ICL 1.5: Skin & Soft Tissue Infections Flashcards
what is cellulitis? what causes it?
an infection of the dermis and subcutaneous tissues
usually caused by streptococci (group A*, B, C, G etc) or Staphylococcus aureus
gram negatives can play a role in patients with preexistent conditions
acute!! there’s no chronic cellulitis
how do you diagnose cellulitis?
diagnosis is clinical; there is no blood test or x-ray that you can take to do it
- redness
- heat
- pain
- swelling
why is it important to differentiate between cellulitis and other stuff?
because when you treat people with antibiotics because you think they have cellulitis, you can give them c. diff or line infections or other problems
what is the pathology of cellulitis?
the stratum corneum acts as a barrier, which is normally dry, tough, of low pH – “bricks and cement”
but breaks in this barrier may lead to pathogen invasion of deeper tissues and lead to cellulitis
what are the risk factors for cellulitis?
- any reason for skin barrier disruption (abrasion, penetrating wound, insect bite, venous ulcer, injection drug use) – not always evident!
- edema secondary to heart failure or lymphedema secondary to mechanical blockage (damage to lymphatic veins)
- lower extremities with stripped veins for coronary artery bypass graft (CABG) because they don’t have as good venous return to clear stuff out of the body
- immunosuppression
- fungal skin infection and vesicular viral rashes (varicella, zoster)
- diabetes-induced neuropathy -> decreased sensation > ulcers > poor healing > bacteria can enter
what is onychomycosis?
gross looking toe nails
it’s a risk factor for cellulitis
what is stasis dermatitis?
it’s a risk factor for cellulitis due to chronic venous insufficiency
- decreased sensation
- red/violaceous/yellow skin changes
- areas of chronic inflammation and areas of fibrosis
- loss of hair
- edema
- cool skin, not warm as in cellulitis and it’ll be bilateral
- chronic; not acute
many times confused with cellulitis; it is a risk factor, but not an infection
where are the bacteria coming from that cause cellulitis?
it comes from the patients themselves!
- S. aureus is carried in the anterior nares by 20-40% of adults at any given time, even higher rates in the inguinal area and in axillae
- Group A Streptococci are carried in the nasopharynx by 15-20% of children (much lower in adults)
what are the virulence factors that can cause cellulitis?
strep tends to be more rapidly invasive than staph which will form abscesses
staphylococci produce a dermonecrotic, hemolytic toxin (alpha toxin) and potent leukocidins, which kill neutrophils.
streptococci have M proteins, which enable them to escape phagocytosis and a hyaluronidase, which may allow them to spread rapidly in the tissues
what is paronychia?
a collection of pus around the fingernail on the dorsal
you just treat it by opening it up and draining it (might need antibiotics)
staph can cause this or other gram negatives
what is a felon?
it’s an infection in the pulp of the finger and is more aggressive than paronychia
caused by the same bacteria as paronychia
you can see this in people who chew their fingernails
what is impetigo?
very superficial infection caused by staph or strep
usually in kids
honey colored crusts
you can just do local care; soap and water can help but topical or oral antibiotics will help more
what is erysipelas?
superficial infection of the skin caused by group A strep
the rash has well defined borders that are raised
usually you see it on the face but can have it on the lower extremities too
it kind of looks like cellulitis
what is folliculitis?
it’s infection of the oil gland accompanying the hair follicle
aka a pimple at the hairs
usually caused by staph (or pseudomonas) but will go away with soap and water
what is a furuncle/carbuncle ?
bigger collection of pus but not quite an abccess yet
starts at the base of a hair follicle and it is caused by steph
more than one lesion connected by tunnels under the skin surface is a carbuncle
what hidradenitis?
changes in the sweat glands that lead to a collection of stuff that looks like pus but isn’t
NOT treated with antibiotics
so you’ll see them in the armpits and butt
what is an abccess? what causes is?
staph aureus 75% of the time
it’s hot, tender, white area in the middle, and you can feel like the fluid inside; it’s not just a hard mass
they may drain spontaneously but usually requires incision and drainage – antibiotics don’t really help
send a culture!!!! so you can figure out which staph it is
how do you treat cellulitis?
think strep
1st generation cephalosporin
if you have periorbital/perirectal or skin necrosis along with cellulitis add a gram negative and anaerobic coverage antibiotics
how do you treat an abscess?
think staph
1st generation cephalosporin even if someone is allergic to penicillin
what are the two types of periorbital cellulitis?
cellulitis around the eyes
- preseptal/periorbital = outside-in
frequent, lower mortality, caused by staph or group A strep – treat with antibiotics
- postseptal/orbital = inside-out
rare, higher morbidity, caused by pneumococcus or fungi in diabetics
you can lose your vision from this
treat with antibiotics +/- surgical drainage
what are the complications of orbital cellulitis?
septic cavernous sinus thrombosis
abrupt onset with diplopia, photophobia, orbital edema, and progressive exophthalmos
can be secondary to sinusitis, tooth infection, facial furuncles
rare, but high mortality
you have to treat it with surgical decompression of the source and antimicrobials (broad spectrum)
what is necrotizing fasciitis?
involves usually superficial fascia
not common; you see it in immunocompromised or obese patients but it’s very serious and can spread reallllyyyy fast through the tissue
may be secondary to minor trauma, surgery or starting as a furuncle
you might feel crepidis = gas in the tissue
pain out of proportion when you touch the skin or the opposite; they can’t feel when you touch them
what are the 3 types of necrotizing fasciitis?
- type I = mixed flora, anaerobes + strep (non group A) + gram negatives (enterobacteriaceae, rarely pseudomonas)
- type II = Group A strep
- type III = clostridium perfringens (gas gangrene or clostridial myonecrosis)
what is Fournier’s gangrene?
necrotizing fasciitis in the genital area
