Staph Aureus Bacteraemias Flashcards
Does Staph Aureus cause disease via a toxin mediated mechanism or non-toxin mediated mechanism?
Causes disease via both toxin mediated and non-toxin mediated mechanisms
Is staph aureus gram positive or gram negative? How does it appear on gram stain?
- Gram positive
- Forms grape like clusters and appears purple in colour on gram staining
What percentage of people are persistently / transiently colonized by S. aureus? Who is most vulnerable to colonization?
- 25-50% of people persistently / transiently colonized
- Insulin dependent diabetes
- HIV infection
- Patients undergoing haemodialysis
- Individuals with skin damage
Most common sites of S. aureus colonization?
- Nostrils (anterior nares)
- Skin
- Vagina
- Axilla
- Perineum
- Oropharynx
How are S. aureus blood stream infections classified?
- Environment of acquisition:
- Healthcare associated
- Community acquired - Absence or presence of associated infection sites
- Primary
- Secondary
What are some different ways S. aureus infection can manifest itself in the patient?
- Skin & soft tissue infection
- Localized pyogenic infections (carbuncle etc.)
- Deep seated abscess (necrotizing fasciitis etc.)
- Bone infection (osteomyelitis etc.)
- Infective endocarditis
- Pneumonia / empyema
What are the most frequent sites for S. aureus infection to metastasize to?
- Bones and joints (esp. prosthetics)
- Epidural space and intervertebral discs
- Cardiac valves (native / prosthetic) & cardiac devices
- Visceral abscesses in spleen, kidneys & lungs
What investigations can be used for suspected S. aureus infection?
- Blood culture / microscopy (multiple)
- Bone biopsy (if bone infection)
- XRay, CT, MRI, radionucleotide screening
- TOE: transthoracic echocardiography
(heavily dependent on manifestation of the infection)
Management of S. aureus infection?
- Antibiotic therapy
- Source identification & clearance
- Surgical intervention where appropriate (abscess drain etc.)
List the different antibiotics that can be used to treat S. aureus infection
- Flucloxacillin
- Vancomycin
- Teicoplanin
- Linezolid
- Daptomycin
What needs to be known about the S. aureus infection before antibiotic treatment can be planned?
whether it is MRSA or MSSA
- MRSA will not respond to methicillin based antibiotics such as flucloxacillin
What is the first line antibiotic for MSSA? Describe the course of treatment
- Flucloxacillin
- Minimum course of treatment is 14 days
What is the first line antibiotic for MRSA? What are some of the downsides to use of this antibiotic?
- Vancomycin
- Has poorer tissue penetration (bone & lung manifestations) & may have inconvenient side effects
Which antibiotic has the best tissue penetration, making it useful for bone & lung manifestations of S. aureus infection? Downsides?
- Linezolid
- Has harsh side effects such as peripheral neuropathy, toxicity etc.