Viral Inf of Gut & Nosocomial Diarrhea

Question 1

What are the major viral causes of gastroenteritis?

Answer 1

Rotavirus (peds > adults)
Norovirus (older children & adults > children)
Enteric adenovirus and astrovirus - mostly peds

Question 2

What populations does rotavirus affect?

Answer 2

young children and elderly (nursing homes)

*can cause chronic diarrhea in immunocompromised

Question 3

What are characteristics of rotavirus?

Answer 3

reovirus family
non-enveloped but resistant to drying, gastric acid, detergents, disinfectants - *allows survival in environment
RNA w 11 segments - can reassort

Question 4

What is the structure of the rotavirus shell?

Answer 4

3 concentric shells

*outer - major antigens are surface glycoprotein VP7 and protease cleaved protein (VP4)

Question 5

What are the different groups of rotavirus?

Answer 5

7 serogroups (A-G), A-C infectious
A - children
B, C - adults

Question 6

What is the role of animals with rotavirus?

Answer 6

significant agricultural pathogen but transmission from animals to humans is rare

Question 7

How does rotavirus infect?

Answer 7

*inf dose <10 virions
*fecal-oral spread
*daycare centers! (and nursing homes)
winter peak
infects at villous tip in small intestine

Question 8

What are the dz manifestations of rotavirus?

Answer 8

incubation 1-3 days
vomiting is short-lived - *distinguishes from noro
watery diarrhea - dehydration common
lasts 3-4 days
stool leukocytes in small pop

Question 9

What are the multiple mechanisms for diarrhea caused by rotavirus?

Answer 9

lytic growth destroys mature absorptive cells
immature cells take their place
NP4 is secretogogue - secretory diarrhea

Question 10

How does immunity to rotavirus work?

Answer 10

transient - need repeated exposure
intestinal IgA and maternal antibody in breast milk are protective
serotype specific

Question 11

What is the treatment for rotavirus?

Answer 11

no antivirals
symptomatic and supportive
rehydration - oral first

Question 12

What are the criteria for IV rehydration in rotavirus?*

Answer 12

intractable vomiting
altered mental status (can’t follow directions)
loss of >10% BW

Question 13

What are characteristics of the norovirus?

Answer 13

calicivrus family - 2 of 4 genera affect humans
ss+RNA
non-enveloped, resistant to detergents, drying, etc.

Question 14

How does norovirus infect?

Answer 14

inf dose is 10 virions
fecal-oral
epidemics common - hospital, *cruise ships

Question 15

What are the dz manifestations of norovirus?

Answer 15

incubation 1-2 days
*VOMITING
less diarrhea than rotavirus
spontaneous improvement 2-3 days

Question 16

How does immunity to norovirus work?

Answer 16

shortliveed, 4-6 mos
repeated exposure necessary
strain specific

Question 17

What are the different causes of diarrhea in a hospital setting?

Answer 17

inf or non-inf
viral (rota, noro)
*antibiotic associated, not caused by c. dif
c. dif is most severe

Question 18

What is c. dif?

Answer 18

strictly anaerobic
spore forming - spores can survive in environment
gram +rod

Question 19

Where and how do lots of outbreaks of c. dif occur?

Answer 19

*nursing homes, hospitals
*carried on shoes, hands, clothing of healthcare workers
dz requires presence of toxin A & B

Question 20

What is the most important risk factor for CDAD?

Answer 20

*previous or current antibiotic therapy

Question 21

What are important clinical manifestations of c. dif?

Answer 21

*pseudomembranous colitis
*toxic megacolon
*elevated peripheral WBC
stool leukocytes and occult blood

Question 22

What does the psuedomembrane consist of?

Answer 22

fibrin, PMNs, mucin, dead enterocytes

Question 23

What is the treatment of c. dif colitis?

Answer 23

discontinue antibiotic
oral metronidazole (cheaper) and oral vanc
*vanc may be better for more severe dz
*IV vanc ineffective

Question 24

When is oral vanc used as opposed to metronidazole for treating c. dif?

Answer 24

metronidazole fails or isn’t tolerated

pregnancy or lactation

Question 25

What is one way to treat relapsed or recurrent c. dif?

Answer 25

*stool transplant

Question 26

What is the most important method of controlling c. dif inf?

Answer 26

*frequent washing of hands w soap and water