F4

1. Skin and Skin-Associated Infections

UKNEQAS - UK National External Quality Assessment Scheme

EQAS = Simulated samples are sent to all UK clinical laboratories (UKAS accredited) to test their performance in correctly identifying/quantifying pathogens within a designated timeframe. (RELATED TO POCT PLACEMENT FOR EQA OF YUMIZEN)

Participation is on a voluntary, confidential basis and is open to all public and private sector clinical laboratories, as well as pharmaceutical and veterinary laboratories worldwide

Laboratory participants in UKNEQAS scheme are identified by a code

UKNEQAS publish correct results and performance of laboratory compared to others nationally

UKNEQAS provide Schedule for Proficiency testing in laboratories (dependent on diagnostic tests

Skin Defences

The skin has two layers:

Epidermis - Thin outer layer of epithelial tissue which contains Langerhans cells, dead cells, and keratin (waterproof)

Dermis - Thick inner layer of connective tissue.

  • The purpose of these skin defences are providing a physical barrier to entry for pathogens.

  • Skin shedding

  • Temperature (Skin surface)

  • Low humidity

Skin chemical defences

Sebum: Oily substance produced by sebaceous glands which forms a protective layer over skin - containing unsaturated fatty acids which inhibit growth of certain pathogenic bacteria and fungi

pH: Low, skin pH usually between 3 and 5 - caused by lactic acid and fatty acids

Perspiration: Produced by sweat glands - contains lysozyme and acids

Lysozyme: Enzyme that breaks down Gram-positive cell walls - found in nasal secretions, saliva, and tears

Skin defence exceptions

  • Parasites

    • roundworms Dracunculus medinensis (Guinea worm),

    • hookworms, Schistosoma spp, Wuchereria bancrofti),

  • Bacteria

    • spirochaetes such as Leptospira, Borrelia burgdorferi

  • Fungi - dermatophyte fungi-such as

    • Trichophyton,

    • Microsporum,

    • Epidermophyton

Types of skin pathogens

Bacteria

Protozoa

Viruses

Staphylococcus aureus

• Streptococcus spp (especially Beta Haemolytic Streptococci), such a S. pyogenes (Beta Haemolytic Streptococcus Group A)

• Leptospira interrogans (Weil’s disease) gain entry via intact skin

• Mycobacterium leprae (Hansen’s bacillus)

Dracunculus medinensis (Guinea worm) gain entry via skin

• Schistosoma spp (S. haematobium, S. mansoni, S. japonicum) gain entry via skin

Varicella zoster (chickenpox)

Wound Infections/Skin infections

Chronic wounds common feature - FAILURE OF WOUND TO HEAL AND PROGRESSIVE DETERIORATION OF WOUND

However other factors can contribute to poor wound healing e.g. diabetes , cardiovascular problems can contribute to delayed wound healing.

Features of wound infections

  • increased exudate

  • increased swelling

  • increased erythema

  • increased pain

  • increased local temperature

  • Periwound cellulitis, ascending infection, change in appearance of granulation tissue (discoloration, prone to bleed, highly friable)

Nurses specialising in this area will treat wound infections – using honey, maggots