staphylococcus aureus bacteraemia Flashcards
Is staph aureus part of the human flora
Yes it is a part of the normal human flora
How does staph aureus look under microscope
Gram positive cocci - forming clusters
What are the toxins that staph aureus contains
cytotoxic, exfoliative, enterotocins and TSST-1
How do cytotoxins work
They lyse neutrophils which releases lysosomal enzymes that damage surrounding tissue
What does exfoliative toxins cause
Staphylococcal scalded syndrome which is characterised by exfoliative dermititis
What are the enterotoxins of staph aureus associated with
Food poisoning and pseudomembranous enterocolitis - presents with diarrhoea
What does TSST-1 cause
Menstruation and non-menstruation related staphylococcal toxic shock syndrome
Who is most commonly colonised by staph aureus
HIV, insulin dependant diabetes, haemodialysis and skin damage individuals
What is the most common site of colonisation in staph aureus
ANterior nares (nose)
skin, vagina, axilla, perineum and oropharynx can also be colonised
What is a common complication of staph aureus bacteraemia
they have local complications or distant septic metastaes
(endocarditis when it metastasises to the heart valves)
Where are common sites of staph aureus metastases
bones and joints
intervertebral disc
prosthetic cardiac valves and cardiac valves
Visceral abscesses in spleen, kidney and lungs
What investigations are done for staph aureus
Microscopy and culture
Multiple blood cultures before starting antibiotics
Repeat the blood cultures 2-3 days after starting antimicrobial therapy
Biopsy of bone
X-ray, CT, MRI
Transthoracic echocardiography , trans-oesophageal echocardiogram
Why is it important not to delay treatment of staph aureus
Delay in administration of antibiotics is associated with higher risk of complications
What is the antibiotic treatment for MSSA (Methicillin sensitive staph aureus)
first line - flucloxacillin - 2 week treatment
What is the antibiotic treatment for MRSA
vancomycin
teicoplanin
linezolid
daptomycin
