Flashcards in Scenario 15 Deck (102)
How do you treat e coli?
How do you distinguish pseudomonas aerginosa
Gram negative non sporing bacillus, non lactose fermenting, outer membrane with LPS, porins and proteins, large genome
What are the virulence factors of pseudomonas aerginosa
Endotoxins, exotoxins, iron binding proteins
Where is it found and how is it transmitted?
Soil and water, colonises UT, transmitted on medical equipment, water, spas and whirlpools
How do you treat p. aeruginosa?
Resistant to co-amoxiclav, trimethoprim, nitrofurantoin use piperacillin-tazobactam and gentamycin
How do you distinguish Haemophilus influenzae?
Gram negative rod (sometimes coccobacillus) needs media with growth factors and cell membrane with LPS, proteins and porins
What virulence factors are present in haemophilus influenza?
Endotoxin, large polysaccharide capsule, IgAse, adhesins in cell wall
Where is h.influenzae found?
Mucosal surfaces transmitted with close contact and droplets
What infections does it cause?
Bloodstream infection in young children (capsulate) and ottis media, sinusitis, conjunctivitis all ages (not capsulate)
How do we treat H.i?
Vaccine in childhood, amoxicillin (15% resistance) chemoprophylaxis, IV ceftriaxone for invasive infections
What other gram negative bacteria are there?
Bacteroides (rod- colonise the mouth), neisseria (cocci in pairs, mucous membranes, inside neutrophils- meningococcus, gonococcus), legionella (rod, pneumonia), heliobacter pylori (rod, stomach)
What is the basic structure of a virus?
DNA or RNA core with protein coat, some have an envelope studded with glycoproteins
Where do non-enveloped viruses survive best?
Outside of cells and bile resistant
Where do enveloped viruses survive best?
In cells- only spread by close contact eg. Hep B HIV
Which viruses are RNA?
Retrovirus, coronvirus, picornavirus
Which viruses are DNA?
Adenovirus, herpesvirus, poxvirus
What are the steps in viral replication?
Attachment, penetration, uncoating, transcription, translation, replication, assembly, release
How do DNA viruses replicate?
Large replicate on their own, small encode only a few genes and use host cell DNA polymerase etc
How do RNA viruses replicate?
Most RNA viruses encode their own RNA-dependent RNA polymerase using complementary RNA as template
-Positive strand RNA- equivalent to mRNA can often be immediately translated into proteins then synthesise a -ve copy copied back into -ve mRNA messages to produce structural proteins to package progeny +ve RNA into visions
-Negative strand RNA- first converted into +ve RNA (.RNA) by RNA dependent RNA polmerase then same as abover
Why do RNA viruses replicate more quickly?
RDRP lacks proofreading ability and makes more mistakes
How do retroviruses replicate?
encode reverse transcriptase which makes dsDNA from RNA
What is a latent infection?
Viral DNA persists but doesnt replicate to produce new infectious virus e.g. herpes, varicella zoster
What is pathogenesis?
Process where infecion leads to disease
What are the virus properties that allow it to inhabit cells?
Concealment (prevent antigen presentation, latency, integration into genome- retrovirus), intefere with cytokine network (mimic receptors and inhibitory cytokines and interfeon), antigenic variation (mutation and antigenic shift), modulation of lymphocyte function (immuno suppression)
What is the eclipse phase?
Virus entry until new infectious virions released
What is the classification of family herpesviridae?
Large dsDNA icosahedral capsid and lipid envelope
What subfamiliy does varicella zoster belong to?
Where is chicken pox latent?
Dorsal root or cranial nerve ganglion- reactivation= chicken pox
What is the incubation period for varicella?
10-21 days- prodrome (fever, pharyngitis, malaise)