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Chapter 21






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Chapter 21 Chapter 21 Presentation Transcript

  • 21 Microbial Diseases of the Skin and Eyes
    • Perspiration salt inhibits
    • Lysozyme hydrolyzes peptidoglycan.
    • Sebum fatty acids inhibit
    • Kerotin waterproofing protein
    • Defensins are antimicrobial peptides (also found in GI membranes).
    Skin Figure 21.1
  • Mucous Membranes
    • Line body cavities.
    • The epithelial cells are attached to an extracellular matrix.
    • Cells secrete mucus, acidic nature
    • Some cells have cilia.
    View slide
  • Normal Microbiota of the Skin
    • salt-tolerant & resistant to drying
    • Hand washing can reduce numbers, some remain in follicles and reestablish populations
      • Malssezia furfur (yeast) capable of growing on oily skin, dandruff
    Figure 14.1a View slide
  • Microbial Diseases of the Skin
    • Vesicles- small fluid filled
    • Bullae- larger
    • Macules- flattened lesions
    • Papules- raised lesions
    • Pustules- raised lesions containing pus
  • Microbial Diseases of the Skin Figure 21.2
  • Bacterial Diseases of Skin
    • Two genera, Staphylococcus and Streptococcus are frequent causes of skin-related diseases
    • This bacteria comes into contact with skin often
    • Both produce invasive enzymes and damaging toxins that contribute to the disease process
  • Staphylococcal Skin Infections
    • S. aureus
      • Most pathogenic of staphylococci
      • Gram-positive cocci and coagulase-positive (clots protect microbes from phagocytosis)
      • Toxins= enterotoxins affecting GI tract
      • Hospital environment problem b/c carried in by patients, staff, visitors infecting surgical wounds
      • . Nasal passage favorable environment or via hair follicle
  • Staphylococcal Skin Infections
    • S. epidermidis
      • Gram-positive cocci and coagulase-negative
      • 90% of normal biota, pathogenic on broken skin: catheter in veins
        • On the surface of the catheter the bacteria are surrounded by slime layer (biofilm) that protects them from drying out
  • Staphylococcal Biofilms Figure 21.3 Slime producing bacteria, covers the surface
  • Staphylococcal Skin Infections
    • Folliculitis: Infections of the hair follicles.
    • Sty: Folliculitis of an eyelash.
    • Furuncle: Abscess; pus surrounded by inflamed tissue.
    • Carbuncle: Inflammation of tissue under the skin: deep, & firm, extensive damage, generalized illness & fever
  • Staphylococcal Skin Infections
    • Impetigo of the newborn
    • Carry the risk of toxins in the blood= toxemia
    • Scalded skin syndrome-under age 2, serious
    • Toxic shock syndrome-once associated with tampons, now surgery packing
    Figure 21.4
  • Streptococcal Skin Infections
    • S. pyogenes- cause a wide range of diseases beyond this chapter
    • Secrete toxins
      • Hemolysins-lyse RBC
      • Streptokinases-blood clot dissolving enzyme
      • Hyaluronaidase-CT dissolving enzyme
      • Deoxyribonucleases- DNA degrade enzyme
      • Streptolysins- lyse RBC, toxic to neutrophils
    Figure 21.5
  • Streptococcal Skin Infections
    • Erysipelas
      • Infects dermal layer
      • Could enter the
      • Bloodstream-sepsis
    • Impetigo
      • spread by touch
    Figures 21.6, 21.7
  • Invasive Group A Streptococcal Infections
    • Flesh eating bacteria
    • Destroy tissue as fast as surgeon can remove it.
    • 40% mortality
    • Cellulitis-solid tissue
    • Myositis-muscle
    • Necrotizing fasciitis-muscle covering
    Figure 21.8
  • Infections by Pseudomonads
    • P. aeruginosa
      • Capable of living on traces of organic matter (soap films, cap liner adhesives)
      • Pyocyanin produces a blue-green pus
    • P. dermatitis- 2weeks duration, pools & hot tubs
      • Otitis externa-swimmer’s ear
      • Post-burn infections of 2 nd & 3 rd degree, may produce blue/green pus (pigment pyocyanin)
  • Acne
    • Most common skin disease, Classified by lesion in 3 categories
    • 1. Comedonal acne occurs when sebum channels are blocked with shed cells. Whiteheads- comedos, blackheads due to lipid (sebum) oxidation
    • 2. Inflammatory acne- sebum being metabolized by bacteria attracts WBC which secrete enzymes damaging hair follicle creating pustules & papules
    • Treat to reduce sebum production
  • Acne
      • Nodular cystic acne (progressive inflammatory acne) has nodules or cysts- inflamed lesions filled with pus deep within the skin, scarring
  • Viral diseases of the Skin
    • Many, although system in nature and transmitted by respiratory or other routes, are most apparent by their effects on the skin.
  • Warts
    • Benign skin growths, transmitted by contact
    • After infection, incubation of several weeks
    • Papillomaviruses- 50 types
        • Removal by cryotherapy, electrodesiccation
          • Imiquimod (stimulates interferon production)
          • Laser as last resort b/c the production of aerosols
  • Poxviruses
    • Smallpox (variola)
    • 15 th century France where syphilis introduced as “the great pox” (la grosse verole)
    • Transmitted via respiratory & moves into blood stream to the skin
    • 1 st disease of immunity & eradicated
    • Vaccination in US ended in 1970
    Figure 21.9
  • Poxviruses
    • Monkeypox
    • Appeared among zoo monkeys, occasional human outbreaks
    • Transmitted by respiratory
      • Prevention by smallpox vaccination
  • Herpesviruses
    • Varicella-zoster virus
    • (human herpes virus 3) Chickenpox pus-filled vesicles
    • Transmitted by the respiratory route
    • Causes pus-filled vesicles
    • Virus may remain latent in dorsal root ganglia (near spine)
    Figure 21.10a
  • Shingles (Latin-cingulum= girdle or belt)
    • Reactivation of latent HHV-3 releases viruses that move along peripheral nerves to skin,
    • Typically distributed along waist
    • Vaccine 1995
    Figure 21.10b
  • Herpes Simplex 1
    • Human herpes virus HHV1
    • Tranmitted by oral or respiratory
    • Cold sores or fever blisters (vesicles on lips)
    • Herpes gladiatorum, skin contact among wrestlers (vesicles on skin)
    • Herpes whitlow, contact among nurses, physicians, dentists (vesicles on fingers)
    • HHV-1 can remain latent in trigeminal nerve ganglia.
  • Herpes Simplex 2
    • Transmitted by sexual contact
    • HHV-2 can remain latent in sacral nerve ganglia.
    • Very rare: HHV 1 or 2 can spread to brain
    • Herpes encephalitis (HHV-2 has up to a 70% fatality rate)
  • Measles (Rubeola)
    • Measles virus
    • Extremely contagious
    • Transmitted by respiratory
    • Macular rash and Koplik's spots (tiny red patches with white specks in mouth)
    • Vaccine MMR, given at 12 mo
    • Encephalitis in 1 in 1,000 cases .
    Figure 21.14
  • Rubella (German Measles)
    • Rubella virus
    • Transmitted respiratory
    • Macular rash and fever
    • Congenital rubella syndrome causes severe fetal damage, infection during 1 st trimester
    • Vaccine 1969
    Figure 21.15
  • Other viral rashes
    • A 1905 list of skin rashes included (1)measles, (2)scarlet fever, (3)rubella, (4)Filatow-Dukes (mild scarlet fever), and
      • (5)Fifth Disease: Erythema infectiosum
        • Human parvovirus B19 produces mild flu-like symptoms and facial rash.
    • Roseola
      • Human herpesvirus 6 causes a high fever and rash, lasting for 1-2 days, recovery leads to immunity
  • Fungal diseases of the skin and nails
    • Most susceptible to microbes that can resist high osmotic pressure and low moisture
  • Cutaneous Mycoses
    • Transmitted by contact
    • Dermatomycoses- colonize epidermis
        • Tineas (Latin for clothes moth) ringworm
          • Capitis-scalp, cruis-groin, pedis-foot, unguium-nails
    • Trichophyton : Infects hair, skin, and nails
    • Epidermophyton : Infects skin and nails
    • Microsporum : Infects hair and skin
  • Cutaneous Mycoses Figure 21.16
  • Subcutaneous Mycoses
    • Caused by fungi from soil (gardeners)
    • Sporotrichosis
      • enters puncture wound then enters the lymphatic system
  • Candidiasis
    • Candida albicans (yeast)
    • Candidiasis may result from suppression of competing bacteria by antibiotics.
    • Natural biota in skin; mucous membranes of genitourinary tract and mouth.
    • Thrush is a whitish infection of mucous membranes of mouth in infants.
  • Parasitic Infections of skin
    • Can infest the skin and cause disease
  • Scabies
    • Sarcoptes scabiei (mite) burrows in the skin to lay eggs
    • intense itching
    • Tranmitted by intimate contact
    Figure 21.18
  • Pediculosis
    • Pediculus humanus capitis (head louse)
    • P. h. corporis (body louse)
      • Feed on blood.
      • Lay eggs (nits) on hair.
      • Tranmitted by contact
    Figure 21.19
  • Bacterial Diseases of the Eye
    • Usually originate from the skin and upper respiratory tract
  • Bacterial Diseases of the Eye
    • Conjunctivitis (pinkeye)
      • Haemophilus influenzae
      • Various microbes
      • Associated with unsanitary contact lenses
    • Neonatal gonorrheal ophthalmia
      • Neisseria gonorrhoeae
      • Transmitted to a newborn's eyes during passage through the birth canal.
      • Prevented by treatment of a newborn's eyes with antibiotics
  • Bacterial Diseases of the Eye
      • Inclusion conjunctivitis
      • Chlamydia trachomatis
        • Transmitted to a newborn's eyes during passage through the birth canal could lead to trachoma
        • Spread through swimming pool water
      • Trachoma (Greek word for rough)
        • Leading cause of blindness worldwide
        • Infection causes permanent scarring; scars abrade the cornea leading to blindness
  • Trachoma Figure 21.20a
  • Viral Diseases of the Eye
    • Conjunctivitis
    • Transmitted by contact
      • Adenoviruses
    • Herpetic keratitis (infection of cornea)
    • Transmitted by contact, latent infection
      • Herpes simplex virus 1 (HHV-1).
      • Infects cornea and may cause blindness
  • Protozoan Disease of the Eye
    • Acanthamoeba keratitis
      • Transmitted from water
      • Associated with unsanitary contact lenses
      • Mild at first, then painful