skin and soft tissue Flashcards
what is an enanthem
lesion on mucosal membrane
what is an ecchymosis
large area of bruising
how is dry skin a risk factor for skin infections
subaceous fluids keep pH low, together with fatty acids help to inhibit microbial growth
what microbes are more commonly responsible for skin infections in diabetics
s aureus
grp b strep
anaerobes
g -ve bacilli
what microbes are more commonly responsible for skin infections in IVDU
MRSA
Ps aeruginosa
is staph aureus an anaerobe aerobe or facultative organism
facultative
what is MRSA usually resistant against
flucloxacillin
name a few antibiotics that can be used against MRSA
vancomycin
daptomycin
tetracycline
clindamycin
what does crepitus in a skin infection indicate
gas gangrene
in severe infections, what can thrombocytopaenia be an early indicator of?
DIC
what blood marker will be different in rhabdomyolisis
hypocalcaemia
order by depth of infection
erysipelas necrotising fasciitis ecythema cellulitis impetigo
impetigo erysipelas ecythema cellulitis necrotising fasciitis
what is impetigo caused by
staph aureus
how deep does erysipelas go to
upper dermis
where does erysipelas usually affect
face cheeks, periorbital region
what causes ecythema
group a beta haemolytic streptococcus
what do these affect? - folliculitis, furuncles, carbuncles
hair follicles
name 2 organisms that can cause cellulitis
strep pyogenes
staph aureus
clinical features of cellulitis
hot swollen tender skin
usually unilateral and on lower limbs
systemic features of cellulits
fever
sweats
rigors
antibiotic used for cellulitis
flucloxacillin
describe 2 types of necrotising fasciitis
type 1 is polymicrobial
type 2 is monomicrobial
what virulence factor causes necrotising fasciitis to be so severe
enzymes that break down tissue e.g.
streptokinase
hyaluronidase
why is the fascia more easily infected
poor blood supply
clinical features of necrotising fasciitis
erythema with diffuse borders edema severe pain blisters rapid progression systemic features skin anaesthesia skin necrosis
treatment for necrotising fasciitis
surgical treatment
amputation
antibiotics
bacteria responsible for trauma-related gas gangrene
clostridium perfringens
what are 2 structures within bone that can serve as conduits for infection in and out of the bone
volkmann’s and haversian channels
why is chronic osteomyelitis very hard to treat
bacteria is embedded into the bone matrix
difference between pyogenic and non-pyogenic osteomyelitis
pyogenic OM involves accumulation of neutrophils, usually bacterial caused
non-pyogenic OM does not involve neutrophilic response, caused by organisms like TB, aspergillus etc.
3 routes of non-iatrogenic OM?
haematogenous
contiguous
trauma
in IVDU what route of OM is more likely
haematogenous
2 ways of acuiring iatrogenic OM
post-operative
device related
what is engrafting and why is it bad
when fibrotic tissue forms around new prosthetic joint/shaft, biofilm that forms inside has poorer blood supply due to fibrosis; restrict immune response and antibiotic efficacy
what is sequestrum and involucrum
sequestrum = necrotic segment within the bone
involucrum = new bone formation outside of periosteum in response to bone damage due to infection
in which kind of OM is sequestrum more likely to be found?
chronic OM
in acute OM, bone can rapidly necrose causing delibitating pain and pathological fractures - T or F?
False - necrotic bone segment is more commonly found in chronic OM
pus discharging sinus is an early sign of OM - T or F?
False - it is a late sign of chronic OM
no.1 most common organism causing OM
stpah aureus
in children, which part of the body is most likely to be affected with osteomyelitis?
metaphysis, just under the growth plates
in acute haematogenous OM for adults, where is it most likely to be affected?
vertebral bodies
in spinal osteomyelitis, 2 adjacent vertebrae and the disc in between is a common pattern of infection - T/F? and why?
True - because they are usually supplied by the same 1 spinal artery
recent infection can predispose you to OM - T or F
T
why is a urinary catheter a risk for OM?
because bladder venous plexus drains into the spinous veins
what is the most common route of infection in chronic pyogenic osteomyelitis?
haematogenous
what imaging is best for suspected OM?
xrays for quick assessment
CT and MRI are best to show sequetreum/involucrum/soft tissue/joint pathology
most common antibiotic used for OM
flucloxacillin
