Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Micro Exam 1 > Jackson: Skin and Soft Tissue Infections I > Flashcards

Jackson: Skin and Soft Tissue Infections I Flashcards

1
Q

Definitions:

Macule
Papule
Vesicle
Boils (Furuncle) and Carbuncles

A

Macule: flat, red inflammatory response to microbe or toxin

Papule: raised, red with more marked inflammation

Vesicle: blister

Boils (Furuncle) and Carbuncles: due to infection of hair follicle (folliculitis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Definitions

Ulcer: 
Impetigo: 
Erysipelas: 
Cellulitis:
Necrotizing Fascitis:
A

Ulcer: epithelium ruptures and microbe is discharged

Impetigo: bullous, crusted or pustular eruption

Erysipelas: well-defined spreading inflammation of dermal lymphatics

Cellulitis: acute inflammation due to infection of subcutaneous fat

Necrotizing Fascitis: inflammatory response in soft tissue below the site of infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Dermatophytic fungi

Infection site:
Disease:

A

Keratinized epithelium

Ringworm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Impetigo

Infection site:
Microbe:

A

Epidermis

S.pyogenes and/or S.aureus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Erysipelas

Infection site:
Microbe:

A

Dermis

S.pyogenes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Folliculitis, boils (furuncles), carbuncles

Infection site:
Microbe:

A

Hair follicles

S.aureus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Cellulitis

Infection site:
Microbe:

A

Subcutaneous fat

S.pyogenes or S.aureus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Necrotizing faciitis

Infection site:
Microbe:

A

Fascia

Anaerobes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Gas gangrene

Infection site:
Microbe:

A

Muscle

Clostridium perfringens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Typhoid Fever

Pathogen:
Skin manifestation:

A

Salmonella typhi

Contaminated petechia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does Neisseria meningitidis cause?

Skin manifestation:

A

Septicemia, meningitis

Contaminated petechia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What causes scarlet fever?

A

S. pyogenes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What causes TSS?

A

S.aureus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What causes Blastomycosis?

Skin manifestation:

A

Blastomyces dermatitidis

Granulomatous lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Staphylococcus Aureus

Virulence Factors (Relevant to Skin/Soft Tissue Infections) (6):

A 
Alpha toxin
Toxic Shock Syndrome Toxin (TSST-1)
Exfoliative Toxins
Exoproteins for spread
Antiphagocytic components
Quorum sensing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Staphylococcus Aureus

Alpha toxin

A

o 7 subunit pore-forming cytolysin (complement-like MOA)

o Pore permits fluid loss from cell (kills erythrocytes, leukocytes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Staphylococcus Aureus

Toxic Shock Syndrome Toxin (TSST-1):

A

Pyrogenic exotoxin (related to those produced by Group A strep)

Superantigen that cross-links T cell receptor and MHC class II, resulting in cytokine release

Cytokines cause diverse effects, including endotoxic shock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Staphylococcus Aureus
Exfoliative Toxins:
Two types:

A

Two types:

Chromosomal

Plasmid-encoded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What causes scalded skin syndrome?

What layers are split?

A

Staph Aureus exfoliative toxins cause scalded skin syndrome by inducing intercellular splitting between straum spinosum and stratum granulosum (desquamation of upper layers of epidermis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Staphylococcus Aureus

Exoproteins for Spread (2):

A

Hyaluronidase (hydrolyzes connective tissue)

Staphylokinase (promotes fibrinolysis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q 
Staphylococcus Aureus
Antiphagocytic Components (3):
A

Protein A: binds Fc portion of IgG (Ab binds upside down)

Coagulase: promotes surface polymerization of fibrin to resist phagocytosis

Catalase: neutralizes hydrogen peroxide (protective mechanism since it is an aerobe)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Quorum sensing regulates:
Upregulates what at low density?
What at high density?

A

Quorum sensing regulates virulence factor expression in response to cell density

  1. Upregulation of coagulase at low cell densities for colonization
  2. Upregulation of staphylokinase at high densities for spread
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Staphylococcus Aureus

Transmission:

A

o High skin and nasal carriage rates in humans
o No acquired immunity
o Transmission occurs by fomites (inanimate objects)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Staphylococcus Aureus

Pathogenesis:

Furuncle:
Carbuncle:
Scalded Skin Syndrome (Bullous Exfoliation):
Toxic Shock Syndrome:
Wound Contamination:
A

Furuncle:
Colonization of hair follicle (folliculitis)
Coagulation of fibrin around lesion

Carbuncle:
	Focal suppuration (abscess)
	May lead to entry of organism into bloodstream via lymphatics

Scalded Skin Syndrome (Bullous Exfoliation):
Common in neonates and children (often pick up from hospital workers)
Caused by exfoliative toxin
Bullous Impetigo

Toxic Shock Syndrome:
Caused by TSST-1
Results from vaginal colonizers (ie. tampons in too long) or wound infection

Wound Contamination:
Bacteremia and endocarditis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is bateremia?

What can it lead to? (4)

A 
Bacteremia: spread to blood stream via lymphatics; can result in
	Endocarditis
	Osteomyelitis
	Meningitis
	Pulmonary infection
26
Q

What is Bullous Impetigo?

A

Localized scalded skin syndrome

27
Q

Staphylococcus Aureus
Clinical Identification of Organism:

Collection
G+ or G-?
Catalase
Coagulase
Antimicrobial Susceptibility testing
A

Specimen Collection: surface swab, blood, pus (pyogenic) cultured on blood agar

Gram positive cocci in clusters

Catalase Positive:

Coagulase Positive:

Antimicrobial susceptibility testing allows you to determine the MIC of a particular antimicrobial against S.aureus

28
Q

Staphylococcus Aureus
Antimicrobial Susceptibility Testing:
Allows you to determine:

A

o Allows you to determine the MIC (minimum inhibitory concentration) of a particular antimicrobial against S.aureus
o Once you determine MIC, can determine if that drug is a therapeutic option (ie. does MIC fall into proper dosing range)

29
Q

Staphylococcus Aureus

Coagulase Positive:

Differentiates from:

A

Coagulation of citrated plasma by culture

Differentiates from other staphs (S.epidermis or S.saprphyticus, which are less virulent)

30
Q

Staphylococcus Aureus

Catalase Positive:
Produces:
Differentiates from:

A

Produces O2 bubbles when hydrogen peroxide is added

Differentiates from strep (catalase negative)

31
Q

Streptococcus Pyogenes

Virulence Factors (Relevant to Skin/Wound Infections) (5):

A

M protein

Protein F and Protein G

Streptolysin O and Streptolysin S (cytolysins)

Streptococcal Pyrogenic Exotoxins (SPE A-C)

Hydrolytic Enzymes

32
Q

Streptococcus Pyogenes

M Protein:

Function
Structure
Molecular mimicry

A

Function:

  • Anti-phagocytic (subject to antigenic variation)
  • Mediates binding to epidermis

Structure:

  • Fibrillar structure with C-terminus anchored in the peptidoglycan of the cell wall
  • Amino terminus variable due to genetic recombination (over 80 serotypes)

Molecular Mimicry:

  • Believed to undergo in order to conceal itself during an infection (looks like our own cells)
  • Cross-reactive Abs contribute to acute glomerulonephritis
33
Q

Streptococcus Pyogenes

Protein F and Protein G:

A

Protein F: mediates fibronectin binding at wound sites

Protein G: synonymous with protein A in S.aureus; binds the Fc portion of Abs

34
Q

Streptococcus Pyogenes
Streptolysin O and Streptolysin S (Cytolysins):

Cause of:
Streptolysin O:

A

Cause of beta-hemolysis on blood agar plates

SLO:

  • Oxygen labile (sulfhydryl-activated)
  • Cytolysin that attacks cell membranes and forms large pores
  • Abs to SLO can mediate self-attack and augment cell lysis
35
Q

Streptococcus Pyogenes

Streptococcal Pyrogenic Exotoxins (SPE A-C): (3)

A

SPE A: produced by lysogenized (bacteriophage-carrying) Group A strep

Superantigens that have sequence homology with staphylococcal pyrogenic exotoxins

Induce cytokine release (fever, rash, T-cell stimulation and endotoxin sensitivity)

36
Q

Streptococcus Pyogenes
Hydrolytic Enzymes:
Streptokinase:

A

Responsible for thin, runny pus found in streptococcal infections

Streptokinase: dissolves fibrin and facilitates spread (used therapeutically to dissolve blood clots)

37
Q

Streptococcus Pyogenes
Impetigo (Pyoderma)
Transmission:

A

Infection through minor trauma (ie. insect bite) typically on face and lower extremeties; usually auto-inoculation (scratching)

Can also be person-to-person and by fomites

Epidemics occur in children, especially in hot, humid climates, and due to poor hygiene/crowding

38
Q

Streptococcus Pyogenes

Impetigo (Pyoderma)
Appearance:
Role of M proteins:

A

Appearance:

  • Small vesicle ruptures, resulting in serous exudates, superficial spread and honey-colored crust
  • S.aureus can also cause bullous (blister) impetigo or cause secondary super infection of streptococcal lesions

Role of M Proteins:
- Causative M protein serotypes in impetigo differ from the respiratory serotypes (ie. those seen in strep throat)

39
Q

Poststreptococcal Sequelae: Acute Glomerulonephritis

May follow:
Results in:
Cross-reactivity with:

A

Can follow impetigo (rarely follows respiratory strep infections in children)

Results in edema, HTN, hematuria and proteinuria (kidney dysfunction) 3 weeks following skin infection

Cross-reactivity with nephritogenic M serotypes results in deposition of immune complexes in the glomerulus

40
Q

Erysipelas:

Infection of:

Commonly seen where?

Associated symptoms:

A

Rapidly spreading infection of deeper layers (can progress to necrosis and septicemia)

Commonly seen on the face following streptococcal throat infection

Symptoms Associated:
Edema
Fever
Lymphadenopathy (swollen/enlarged LNs)

41
Q

Cellulitis:

A

Extension of skin infection or wound

Caused by S.pyogenes or S.aureus

42
Q

Streptococcus Pyogenes

Nosocomial Infections:

A

Rates decreasing due to better infection control (ie. in surgical wounds and burn patients)

Puerperal (Childbed) Fever: 19th century disease caused via physician transmission

43
Q

Toxic Shock-Like Syndrome (TSLS):

Cause:
Symptoms: (6)
Compare to TSS:

A

Streptococcus Pyogenes

Cause: highly invasive “flesh-eating” strains that produce SPE A (superantigen)

Symptoms:
	Shock
	Renal impairement
	Rash
	Respiratory failure
	Diarrhea 
	Rapid death

Up to 30% mortality rate: as compared to 3% for TSS caused by S.aureus

44
Q

Streptococcus Pyogenes

Clinical Identification of Organism:

Specimen collection
Classification
Biochemical Tests
Serologic Tests

A

Specimen Collection: surface swab, blood, pus (pyogenic) cultured on BAP with 10% CO2

Classification:
o Gram (+) cocci in chains
o B-hemolytic on blood agar plates (due to SLO and SLS)
o Pyogenic (pus forming)
o Group A Lancefield Classification (carbohydrate Ag in cell wall)

Biochemical Tests:
o Catalase negative (differentiate from staph)
o Serotyping for Lancefield Group A (cell wall)
o Bacitracin sensitivity assay on agar plate (differntiate from other beta-hemolytic streptococci)

Serologic Tests:
o Rise in Ab titers to S.pyogenes Ags (SLO, M protein)

45
Q

Propionibacterium spp.

Virulence Factors (Relative to Skin and Wound Infections):

A

These are skin flora that break down sebum lipids to fatty acids

Organic propionic acid produced by organism contributes to inflammatory process

Hormone production at puberty alters sebum secretion and enhances the growth of P.acnes

46
Q

Propionibacterium spp.

Etiology/Pathogenesis:

What is Acne vulgaris?
What is a blackhead?

When can normal flora cause infection?

A

P.acnes: predominant anaerobe of normal skin flora
o Can contribute to acne:
Increased sebum production at puberty (due to hormones)
High cell numbers in hair follicles and associated sebaceous glands

Acne vulgaris: inflammation of hair follicle and associated sebaceous glands
Blackhead: keratin, sebum and bacteria

As normal flora, can cause infections:

  • In immunocompromised
  • Endocarditis, contamination of prosthetic heart valves, cerebrospinal shunts
47
Q

Propionibacterium spp.

Clinical Identification of Organism:

A

Gram positive rods:

  • Pleiomorphic (multiple shapes)
  • Resemble Corynebacterium

Anaerobic or microaerophilic growth

48
Q

Special Case Bacterial and Soft Tissue Infections:

Pasturella multocida:

Clostridium perfringens:

Clostridium tetani:

A

Pasturella multocida: Gram (-) rods; animal bites

Clostridium perfringens: Gram (+) rod, anaerobic, spores; gas gangrene after wound

Clostridium tetani: Gram (+) rod, anaerobic, spores; tetanus after wound

49
Q

Candida Albicans

Virulence Factors (Relevant to Skin and Wound Infections):

Adhesion
Invasion
Immune system evasion

A

Adhesion: through mannoproten complexes extending from cell wall; receptor site in humans is fibronectin

Invasion:
o Hyphae bind fibronectin, collagen and laminin to extend across mucosal barriers
o Proteases and elastases may also be involved

Immune system evasion: neutrophils are first line of defense; chronic candida infections indicate T cell problem

50
Q

Candida Albicans

Etiology/Pathogenesis:

Folliculitis:
Intertrigo:
Occupational Hazards:
Chronic Mucocutaneous Candidiasis:

A

Folliculitis: infection of hair follicle

Intertrigo: infection in folds of skin (crural folds)
o Wet, macerated surfaces are chronically exposed
o Erythematous papules and tender cracked areas associated with chronic irritation

Occupational Hazards:
o Dishwashers: infection on hands
o Diaper rash

Chronic Mucocutaneous Candidiasis:
o Localized to skin, hair or mucocutaneous junctions
o Indicates T cell deficiency

51
Q

S.pyogenes

Hemolytic reaction
Lancefield group
Disease

A

Beta

A

Impetigo, Scarlet fever, Rheumatic fever

52
Q

S.agalactiae

Hemolytic reaction
Lancefield group
Disease

A

Beta

B

Neonatal sepsis, meningitis

53
Q

Candida Albicans
Clinical Identification of Organism:

Specimen Collection:
KOH/Gram Stain:
Germ Tube (Hyphae):

A

Specimen Collection: exudates or epithelial scrapings

KOH/Gram Stain: budding round/oval yeast cells with hyphae (unicellular in the body)

Germ Tube (Hyphae): outgrowth released by spores of spore-releasing fungi during germination; indicative that it is C.albicans

54
Q

Sporothrix Schenckii:

Etiology/Pathogenesis:

Sporotrichosis:
Multiplication at site:

A

Sporotrichosis: subcutaneous infection caused by this fungi

  • Ubiquitous saprophyte in the soil
  • Inoculation of conidia (spores) by trauma, usually in the extremities of gardeners and farmers

Multiplication at Site: local pyogenic/granulomatous inflammatory reactions

  • Initial stage painless papule (weeks to months after inoculation)
  • Papule can ulcerate/become chronic and drain into lymph channels
  • In worst cases, can spread to bone, eyes, lungs and CNS (less than 1% of cases)
55
Q

Sporothrix Schenckii:

Clinical Identification of Organism:
Diagnosis:
Dimorphic Growth Phases:

A

• Clinical Identification of Organism:
- Diagnosis: requires culturing of infected pus or tissue
- Dimorphic Growth Phases:
o Cigar shaped yeast in tissue/culture at 37 degrees (body temperature)
o Mold with thin, septate hyphae and terminal conidia (spores) at 25 degrees (room temperature)

56
Q

Dermatophytes: Epidermophyton, Trichophyton, Microsporum (Ringworm)

Virulence Factors (Relevant to Skin and Wound Infection):

Adaptation to:
Invasion of hair shaft by:

A

Adaptation to nonliving keratinized tissue of hair, nails, and stratum corneum of skin

Invasion of hair shaft by arthroconidia

57
Q

Dermatophytes:

Genera (4):

What results in pityriasis/tinea versicolor?

A

o Tricophyton
o Epidermophton: never infects hair
o Microsporum: rarely infects nails
o Malassezia furfur: commensal that can cause superficial mycoses
- Results in pityriasis/tinea versicolor (a patchy discoloration)

58
Q

Dermatophytes: Epidermophyton, Trichophyton, Microsporum (Ringworm)

Cause what?

Common Names:
tinea corporis
tinea pedis
tinea cruris

A

Cause superficial infections of the skin (usually the extremeties);

Common Names:
Ringworm: tinea corporis
Athlete’s Foot: tinea pedis
Jock Itch: tinea cruris

Lesions occur most often in moist skin folds (maceration/softening promotes infection)
o Arthroconidia can invade outside/within hair root, plugging the root and causing ring-shaped hair loss
o Invasion of nail bed causes malformed growth

59
Q

Dermatophytes: Epidermophyton, Trichophyton, Microsporum (Ringworm)

Source of Infection:

The infection induces advanced skin growth, limiting its spread:

Infection normally induces:
Immunosuppressive agents do what to infection?

A

Source of Infection:
o Domestic/wild animals or soil
o Have low infectivity and virulence; person to person transmission requires close contact with infected skin or hair

The infection induces advanced skin growth, limiting its spread
o Infection normally induces DTH reaction; because of cell-mediated response, immunity can be acquired
o Immunosuppressive agents prolong infection (decreased shedding of keratinized layers); chronic infections associated with impaired T cell function

60
Q

Dermatophytes

Clinical Identification of Organism: (3)

A

Sampling: scrapings from edge of lesion or infected hairs

Stained with KOH or Calcifor: culture and microscopy used for identification

Microsporum spp: fluoresce under UV light (Wood’s lamp)

Micro Exam 1 (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions