Chapter 21 Flashcard

Structure of human skin

  •  1st line of defense against pathogens
  • Enter through skin breaks
  • Skin mostly inhospitable for microbes
  • Salt inhibits microbes
  • Lysozyme breaks apart peptidoglycan
  • Perspiration and sebum contain nutrients
  • Moisture of armpits, etc have higher population
  • Contribute to body odor

Mucous Membranes

  •  Line body cavities
  • The epithelial cells are attached to an extracellular matrix
  • Cells secrete mucus
  • Often acidic
  • Some cells have cilia
  • In eyes, washed by tears with lysozyme

Normal Microbiota of the skin

 

  • Gram-positive, salt-tolerant bacteria
  • Staphylococci
  • Micrococci
  • Diphtheroids

Skin Lesions

  • Vesicle: fluid-filled superficial lesion
  • Bulla: similar to vesicle, larger than 1 cm
  • Macule: slightly raised reddish rash or lesion (Measles)
  • Pustule (papule): contains pus well beneath cutaneous layer

Staphylococcus epidermidis

 

  • Gram-positive cocci, coagulase-negative (enzyme clots blood)
  • 90% normal mibrobiota
  • Less pathogenic
  • Staphylococcal skin infection

Staphylococcus aureus

  •  Gram-positive cocci, coagulase-positive
  • 20% population have in nasal passages; another 60% carry it
  • More pathogenic
  • Staphylococcal skin infection
  • Numerous virulence factors
  • Some strains produce enterotoxins
  • Associated with resistance
  • MRSA (methicillin resistant S. aureus)

Folliculitis

  • Infection of the hair follicles
  • Pus is formed

Sty

  • Folliculitis of an eyelash

Furuncle

  • Abscess; pus surrounded by inflammed tissue
  • 1-2 cm EX: boil

Carbuncle

  • Inflammation of tissue under the skin

Impetigo

  • Crusting (nonbullous) sores, spread by autoinoculation

Toxic shock syndrome (TSS)

 

  • Toxic shock syndrome toxin 1
  • Associated with high-absorbency tampons and absorbent packing following nasal surgery

Scalded skin syndrome

 

  • Bullous impetigo
  • Impetigo of the newborn

Streptococcus pyogenes

 

  • Gram-positive; grow in chains
  • Group A
  • beta-hemolytic streptococci (lyse RBCs)
  • “strep throat”
  • can lead to scarlet fever

Erysipelas

 

  • dermal layer of skin affected; red patches
  • Can cause sepsis
  • Can occur in untreated strep throat cases

Group A Streptococcal Infections

 

  • Necrotizing fasciitis
  • Exotoxin A
  • Superantigen antigen that activates serious immune reaction
  • Mortality- 40%

Pseudomonas aeruginosa

  • Gram-negative, aerobic rod
  • produces a blue-green pus
  • Otitis externa, or “swimmer’s ear
  • Post-burn infections
  • Opportunistic

Comedonal Acne

  • Mild
  • Sebum channels blocked with shed cells
  • Treatment
  • Topical agents
  • Salicylic acid preparations
  • Retinoids– vitamin A derivatives (Retin-A)

Inflammatory Acne

  • Propionibacterium acnes
  • Gram-positive, anaerobic rod
  • Form fatty acids after metabolizing sebum as a nutrient; causes inflammatory response
  • Treatment
  • Preventing sebum formation (isotretinoin-Accutaine); causes severe birth defects
  • Antibiotics
  • Benzoyl peroxide to loosen clogged follicles
  • Visible (blue) light (kills P. acnes)

Nodular Cystic Acne

 

  • Severe
  • Treatment
  • Isotretinoin

Papillomavirus

  • Warts
  • Very contagious
  • Treatment
  • Removal
  • Cryotherapy
  • Electrodesiccation
  • Salicylic acid

Genital Warts

  • associated with cervical cancer

Smallpox (variola)

  • Smallpox virus (orthopox virus)
  • Variola major has 20% mortality
  • Variola minor has <1% mortality
  • Eradicated by vaccination
  • Only 2 stocks of the virus in world: CDC and Russia
  • Bioterrorism concern
  • Vaccination of military

Monkeypox

 

  • Prevention by smallpox vaccination
  • 2003- US outbreak in prairie dog owners

Chickenpox

  •  Varicella-zoster virus (human herpesvirus 3)
  • Mild childhood disease
  • Transmitted by the respiratory route
  • Causes pus-filled vesicles
  • Virus may remain latent in nerves
  • Prevention: Live attenuated vaccine
  • Breakthrough varicella in vaccinated people
  • Booster needed

Shingles

  • Herpes zoster
  • Reactivation of latent HHV-3 releases viruses that move along peripheral nerves to skin
  • Trigger- stress; lower immunity ass. With aging
  • Rash unilateral
  • Postherpetic neuralgia: severe burning/pain lasting years
  • Prevention: Live attenuated vaccine
  • Acyclovir may lessen symptoms

Human herpesvirus 1: HSV-1

  • 90% population infected; most subclinical
  • Many cases: cold sores or fever blisters (vesicles on lips)
  • Not same canker sores (different location)
  • Latent in nerves- trigger sun, stress, hormones
  • Herpes gladiatorum (vesicles on skin)
  • Herpetic whitlow (vesicles on fingers)

Human herpesvirus 2: HSV-2

  •  can remain latent in nerves
  • Sexually transmitted disease
  • HSV-2 encephalitis: 70% fatality
  • Can occur in infants born to HSV-2 positive mothers
  • Treatment: Acyclovir

Measles virus (Rubeola)

 

  • Transmitted by respiratory route
  • Macular rash (starting on face) and Koplik’s spots
  • Prevented by vaccination

Rubella virus (German Measles)

;

  • Macular rash and fever
  • Congenital rubella syndrome causes severe fetal damage
  • Prevented by vaccination

Fifth Disease

  • ;Erythema infectiosum
  • Name derived from a 1905 list of skin rashes, which included
  • Human parvovirus B19 produces mild flu-like symptoms and facial rash
  • ;slapped cheek; facial rash

Roseola

;

  • Caused by human herpesvirus 6 (HHV-6) and 7 (HHV-7)
  • Mild childhood illness
  • High fever and rash lasting for 1;2 days

Dermatomycoses

  • Fungal infections of the hair, nails and outer layer of skin
  • Also known as tineas or ringworm
  • Metabolize keratin
  • Tinea capitis (scalp), tinea cruris (groin), tinea pedis (foot), tinea unguium (nails)
  • Treatment- topical miconazole
  • Cutaneous Mycoses

Candidiasis

  • ;may result from suppression of competing bacteria by antibiotics
  • Occurs in skin and mucous membranes of genitourinary tract and mouth
  • Topical treatment with miconazole or nystatin
  • Fulminating disease can result in immunosuppressed individuals (HIV)
  • Treatment: Fluconazole

Scabies

  • ;Sarcoptes scabiei: mite that burrows in the skin to lay eggs
  • Inflammatory skin lesions
  • Transmitted sexually; intimate contact
  • Treatment with topical insecticides

Pediculosis (Lice)

  • Pediculus humanus capitis (head louse)
  • P. h. corporis (body louse)
  • Head to head contact
  • Feed on blood
  • Lay eggs (nits) on hair
  • Treatment with topical insecticides

Conjunctivitis

  • ;An inflammation of the conjunctiva
  • Also called pinkeye or red eye
  • Commonly caused by Haemophilus influenzae
  • Various other microbes can also be the cause
  • adenovirus
  • Associated with unsanitary contact lenses

Ophthalmia neonatorum

  • ;Caused by Neisseria gonorrhoeae
  • Transmitted to a newborn’s eyes during passage through the birth canal
  • Prevented by treating a newborn’s eyes with antibiotics

Chlamydia trachomatis

  • ;Causes inclusion conjunctivitis, or chlamydial conjunctivitis
  • Transmitted to a newborn’s eyes during passage through the birth canal
  • Spread through swimming pool water
  • Treated with tetracycline
  • Causes trachoma
  • Leading cause of blindness worldwide
  • Infection causes permanent scarring; scars abrade the cornea leading to blindness

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