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micro I


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Non-lactose fermenters on MacConkey agar
salmonella, shigella, yersenia, campylobacter
Do E coli ferment lactose?
Most common cause aseptic meningitis
How do + strand RNA viruses replicate?
+ strand RNA = mRNA, can be immediately translated. First translate proteins for the viral replicase, which is an RNA-dependent RNA polymerase to make + into -, then to +. + strands can be used to make proteins, amplify infection, or be template for more - strand
How do enteroviruses infect the CNS?
ingest fecal material -> virus infects mucosal + lymphoid cells in pharynx/intestine (1* viremia)-> start excreting in feces, seeds to extraneural cells -> either cross BBB in WBC, or via retrograde axonal transmission
Salk created which vaccine?
IPV (killed virus, get IgM/IgG, no reversion, but poor mucosal immunity)
Herpes virus structure? Where do they replicate?
Icosahedral capsid, surrounded by envelope, linear ds DNA. Replicate in nucleus
How are herpes viruses spread?
need close contact, like between mucosal surfaces, b/c they are fragile and don't survive well outside of body
Three classes of herpes viruses and examples
Classified by biologic/molecular methods. Alpha = HSV-1,2, VZV (grow rapidly, lyse infected cells, latent in sensory ganglia). Beta - CMV (slow growth, lysis slow, latent in WBC). Gamma - EBV (replicate in lymphoid, some lytic. Latent in B cells)
Replication cycle for herpes
glycoproteins on envelope tether to cell surface receptors -> fuse -> capsid/virus to cytoplasm -> to nucelus -> vmRNA made by host (IE,E,L). Capsid assembles in nucleus, get envelope from nucleus,
Criteria for viral latency
can detect viral DNA but no infectious viruses
Genes expressed during latency
no viral antigens or capsids, but some low-level transcription of other genes
VZV pathogenesis
spread by droplet nuclei or direct contact w/ lesions -> infect lymphoid tissue in pharynx -> viremia infects multiple organs and skin -> proceeds up local sesnory nerves to establish latency in ganglia
Pathogenesis of herpes zoster
latent VZV present, periodically reactivates, usually quelled by T cells. Immunity decr w/ age, so virus can travel back down nerve -> illness. This boosts immunity again so only get 1 case/lifetime
Which streptococci are resistant to penicillins

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