Staph. Aureus Bacteraemias Flashcards
What type of bacteria is Staph Aureus?
Gram positive cocci
Which bacteria is the most virulent* within the staphylococcal species?
*harmful
Staph Aureus
How can S.aureus survive in the body?
Has an environment resistant peptidoglycan wall surrounded by a microcapsule
Produce a range of surface proteins involved in host colonisation, tissue invasion and also produce toxins
Which toxins can S.Aurues produce?
Cytolytic toxins
Exfoliative toxins
Enterotoxins
TSST-1
What do cytotoxins do?
Break down neutrophils releasing lysosomal enzymes in surrounding tissues
What is Staphylococcal scaled skin syndrome?
A condition which is mediated by exfoliative toxins and characterised by exfoliative dermatitis
Which symptoms are enterotoxins usually related to?
GI symptoms
Which type of staphylococcal toxins is associated commonly with food poisoning?
Enterotoxins
Which type of toxin is associated with toxic shock syndrome?
TSST-1
Staph aureus is found in healthy humans as well, it makes up a part of the gut flora.
In which patient is the rate of colonisation higher?
In patients with:
-Insulin-dependant diabetes
-HIV
-Haemodialysis
-Skin damage
Which part of the body is the most frequent site of colonisation?
Anterior nares (nose)
->skin, vagina, axilla, perineum and oropharynx may also be colonised
What are the different classifications of S.Aurues blood stream infections?
Healthcare or community associated
Primary or secondary infections
Which bone related infections is S.Aureus responsible for?
Osteomyelitis
Septic arthritis
Discitis
Which skin related infections is S.Aureus responsible for?
Deep-seated abscesses
Necrotising fasciitis
Pyomyositis
Which cardio related infections is S.Aureus responsible for?
Infective endocarditis
Which lung related infections is S.Aureus responsible for?
Pneumonia
Empyema
Approximately 1/3 of patients with staph aureus bacteremia develop local complications or distant metastatic complications.
Where are some of the frequent sites of distant metastases?
Bones and joints, especially where prosthetic materials are present
Epidural space and IV discs
Native and prosthetic cardiac valves, cardiac devices
Visceral abscesses in spleen, kidneys and lung
Which investigations are used to investigate S.Aureus infections?
Microscopy and culture of specimens
Biospy samples for bone infections
XR, CT, MRI depending on issue
Transthoracic ECHO
What is important to note about blood cultures?
Multiple required before commencing antibiotic therapy
Recommended to repeat cultures 48-72hrs after commencing antimicrobial therapy
Which imaging is bets for bone infections like osteomyelitis?
Xray
Which imaging is best to look for abscesses?
CT
Which imaging is best for looking for any spine infections?
MRI
What is the management of S.Aureus infections?
Antibiotic therapy
Source identification and clearance
Any appropriate surgical intervention
Okayyyy…antibiotic management xx
What is the minimum duration of treatment of flucloxacillin for an uncomplicated S.Aureus infection?
14 days
Okayyyy…antibiotic management xx
Why is Vancomycin a poor choice of antibiotic for S.Aureus infection?
Poor tissue penetration
Slow bactericidal activity
Inconvenient administration
Adverse side effects
Okayyyy…antibiotic management xx
What are the advantages of Telcoplanin in S.Aureus infections?
Single daily dosing
Okayyyy…antibiotic management xx
What are the advantages of Linezolid in S.Aureus infections?
Good penetration into bone
Very good oral bioavailability
Okayyyy…antibiotic management xx
What are the advantages of Daptomycin in S.Aureus infections?
Well tolerated
Once daily dosing
First thing to do when choosing which antibiotics to use if determining if the S.Aureus is methicillin resistant (MSSA/MRSA).
What is the first line treatment for a MSSA S.Aureus infection?
Flucloxacillin
First thing to do when choosing which antibiotics to use if determining if the S.Aureus is methicillin resistant (MSSA/MRSA).
What is the first line treatment for a MRSA S.Aureus infection?
Any other antibiotic previously mentioned e.g. Vancomycin, Telcoplanin, Linezolid, Daptomycin
For S.Aureus bacteremia, what is the treatment duration?
14 days, IV antibiotics
If patient has a penicillin allergy, flucloxacillin cannot be used. What is the alternative?
Vancomycin
Why is Daptomycin not suitable for lung infections?
It is inactivated by pulmonary surfactant in the lungs
