S.aureus bacteraemia Flashcards
What type of bacteria is staphylococci?
Gram positive cocci
What do clusters of staphylococci look like on gram stain?
Grape-like clusters
What is the most virulent of the staphylococcal species?
Staphylococcus aureus
Is staphylococcus aureus responsible for HAI or community based infections?
Both
S.aureus is part of the normal human flora: true or false?
True
S.aureus causes disease through which mechanisms?
Toxin-mediated
Non-toxin mediated
What percentage of healthy persons may be persistently or transiently colonised with S.aureus?
25-50%
Which patients are most at risk of colonisation of S.aureus?
Insulin-dependent diabetes
HIV infection
Patients undergoing haemodialysis
Patients with skin damage
Where is the most frequent site of S.aureus colonisation?
Anterior nares
Where are sites which S.aureus commonly colonises?
Anterior nares Skin Vagina Axilla Perineum Oropharynx
Why are colonisation sites of S.aureus important?
Serve as reservoir for future infections
Persons colonised with S.aureus are at greater risk of subsequent infection than uncolonised individuals: true or false?
True
How are S.aureus blood stream infections traditionally classified?
By environment of acquisition: healthcare associated or community acquired
With what type of infections is S.aureus the most commonly identified agent?
Skin and soft tissue infections
What is another word for a furcuncle?
A boil
What are furuncles and carbuncles?
Localised pyogenic staphylococcal infections
What is a carbuncle?
A cluster of boils
What type of infections in hospital may be caused by S.aureus?
Wound infection, vascular line, catheter-related infection
What are frequent sites of distant metastases of S.aureus bacteraemia?
Bones and joints (esp prosthetics)
Epidural space and IV discs
Native and prosthetic cardiac valves/cardiac devices
Visceral abscesses in spleen, kidneys and lungs
What investigations would you do for suspected S.aureus infections?
Microscopy and culture of specimens
Multiple blood cultures
Repeat blood cultures after commencing antimicrobial therapy
Biopsy samples (bone infections)
Imaging: X-ray, CT, MRI, radionuclide imaging
Transthoracic echocardiography, TOE
What is the basis of treatment for invasive staphylococcal infections?
Antibiotic therapy
Source identification and clearance
Appropriate surgical intervention
What has been associated with an increased risk of complications and higher mortality in S.aureus infections?
Delay in the administration of appropriate antibiotic therapy and persistent bacteraemia
What antibiotics are indicated for S.aureus infections?
Flucloxacillin Vancomycin Teicoplanin Linezolid Daptomycin
What is the minimum duration of treatment for uncomplicated S.aureus bacteraemia with flucloxacillin?
14 days
Why is vancomycin not the ideal drug to use for a sensitive S.aureus infection?
Poor tissue penetration, slow bactericidal activity, inconvenient administration and side effects
Why is teicoplanin a good antibiotic for S.aureus infections?
Single daily dosing and use three times weekly after appropriate loading
Why is linezolid a good antibiotic for S.aureus infections?
Bacteriostatic, synthetic oxazolidinone, good penetration into bone and excellent oral bioavailability
Why is daptomycin a good antibiotic for S.aureus infections?
Rapid bactericidal activity against S.aureus, well tolerated, once daily dosing
What is the first line treatment for MSSA?
Flucloxacillin
What type of administration is flucloxacillin for S.aureus infection?
IV
What is the first line treatment for MRSA?
Vancomycin
47yr old lady IVDU, 5 day history fever, cough, SOB. Painful swollen right groin. Alert and orientated. 90% O2 on air. Pyrexial at 38.5C. BP 110/60. 110HR. 32RR.
Bloods: WCC 31.9, urea 8
Doppler US DVT? infected right leg
What organism likely to be responsible for CXR findings?
Antibiotics commence on?
Staph aureus
IV flucloxacillin
Blood cultures positive for S.aureus. 2wks therapy, ongoing cough, fever, right sided chest discomfort and right groin pain/discharge.
Bloods: WCC 18, CRP 210
Which investigations?
What does CXR show?
ECHO
CXR
Repeat blood cultures
US groin
Post-pneumonic effusion
