Infections of the skin and soft tissue I&II - Stillwell Flashcards

1
Q

cellulitis

A
  • inflammation of skin and underlying subcu tissue (deeper than impetigo)
  • cause: strep A (GAS) mainly - also group B,C,G,F; also staph aureus, MRSA, MSSA*
  • pink –> reddish –> peels like sunburn; no margins
  • gets worse before it gets better*
  • neutrophils infiltrate subcu
  • use antibiotics that treat both staph and strep*
  • red area around bullous cellulitis (no red around bullous impetigo - only by staph aureus)
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2
Q

bullous cellulitis vs. bullous impetigo

A
  • bullous cellulitis –> staph or strep; erythema around edge
  • bullous impetigo –> only staph aureus; no erythema
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3
Q

erysipelas

A
  • infection of dermis and lymphatics
  • more superficial than cellulitis
  • cause: group A strep (GAS)
  • face or extremities
  • lymphatic and venous insufficiency
  • bright red, good margins
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4
Q

erythema

A
  • redness of skin/mucous membranes
  • cause: increased blood flow
  • due to infection (not always), inflammation, skin injury
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5
Q

exanthem

A
  • widespread rash
  • cause: infection, toxin, drugs, autoimmune
  • ex. measles
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6
Q

enanthem

A
  • rash on mucous membranes of mouth
  • viral infection
  • ex. herpangina (enterovirus)
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7
Q

pustule (pimple)

A
  • collection of pus in skin (inflammatory cells and fluid)

- small abscess

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8
Q

folliculitis

A
  • inflammation or pustular infection of hair follicle (micro abscesses)
  • cause: staph aureus
  • hot tub –> pseudomonas aeruginosa
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9
Q

furunculosis

A
  • multiple boils around hair follicles

- larger than folliculitis, smaller than abscesses

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10
Q

skin abscess

A
  • collection of pus in dermis and subcu tissue
  • cause: infection or foreign material
  • can be sterile or infectious
  • larger than furuncle
  • staph aureus –> musty odor
  • dental abscess –> mixed flora
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11
Q

carbuncle

A
  • cluster of abscesses walled off in separate pockets (loculated) by fibrosis
  • many chambers
  • I&D to break up pockets
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12
Q

impetigo

A
  • superficial bacterial skin infection (epidermis) –> honey colored rust
  • cause: Staph most common (in north); strep most common (in south)*; staph in infants/children
  • bullous impetigo –> ONLY staph aureus –> exfoliative toxin (targets desmoglein1) –> cleave off stratum corneum
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13
Q

ecthyma

A
  • same as impetigo, but deeper into dermis
  • shallow ulcer that contains pus (punched out lesion)
  • brown/black crust; purple, red around edges
  • sometimes necrotic
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14
Q

pyoderma

A

-any skin disease/dermatitis with pus

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15
Q

lymphangitis

A
  • infection of deep lymphatics

- red streaking

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16
Q

lymphadenitis

A
  • infection/inflammation of lymph node –> node enlargement and erythema
  • causes: chlamydia and herpes
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17
Q

parnoychia

A
  • infection around nail
  • cause: staph aureus (main); can be mix (aerobes and anaerobes)
  • recurrent –> herpetic whitlow (HSV1>HSV2) –> vesicles and ulcers
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18
Q

felon

A
  • fingertip abscess (palmar side)
  • can be on toe
  • can form pus pocket –> I and D
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19
Q

onychomycosis

A

-fungal infection of nail –> nail thickening

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20
Q

intertrigo

A
  • jock itch - skin inflammation/infection
  • many regions; moist areas
  • common in diabetics and immunocompromised
  • antibiotics –> wipe out normal flora –> fungal overgrowth
  • causes: candida –> satellite lesions
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21
Q

miliaria

A
  • heat rash
  • inflamed/blocked sweat glands
  • backs of patients that are bed ridden
  • no antibiotics necessary
  • become infectious w/o proper treatment
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22
Q

scarletina

A
  • sandpaper rash
  • cause: mainly strep; can be staph
  • from toxins released
  • scarletina –> scarlet fever –> TSS
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23
Q

Panniculitis

A
  • inflammation of deep, subcu fat (infiltrate of inflammatory cells)
  • nodules over extremities and abdomen
  • infectious, autoimmune, traumatic, or other diseases
  • ex. erythema nodosum (immune response due to infection) and necrotizing panniculitis (necrosis and vasculitis)
  • confused with Sweet’s syndrome (superficial nodules in dermis, neutrophil infiltrate, necrosis, non-infectious)**
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24
Q

epidermis

A
  • no blood vessels or nerves
  • stratum corneum (dead cells)
  • Langerhan cells (macrophages)
  • acidic pH of skin
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25
Q

dermis

A
  • macrophages (surveillance)
  • fibroblasts
  • adipocytes
  • contain blood and lymphatic vessels and nerves
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26
Q

subcutaneous tissue (hypodermis)

A
  • fat and connective tissue
  • larger vessels and nerves
  • macrophages and mast cells
  • hair follicles and sweat/sebaceous glands
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27
Q

normal skin flora

A
  • help protect from pathogenic organisms
  • only worry about in immune compromised or prosthetic devices**
    1. staph coagulase neg. species –> staph epidermidis (body odor)
    2. propionibacterium (acne)
    3. bacillus (foot odor)
    4. Cornebacterium
    5. micrococcus
    6. 30% colonized with MSSA; 1-5% with MRSA –> high chance of infection with surgery, trauma, lesions
28
Q

ways to get skin and soft tissue infections

A
  • skin barrier disruption (abrasions, wounds, IVDA, gun shot)
  • skin inflammation (psoriasis, sunburn, vasculitis)
  • penetrate skin (hair follicles, glands)
  • secondary infection
  • infection spread from blood to skin
  • heavy colonization of pathogens
  • edema (decreased lymphatic and venous drainage) –> stasis dermatitis in surgeons, truck drivers
  • deficient immune system (chemo, diabetes)
  • obesity (low blood flow)
29
Q

pathogens of skin/soft tissue infection

A
  • strep and staph most common –> many virulence factors
  • hyaluronidase aka spreading factor (both staph aureus and GAS) –> break polysaccharides and connective tissue*
  • coagulase (staph aureus) –> fibrinogen to fibrin forming clots
  • M protein in GAS –> prevent opsonization
30
Q

cellulitis pathogens

A
  1. GAS (common) –> also causes erysipelas

2. Staph aureus (rare)

31
Q

abscess pathogens

A
  1. staph aureus (common)
32
Q

skin infection - unvaccinated children pathogen

A
  1. H. influenza
33
Q

skin infection - water exposure pathogen

A
  1. aeromonas hydrophilia (freshwater)
  2. vibrio vulnificus (saltwater, oysters)
  3. mycobacterium marinum (fresh/saltwater, fish tanks)
  4. pseudomonas aeruginosa and edwardsiella (freshwater)
34
Q

wounds infections - dog and cat bites pathogens

A
  1. pasteurella multocida (toxin decreases dendritic cells)
  2. capnocytophaga canimorsus (splenectomy –> septic)
  3. bartonella hensalae (cat scratch)
  4. anaerobes (fusobacterium, prevotella, bactericides)
35
Q

wound infections - human bites pathogens

A
  1. Eikenella corrodens (IV drug abusers)
  2. staph aureus (common)
  3. strep viridans (mouth)
36
Q

wound infections - rat bite pathogens

A
  1. streptobacillus moniliformis
  2. spirillum minus
    - both cause rat bite fever –> may lead to sepsis
    - septic arthritis or endocarditis
    - osler nodes, laneway lesions, petechia
37
Q

wound infections - snake bite pathogens

A
  1. pseudomonas aeruginosa
38
Q

wound infections - primate bite pathogens

A
  1. Herpes B virus (herpes simiae)

2. monkey pox (orthopox virus)

39
Q

skin lesions - sheep and goats

A
  1. orf (paravox virus)
40
Q

skin lesions - cattle

A
  1. cowpox (orthopox virus)

2. bacillus anthracis (anthrax)

41
Q

surgery site infections pathogens

A
  1. staph aureus (common)
  2. gram negative rodds
  3. strep
42
Q

intertrigo pathogens

A
  • fungal infections
    1. trichophyton
    2. epidermophyton
    3. microsporum
    4. candida –> satellite lesions is cardinal sign**
43
Q

puncture wound through shoe pathogens

A
  1. pseudomas aeruginosa
44
Q

cellulitis in butchers, fisherman, farmer pathogens

A
  1. erysipelothrix rhusiopathiae (erysipeloid in humans)

- gram positive rod

45
Q

erythrasma pathogens

A
  1. cornebacterium minutissimum (fluoresces, diabetics, obese)
    - groin, armpits, under pannus and breasts
46
Q

ecthyma gangrenosum pathogens

A
  1. pseudomonas aeruginosa

- usually elderly people who are septic**

47
Q

hot tub folliculitis pathogens

A
  1. pseudomonas aeruginosa
48
Q

rocky mountain spotted fever pathogens

A
  1. rickettsia rickettsia (rash on palms, soles, ankles, wrists)
    - central petechia
    - involves endothelial cells
49
Q

bacterial toxins in skin and systemic tissue infections

A
  • major virulence factors
  • exotoxins –> skin changes/damage
  • superantigens –> activate immune system –> produce cytokine and lymphokine
50
Q

exotoxins with local effects

A
  1. staph aureus –> hemolysins (form lytic pores causing lysis); ex. PVL (in community acquired MRSA infections)–> tissue necrosis around wound (not spider bite)
  2. pseudomonas aeruginosa –> protease inhibit fibrin formation; tissue necrosis/apoptosis
  3. clostridium perferinges –> lecithinase degrades cell membranes and produce liquifactive necrosis
  4. bacillus anthracis –> 3 exotoxins causing edema, lysis, and decrease in macrophages; form black eschar
51
Q

exotoxins with distal effects

A
  1. streptococcus –> pyrogenic exotoxins –> scarletina, scarlet fever, TSS
    - scarletina (sandpaper rash, pastia lines, spares palms/soles)**
    - scarlet fever (more sever, GAS, fever, pharyngitis, strawberry tongue)
    - TSS (hypotension, organ failure, scarletinaform rash) –> progress to necrotizing fasciitis and pneumonia
  2. staph aureus –> TSST-1 and enterotoxin/exfoliative toxins –> staph scarletina, staph scalded skin syndrome (SSSS), staph TSS
    - staph scarletina (less common than strep)
    - SSSS (scarletinaform rash, Nikolsky sign*, bullous impetigo)
    - staph TSS (scarletinaform rash that desquamates, hypotension, organ failure) –> can get from menstrual or nonmenstrual
52
Q

necrotizing fasciitis aka gas gangrene or flesh eating

A
  • polymicrobial (aerobes and anaerobes)
  • causes: clostridium perferinges (main), clostridium septicum, fusobacterium, peptostreptococcus, bacteroides, prevotella
  • also staph aureus and strep, which make exotoxins
  • need antibiotics and debridement
53
Q

Fournier’s gangrene**

A
  • type of necrotizing fasciitis
  • perineum, groin, thighs (entire scrotum lost)
  • poorly controlled diabetics and alcoholics
  • bad mortality
54
Q

hidradenitis suppurativa (acne inversa)

A
  • occur after puberty
  • dysfunctional apocrine sweat glands and hair follicles
  • inflammatory nodules –> abscesses –> scars
  • excise glands following with skin graft
  • genetic and environmental
55
Q

acne

A
  • clogged hair follicles and oil glands
  • genetic and increase in testosterone
  • cause: propionibacterium acne –> pustular infection
  • secondary infection of lesions with staph. aureus
56
Q

Vibrio vulnificus**

A
  • marine environments, fresh/saltwater
  • oyster shucking/eating
  • worry about immune compromised (cirrhosis due to alcoholics, hemochromatosis from bad Fe metabolism)
  • develop shock, bullous lesions (dark, purple/black), necrotizing infections
57
Q

localized lymphadenitis

A
  • inflammation of lymphatic vessels
  • usually pyogenic secondary to staph or strep
  • causes: Tularemia and cat scratch disease/bartonella (common), some STIs like chancroid and chlamydia, mycobacterium TB and atypical mycobacterium, plague (yersinia), and fungal infections (blastomycosis/histoplasmosis)
58
Q

mycobacterium marinum*

A
  • fish tank granuloma**

- AFB stains and cultures –> tissue fite

59
Q

tuberculous leprosy (Hansen’s disease)

A
  • atypical mycobacterium (mycobacterium leprae) –> noncaseating granulomas
  • inflammation in nerves
  • biopsy with AFB stain to prove
  • does not grow on culture
  • hypopigmented plaques
  • malaysian people
60
Q

periorbital (preseptal) cellulitis

A
  • inflammation/infection around orbit –> eyelid shut
  • spread from sinuses or dental infections
  • antibiotic therapy alone
  • risk of retrograde seeding –> venous plexus and cavernous sinus –> septic phebitis and cavernous sinus thrombosis
  • can damage cranial nerves (3,4,5)
  • orbital cellulitis (more severe) –> restrict extra ocular muscles, cause proptosis
61
Q

dacrocystitis

A

infection of lacrimal sac due to obstruction of nasal lacrimal duct
-need surgical drainage

62
Q

pyoderma gangrenosum (PG)

A
  • not infected, use steroids or immunosuppressives instead
  • immune mediated –> “sea of neutrophils” –> vasculitis and fibrin clot
  • ulcerative lesion with localized necrosis
  • arms, legs, face –> occur at trauma sites or pinpricked
  • not treated with antibiotics
63
Q

methods to diagnose skin/soft tissue infections - lab

A
  1. blood cultures (always done prior to antibiotics; both aerobic and anaerobic)
  2. injection of saline and re-aspiration
  3. swabs or tissue biopsy from open wounds for culture
  4. aspiration of fluid from abscess
  5. swabs and fluid sent for gram stain, aerobic and anaerobic cultures
  6. tissue sent for histology/H&E stain
64
Q

histology/H&E stains

A
  1. warthin-starry cat scratch stain –> bartonella
  2. GMS stain –> fungal/yeast (ex. aspergillus)
  3. mucicarmine stain –> cryptococcus
65
Q

methods to diagnose skin/soft tissue infections - radiology

A
  1. X ray (tissue swelling, gas)
  2. sonography (fluid, aspiration guidance)
  3. CT (inflammation, fluid/gas, aspiration guidance)
  4. MRI (best; soft tissue)