Skin

Skin Layers

Epidermis - tight layer with constant shedding and a dead skin layer on the surface ‘

• keratin, dermis

• sweat lysozyme, sebum, and other antimicrobial peptides

• sebum secreted by oil glands that have fatty acids that inhibit pathogens

Mucous membranes - lines body cavities opening to the exit

• epithelium - covered in mucin, tight layer of cell with constant shedding (no dead skin)

Normal flora

• compete with pathogens and prevent from establishing presence

• bacteria, yeast NO VIRUS

Skin Rash/Lesion

Exanthem - skin arising from disease

Vesicle - small fluid-filled lesion

Macule - flat, reddened lesion

Papules - raised lesions

Pustules - raised pus filled lesion

S. Aureus - Bacteria

Avoid defenses in the skin

• secretes proteins/toxins that kill phagocytes

• gram positive

• cocci - cluster, in nasal passages

• MRSA - some becomes antibiotic resistant

  • produces damaging toxins and can cause sepsis

S. Aureus Virulent Factors

• coagulase - clot fibrin

• Hyaluronidase - breaks cement holding cells together / spreading factor

• Leucocidins - destroy WBCs

• Capsule - avoid phagocytosis

• Exotoxins - exfoliative toxin (peels top layer of skin off), TSST

Staphyloccous Epidermis

• coagulase negative

• HAI

• forms biofilms on catheters

  • 90 percent of skin normal flora/bacteria

Diseases from S. Aureus or Staphy.

• impetigo - crusted sores (spread by autoinoculation)

• Scaled skin syndrome - Toxin B - exfoliation

• Sty - folliculitis of the eyelash

• folliculitis

• furuncle (boil) - localized region of pus surrounded by inflamed tissue (type of abscess

• Carbuncle - damage and inflammation of deep tissue from the spreading of a furuncle

• Toxic shock syndrome

  • fever, vomiting, shock, and organ failure from TSST-1 in the bloodstream

• MRSA

Group A Strep (GAS)

• dangerous group of diseases

• gram postive, cocci in chains

• part of normal flora in mouth and respiratory tract

• M protein - adhere and avoid immune system

• capsule, hyaluronidase, TSST

• Hemolysin

  • beta hemolytic strep (kills RBCs)

GAS diseases/conditions -

• erysipelas - superficial patch of redness

• S. Pyogenes - dermal layers (sepsis + destruction) - exotoxin A causing superantigen

• impetigo

• respiratory infection

• Strep. TSST syndrome

• necrotizing fasciitis

• sore throat

• invasive systemic infection

Other - Pseudomonas

• opportunistic in burn victims

• causes swimmers ear

• has holes inside that does not let antibodies in

  • ubiquitous, resist many antibodies, forms biofilm

Other - Propionibacterium Acne

• The most common skin disease in humans

• skin cells shed in the hair follicle and combine with sebum (this traps bacteria)

• Sebum formation is due to hormones, not diet

• mild acne - easily treated with topical formulations

• severe acne - inflamed lesions with pus deep in the skin

Skin virus - VZV

Chicken pox by varicella zoster

• can become latent (in the central nerve ganglia )

• Reyes syndrome - vomiting and brain dysfunction

• prevented with live attenuated vaccine

Shingles by herpes zoster

• the reactivated form of latent VZV (caused by stress or low immunity)

Skin - Viral - HSV

Herpes Simplex

• cold sore, blister, fever, genital lesions

• oral or genital

• remains latent in the cell nerves indefinitely

  • genital warts (not a rash, caused by HPV, could cause cervical cancer

Measles

red spots in the mouth - Kopliks spot

• MMR VAX

Rubella

• german measles

• congenital rubella syndrome (damages the fetus or causes death)
  

Roseola - Herpes virus 6

• 5th disease mild infection

Skin and Nail Fungi: Cutaneous Mycosis

• hair, skin, nail, outer epidermis

• dermomycoses - cause ringworm (nail + scalp ringworm, jock itch, atheletes foot

Candidiasis -

• opportunistic overgrowth of candida yeast

• occurs in skin and mucouse membrane of GU tract + mouth

• causes: antibiotic use, diabetes, hormones

Oral Candida - thrush

Fulminant disease in immunocompromised

vulvovaginal - vanginatis, yeasty, thick, yellow discharge

Eye Infection - Ophthalmia

Ophthalia Neonatreum

• cause: n. gonorrhae

• obtained as fetus passes through birth canal

• preventing by putting antibiotics in fetus eyes

• pus, ulceration of cornea leading to blindness

Inclusion Conjunctivitis

• chlamydia trachomatis

• bacterium grows as a OIP

• in new bron eyes during birth

• spread with pool water

  • treat: tetracycline

Trachoma

• top non-traumatic cause of blindness

• cause: serotypes of chlamydia trachomatis

• abrades cornea due to permanent scaring

• treatment: oral azithromycin