L 69 Skin and Subcutaneous Bacterial Infections Flashcards
Some characteristics of skin that make it a good defense to disease
Acidic pH
Lower temperature than body
Low moisture
Excreted sebum, salt, urea, fatty acids
Normal microbiota: Staph. epidermis, Micrococcus luteus, E. coli
Langerhans cells in the skin to capture and present microbes to T-Cells
Name for a flat, non-palpable skin lesion
Macule
Name for palpable skin lesions
Papules
Name for palpable fluid-filled lesions
Vesicle
Name for palpable skin lesions filled with pus
Pustules
What are the 5 factors that determine if you will get acne vulgaris?
1) Genetics
2) Follicular hyperkeratinization: increased androgen production increases proliferation of keratinocytes
3) Increased sebum production: regulated by hormones
4) Propionibacterium acnes: bacteria lives in follicles and releases pro-inflammatory mediators
5) Inflammation: Proliferation of P. acnes releases enzymes, surface proteins, heat-shock proteins
Characteristics of P. acnes
Gram (+)
Pleomorphic bacterium
Aerotolerant anaerobe
Normal skin flora, likes sebaceous glands
Can be an opportunistic infection in patients with prosthetic devices and I.V. lines
Acne Vulgaris treatment
Retinoids: comedolytic and anti-inflammatory, adapalene, tretinoin, oral isotretinoin
Antibiotics: erythromycin and clindamycin
doxycyclin and minocycline
Benzoyl peroxide: antimicrobial
Acne vs folliculitis
Acne is a type of folliculitis
What is folliculitis?
superficial infection of the hair follicles with purulent material in the epidermis
What bacteria are the cause of folliculitis?
Staph. aureus
Pseudomonas auruginosa
Characteristics of S. aureus
Gram (+) coccus
Catalase positive (distinguishes it from strep)
Beta-hemolytic
Normal flora on much of the skin
Enzymes of S. aureus infection
Coagulase: clots the plasma to form a fibrin protective layer around it
Hemolysis: lyses RBC’s
Leukocidin: lyses WBC’s to release tissue damaging enzymes that damage eukaryotic membranes=> necrotic pulmonary disease
Clumping Factor: binds fibrinogen and causes clot formation
Forms of S. aureus folliculitis
Folliculitis barbae: areas of shaving, nasal carriers of staph, erythematous follicular papules that rupture and leave a yellow crust
Sty (hordeolum): folliculitis of the eyelid
Characteristics of Pseudomonas aeruginosa
Gram (-) bacilli Opportunistic pathogen Fruity smell Pyocyanin–blue pus Pyocerdin–green fluorescent siderophore