Derm 2 + 3 Flashcards
(35 cards)
What is the structure of the skin?
The dermis lies beneath the epidermis, attached by collagen fibres, and is pierced by ducts and appendages.
How does skin act as a barrier to microbes?
Most bacteria inhabit outer layers or pilosebaceous units; they grow as microcolonies and are shed with skin scales.
What is the difference between resident and transient skin flora?
Resident flora is stable and re-establishes itself; transient flora only inhabits skin temporarily.
What bacteria are found above and below the waist on normal skin?
Above: Gram-positives (Cutibacterium, Corynebacterium, Staphylococci); Below: Gram-positives and Gram-negatives (Enterobacteriaceae, Enterococcus).
What non-bacterial organisms inhabit skin?
Mites (Demodex) and fungi (Malassezia spp.).
What factors control microbial populations on skin?
Dryness, pH (acid mantle), salt concentration, skin turnover, and physical barrier.
How does dryness protect skin?
It inhibits Gram-negative bacteria; occlusion increases moisture and promotes Proteus or Candida overgrowth.
How does skin pH help protect against infection?
Normal pH 4.0–6.0 inhibits environmental bacteria but supports resident flora.
How does salt concentration protect skin?
High salt in sweat deters most bacteria; resident flora is salt-tolerant.
What happens to bacteria on skin due to turnover?
Bacteria are shed before transient species can adapt.
How does the epidermis act as a physical barrier?
It is waterproof, tough, and constantly sheds dead cells to prevent colonisation.
What skin cleansers and antiseptics are used?
Soap, emollients, chlorhexidine, povidone-iodine, hydrogen peroxide, potassium permanganate.
How does chlorhexidine work?
At low doses it is bacteriostatic; at high doses bactericidal by disrupting membranes and binding nucleic acids.
What is cetrimide’s mode of action?
It binds to cell membranes causing leakage at low doses; at high doses it solubilises membrane components.
What is the action of povidone iodine?
Releases iodine (I₂, HOI) which oxidises microbial proteins, nucleic acids, and membranes.
What are common skin infections?
Folliculitis, pustules, boils, carbuncles, abscesses, acne.
What causes folliculitis?
Inflammation of hair follicles, mainly due to Staphylococcus aureus.
What are pustules?
Small skin elevations with purulent exudate (white, yellow, or green).
What are boils (furuncles)?
Deep bacterial folliculitis, usually from Staphylococcus aureus; may need drainage.
What is a carbuncle?
Cluster of boils, usually at the neck, back, or thighs, can spread bacteria.
What is an abscess?
Localised pus collection due to tissue breakdown or necrosis.
What contributes to acne?
Increased sebum, androgenic hormones, Cutibacterium acnes imbalance.
When are antibiotics used for skin infections?
Only when self-care fails or systemic infection develops; flucloxacillin is first-line.
What are superficial spreading skin infections?
Impetigo, erysipelas, cellulitis, scalded skin syndrome.
