Flashcards
S. Aureus
Flashcards do conjunto (19)
- 1MRSA resistance is mediate by what?By production of a new penicillin binding protein - PBP2a – which has very low affinity for β-lactams e.g flucloxacillin.
- 2What encodes PBP? Where is this found?mecA gene which is carried on the SCCmec element present in the MRSA chromosome (Types I-XI), however usually found on types I-III.
- 3What were the most common clones of epidemic MRSA?15 and 16, however 16 has declined and now CC5 is second most common.
- 4Risk factors for CA-MRSA?Young age – children and young adults more likely to develop serious pneumonia
Contact sports - skin abrasion
Sharing towels and athletic equipment
Those with weakened immune systems e.g HIV/AIDS
Overcrowded and unsanitary conditions – military facilities, prisons - 5What is different about CA-MRSA isolates in comparison with HA-MRSA?More genetically diverse, associated with types IV and V elements. Usually only resistance to B-lactams, however new evidence shows type V strains my be resistant to non B-lactams
- 6Most CA-MRSA isolates carry what gene?PVL, panton valentine leukocidin
- 7What is PVL encoded by? How is PVL toxic?By 2 co-transcribed genes luk-S-PV and luk-F-PV, bacteriophage encoded.
It is toxic for polymorphs – binds to a receptor for a complement protein on human and rabbit cells and causes cell lysis. - 8PVL producing S. Aureus commonly causing what?Most commonly causes recurring skin and soft tissue infections - furunculosis and abscesses.
In the UK, MSSA producing PVL actually appear to be more common - 9What are the three newer and more virulent strains of PVL producing S. aureus?Purpura fulminans – associated with MSSA and has a mortality of 60%
Skin sepsis – associated with outbreaks of CA-MRSA infection in individuals with no known risk factors
Necrotizing pneumonia - 10Detail the virulence of nectrotizing pneumonia?Often arises from bloodborne spread.
May follow viral respiratory infection e.g flu in young, fit individuals in the community.
? Collagen binding important in establishing infection in the lung.
PVL destroys polymorphs – releases inflammatory mediators.
Causes necrotizing vasculitis, infarction and haemorrhage. - 11Does PVL alone explain the increase of CA-MRSA virulence?No, mouse studies showed that an isogenic mutatant strain lacking PVL still caused soft tissue and skin infections.
- 12State another virulence factor of CA-MRSAPhenol soluble modulin peptides which induce an inflammatory response by chemotaxis and production of IL-8, including lysis of neutrophils.
- 13And another virulence factor?Alpha haemolysin, produced in virtually all strains, causing damage to cell membranes such as macrophages and erythrocytes.
- 14Name some molecular methods for typing of S. AureusPFGE – (Pulsed Field Gel Electrophoresis)
MLEE – (Multi Locus Enzyme Electrophoresis)
MLST – (Multi Locus Sequence Typing)
Spa typing (sequencing of repeat regions of spa)
SCCmec – (Staphylococcal Chromosome
Cassette mec) typing
Ribotyping
PCR - 15Describe multi locust sequence typing (MLST).Involves DNA sequencing of fragments of 7 housekeeping genes from S. aureus isolates.
Looks for sequence differences to identify different alleles between strains. - 16Describe spa typingSpa gene encodes S. aureus protein A. Sequence carries a repeat region and DNA sequencing of repeat region identifies different spa types. Can be used for outbreak info.
- 17What are the initial antibiotic treatments?Flucloxacillin, if MRSA or penicillin allergy then vancomycin. A combo of the two with either fusidic acid or rifampicin if deeper infection.
- 18State the treatments in: A) Endocarditis B) Skin and soft tissues C) MRSA pneumonia D) Trivial infectionsA) May use combinations of vancomycin/flucloxacillin and gentamicin.
B) Clindamycin.
C) Linezolid
D) Erythromycin/tetracycline - 19—
Informações
- Descrição
- Human Pathogens FlashCards sobre S. Aureus, criado por Zack Cooper em 14-12-2018.
- Criado por
- Zack Cooper
- Visualizações
- 0
- Avaliação