Staphylococcus aureus Bacteraemia Flashcards
Staphylococcus aureus facts (5)
Most virulent of the many staphylococcal species.
Remains a major cause of morbidity and mortality.
Causes disease through both toxin-mediated and non-toxin-mediated mechanisms.
Responsible for both healthcare associated and community-based infections.
S.aureusis a part of the normal human flora.
How does staph A cause disease
through both toxin-mediated and non-toxin-mediated mechanisms.
S.aureusis a part of the?
normal human flora
Staphylococci are
Gram-positive cocci that form grape-like clusters on Gram stain.-PURPLE
Where is the rate of colonisation greater (4)
among patients with insulin-dependent diabetes, HIV infection, patients undergoing haemodialysis, and individuals with skin damage.
Where are the most frequent sites of colonisation.
Anterior nares
Where else can it colonise?
Skin (especially when damaged), vagina, axilla, perineum, and oropharynx may also be colonised.
These colonisation sites serve as a
reservoir for future infections
Persons colonised withS. aureusare at greater risk of ?
of subsequent infection than uncolonised individuals.
S. aureus Blood stream infections are classified by?
environment of acquisition
healthcare associated or
community acquired
Absence or presence of identified associated sites
of infection can be
primary or secondary
Spectrum of infection
vast - could be a boil
What agent causes the most common infections
Skin & Soft Tissue Infections- S. aureusis the most commonly identified agent.
Where else can you see S.Aureus infections (5)
Localised pyogenic staphylococcal infections- furuncles and carbuncles.
Deep-seated abscesses, necrotising fasciitis, pyomyositis
Osteomyelitis, Septic arthritis, Discitis
Infective endocarditis
Pneumonia, Empyema
In the hospital setting- wound infection
Approximately one-third of patients with S.aureus
bacteraemia develop?
local complications or distant
septic metastases.
Frequent sites of distant metastases (4)
Bones and joints (especially when prosthetic materials are present)
Epidural space and intervertebral discs
Native and prosthetic cardiac valves, Cardiac devices
Visceral abscesses in spleen, kidneys and lungs
Investigations (6)
Microscopy and culture of specimens.
multiple blood cultures before commencing antibiotic therapy.
Repeat blood cultures are recommended 48–72 hours after commencing antimicrobial therapy.
Biopsy samples may be of value for bone infections
Imaging- X-ray, CT, MRI, Radionuclide imaging
Transthoracic echocardiography, TOE
How many blood cultures before antibiotic therapy
2
Biopsy …
especially if blood culture is negative
Management Basis of treatment for invasive staphylococcal infections- (3)
- Antibiotic therapy
- Source identification and clearance
- and appropriate surgical intervention
What is associated with with an increased risk of complications and higher mortality?
Delay in the administration of appropriate antibiotic
therapy and persistent bacteraemia after 72–96 hours of
appropriate therapy
Antibiotic management (5) - timings of drugs/managements
Flucloxacillin- minimum duration of treatment for uncomplicatedS. aureusbacteraemia is 14 days. IV therpay
Vancomycin- far from an ideal drug due to poor tissue penetration, slow bactericidal activity, inconvenient administration and side effects. First line for MRSA
Teicoplanin- has an advantage in terms of its single daily dosing and could also be used three times weekly after appropriate loading
Linezolid- bacteriostatic, synthetic oxazolidinone, good penetration into bone and excellent oral bioavailability.
Daptomycin- cyclic lipopeptide with rapid bactericidal activity againstS. aureus. Well tolerated. Has the advantage of once daily dosing. Good for people with difficult venous access.
