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Exam 2 Skin block > Skin infections > Flashcards

Skin infections Flashcards

1
Q

Impetigo

A

Superficial skin infections, most frequently in children

spreading infection confined to the epidermis

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2
Q

folliculitis

A

pyogenic infection in the hair folicles

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3
Q

furuncles (boils)

A

extension of folliculitis (stye)

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4
Q

Carbuncles

A

infection extends to the deeper subcutaneous tissue (chills and fever due to systemic spread with single inflammatory mass

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5
Q

erysipelas

A

spreading infection involving the dermal lymphatics

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6
Q

cellulitis

A

spreading infection when the major factor is the subcutaneous fat layer

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7
Q

Abscess formation

A

folliculitis, boils (furuncles), and carbuncles

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8
Q

necrotizing infections

A

fasciitis and gas gangrene (myonecrosis)

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9
Q

Macules

A

flat and non palpable lesions

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10
Q

papules

A

palpable lesions

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11
Q

vesicles

A

palpable, fluid filled lesions (chiken pox)

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12
Q

pustules

A

palpable and contain pus.

When looking at a slide, you will see an accumulation of neutrophils with serous fluids within or beneath epidermis

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13
Q

Bulla

A

collection of serous fluid and have small numbers of inflammatory cells

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14
Q

Characteristics of S. Aureus

A

gram positive: most resistant of the non spore formers to adverse condition

non motile

facultative anaerobic

catalase and coagulase positive

can grow in 10% NaCl

Abscesses, systemic diseases, food posioning, toxic shock syndrome

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15
Q

virulence factors of S. aureus

A

staphylocococcal toxins (alpha, beta, delta, gamma, and P-V)

exfoliative toxins

enterotoxins

toxic shock syndrome toxins

enzymes: coagulase, catalase, hyaluronidase, fibrinolysin, lipases, nucleases

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16
Q

Characteristics of streptococcus

A

gram + arranged in chains

avoid phagocytosis mediated by capsule, M proteins, C5a peptidase

non motile

facultatively anaerobic

catalase negative

nutritional requirement; complex, need blood or serum enrich media for isolation.

carbohydrate: lancefield groups

M protein: 80 types

Streptolysin O and S

Hyaluronidase, DNASE

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17
Q

Skin abscesses, furuncles, and carbuncles

A

all related to hair follicle

collection of pus within the dermis and deeper skin tissues (pustule)

risk factors: diabetes, immunologic abnormalities and breaches to the skin barrier.

most are caused by infections. may be polymicrobial or monomicrobial. S. aureus occurs in up to 50% cases

TX: small furuncles, warm compresses to help drainage. Incision and drainage. The role of ancillary antimicrobial therapy is unclear.

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18
Q

Impetigo (pyoderma, impetigo contagiosa)

A

contagious superficial infection primarily seen in young children (2-5 years).

poor personal hygiene

purulent with crusting

commonly caused by streptococcus pyogenes either alone or together with staphylococcus aureus

19
Q

non bullous impetigo vesiculopusules with crusting

A

papules progress to vesicles surrounded by erythema

most frequently observed in children ages 2 to 5 years

usually occurs in warm, humid conditions

risk factors: poverty, overcrowding, poor hygiene, and underlying scabies

GAS and S. aureus are most common causes

impetigo caused by nephrogenic GAS can lead to post streptococcal glomerulonephritis

20
Q

pustular impetigo

A

intraepidermal vesicles filled with exudate (pus)

crusted lesions

S. aureus, or GAS

seen in exposed areas of the body during the warm, moist weather

21
Q

bullous impetigo

A

localized staphylococcal scalded skin syndrome

caused by S. aureus of phage group II that produces exofliative toxin A (no cell adhesion)

happens in newborns and young children

culture positive

no nikolsky’s sign

high communicable

22
Q

erysipelas 2 (long and explained)

A

tender, superficial erythematous and edematous lesions

the infection spreads primarily in the upper dermis and superficial lymphatics (deeper dermis and subcutaneous fat is cellulitis)

mainly affected young and elders. Fiery red (salmon red), advancing erythema

the rash is usually confluent and sharply demarcated rom the surrounding, normal skin.

It is always caused by GAS.

23
Q

Cellulitis: acute inflammation

A

Redness, induration, heat, and tenderness, the distinction between infected and noninfected area is not as clear

often accompanied by inflammation of the draining lymph nodes

90% of cases are caused by GAS and S. Aureus

In unimmunized children, infection with H. Flu type B

cellulitis associated with bites or scratches from cats or dogs (p. multocida)

all develop rapidly (24 to 48 hrs) from minor injury to severe speticemia

elevation of the affected area and empiric antibiotic therapy

24
Q

Necrotizing infections of the skin and fascia

A

common features: extensive tissue destruction, throbosis of blood vessels, bacteria spreading along fascial planes, and unimpressive infiltration of inflammatory cells

necrotizing fasciitis is a deep seated infection of the subcutaneous tissue leading to destruction of fascia and fat but may spare skin

25
Q

Type 1 necrotizing fasciitis

A

a mixed infection caused by aerobic nd anaerobic bacteria and occurs most commonly after surgical procedures and in patients with diabetes and peripheral vascular disease.

26
Q

type 2 necrotizing fasciitis

A

monomicrobial infection caued by group A streptococcus (GAS, streptoccus pyogenes).

Necrotizing fasciitis caused by community associated methaicillin resistant staphylococcus aureus (MRSA) as a monomicrobial infection has also been described.

27
Q

Necrotizing fasciitis caused by V. vulnificus

A

rapidly progressive wound infections after exposure to contaminated seawater

the wound infections are characterized by initial swelling, erythema, and pain followed by the development of vesicles or bullae and eventual tissue necrosis

mortality: 50%

28
Q

Myonecrosis

A

Most often due to C. perfringens, C. septicum, C. histolyticum or C. Sordellii

usually associated with local trauma

Gas is always found in the skin, but fascia and deep muscle spared

Non clostridial cellulitis is due to infection with a mixed anaerobic and aerobic organisms that produce gas. Associated with diabetes with a foul odor.

Myonecrosis is found in 50% of patients with necrotizing fasciitis caused by GAS.

29
Q

Staphylococcal scalded skin syndrome (ritter’s disease)

A

perioral erythema covers entire body within two days

psoitive nikolsky’s sign: large blisters with clear fluid, no organism, no leucocytes

exfoliative toxin destroys the intracellular connections in the skin

30
Q

Pseudomonas aeruginosa

A

Gram negative

aerobic and (anaerobic)

rod shaped

motile (pili and flagella)

grape like odor

environmental bacterium

simple growth requirement

31
Q

Pseudomonas folliculitis

A

resulting from immersion in contaminated water such as hot tubs, whirlpools, swimming pools

a secondary infection in people who have acne or who depilate their legs

fingernail infection

32
Q

Mycobacterium leprae

A

an obligately aerobic rod with gram + like wall

the infections are caused by aerosols

can not be grown in vitro

two animal models: armadillo and in the footpads of mice

grow best in skin histocytes, endothelial cells and the schwann cells of peripheral nerves

33
Q

Lepromatous leprosy

A

multibacillary. Growth of bactera is relatively unimpeded. Lesions show dense infiltration. Large numbers of bacilli reach bloodstream

skin lesions are diffuse, extensive, depiliated, extesnive tissue destruction

cell mediated immunty is deficient Th2 response

infectivity: high

analgous to miliary TB

nonreactive to lepromin

34
Q

Treatment of lepromatous leprosy

A

for epromatous leprosy, the triple therapy with dapsone, ribiospfampin, and clofazimine for a minimum of two years, and maybe lifelong or until biopsies are negatie for acid fast rods

for tuberculoid leprosy, a combination of dapsone and rifampin for 6 months is recommended.

35
Q

Tuberculoid leprosy

A

red blotchy lesions with anesthetic areas. Cell mediated response TH1. Infectivity low.

36
Q

Bacillus anthracis

A

gram psoitive spore forming

capsule (D glutamic acid)

exotoxin with three parts: edema factor, lethal factor, protective antigen

37
Q

typical A-B type binary toxin: edema factor and protective antigen + edema toxin

A

A portion of the edema toxin, adenylate cyclase, similar to the one produced by bordetella pertussis, activated by human calmodulin, resulting in increased intracellular cAMP-impared flow of ions and water

38
Q

typical A-B type binary toxin: lethal factor + protective antigen = lethal toxin

A

a portion of the letal toxin, a protease induces macrophage to produce high levels of cytokines that trigger the shock

39
Q

protective antigen

A

B portion of the A-B toxin that promotes entry of EF into phagocytic cells

40
Q

Inhalation ahtrax

A

by inhalation of aerosolized spores.

mediastinal widening

replication occurs wtihin the lung with local exotoxin release

fever, shortness of breath, cough, HA, vomiting, chills, and chest and abdominal pain. Later progression: respiratory distress and death within 3 days of initial symptoms

41
Q

cutaneous anthrax

A

most common. Painless papule at the site of incoulation progress to an ulcer surrounding vesicles. necrotic eschar

germination, rapid proliferation, taxin release and localized tissue necrosis. Round black lesion with a rim of edema: malignant pustule

42
Q

B. anthracis: Lab diagnosis

A

microscopic examination of material from papules. No spores in clinical specimen, serpentine chain of bacilli

culture: non hemolytic, sticky, colonies

biochemical tests ultimately should confirm presumptive diagnosis

43
Q

B anthracis: protection and terapy

A

inactivated cell free product as vaccine against PA short term. Live attenuated vaccine is also available

treatment should last for 60 days with: penicillin, ciprofloxacin, doxycycline

Exam 2 Skin block (22 decks)

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