Enteric bacteria

Question 1

Actin polymerization organisms (2)

Answer 1

Shigella

Listeria (not in this unit)

Question 2

Shigella bacteriology (gram, lactose, H2S, intra/extra cellular)

Answer 2

Gram (-) rod

Non-lactose fermenting

Non-H2S fermenting

Non-motile

Question 3

Lactose fermenters (4)

Answer 3

CEEK

1. Citrobacter
2. Enterobacter
3. Escherichia
4. Klebsiella

Question 4

Non-lactose fermenters (4)

Answer 4

ShYPS

Nonmotile, non-H2S producers

• Shigella
• Yersina

Motile, H2S producers

• Proteus
• Salmonella

Question 5

Shiga toxin

Answer 5

Similar to EHEC shigella-like toxin

Produced by S. dysenteriae

3 activities: neurotoxic, cytotoxic, enterotoxic

• AB component toxin – inhibits protein synthesis by clipping 60S ribosomal subunit

Question 6

Shiga toxin - complications

Answer 6

1. HUS – occurs when the toxin starts to bind to kidneys
2. Reactive arthritis (Reiter’s syndrome)

Question 7

Shiga toxin - toxicities (3)

Answer 7

• Neurotoxic – to neurons
• Cytotoxic – to cells (in general)
• enterotoxic – to gut

Does this b/c it is an AB component toxin that inhibits protein synthesis at the 60S subunit

Question 8

Is Shigella invasive?

Answer 8

Yes.

Invades the M cells (cells of Peyer’s patch) –> will cause bloody diarrhea once it begins invasion

Question 9

Shigella - disease in humans

Answer 9

• extremely acid resistant (only need 1-10 organisms to start an infection)
• 1-4 day incubation
• Fever (generally > 101 F), first watery diarrhea followed by bloody diarrhea once the organism invades.
  
  • invasion rarely causes septicemia, but it does cause shallow ulcers

Question 10

Shigella - most severe strain

Answer 10

S. dysenteriae type 1 (has the Shiga toxin)

Question 11

Non-infectious foodborne disease (3)

Answer 11

1. S. aureus – toxin secreted into room temp food that patient later ingests
2. B. cereus – rich/starches, also associated w/ foods left out too long
3. C. botulinum – airtight-packed foods (flaccid paralysis)

Onset for all 3 are very fast (preformed toxin)

Question 12

Salmonella - bacteriology

Answer 12

Gram (-) rod

motile, H2S (+)

oxidase (-), urease (-)

Seldom lactose fermenting

Question 13

What predisposes you to Salmonella infections? (2)

Answer 13

1. Impairment of mononuclear cells (ie Sickle cell)
2. Decreased stomach acid

Question 14

What species do you have to worry about in Salmonella?

Answer 14

S. typhi – typhoid fever

other subsets (many), but predominantly, S. enteritidis, and S. typhimurium

Question 15

Is Salmonella sensitive to acid?

Answer 15

Yes. Need huge dose to catch it. (also why you are more susceptible to it if you have decreased stomach acid)

Fecal-oral transmission (from human carriers – gallbladder)

Question 16

Salmonella typhi - pathogenesis

Answer 16

• Reaches M cells then travels around using macrophages
• Survives intracellularly and replicates in macrophages
  
  • decreased fusion of lysosomes with phagosomes
  • defensins (proteins) allow it to withstand O2-dependent and O2-independent killing
• Released from macrophages, the Vi capsular antigen (S. typhi only) withstands complement-mediated killing
• Tends to infect the biliary system and stay in the gallbladder (organisms enter the intestinal tract in bile)

Question 17

Salmonella typhi - overall prognosis and treatment?

Answer 17

Causes typhoid fever, which isn’t that lethal, however the morbidity is very high (with a lot of fever, headache, abdominal pain

• Constipation is more common than diarrhea

Treat with: fluoroquinolones or 3rd gen cephalosporins

Question 18

Salmonella typhi - what occurs more diarrhea or constipation?

Answer 18

Despite it being an enterobacteria, it commonly causes more constipation than diarrhea. Typically occurs first and then followed by diarrhea.

Question 19

Salmonella typhi - complication(s)

Answer 19

• Necrosis of Peyer patches with perforation (local endotoxin triggered damage)
• thrombophlebitis
• cholecystitis
• pneumonia
• abscess formation

etc…

Question 20

Salmonella typhi - which organ does it like the most?

Answer 20

Gallbladder – organisms can enter intestinal tract via bile

Question 21

Salmonella typhi - prevention

Answer 21

Sanitation

Three vaccines (either against the S. typhi or against the polysaccharide capsule)

Question 22

Salmonella typhi - how does it travel throughout the body?

Answer 22

In macrophages

• decreased fusion of lysosomes with phagosomes
• defensins (proteins) allow it to withstand O2 dependent and independent killing
• Vi capsular antigen withstands complement mediated killing

Question 23

Salmonella - laboratory detection test

Answer 23

Antibodies to O, Vi and H antigens in patient’s serum can be detected by agglutination (Widal test)

• Vi antigen ONLY for typhi

Question 24

Patient with fever, abdominal pain

Travel to an endemic area

Gram (-), encapsulated, nonlactose fermenter, produces H2S gas

Widal test

Answer 24

Salmonella typhi

Question 25

What agar can be used to culture H2S (+) organisms? What is their appearance?

Answer 25

Hektoen agar

If H2S (+) –> black colonies

Question 26

Chronic carriers of Salmonella typhi carry the bug where?

Answer 26

In their gallbladder

Question 27

Salmonella typhi - clinical presentation

Answer 27

Rose collared spots (trunk/abdomen)

Constipation more common than diarrhea

Complications

• necrosis of Peyer patches w/ perforation (local endotoxin mediated)
• thrombophletitis
• cholecystitis
• pneumonia
• pea-soup diarrhea