skin and wound infections Flashcards
list the layers of the epidermis
what is the function of the dermis?
to provide strength and flexibility
what is the function? of the hypodermis
to anchor the skin to underlying tissues
what are the normal flora of the skin?
- staphylococcus epidermis
- staphylococcus aureus
- alpha-hemolytic and nonhemolytic streptococcus
- micrococcus
- Peptostreptococcus
- Neisseria
- candida
- diphtheroid
- acinetobacter
what is the mechanism of pathogenesis for cocci?
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
list the staphylococcus skin infections
- folliculitis
- Furuncles
- Carbuncles
- abscesses
- impetigo
- impetigo of newborn
- scalded skin syndrome
list the staphylococcus skin infections.
- Scarlet Fever
- Erysipeles
- necrotizing facilitis
- acne
- antrax
- gas gangre
list the viral infections of the skin
- chicken pox
- shingles
- German Measles
- Measles
- Warts
list the fungal infections of the skin
- Dermatophytosis
- Dermatomycosis
- Tinea (ringworm infection)
list the protozoal skin infections.
- leishmaniasis
- scabies
Vesicles
small, fluid-filled lesions
Bullae
vesicles that are larger than 1cm
macules
flattened, reddened lesions
Papules
raised rounded lesions
pustules
raised lesions w/puss
Exanthem
a skin rash that arises from disease condition
enanthem
rash inside the body like on mucous membranes
Furuncle
painful, firm or fluctuant abscess that originated from hair follicle
carbuncle
network of furuncles connected by sinus trackt
cellulitis
painful, erythematous infection of deep skin
Erysipelas
fiery red, painful infection of superficial skin w/ sharply demarcated border
folliculitis
papular or pustular inflammation of the hair follicles
impetigo
Also called pyoderma
large vesicles and/or honey crusted sores
what are the common causes of infected skin wounds
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
what are the common signs of an infected wound
- 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
what are the virulence factors of Staphylococcus aureus
- 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
what are the reservoirs and mode of transmission for Staphylococcus skin infections
infected humans: drainage from lesion or any purlent drainage
scalded skin syndrom
reddening and wrinkling of skin that typically begins near mouth and then spreads over entire body then large blisters (no bacteria or WBC).
- SSSS
Staph Scalded Skin Syndrome (SSSS)
SSSS
- produced by strains of S. aureus that produce exfolitive toxin
what are the clinical findings of staphylococcus skin infection
- the different type of lesions
- furuncle
- carbuncle
- impetigo
- Stye
- folliculitus
- Scalded Skin Syndrome
- majority of skin lesions are localized, discrete and uncomplicated.
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how do you test for staphylococcus skin infections
- isolation culture media and ID by biochemical or enzyme test
- susceptibility test must be performed b/c many S. aureus are multi-drug resistant
list the different types of diagnostic laboratory test for staphylococcus skin infections
- smears
- cultures
- catalase test
- coagulase test
- susceptibility test- antibiotic susceptibility test
- serologic and typing test
- molecular typing test
what is tetracycline used for
- antibiotic used for long term treatment
what medication would you use to reduce post-surgical wound infections?
ID hospitalized pt w/ 5 days mupirocin w/ or w/o bathing while using chlorhexidine which is an antiseptic
B-Lactamase-resistant penicillin
used for bacteremia, endocarditis, pneumonia and other sever infections from Staphylococcus aureus. requires long term IV of B-lactamase-resistant penicillin
Vancomysin
reserved for use w/ nafcillin-resistant staphylococci
what are lancefield antigens? on what kind of bacteria can they be found?
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
what are the reservoirs and mode of transmission for streptococcus skin infections
- 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
what are the virulence factors of Streptococcus skin infections
- 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
what are the skin and wound infections caused by streptococcus pyognes
- 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
what is the pathogenesis of Necrotizing fasciitis?
- Streptococcus pyogenes is passed person to person and enters body through breaks in the skin.
- 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
- 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
- secretion of toxins that damage tissues
- enzymes and toxins released by S.pyogenes can destroy tissue at a rate of several cm/hour
what are the signs and symptoms of necrotizing fasciitis?
redness, intense pain and swelling at site of infection
- patients develop fever, nausea, and malaise and mentally confused as their blood pressure drops severely
what are the characteristics of Pseudomonas aeruginosa
- gram-
- aerobic, bacillus
- metabolizes wide range of organic carbon and nitrogen sources
- motile, non-sporing, non-capsulated
what are the virulence factors of Psuedonomas aerginosa
- 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.
what are the characteristic of bacteria responsible for acne?
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
what are the reservoir for Propionibacterium acnes and pathogenesis?
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
describe the characteristics of Cutaneous Antrax
caused by Bacillus anthrasis
- larege, gram+, aerobic, non-motile, spore-bearing, encapsulated bacillus
what are the reservoir for Cutaneous anthrax (Bacillus anthrasis) and mode of transmission
reservoir: animals (zoonotic infection)
mode of transmission: endospores that are often shed by infected animals0 and enter through damaged skin
what are the virulence factors for Cutaneous Anthrax (Bacillus anthrasis)
- endospore
- capsule
- 3 anthrax toxins
major virulence factors encoded on 2 virulence plasmids PXO1 & PXO2
PXO1
virulence factor of B. anthrasis
virulence plasmid that codes for 3 toxins that cause haemorrhage, oedema and necrosis
