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Micro last plus one anatomy 5 > bacterial infection of the skin and soft tissue joints and bone > Flashcards

bacterial infection of the skin and soft tissue joints and bone Flashcards

1
Q 
what bacteria do these risk factors point to?
DM
neutropenia
hot tub exposure
IV drug use
A

DM- s. aureus, group b strep, anaerobes and gram neg bacilli
neutropenia- pseudomonas aeruginosa
hot tub exposure- pseudomonas aeruginosa
IV drug use - MRSA, P. aeruginosa

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2
Q

what do you call an infection that only involves the pores?
the epidermis?
the dermis
the deeper skin structures and muscle?

A

pores- faruncles, folliculitis and carbunkles
epidermis- erysipelas
dermis- cellulitis
deeper- fasciitis or myositis

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3
Q

Impetigo presentation

A
  • most superficial bacterial skin infection
  • caused by s. pyogenes and less s. aureus
  • HONEY CRUSTED LESIONS -that start off as vesicles and become pustules that crust over -AROUND MOUTH
  • most common bacterial infection
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4
Q

bullous impetigo

A
  • mostly s. aureus
  • blisters initially filled with cloudy fluid and rupture resulting in erosions and crusting
  • BLISTERS CAUSED BY EXFOLIATIVE TOXIN MADE BY S. AUREUS
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5
Q

ecthyma

A
  • DEEPER FORM OF IMPETIGO with resultant scarring and ulceration- do to lack of treatment or neglect
  • cause PUNCHED OUT lesions
  • treat with ecthyma and impetigo
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6
Q

treatment for impetigo and ecthyma

A
  • debridement and topical antibiotic with oral antibiotics
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7
Q

what’s a faruncle or boil?

A
  • caused by s. aureus
  • deep seated infection of hair follicle
  • large, painful, raised nodules that have collection of dead and necrotic tissue
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8
Q

carbuncle?

A
  • caused by s. aureus
  • MULTIPLE faruncles/ boils that coalesce and extend into deeper subcutaneous tissue
  • patient gets FEVERS AND CHILLS
  • often systemic spread- osteomyelitis, endocarditis, bacteremia
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9
Q

what is folliculitis

A
  • it is the infection/ inflammation of a hair follicle caused by many different organisms
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10
Q

erysipelas

A
  • acute infection
  • causes inflammation and lymph node enlargement
  • CHILLS AND FEVER
  • DENOTED BY SHARP BORADER BETWEEN INVOLVED SECTION OF THE SKIN AND UNINVOLVED
  • usually preceded by a respiratory or skin infection by s. pyogenes
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11
Q

cellulitis

A
  • skin and subcutaneous tissue
  • inflammation and systemic symptoms like fever
  • no distinct boarder between infected and noninfected***
  • caused by many microbes
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12
Q

what can cellulitis be caused by after
dog/cat bite
normally
salt water exposure

A

dog/cat bite- pasteurella multocida
normal- s. aureus
saltwater- vibrio vulnificus

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13
Q

paronychia
what is it
acute species
chronic species

A
  • localized superficial infections of the nail folds
  • most common infection of the hand
  • acutely- can be painful abscess at nailfold- s. aureus
  • chronic- there longer than 6 weeks- c. albicans
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14
Q

necrotizing fasciitis
what is it?
treatment?

A
  • caused by s. pyogenes
  • acute subcutaneous tissue infection that includes redness and involves deep tissue
  • destroys fat and muscle
  • cellulitis followed by bullae and gangrene
  • leads to organ failure, toxicity and death
  • treat with antibiotics and surgical debridement
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15
Q

what kind of bacteria is pseudomonas aeruginosa?

A

gram neg rod

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16
Q

how do you distinguish between s. aureus and streptococcus pyogenes

A

s. aureus is catalase pos and pyogenes is neg
- s aureus is in clusters, s. pyogenes is in chains
- both are gram pos cocci

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17
Q

staphylococci breaks down? are they motile or spore forming?

A
  • breaks down H2O2 to H20 and O2

- non flagellate and nonmotile

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18
Q

what is the main way to shed s. aureus?

A
  • nasal shedding

- but can spread without hand washing, environmental surfaces

19
Q

is s. aureus alpha or beta hemolytic? what can occur to it once it is older or the infection has resolved? what color does it look like under a microscope

A

it is beta hemo
it can lose its gram positivity
aureus = gold

20
Q

what are some s. aureus virulence factors?

A
  • capsule (antiphagocytic), biofilm (to adhere to surface of foreign bodies like valves and catheters), peptidoglycan (endotoxin like activity), teichoic acid (for adhesion) and protein A (inhibits antibody mediated clearance via binding Igg Fc domain- basically binds the part that the phagocyte is supposed to bind, not the pathogen)
  • Toxins- cytotoxin (alpha thru gamma- toxic to many cells), exfoliative toxins,
  • has hydrolases that hydrolyze host tissue to aid in spread of the bacteria throughout the body
21
Q

what are the two forms of exfoliative toxins

A

ETA and ETB

  • serine proteases that break down desmosomes (intraepidermal junctions)
  • MEDIATE STAPH SCALDED SKIN SYNDROME
22
Q

Protein A

A

inhibits antibody mediated clearance via binding Igg Fc domain- basically binds the part that the phagocyte is supposed to bind, not the pathogen

23
Q

what is the main enterotoxin that is found in s. aureus? what’s it associated with

A

enterotoxin A- insensitive to heat and gastric enzymes

associated with food poisoning

24
Q

Hyaluronidase
fibrinolysin
lipases
nucleases

A
  • hydrolyzes hyaluronic acid in connective tissue to spread bacteria thru body
    breaks down fibrin
    hydrolyzes lipase
    hydrolyzes DNA
25
Q

**pathogenesis of s. aureus?

A
  • staph binds cell via teichoic acid
  • it then secretes alpha toxin that pokes holes in cell so that the bacteria can enter
  • once inside, the bacteria secretes protein A to sop up the antibody at the Fc region and prevent it from binding and eliminating the bacteria
  • capsule serves as an antiphagocytic agent as well
26
Q

what is scalded skin syndrome?

A
  • s. aureus infection
  • usually in babies that got it from mom
  • looks like scalded skin and can only culture in nasal area even though it starts in the nose and spreads systemically on skin
  • TOXIN MEDIATED
27
Q

what actually causes the scalded skin

A

the exfoliative enzymes ETA and ETB

28
Q

*why is staph aureus not culturable from skin?

A

because it’s a toxin mediated disease

don’t get leukocytes either- does not cause inflammation, just blistering

29
Q

how do eta and etb work?

A
  • they are serine proteases that attack desmosomes, DESMOGLEIN-1 that is responsible for linking together the intercellular bridges in the stratum granulosum of the epidermis
  • protective antibodies result to fight of the infection eventually
30
Q

what does staph aureus induced scalded skin syndrome present ?

A
  • first presents as just an infection of the conjunctiva, nasopharynx or umbilicus
  • the reaches exfoliate phase (in second day) where you break in in bulla and then they break easily with manual pressure = NIKOLSKY SIGN - resembles scalded skin
  • 3-5 days: skin desquamates leaving normal skin in 7-10 days
31
Q

how do you manage scalded skin syndrome

A

fluid replace, antibiotics (vanco and oxacillin)

32
Q

diagnosis of SSSS

A

presentation of skin biopsy in nasal area

-histology reveals a CLEAVAGE PLANE in the upper epidermis

33
Q

How are staphylococci generally able to establish infection in immunocompetant people

A
  • it can do so when it enters with a foreign body
34
Q

MRSA

A
  • methicillin resistant staphalococcus aureus- mostly a skin infection that can go systemic
  • has beta lactamases (usually by plasmid exchange) that resist beta lactam of PCN
  • as a result we started treating with semisynthetic PCN resistant to B lactamase like methicillin and oxacillin and nafcillin BUT
  • MRSA- has Mec A gene that codes for a PCN biding protein that is on the peptidoglycan and has a low affinity for methicillin and other synthetic PCN and cephalosporins
35
Q

treatment for MRSA?

A

vanco

36
Q

what do you prescribe for s. aureus with beta lactamases?

A

penicillinase-resistant PCN like nafcillin and oxacillin

37
Q

what is osteomyelitis

A
  • bone pain, fever, swelling and malaise

- almost always associated with bacterial infection

38
Q

what are some risk factors for osteomyelitis

A
  • DM, bone surgery, untreated tissue infections near bone, kidney dialysis, sickle cell, foreign body
    =anything that might impair blood flow to the bone
39
Q

what is osteomyelitis mostly caused by

A

s. aureus

40
Q

what is septic arthritis

A

painful, erythematous joint with purulent material obtained on tapping
usually in large joints- shoulder, hip elbow
THE MOST COMMON REASON WHY KIDS AND ADULTS RECEIVE INTRAARTICULAR INJECTIONS OF WHO HAVE MEHANICALLY ABNORMAL JOINTS

41
Q

what is the most common cause of septic arthritis? in sexually active individuals?

A

s. aureus

N. gonorrhea -mostly in women and present as grey/white lesions on skin

42
Q 
what are these virulence factors associated with
exfoliative toxin
enterotoxin a
tsst-1
lipopolysaccharide
capsule
A 
exfoliative toxin- ssss
enterotoxin a- food poisoning
tsst-1- toxic shock syndrome
lipopolysaccharide- endoxin that's gram neg
capsule- general s. aureus infection
43
Q

what is important when diagnosing SSSS, what should you remember?

A
  • it is not going to be detected at lesions of the skin and there will be no leukocytes present

Micro last plus one anatomy 5 (8 decks)

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