staph aureus Flashcards
what type of infection does s.aureus cause
soft pains soft tissue/surgical osteomyelitis and septic a food poisoning toxic shock syndrome pneumonia abscesses (psoas) infective endocarditis necrotising fasciitis scalded skin syndrome
gram stain s.aureus
cluster of cocci and is coagulase positive -golden
where is s.aureus found on the body
- upper resp tract
- normal vaginal flora
- skin in healthy individuals
what helps s.aureus to adhere to dry and salty conditions
techoic acid
screening for s.aureus
swab throat
swab nose
groin
axilla
how does s.aureus evade the immune system
- anti-opsonizing proteins and protein A on cell surface are antiphagocytic
- leukotoxins eg panton valentin leucocidin toxin kills white blood cells
- superantigens: subvert the normal immune system by inducing strong, polyclonal stimulation and expansion of t-cells
how does s.aureus invade the skin
produces exfoliative toxins that can disrupt the skin barrier
how does s.aureus damage skin, and prosthetic devices and heart valves
produces biofilms that protect against immune cells and may restrict penetration of some antibiotics
what toxins does s.aureus secrete
- panton valentin leucocidin
- enterotoxins
- toxic shock syndrome 1 TSST-1
- epidemolytic toxins (a and b)
what does panton valentin leucocidin toxin cause
- recurrent ssti
- necrotizing pneumonia
- attacks white blood cells
what do enterotoxins cause
gastroenteritis
what do epidemolytic toxins cause
- scalded skin syndrome
- severe infection in babies with skin shedding
what does coagulase positive mean
converts fibrinogen to fibrin
important note
- if labs comes back with coagulase positive then it is s.aureus and not a contaminant so must treat patient
- if labs comes back with coagulase negative it is probably a contaminant but must be sure it is not s.aureus
patients at risk of SAB
- loss of skin barrier eg ulcers, ivdu, surgical
- immunocompromised: renal.liver, diabetes
- prosthetic: cannula, central lines, prosthetic joints and heart valves
management of severe cellulitis
- senior review for necrotising f
- mark border of erythema and limb elevation
- swab and cultures
- fluid balance
- flucoxacillin IV
- or vanc for mrsa
how long does sab have to be treated even if the patient is better
minimum of 2 weeks iv
what else needs to be investigated
- deep source of infection
- prothetics could be infected
- remove indwelling IV devices
what is the fluid choice for sepsis
0.9% saline to increase IV volume
complications of sab and precautions for each
- endocarditis: do an echo
- psoas abscess: assess hip and back pain
- discitis: palpate spine
- prosthetic related infection
- osteomyelitis
what gene creates MRSA
mecA gene on the resistance island called the staphylococcal cassette chromosome
risk factors for MRSA
o History of MRSA
o Nursing home resident
o Family member with MRSA
o Prolonged hospitalization
what is panton valentin leucocidin linked too 2
-recurrent SSTI and necrotising pneumonia
what does the PVL toxin do
haemolysin and destroys white blood cells
