Gram Negative Bacteria Flashcards
1
Q
List the virulence factors that make *Pseudomonas *such a formidable pathogen.
A
- Flagellum (for motility)
- Capsule/ slime layer (avoid phagocytosis, retain moisture/ prevent dehydration, prevent antimicrobial penetration)
- Quorum sensing (cell-to-cell communication, biofilm coordination, cell aggregation)
- Endotoxins (release of toxins causing shock)
- Cytophores (acquisition of iron from the host, important for bacteria undergoing binary fission)
- Polysaccharide coating (hinders attachment of membrane attack complexes)
2
Q
Epidemiology of Pseudomonas aeruginosa
A
- “The green pus bacteria”
- Environmental organism
- Found in water, soil, on the skin, intestinal tract
- Opportunistic pathogen/ secondary invader (often affecting wounds, bites scratches, damaged tissues or immunocompromised individuals)
- Common in noscomial infection (e.g. IV and urinary catheters)
3
Q
Pathogenesis of Pseudomonas aeruginosa
A
- Wide array of virrulence factors (capsule, slime layer, flagellum, quorum sensing, adhesions/ pilli, endotoxins, polysacharide coating)
- Resisitant to many antimicrobials
- Umbicuitous (non-specific in nature, infecting many species and humans)
- Found everywhere (soil, skin, intestines, water etc.)
4
Q
Why is pseudomonas an opportunistic and not a primary pathogen?
A
- Becuase of its route of entry, causing infection
- Enters via damaged tissue (e.g. bites, scratches, wounds, samaged tissue) or via immunocompromised individuals
- It has a widespread resistance to antimicrobials which aid its its host defences
- umbicuitous (can infect many species including humans)
- Common noscomial infections associated (IV catheter or urinary catheter)
5
Q
How would you diagnose a Pseudomonas infection?
A
- Important to remember that pseudomonas is an aerobic pathogen and will only grow in aerobic environments (Mconkey Agar)
- Depends on the location of wound for sample (opportunisitc infection)
- Culture on Mconkey Agar
For example:
* Cystic fibrosis: respiratory aspirates
* Burn: pus from site
* Mastitis: milk sample
6
Q
Treatment of a Pseudomonas infection
A
- Debridment of wound
- Treatment varies depending on cause of bacterial overgrowth
- Invitro suseptibility testing should be performed on all isolated to determine drug of choice
- Can us a combination of an aminoglycoside and B lactam in serious cases