Soft Tissue infections, Abcesses etc

Question 1

What is the difference between impetigo, erysipelas and cellulitis?

Answer 1

impetigo- infection of superficial, outer keratin layer of skin- gives crusty lesions (more common in children)
erysipelas- infection of the superficial epidermis of skin
cellulitis- subcutaneous infection of the skin (more common in adults, also diabetics)

Question 2

Most relevant causative organism in SSTIs?

Answer 2

beta hemolytic (clearing) Streptococcus
Group A - strep pyogenes.
(+/- staph aureus)

Question 3

in what sorts of people might you get atypical organisms causing SSTIs?

Answer 3

drug users

immunocompromised (ie HIV)

Question 4

how are SSTIs normally acquired?

Answer 4

through breach in body’s defences:
break in the skin
i.e. eczema, skin ulcer, athletes foot, insect bite)

Question 5

What is an abscess and what organism(s) often cause them?

Answer 5

localised collection of infection - i.e. pus
staphlococcus aureus often will esp on skin
(+ others more specific to site- i.e. gut organisms or lung organisms)

Question 6

what samples should you take if SSTI is suspected?

Answer 6

if port of entry is identified: swab
blood cultures
if abscess present: pus sample

NB: if in cannula site, can cut off tip of cannula to send away to be cultured also

FBC for all

Question 7

if impetigo is suspected, what colour swab would you swab the lesion with?

Answer 7

black- charcoal, as is for bacteria (impetigo = bacterial infection )

Question 8

summarise the tests and results expected for staph aureus

Answer 8

direct microscopy with gram stain:
purple (gram positive), cocci,
in clusters = staph

Catalase: positive (produces bubbles in h2o2 as produces oxygen): ensure staph not strep

Coagulase: positive (if negative, its epidermidis)

Question 9

first line antibiotic for a staph aureus infection?

Answer 9

flucloxacillin

Question 10

what 3 aspects are critical to the success of taking blood culture to find infection?

Answer 10

contamination is avoided- i.e. wipe skin, bottle caps etc keep sterile
fill bottle with enough blood
take from 2+ locations, at 2+ times

Question 11

you have found streptococcus which is beta hemolysing- what test do you do next to get a more specific identification?

Answer 11

latex agglutination test- to lance field group

Question 12

what lancefield group would you assume a SSTI to be caused by?

Answer 12

group A - strep pyogenes

Question 13

what is the first line antibiotic to treat strep pyogenes?

Answer 13

benzyl penicillins

Question 14

what does MRSA stand for and what does this mean?

Answer 14

methicillin resistant staphlococcus aureus
(actually resistant to flucloxacillin as no one uses methicillin any more, fluclox came after it as a close family member)
it is resistant to all penicillins, also beta lactams (carbapenems, cephlosporins)

Question 15

what do you treat MRSA with?

Answer 15

VANCOMYCIN

Question 16

what additional tests would you perform on some with identified with (MR)Staph A. infection?

Answer 16

Echocardiogram: as few will get endocarditis as staph aur. likes heart valves

MRI spine- to check for discitis as can get spinal infection

Question 17

when treating someone with vancomycin for their MRSA infection- what should you do and why?

Answer 17

need their serum levels of vancomycin monitoring
because vancomycin is a nephrotoxic drug, so too high will damage kidneys
but too low will not kill the MRSA (+form possible resistance to it)