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© 2004 Wadsworth – Thomson Learning Chapter 26 Chapter 26 Infections of the Infections of the Body’s Surfaces Body’s Surfaces

© 2004 Wadsworth – Thomson Learning Chapter 26 Infections of the Body’s Surfaces

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© 2004 Wadsworth – Thomson Learning

Chapter 26Chapter 26Infections of the Body’s Infections of the Body’s

SurfacesSurfaces

© 2004 Wadsworth – Thomson Learning

Anatomy of the Skin

Figure 26.1

© 2004 Wadsworth – Thomson Learning

Bacterial Skin Infections• Streptococcus

pyogenes• Types of infection

• depth of infection

• virulence of strain

– Impetigo• superficial tissue

– Erysipelas• deeper--underlying

tissue

• red rash

• require treatment

– Streptococcal gangrene• subcutaneous layer

• Virulence– M protein

• prevents phagocytosis

– toxins• leukocidins

– enzymes• streptolysins• streptokinase• hyaluronidase

© 2004 Wadsworth – Thomson Learning

Bacterial Skin Infections• Staphylococcus aureus

– folliculitis• hair follicle

– sty• eyelash follicle

– furuncle (boil)• inflamed, encrusted

– cellulitis• diffuse in underlying tissue

– impetigo• reddish, thin walled vessicles

– scalded skin syndrome• exfoliative toxin

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Bacterial Skin Infections

• Pseudomonas aeruginosa– opportunist organism

• pili for attachment• extracellular slime layer

– interferes with phagocytosis

– burn patients• blue-green pus

– folliculitis--rash• pools and hot tubs

– swimmer’s ear• otitis externa

© 2004 Wadsworth – Thomson Learning

Bacterial Skin Infections

• Clostridium perfringens– Gas Gangrene

• anaerobic growth• deep wounds--necrotic tissue• dirt-contaminated wounds

– spore in soil

• gas• tissue blackened• removal of tissue

– amputation

© 2004 Wadsworth – Thomson Learning

Bacterial Skin Infections• Acne

– small inflamed• papules and pustules

– inflammatory disorder• increased output of sebum• trapped in pores• forced in subsurface tissue• bacteria break down sebum

– Propionibacterium acne

– Treatment• creams remove outer layers• antibiotics for serious cases• isotretinoin (Accutane) (cystic acne)

© 2004 Wadsworth – Thomson Learning

Bacterial Skin Infections• Leprosy (Hansen’s Disease)

– Mycobacterium leprae– skin and peripheral nerves

• chronic skin rash• loss of sensation• indeterminate leprosy• tuberculoid leprosy

– cell-mediated response

• lepromatous leprosy– gross disfigurement

– grows at lower temperatures• cooler body parts• armadillos

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Viral Infections• Chickenpox and Shingles

– Varicella Zoster virus• herpesvirus• most infected by adulthood

– Pathogenesis• upper respiratory tract• dissemination throughout body• incubation--10-12 days• rash

– latency• spinal ganglia

– Treatment--acyclovir– Prevention--vaccine

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Varicella Zoster virus

Day 0 5 10 15 20

Infection of mucosa of upper respiratory tract

Replication in regional lymph nodes

Primaryviremia

Replication in liver, spleen and other organs

Secondaryviremia

Infection of skin and appearance of vesicular rash

Fever

Incubation period Contagious period

© 2004 Wadsworth – Thomson Learning

Viral Infections• Gingivostomatitis and Fever blisters

– Herpes simplex virus type 1– Pathogenesis

• vesicles of infected skin• mucous membranes--uclers• fluid contains virus

– Latency• nerve cells• reactivation

– fever, sunlight, stress

© 2004 Wadsworth – Thomson Learning

Viral Infections

• German measles--Rubella– prolonged exposure– low rate of infectivity– pathogenesis

• replication in mucosal cells• disseminated throughout body• rash--18 days after initial infection• complication in pregnancy

– congenital rubella syndrome– multiple abnormalities

– vaccine

© 2004 Wadsworth – Thomson Learning

Viral Infections• Measles (Rubeola)

– Measles virus• RNA virus• human is only reservoir

– pathogenesis• mucosal lining of URT• spread in lymphoid tissues• shed respiratory tract, eye and urine

– Koplik spots

• skin rash--14 days after exposure

– vaccine– Subacute sclerosing panencephalitis (SSPE)

• rare complication in young age

© 2004 Wadsworth – Thomson Learning

Viral Infections

• Smallpox– Eradicated worldwide in 1977– Possible weapon of bioterrorism– Variola: smallpox virus

• ds DNA virus• Variola major—most virulent strain

– High fever– Blister rash– 50% fatality

– Vaccinia: virus used for immunization

© 2004 Wadsworth – Thomson Learning

Viral Infections

• Papilloma virus– 65 + types of virus– benign wart– cervical carcinoma

• three types associated with this cancer• one of the sexually transmitted diseases

– higher incidence in sexually active--multiple partners

– difficult to grow in culture• infect specific differentiated epithelial cell

© 2004 Wadsworth – Thomson Learning

Fungal Infections

• Ringworm (not a worm)– Tinea=small insect larvae

• tinea corporis--smooth skin• tinea pedis--athlete’s foot• tinea capatis--scalp• tinea ungulum--nails• tinea cruris--groin

– Dermatophytes• enzymes digest keratin

© 2004 Wadsworth – Thomson Learning

Fungal Infections

• Candidiasis– Candida albicans

• opportunistic pathogen• infants and elderly• vagina• mouth• diaper area

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Arthropod Infections

• Scabies– Sarcoptes scabiei (mite)– Transmission

• direct contact• fomites

– Pathogenesis• epidermis of human skin• skin burrows

– Treatment• arachnicide

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Arthropod Infections• Pediculosis (lice)

– Pediculus humanus capitis (head louse)– Pediculus humanus corporis (body louse)– Transmission

• direct body contact• fomites

– Pathogenesis• itching• skin breakdown and superinfection

– Treatment• insecticides

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Anatomy of the Eye

Figure 26.2

© 2004 Wadsworth – Thomson Learning

Eye infections

• Chlamydia trachomatis• Inclusion Conjunctivitis

– infects genital tract– transmitted during birth

• Trachoma– keratoconjunctivitis

• blindness– inflammation resulting in scarring

• Prevention– sensitive to antibiotics

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Eye infections

• Neonatal Gonorrheal Ophthalmia– Neisseria gonorrhoeae– infected mother to newborn

• antibacterial treatment after birth

• Herpetic keratitis– Herpes simplex virus

• Epidemic viral conjunctivitis (pinkeye)– adenoviruses and enteroviruses

© 2004 Wadsworth – Thomson Learning

Eye infections

• Onchocerciasis (River blindness)– Africa and Latin America– Onchocerca volvulus

• Loaiasis (Loa Loa)– Africa– nematode infection of eye