20

Ceftriaxone, Flurorquinolones

Typhoid vaccine available for travelers to high risk areas

Question 21

What are some characteristics of Shigella?

Answer 21

Invades mucosal cells (M cells in Peyer’s patches)

Spreads cell to cell, not through blood

Nonmotile

Produces shigella toxin, but non-toxin strain can cause disease as well

Question 22

What is the virulence mechanism in Shigella?

Answer 22

Targets M cells in Peyer’s Patches

S. dysenteriae strains produce Shiga toxin

Question 23

What is Reiter’s Syndrome?

Answer 23

Arthritis, conjunctivitis and urethritis appear after the intestinal infections by one of the intestinal pathogens

Cause is unclear, most patients are male

Question 24

What is the treatment for Shigella?

Answer 24

Fluids, electrolytes

Antibiotics improve symptoma

Ceftriaxone and cirprofloxacin

Question 25

What is Proteus?

Answer 25

Rare cause of UTIs

Swarm phenotype: Long flagella, Bullseye on agar plate

Produce urease

Associated with struvite kidney stones

Question 26

What is enterobacter?

Answer 26

Rare cause of nosocomial UTIs

Resistant to many antibiotics, most beta-lacams

Treated with Carbabpenems

Question 27

What are Cirtobacter and Serratia?

Answer 27

Not dominant pathogens for any condition

Resistant to many antibiotics

Cirtobacter - GN sepsis

Serratia - distinctive red colonies, hospital outbreaks, sometimes osteomeylitis