DLA8, DLA10- Skin Overview and Infections Flashcards Preview

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Flashcards in DLA8, DLA10- Skin Overview and Infections Deck (41):
1

list the 5 layers of epidermis

(superficial to deep)
-stratum corneum
(-stratum lucidum, thick skin only)
-stratum granulosum
-stratum spinosum
-stratum basale

2

list the natural defense mechanisms of the skin

-keratin
-AMPs (antimicrobial peptides) host defense
-skin sloughing
-Sebum: low pH, lipids (sphinoid bases)
-Sweat: low pH, high salt, lysozymes (peptidoglycan disruption)

3

(1) and (2) are common infections related to poor hygeine

-impetigo
-furuncles = clustered boils

4

____ is a common disease contracted from beaches or soil in tropical areas

cutaneous larva migrans (nematodes, hookworms)

5

primary skin infections are caused by (1) to affect (2); examples include: (3)

(primary pyodermas)
1- single pathogen
2- normal skin
3- S. aureus, β-hemolytis streptococci, coryneform bacteria

6

Secondary skin infections are defined as (1), caused by (2).

(secondary pyoderma)
1- infection of existing skin lesion (ex. insect bites, scratching, cracks, etc)
2- mix of infectious and non-infectious causes: scabies, psoriasis, poison ivy, atopic dermatitis, eczema, herpeticum, kerion

7

describe mechanism of 'athletes's foot'

-toe web infection -- secondary pyoderma
-1st thought to only be fungal infection
-Now thought dermatophytes (fungi) first must cause skin damage
-this allows bacterial growth of coryneform bacteria and brevibacterium (& Gram-)

8

compare macule, nodule, papule

-Macule: patch of skin altered in color, no elevation ---- if >1cm diameter = patch

-Papule: small, solid, conical elevation of skin

-Nodule (tumor): small mass, rounded/irregular shape, palpable (slightly larger and extend deeper than papules)

9

define skin patch

-a macule >1 cm in diameter
-skin color alteration
-no elevation

10

define a bulla/vesicle (includ subtypes)

-small, abnormal elevation of outer layer of skin enclosing watery liquid
-Blister/Vesicle = 1-5 mm in diameter
-Bullae > 5 mm in diameter

11

examples of vesicle and bullae diseases

Vesicles: chickenpox (VVZ), oral herpes (HSV1), hand/foot/mouth disease

Bullae: bullous impetigo

12

define a pustule and its associated diseases

-small circumscribed elevation of skin containing pus w/ inflamed base
-acne, chickenpox (VVZ), smallpox

13

(T/F) pustules are always associated with hair follicles

F- they usually are, but not always
ex: folliculite, boils, chickenpox (VVZ)

14

define wheal (include examples)

-localized area of edema, usually irregular and variable in size and color
-ex: hive, insect bite

15

list the primary skin lesions

macule, papule, nodule, vesicle, bulla, pustule, wheal, plaque

16

list the secondary skin lesions

scale, crust, fissure, ulcer

17

define plaque (include examples)

-large, flat, elevated, solid surface
-ex: psoriasis

18

define scale (include examples)

-thin/thick flake of skin varying in color
-secondary to desquamated, dead epithelium
-ex: dandruff

19

define crust (include examples)

-dried residue of exudate
-ex: impetigo residue

20

define fissure (include examples)

-linear crack in skin
-ex: athlete's foot

21

define ulcer (include examples)

-opening of skin caused by sloughing necrotic tissue
-extends past epidermis
-ex: pressure ulcer, stasis ulcer

22

impetigo is a (primary/secondary) pyoderma caused by (2)

1- primary
2- S. aureus, Grp. A Strep

23

cellulitis/erysipelas are a (primary/secondary) pyoderma caused by (2)

1- primary
2- Grp. A Strep

24

folliculitis is a (primary/secondary) pyoderma caused by (2)

1- primary
2- S. aureus, pseudomonas aeruginosa

25

erysipeloid is a (primary/secondary) pyoderma caused by (2)

1- primary
2- erysipelothrix rhusiopathiae

26

erythrasma is a (primary/secondary) pyoderma caused by (2)

1- primary
2- corynebacterium minutissium

27

intertrigo is a (primary/secondary) pyoderma caused by (2)

1- secondary
2- usual skin flora

28

psuedofolliculitis of the beard is a (primary/secondary) pyoderma caused by (2)

1- secondary
2- usual skin flora

29

furuncles/carbuncles are a (primary/secondary) pyoderma caused by (2)

1- primary
2- S. aureus

30

describe differentiating between Streptococcus and Staphylococcus by microscopy

Staph (aureus): Gram+, grape-like clusters, Catalase+, yellow pigment on blood agar (β-hemolytic), penicillin G resistant

Strep (group A, S. pyogenes): Gram+, chain arrangement, Catalase-, no pigment production (although β-hemolysis), penicillin G sensitive

31

Staphylococcus:
-Gram (+/-)
-(non-/motile)
-catalase (+/-)
-oxidase (+/-)
-(aerobic/facultative anaerobic/obligate anaerobic)
-(high/moderate/low) salt tolerance

-Gram+
-non-motile (no flagella)
-catalase+
-oxidase-
-aerobic, some are facultative anaerobic
-high salt tolerance (mannitol salt+, good for sweaty skin)
(some are β-hemolytic on blood agar)

32

what are and how are the Staphylococcus species divided

Coagulase+: S. aureus
Coagulase-: most remaining medically relevant Staph

33

what are and how are the Streptococcus species divided [include where Group A species fall into]

-α-hemolytic (partial): pneumoniae, viridans
-β-hemolytic (complete): pyogenes (Group A, bactracin sensitive), agalactiae (grp. B, bact. resist.)
-γ-hemolytic (none): enterococcus

34

S. pyogenes, aka (1), are (α/β/γ)-hemolytic and bacitracin (sensitive/resistant)

1- group A strep.
2- β-hemolytic
3- bacitracin sensitive

35

describe the method and purpose of PYR test

(pyrrolidonyl arylamidase)
-identification of β-hemolytic Group A/S. pyogenes (+) and enterococci
-Note: β-hemolysis --> PYR => + for grp.A/S. pyogenes (bacitracin sensitive) and - for grp. B/S. agalactiae (bacitracin resistant)
-positive test is bright red, negative is no color change/rxn

36

describe the agars used for C. perfringes

-Blood agar: β-hemolysis with outer layer of α-hemolysis (double zone)

-EYA (egg yolk agar): 1) Lecithinase (phospholipase toxin) => white opaque zone around colonies, 2) Lipase => pearly, iridescent sheen to colonies

37

(1) test is used to differentiate C. perfringes after a (2)+ test on a (3) agar. The (3) plates is divided in halves with (4), and a positive result is if (5) occurs.

1- Nagler test
2- lecithinase+ (clostridium spp)
3- EYA (egg yolk agar)
4- type A antitoxin (and a side w/o)
5- toxin is produced on non-antitoxin side, seen as cloudiness

38

how is a dermatophytic infection identified

-scraping skin scales / infected nails (aspirate if needed)
-mix sample with KOH on slide --> only the hyphae structure remains

39

list the diagnostic tests for Mycobacterial skin infections

-Ziehl-Neelson / Acid-fast stain
-growth on Lowenstein-Jensen agar (4-8 wks)
-growth speed
-pigment production (light/dark)
-sequencing of rpoB, hsp65 genes (gold standard)
-NAAT

40

describe the test used to determine erysipelothrix rhusiopathiae infection

(erysipeloid)
-H2S production test
-does microbe reduce S-containing compounds to Sulfides
-add Fe compounds --> sulfide production is positive if solution has black precipitate

41

Bone and joint infections usually require (1) as investigation and (2) therapy over (3) amount of time

1- analysis of fluid in joint or bone by culture (infectious arthritis, osteomyelitis) [note- radiography will be helpful]
2- antimicrobial therapy
3- wks-mos