staph aureus

Question 1

what type of infection does s.aureus cause

Answer 1

soft pains
soft tissue/surgical
osteomyelitis and septic a
food poisoning
toxic shock syndrome
pneumonia
abscesses (psoas)
infective endocarditis
necrotising fasciitis
scalded skin syndrome

Question 2

gram stain s.aureus

Answer 2

cluster of cocci and is coagulase positive -golden

Question 3

where is s.aureus found on the body

Answer 3

• upper resp tract
• normal vaginal flora
• skin in healthy individuals

Question 4

what helps s.aureus to adhere to dry and salty conditions

Answer 4

techoic acid

Question 5

screening for s.aureus

Answer 5

swab throat
swab nose
groin
axilla

Question 6

how does s.aureus evade the immune system

Answer 6

• 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

Question 7

how does s.aureus invade the skin

Answer 7

produces exfoliative toxins that can disrupt the skin barrier

Question 8

how does s.aureus damage skin, and prosthetic devices and heart valves

Answer 8

produces biofilms that protect against immune cells and may restrict penetration of some antibiotics

Question 9

what toxins does s.aureus secrete

Answer 9

• panton valentin leucocidin
• enterotoxins
• toxic shock syndrome 1 TSST-1
• epidemolytic toxins (a and b)

Question 10

what does panton valentin leucocidin toxin cause

Answer 10

• recurrent ssti
• necrotizing pneumonia
• attacks white blood cells

Question 11

what do enterotoxins cause

Answer 11

gastroenteritis

Question 12

what do epidemolytic toxins cause

Answer 12

• scalded skin syndrome

- severe infection in babies with skin shedding

Question 13

what does coagulase positive mean

Answer 13

converts fibrinogen to fibrin

Question 14

important note

Answer 14

• 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

Question 15

patients at risk of SAB

Answer 15

• loss of skin barrier eg ulcers, ivdu, surgical
• immunocompromised: renal.liver, diabetes
• prosthetic: cannula, central lines, prosthetic joints and heart valves

Question 16

management of severe cellulitis

Answer 16

• senior review for necrotising f
• mark border of erythema and limb elevation
• swab and cultures
• fluid balance
• flucoxacillin IV
• or vanc for mrsa

Question 17

how long does sab have to be treated even if the patient is better

Answer 17

minimum of 2 weeks iv

Question 18

what else needs to be investigated

Answer 18

• deep source of infection
• prothetics could be infected
• remove indwelling IV devices

Question 19

what is the fluid choice for sepsis

Answer 19

0.9% saline to increase IV volume

Question 20

complications of sab and precautions for each

Answer 20

• endocarditis: do an echo
• psoas abscess: assess hip and back pain
• discitis: palpate spine
• prosthetic related infection
• osteomyelitis

Question 21

what gene creates MRSA

Answer 21

mecA gene on the resistance island called the staphylococcal cassette chromosome

Question 22

risk factors for MRSA

Answer 22

o History of MRSA
o Nursing home resident
o Family member with MRSA
o Prolonged hospitalization

Question 23

what is panton valentin leucocidin linked too 2

Answer 23

-recurrent SSTI and necrotising pneumonia

Question 24

what does the PVL toxin do

Answer 24

haemolysin and destroys white blood cells

Question 25

guidelines for treatment of PVL

Answer 25

include clindamycin to suppress toxin production