Staphylococcus Aureus Bacteraemia Flashcards
Describe staphylococcus aureus
Most virulent of many staph types
Responsible for both healthcare associated and community based infections
S. aureus is part of normal human flora
How does S. aureus cause disease?
Through both toxin-mediated and non-toxin mediated mechanisms
How does staphylococci look like on gram stain?
Gram positive cocci which from grape like clusters
When is the rate of colonisation of S. aureus higher?
Among patients with insulin dependant diabetes, HIV infection, undergoing haemodialysis and individuals with skin damage
Describe colonisation of S. aureus
Anterior nares are most frequent site
Skin, vagina, axilla, perineum, and oropharynx may be colonised
Serve as a reservoir site for future infections
25-50% can be persistently or transiently colonised
How are S. aureus blood stream infections classified?
Healthcare associated or community acquired
Absence or presence of identified associated site of infection - primary or secondary
What is the spectrum of infection by S. aureus?
Skin and soft tissue infection
Localised pyogenic staphylococcal infections
Deep seated abscesses, necrotising fasciitis and pyomyositis
Osteomyelitis, septic arthritis, discitis
Infective endocarditis
Pneumonia and empyema
What do approx. 1/3rd of patients with S. aureus bacteraemia develop?
Local complications or distant septic metastases
What are frequent sites of distant metastases for S. aureus bacteraemia?
Bones and joints
Epidural space and intervertebral discs
Native and prosthetic cardiac valves and cardiac devices
Visceral abscesses of the spleen, kidneys and lungs
What investigations are used for staph aureus bacteraemia?
Microscopy and culture of specimens
Multiple blood cultures before commencing antibiotic therapy then repeated 48-72 hrs after starting
Biopsy samples
Imaging - X-ray, CT, MRI and radionuclide, Echo and TOE
What is the basis of treatment for invasive staphylococcal infections?
Antibiotic therapy
Source identification and clearance
Appropriate surgical intervention
What antibiotic management can be used for S. aureus bacteraemia?
Flucloxacillin - MSSA first line
Vancomycin - MRSA
Teicoplanin
Linezolid
Daptomycin
How is flucloxacillin used for treatment?
MSSA first line
Minimum duration of treatment for uncomplicated S. aureus bacteraemia is 14 days
Why is vancomycin not always the ideal drug?
Poor tissue penetration, slow bactericidal activity, inconvenient administration and side effects
What is the advantage of Teicoplanin?
Single daily dosing and could be used 3 x a week after appropriate loading
