Viral Inf of Gut & Nosocomial Diarrhea Flashcards
What are the major viral causes of gastroenteritis?
Rotavirus (peds > adults)
Norovirus (older children & adults > children)
Enteric adenovirus and astrovirus - mostly peds
What populations does rotavirus affect?
young children and elderly (nursing homes)
*can cause chronic diarrhea in immunocompromised
What are characteristics of rotavirus?
reovirus family
non-enveloped but resistant to drying, gastric acid, detergents, disinfectants - *allows survival in environment
RNA w 11 segments - can reassort
What is the structure of the rotavirus shell?
3 concentric shells
*outer - major antigens are surface glycoprotein VP7 and protease cleaved protein (VP4)
What are the different groups of rotavirus?
7 serogroups (A-G), A-C infectious
A - children
B, C - adults
What is the role of animals with rotavirus?
significant agricultural pathogen but transmission from animals to humans is rare
How does rotavirus infect?
*inf dose <10 virions
*fecal-oral spread
*daycare centers! (and nursing homes)
winter peak
infects at villous tip in small intestine
What are the dz manifestations of rotavirus?
incubation 1-3 days vomiting is short-lived - *distinguishes from noro watery diarrhea - dehydration common lasts 3-4 days stool leukocytes in small pop
What are the multiple mechanisms for diarrhea caused by rotavirus?
lytic growth destroys mature absorptive cells
immature cells take their place
NP4 is secretogogue - secretory diarrhea
How does immunity to rotavirus work?
transient - need repeated exposure
intestinal IgA and maternal antibody in breast milk are protective
serotype specific
What is the treatment for rotavirus?
no antivirals
symptomatic and supportive
rehydration - oral first
What are the criteria for IV rehydration in rotavirus?*
intractable vomiting
altered mental status (can’t follow directions)
loss of >10% BW
What are characteristics of the norovirus?
calicivrus family - 2 of 4 genera affect humans
ss+RNA
non-enveloped, resistant to detergents, drying, etc.
How does norovirus infect?
inf dose is 10 virions
fecal-oral
epidemics common - hospital, *cruise ships
What are the dz manifestations of norovirus?
incubation 1-2 days
*VOMITING
less diarrhea than rotavirus
spontaneous improvement 2-3 days
How does immunity to norovirus work?
shortliveed, 4-6 mos
repeated exposure necessary
strain specific
What are the different causes of diarrhea in a hospital setting?
inf or non-inf
viral (rota, noro)
*antibiotic associated, not caused by c. dif
c. dif is most severe
What is c. dif?
strictly anaerobic
spore forming - spores can survive in environment
gram +rod
Where and how do lots of outbreaks of c. dif occur?
*nursing homes, hospitals
*carried on shoes, hands, clothing of healthcare workers
dz requires presence of toxin A & B
What is the most important risk factor for CDAD?
*previous or current antibiotic therapy
What are important clinical manifestations of c. dif?
*pseudomembranous colitis
*toxic megacolon
*elevated peripheral WBC
stool leukocytes and occult blood
What does the psuedomembrane consist of?
fibrin, PMNs, mucin, dead enterocytes
What is the treatment of c. dif colitis?
discontinue antibiotic
oral metronidazole (cheaper) and oral vanc
*vanc may be better for more severe dz
*IV vanc ineffective
When is oral vanc used as opposed to metronidazole for treating c. dif?
metronidazole fails or isn’t tolerated
pregnancy or lactation
