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Microbiology > skin and wound infections > Flashcards

skin and wound infections Flashcards

1
Q

list the layers of the epidermis

A
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2
Q

what is the function of the dermis?

A

to provide strength and flexibility

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3
Q

what is the function? of the hypodermis

A

to anchor the skin to underlying tissues

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4
Q

what are the normal flora of the skin?

A
  • staphylococcus epidermis
  • staphylococcus aureus
  • alpha-hemolytic and nonhemolytic streptococcus
  • micrococcus
  • Peptostreptococcus
  • Neisseria
  • candida
  • diphtheroid
  • acinetobacter
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5
Q

what is the mechanism of pathogenesis for cocci?

A

they gain access through damaged skin, mucosal or tissue site

  • colonize by adhering to cells or extracellular matrix
  • evade host defense mechanisms and multiply
  • cause tissue damage
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6
Q

list the staphylococcus skin infections

A
  • folliculitis
  • Furuncles
  • Carbuncles
  • abscesses
  • impetigo
  • impetigo of newborn
  • scalded skin syndrome
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7
Q

list the staphylococcus skin infections.

A
  • Scarlet Fever
  • Erysipeles
  • necrotizing facilitis
  • acne
  • antrax
  • gas gangre
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8
Q

list the viral infections of the skin

A
  • chicken pox
  • shingles
  • German Measles
  • Measles
  • Warts
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9
Q

list the fungal infections of the skin

A
  • Dermatophytosis
  • Dermatomycosis
  • Tinea (ringworm infection)
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10
Q

list the protozoal skin infections.

A
  • leishmaniasis
  • scabies
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11
Q

Vesicles

A

small, fluid-filled lesions

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12
Q

Bullae

A

vesicles that are larger than 1cm

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13
Q

macules

A

flattened, reddened lesions

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14
Q

Papules

A

raised rounded lesions

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15
Q

pustules

A

raised lesions w/puss

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16
Q

Exanthem

A

a skin rash that arises from disease condition

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17
Q

enanthem

A

rash inside the body like on mucous membranes

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18
Q

Furuncle

A

painful, firm or fluctuant abscess that originated from hair follicle

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19
Q

carbuncle

A

network of furuncles connected by sinus trackt

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20
Q

cellulitis

A

painful, erythematous infection of deep skin

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21
Q

Erysipelas

A

fiery red, painful infection of superficial skin w/ sharply demarcated border

22
Q

folliculitis

A

papular or pustular inflammation of the hair follicles

23
Q

impetigo

A

Also called pyoderma

large vesicles and/or honey crusted sores

24
Q

what are the common causes of infected skin wounds

A

wounds can become infected when microorganisms colonize the cut or puncture wound. this leads to wound deterioration or delayed healing

  • Bites
  • Trauma
  • Burns
  • Post Surgical
25
Q

what are the common signs of an infected wound

A
  • unpleasant odor coming from the wound
  • generalized chills or a fever
  • excess swelling or increase redness around wound
  • increase tenderness or throbbing
  • swelling of lymph nodes in neck, armpit or groin
  • red streaks w/in the skin progressing away from wound
  • pus or drainage
  • warmth near or on wound
26
Q

what are the virulence factors of Staphylococcus aureus

A
  • Capsule: inhibits phagocytosis
  • Coagulase: impedes leukocytes getting into infected areas by producing blood clots
  • proteases, lipases, hyaluronidase: degrade surrounding tissue so infection can spread
  • b-lactamase (penicillinase): degrades penicillin
  • Toxins
    • ​Leukocidin: kills WBC
    • Hemolysin: kills RBC
    • Enterotoxin: causes symptoms in GI tract
    • Exfoliative toxin: causes separation of epidermis and dermis
    • protein A: attaches to antibodies which inhibit phagocytosis. mecA gene provides resistance to methicillin, penicillin and other penicillin like drugs
27
Q

what are the reservoirs and mode of transmission for Staphylococcus skin infections

A

infected humans: drainage from lesion or any purlent drainage

28
Q

scalded skin syndrom

A

reddening and wrinkling of skin that typically begins near mouth and then spreads over entire body then large blisters (no bacteria or WBC).

  • SSSS
29
Q

Staph Scalded Skin Syndrome (SSSS)

A

SSSS

  • produced by strains of S. aureus that produce exfolitive toxin
30
Q

what are the clinical findings of staphylococcus skin infection

A
  • the different type of lesions
  • furuncle
  • carbuncle
  • impetigo
  • Stye
  • folliculitus
  • Scalded Skin Syndrome
  • majority of skin lesions are localized, discrete and uncomplicated.
    *
31
Q

how do you test for staphylococcus skin infections

A
  • isolation culture media and ID by biochemical or enzyme test
  • susceptibility test must be performed b/c many S. aureus are multi-drug resistant
32
Q

list the different types of diagnostic laboratory test for staphylococcus skin infections

A
  • smears
  • cultures
  • catalase test
  • coagulase test
  • susceptibility test- antibiotic susceptibility test
  • serologic and typing test
  • molecular typing test
33
Q

what is tetracycline used for

A
  • antibiotic used for long term treatment
34
Q

what medication would you use to reduce post-surgical wound infections?

A

ID hospitalized pt w/ 5 days mupirocin w/ or w/o bathing while using chlorhexidine which is an antiseptic

35
Q

B-Lactamase-resistant penicillin

A

used for bacteremia, endocarditis, pneumonia and other sever infections from Staphylococcus aureus. requires long term IV of B-lactamase-resistant penicillin

36
Q

Vancomysin

A

reserved for use w/ nafcillin-resistant staphylococci

37
Q

what are lancefield antigens? on what kind of bacteria can they be found?

A

characterized by antigenic properties of C carbohydrate in the cell wall. they are named by letters (A through S)

  • they can be found on some streptococci bacteria
38
Q

what are the reservoirs and mode of transmission for streptococcus skin infections

A
  • Reservoir: infected humans
  • Mode of transmisison: person to person via large respiratory droplets
    • direct contact w/ person or carriers
    • rarely by indirect contact via objects
39
Q

what are the virulence factors of Streptococcus skin infections

A
  • streptolysin: destroys RBC
  • Hyaluronidase: digest hyaluronic acid
  • production of pyrogenic toxins (A, B,C): a superantigen for T cell causing non-specific activation of the immune system
40
Q

what are the skin and wound infections caused by streptococcus pyognes

A
  • cellulitis
  • Erysipelas
  • impetigo
  • necrotizing myositis and fasciitis: (“flesh-eating bacteria”, group A.) quickly destroys muscles, fat, skin tissue and subcutaneous fascia
  • scarlet fever: results in high fever w/ bright red diffuse rash over face, trunk, inner arms and legs and sometimes tongue
  • rheumatic fever, glomerulonephritis and streptococcal toxic shock syndrome
41
Q

what is the pathogenesis of Necrotizing fasciitis?

A
  1. Streptococcus pyogenes is passed person to person and enters body through breaks in the skin.
  2. S. pyogenes secretes enzymes that allow bacteria to invade body
    • streptokinases: dissolve blood clots
    • hyaluronidase: breakds down hyaluronic acid
    • deoxyribonucleeases: breaks down DNA released from damaged cells
  3. other virulence factor include M protein, which is on surface of S. pyogenes, helps it attach to nose and throat cells and after entering the body it allows it to survive phagocytosis
  4. secretion of toxins that damage tissues
  5. enzymes and toxins released by S.pyogenes can destroy tissue at a rate of several cm/hour
42
Q

what are the signs and symptoms of necrotizing fasciitis?

A

redness, intense pain and swelling at site of infection

  • patients develop fever, nausea, and malaise and mentally confused as their blood pressure drops severely
43
Q

what are the characteristics of Pseudomonas aeruginosa

A
  • gram-
  • aerobic, bacillus
  • metabolizes wide range of organic carbon and nitrogen sources
  • motile, non-sporing, non-capsulated
44
Q

what are the virulence factors of Psuedonomas aerginosa

A
  • fimbriae and adhesins attach to host cells and enable formation of biofilm
  • capsule that is composed of mucoid polysaccharides and plays role in bacterial attachment and biofilm formation. shields from phagocytosis
  • Neuroaminidase: modifies host cell receptors to make bacterial attachment to cell more likely
  • Elastase: breaks down elastic fiber, degrades complement components and cleaves IgA & IgG
  • Endotoxin (lipid A): can trigger fever, blood clotting, inflammation or possibly shock
  • Exotoxin A and exoenzyme S: inhibits eukaryotic protein syn. and leads to host cell death
  • pyocyanin: blue-green pigment of Pseudomonas that triggers formation of reactive forms of O (superoxide radical & peroxide anion) that damage host cells.
45
Q

what are the characteristic of bacteria responsible for acne?

A

Name: Propionibacterium acnes

  • non-sporulating, anaerobic, pleomorphic rod
  • slow growing
  • ferments glucose to form propionic acid and other acids
  • fastidious org. and anaerobic conditions also necessary
46
Q

what are the reservoir for Propionibacterium acnes and pathogenesis?

A

Reservoir: infected humans

Pathogenesis: stimulates local inflammation, forms blackheads, more severe form of disease are inflamed pustules (cyst) that when they rupture they form scar tissue

47
Q

describe the characteristics of Cutaneous Antrax

A

caused by Bacillus anthrasis

  • larege, gram+, aerobic, non-motile, spore-bearing, encapsulated bacillus
48
Q

what are the reservoir for Cutaneous anthrax (Bacillus anthrasis) and mode of transmission

A

reservoir: animals (zoonotic infection)

mode of transmission: endospores that are often shed by infected animals0 and enter through damaged skin

49
Q

what are the virulence factors for Cutaneous Anthrax (Bacillus anthrasis)

A
  • endospore
  • capsule
  • 3 anthrax toxins

major virulence factors encoded on 2 virulence plasmids PXO1 & PXO2

50
Q

PXO1

A

virulence factor of B. anthrasis

virulence plasmid that codes for 3 toxins that cause haemorrhage, oedema and necrosis

Microbiology (17 decks)

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