MICRO: Specifics

Question 1

How does shigella invade?

Answer 1

proliferate in epithelial cells and move into LP where is is phagocytosed by macrophages and will apoptose them and lead to inflammation and damage. Spreads via F-actin polymerization (formins)

Question 2

Treatment for shigella.

Answer 2

Ceftriaxone, Ciprofloxacin, Azithromycin

Question 3

1 week incubation, 1 week illness.

Answer 3

Shigella

Question 4

How does shiga toxin work?

Answer 4

B: binds toxin to cell
A: enters cytosol and removes adenine from large 28S ribosomal subunit to inhibit protein synthesis and cause death

Question 5

How long is EHEC infection?

Answer 5

8 days

Question 6

How do you treat EHEC?

Answer 6

DON’T! Antibiotics can lead to HUS

Question 7

How does HUS work?

Answer 7

Shiga toxin is absorbed from GI mucosa into circulation where it alters endothelial cell funciton to activate platelets and cause aggregation. Hemolytic anemia occurs (shistocytes occur as RBCs pass through clotted off area) and renal failure (receptors for shiga on kidney epithelium) and thromboyctopenia (platelets aggregate)

Question 8

How do you treat HUS?

Answer 8

dialysis

Question 9

How does EIEC invade?

Answer 9

Invades colon and proliferates in epithelial cells, extending into adjacent intestinal cells

Question 10

How long does EIEC last?

Answer 10

1 week

Question 11

1-3 day incubation, 3-4 day illness.

Answer 11

Salmonella enteritidis

Question 12

How does salmonella enteritidis infect?

Answer 12

type III secretion system, bacteria grows in endosomes and enters LP where it causes inflammatory response and kills macrophages (may disseminate if immunocompromised)

Question 13

How do you treat salmonella enteritidis?

Answer 13

DON’T unless at risk for dissemination (then use flouroquinolones)

Question 14

5-21 day incubation, 3 week-3 month illness

Answer 14

Salmonella enterica (serotype typhimurium)

Question 15

How does typohoid fever infect?

Answer 15

Taken up in small intestine, invades, macrophage take up and go to lymph tissue which dumps into the RES system. Can enter blood (bacteremia), can proliferate in peyer’s patch (necrosis, perforation, secondary bacteremia), or can chronically carry in GI.

Question 16

How do you diagnose typhoid fever?

Answer 16

blood cultures

Question 17

How do you treat typhoid fever?

Answer 17

Ceftriaxone, Ciprofloxacin, Azithromycin

Question 18

Incubation 1 week, 3-7 day illness

Answer 18

Campylobacter jejuni

Question 19

How does Guillian Barre occur?

Answer 19

molecular mimicry where antibody to C. jejuni cross reacts with peripheral and CNS gangliosides (ascending paralysis)

Question 20

How do you treat campylobacter jejuni?

Answer 20

Usually don’t, only treat severe infections: ciprofloxacin or azithromycin

Question 21

What are the 2 bugs that cause inflammatory diarrhea that are NOT GN anaerobic rods?

Answer 21

Clostridium Difficile (gram positive rods)
Yersinia Enterocolitica (gram neg coccobacilli)

Question 22

What is the overall effect of C. diff exotoxins?

Answer 22

glucosylation of small GTPases (ex. Rho) that are involved with cytoskeletal structure and signal transduction

Question 23

What type of exotoxin is c. diff toxin A?

Answer 23

enterotoxin

Question 24

What type of exotoxin is c. diff toxin B?

Answer 24

cytotoxin

Question 25

What is the action of c. diff toxin A?

Answer 25

disrupts colon epithelial cell Adherence to bassement membrane and damages the villous tips (leading to fluid secretion)

Question 26

What is the action of c. diff toxin B?

Answer 26

depolymerizes actin to decrease cytoskeletal integrity and cause apoptosis of enterocyte

Question 27

What is the common pathway of c. diff toxins A and B?

Answer 27

increase monocytes and macrophages to increase IL-8, recruit PMNs, and disrupt epithelial tight junctions

Question 28

How do you diagnose c. diff?

Answer 28

PCR or EIA for toxins (cell culture cytotoxicity assay, but can be negative)

Question 29

How do you treat c. diff?

Answer 29

Metronodiazole (Flagyl) is first line. PO Vancomycin for severe infeciton Fidaxomycin (newer)

Question 30

How does yersinia enterocolitica cause pain?

Answer 30

multiply in lymphoid tissue and causes LN and peyer patch hyperplasia (ileum, appendix, and right colon)

Question 31

How do you treat yersinosis?

Answer 31

most cases do NOT warrant treatment

Question 32

What is a common feature of (all but 1) of the bugs that causes non-inflammatory diarrhea?

Answer 32

gram negative anaerobic rods

Question 33

What is the only bug that causes non-inflammatory diarrhea that is NOT a gram negative anaerobic rod?

Answer 33

Staph aureus

Question 34

How does ETEC cause infection?

Answer 34

Produces 2 toxins that both increase Cl- and H2O secretion into the intestinal lumen

Question 35

What are the names of the ETEC toxins?

Answer 35

LT and ST

Question 36

What is the action of LT?

Answer 36

(like cholera)--> stimulates adenyl cyclase to increase cAMP and lead to increase Cl- secretion from crypt cells and decrease absorption of NaCl from villous tips

Question 37

What is the action of ST?

Answer 37

activates enterocyte cGMP to stimulate Cl- secreiton and inhibition of NaCl absorption from villous tips

Question 38

How long does an ETEC infection persist?

Answer 38

1-5 days

Question 39

How does EPEC cause infection?

Answer 39

Type III secretion system with LEE (pedestal formation on host surface) which causes diarrhea.

Question 40

How does vibrio cholera cause infection?

Answer 40

Mucinase dissolves glycoprotein in intestine and colonizes to then produce the AB Cholera toxin

Question 41

How does the cholera toxin work?

Answer 41

B: binds to enterocyte A: ADP ribosylates Gs to stimulate adenyl cyclase to increase cAMP and PKA and lead to increase Cl- secretion from crypt cells

Question 42

How do you diagnose vibrio cholera?

Answer 42

TCBS or TTGA agar, colorless on McConkey

Question 43

How do you treat vibrio cholera?

Answer 43

Aggressive volume repletion Tetracycline, Cipro, Azithromycin, Erythromycin Oral vaccine available

Question 44

1 day incubation, 3 day watery diarrhea.

Answer 44

vibrio parahemolyticus

Question 45

What do you use to treat vibrio parahemolytius (if severe)?

Answer 45

volume repletion | doxycycline

Question 46

How do you treat vibrio bulnificus?

Answer 46

doxycycline + cefotaxime/ceftriaxone

Question 47

How does staph aureus cause infection?

Answer 47

heat stable enterotoxin that acts as superantigen to increase IL-1 and IL-2 from macrophages and helper T cells

Question 48

1-6 hour incubation,

Answer 48

Staph aureus

Question 49

8-16 hour incubation, 6-24 hour illness

Answer 49

Bacillus cereus

Question 50

How does B. cereus cause infection?

Answer 50

Spores ingested and illness cause by the emetic (cereulide) and diarrheal toxins

Question 51

What enzymes do anaerobes of the GI tract lack?

Answer 51

``` superoxide dismutase (cannot get rid of O2-) catalase (can't get rid of H2O2) ```

Question 52

Anaerobic GN Bacillus, Capsule, Normal Flora

Answer 52

Bacteriodes Fragilis

Question 53

How do you treat bacteriodes fragilis?

Answer 53

Metronidazole, Carbapenems, Beta-Lactams + Beta-lactamase inhibitors

Question 54

Anaerobic GN coccobacilli, opportunistic, normal flora.

Answer 54

Prevotella melaninogenica

Question 55

Anaerobic GP bacilli, spore formers

Answer 55

Clostridium species

Question 56

Slender, curved motile with polar flagella; Microaerophilic

Answer 56

Helobacter pylori

Question 57

What two stomach infections require a HUGE infectious dose to cause infeciton?

Answer 57

``` Vibrio cholera (killed by stomach acid) Clostridium perfringens (low infectivity) ```

Question 58

What bacteria is resistant to heat but its toxins are NOT?

Answer 58

clostridium botulinum

Question 59

8-16 hour incubation with a 24 hour infeciton.

Answer 59

Clostridium perfringens

Question 60

How do you treat tetanus?

Answer 60

Wound debridement HTIG (neutralize toxin) Metronidazole or Penicillin 3 doses of tetanus toxoid

Question 61

How do you treat botulism?

Answer 61

mechanical ventilation/support >1 yo get Horse Anti-toxin <1 yo get Human-Derived botulism immune globulin (BIG-IV) Do NOT use antibiotics for GI infection (only if skin)

Question 62

How do you diagnose H. pylori infeciton?

Answer 62

Stool antigen urea breath test endoscopy with culture

Question 63

What are the virulence factors for H. pylori?

Answer 63

VacA PAI (type III secretion system) CAG Urease

Question 64

How do you treat H. pylori?

Answer 64

triple or quadruple therapy (PI with 2 or more antibiotics)

Question 65

DS, linear DNA virus

Answer 65

Adenovirus (40, 41)

Question 66

SS+ RNA virus (non-segmented)

Answer 66

Human Astrovirus 1-8 | Norovirus

Question 67

SS+ RNA virus (segmented)

Answer 67

enterovirus

Question 68

DS RNA virus (segmented)

Answer 68

Rotavirus

Question 69

Which viral infection has the quickest incubation period?

Answer 69

norovirus (12 hour to 1 day incubation)

Question 70

Which viral infection has the longest incubation period?

Answer 70

enterovirus (7-14 days)

Question 71

Where does adenovirus replication occur?

Answer 71

Nucleus

Question 72

How is norovirus different from cholera toxin?

Answer 72

the glucose coupled Na+ is impaired by norovirus (which infects villi of small intestine and leads to loss of the lining) but the cAMP is NOT stimulated

Question 73

Where does enterovirus replication occur?

Answer 73

RNA virus (+) strand so by host ribosomes in the cytoplasm

Question 74

What is unique about enterovirus replication?

Answer 74

translation of the RNA by host ribosome yields a large popypeptide that gets self-cleaved by viral encoded proteases to form the RNA polymerase

Question 75

How do you diagnose enterovirus?

Answer 75

throat swab

Question 76

Which virus can undergo drift?

Answer 76

Norovirus and Rotavirus

Question 77

Which virus can undergo shift and drift?

Answer 77

rotavirus

Question 78

What is cool about the structure of rotavirus?

Answer 78

has 2-3 concentric icosahedral capsids

Question 79

What is unique about rota virus replication?

Answer 79

capsid proteins processed, delivery to late endosomes or lysosomes, enzymes within core synthesize mRNA (assymetric so only (+) stands that are capped but NOT polyadenylated)

Question 80

How does rotavirus cause infection?

Answer 80

infects villous epithelium (like norovirus) but also has NSP4 enterotoxin that leads to calcium dependent Cl- secretion

Question 81

What is Rotateq?

Answer 81

Live, attenuated 5 bovine human reassortment virus serotypes (G1-G4 and P8)

Question 82

When do you give Rotateq?

Answer 82

orally at 2, 4, and 6 months

Question 83

What is Rotarix?

Answer 83

live, attenuated human-derived monovalent (G1, P8)

Question 84

When do you give Rotarix?

Answer 84

orally in 2 doses starting at 6 weeks

Question 85

What is the other option for rotavirus protection?

Answer 85

new aerosol (intranasal) that is grown in tobacco plants