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Microbiology Part 2 > Lec 29 Viral GI Illnesses > Flashcards

Lec 29 Viral GI Illnesses Flashcards

1
Q

What is leading cause of childhood death?

A

diarrhea

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2
Q

What is most common viral cause of severe diarrhea in young children?

A

rotaviruses

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3
Q

Who gets rotaviruses?

A

children age 6 - 24 mos

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4
Q

What are signs of rotavirus infection?

A
  • can be asymptomatic or severe dehydrating gastroenteritis
  • fever
  • vomiting
  • watery diarrhea
  • dehydration [more common in rotavirus than with other causes of infectious diarrhea]
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5
Q

Does rotavirus infect immuodeficient? HIV+?

A
  • longer lasting more severe syndrome in immunodeficient

- not a common cause of diarrhea in HIV+ adults

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6
Q

Can reinfections of rotavirus occur?

A
  • can occur but tend to be less severe
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7
Q

Whos gets rotavirus? when?

A
  • almost all children infected before age 3
  • adults infected when caring for infected infants
  • seasonal infection –> peak in colder months, lower humidity
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8
Q

How is rotavirus transmitted?

A
  • fecal oral route
  • resistant to desiccation –> can survive 7 months in feces]
  • shedding of large numbers of rotaviurs prior to, during and after infection
  • short < 48 hr incubation time
  • some evidence of maybe respiratory spread too
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9
Q

How is rotavirus diagnosed?

A
  • ELISA or latex agglutination to detect viral antigen in stool
  • RT-PCR of viral RNA
  • electron micro of stool
  • isolation in cell culture is possible
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10
Q

What are the 7 serogroups of rotavirus? where are they found?

A

groups A, B, C in animals and humans

groups D-G in animals

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11
Q

How are rotavirus serogroups determined?

A

reactivity of antibodies with VP6 [by ELISA]

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12
Q

How are the rotavirus serotypes determined?

A
  • within each group based on reactivity of antibodies with VP7 [G antigen]
  • also type based on reactivity of antibodies wtih VP4 [P antigen]
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13
Q

What are the common serotypes most important for human disease?

A

Group A serotypes G1, G2, G3

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14
Q

What is function of VP4 gene in rotavirus?

A

takes part in cell attachment

contains: hemagglutinin, neutralizing epitopes, P antigen

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15
Q

What is function of VP6 gene in rotavirus?

A

contains major group [A-G] antigen

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16
Q

What is function of VP7 gene in rotavirus?

A

contains neutralizing epitopes, G antigen

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17
Q

What is function of NSP4 gene in rotavirus?

A

codes for enterotoxin that aids in ER protein/assembly

18
Q

What is structure of rotavirus?

A
  • rota = wheel appearance by EM
  • non-enveloped with 3 layer protein struct [double capsid + core]
  • segmented [11 segments]
  • double strand RNA
19
Q

Where in cell does rotavirus replicated?

A

in cytoplasm

20
Q

What proteins are in outer capsid? inner capid? core?

A

outer capsid = VP4 [P] + VP7 [G]
inner = VP6
core = VP2

21
Q

What are important points of rotavirus replication cycle?

A
  • replicated in cyto
  • only uses viral enzymes
  • dsRNA always associated with subviral particles
  • subviral particles form and mature by budding through ER where they acquire outer capsid proteins
22
Q

How do you replicate dsRNA?

A
  • copied into mRNA by RNA dependent RNA pol
23
Q

What is pathogenesis of rotavirus?

A
  • diarrhea begins before signficiant damage to intestinal mucosa
  • get viremia
  • NSP4 enterotoxin plays important part in diarrhea
  • replicated in small intestinal epithelial cells
  • net secretion water and loss of ions
24
Q

What distinguishes bacterial from rotavirus diarrhea?

A

rotavirus diarrhea has minimal intestinal inflammation in comparison

25
Q

What is immune response to rotavirus?

A
  • antibodies in lumen of small intestine most important for protection
  • T cell may play role
  • first infection indunce homotypic immunity [anti-VP7 and VP4]
  • prior infection reduces likelihoood and severity of new infections = cross-protective immunity
26
Q

What are vaccines for rotavirus?

A
  • jennerian vaccines: animal strains attenuated in humans as live vaccines
  • reassortment vaccines
  • attenuated human strain
27
Q

What is mech of RotaTeq?

A
  • live, pentavalent [G1, G2, G3, G4, G6
  • human-bovine reassortment vaccine for rotavirus
  • for infants younger than 32 wks
  • not administered to infants with immunodeficiency
28
Q

Mech of rotarix?

A

monovalent [G1P(8)] vaccine from most common human rotavirus strain

  • attenuated
  • provides partial cross-protection against other serotypes
29
Q

Mech of RotaShield? bad side effect?

A
  • oral tetravalent human-rhesus rotavirus reassortment

- link to intussusception so withdraw from market

30
Q

What is the most common cause of outbreaks of nonbacterial gastroenteritis?

A

norovirus

31
Q

What are the two types of human caliciviurses?

A
  • noroviruses

- sapporo-like viruses

32
Q

What are the bio properties of norovirus?

A
  • difficult to propagate in culture
  • non-enveloped
  • sing strand
  • pos sense
  • linear RNA
33
Q

Where does norovirus replicate in cell?

A

in cytoplasm

34
Q

How is norovirus spread?

A
  • fecal-oral transmision -> person to person, or from contaminated surface, fomites, airborne droplets]
35
Q

What is incubation period of norovirus? how long does it last?

A
  • incubation 1-2 days

- illness 1-2 days

36
Q

How long does viral shedding last in norovirus?

A

viral shedding can last 2 wks

37
Q

Who gets norovirus?

A

older children and adults

38
Q

What are symptoms of norovirus?

A

mild: fever, watery diarrhea
sever: fever, vomiting, headache, constitutional symptoms

adults –> diarrhea
children –> vomitting

can be asymptomatic carrier

39
Q

What is immune response to norovirus?

A
  • infection induces antibodies that prevent illness following administration of homologous virus
40
Q

What is secretor negative phenotype?

A
  • mutations in FUT2 gene encoding gene for H antigen found on epithelial cell surface –> no NV binding, no virus shedding
  • resistant to norovirus
41
Q

How is norovirus diagnosed?

A
  • not usually made in clinical setting

- identify by EM, RT-PCR, ELISA

Microbiology Part 2 (30 decks)

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