Staph Aureus Bacteraemia Flashcards
Where does staph aureus rank by levl of virulence of staphylococcal species?
Most virulent
Through what mechanisms can staph aureus cause disease?
Both toxin-mediated and non-toxin mediated mechanisms
Is staph aureus part of the normal human flora?
Yes
What kind of bacteria is staph aureus?
Gram-positive cocci
Is colonisation of staph aureus normal?
- 25-50% of healthy people have persistent or transient colonisation
- Rate is higher amount patients within insulin dependent diabetes, HIV patients, haemodialysis patients and people with skin damage
What is the most frequent site of staph aureus colonisation?
Anterior nares:
- Skin, vagina, axilla, perineum and oropharynx can also be colonised
Are patients with colonisation at greater or less risk of future infection?
Greater risk
What are S. Aureus bloodstream infections classified according to?
Classified according to environment of acquisition:
- Healthcare associated or
- Community acquired
Or absence or presence of identified associated sites of infection:
- Primary or
- Secondary
33% of patients with S. Aureus bacteraemia develop local or distant septic metastases, what are some common sites?
- Bones and joints
- Epidural space and intervertebral discs
- Native and prosthetic cardiac valves
- Visceral abscesses in spleen, kidneys and lungs
S. Aureus can cause many infections, what are some examples?
- Skin and soft tissue infection
- S. Aureus is most common agent
- Localised pyogenic staph infections
- Deep seated abscesses, necrotising fasciitis, pyomyositis
- Osteomyelitis, septic arthritis, discitis
- Infective endocarditis
- Pneumonia, empyema
- In hospital, wound infection or catheter related infection
What investigation is done for S. Aureus bacteraemia?
- Multiple blood cultures before commencing antibiotic therapy
- Repeat blood cultures 48-72 hours after commencing antimicrobial therapy
- Biopsy for bone infections
- Imaging
- X-ray
- CT
- MRI
- Radionuclide imaging
- Transthoracic echocardiography
What is the basis of treatment for an invasive staph aureus infection?
- Antibiotic therapy
- Source identification and clearance
- Appropriate surgical intervention
What is delay of therapy for an invasive staph aureus infection associated with?
Higher risk of complications and mortality
Describe the possible antibiotic management of a staph aureus infection?
- Flucloxacillin (first choice)
- Minimum duration of treatment for uncomplicated staph aureus bacteraemia is 14 days
- Vancomycin (used if allergic to penicillin)
- Not ideal due to poor tissue penetration, slow bactericidal activity, inconvenient administration and side effects
- Teicoplanin
- Advantage is only single daily dose
- Linezolid
- Bacteriostatic, synthetic oxazolidnone, good pentration into bone and good oral bioavailability
- Daptomycin
- Only one dose a day and well tolerated, rapid bactericidal activity against staph aureus
What are the first 2 choices of antibiotic when treating Stap. A bacteraemia?
- Flucloxacillin (MSSA)
- Vancomycin (if allergic to flucloxacillin) (MRSA)
