Chapter 26 Infections of the Body’s Surfaces

1. Chapter 26Infections of the Body’s Surfaces

2. Anatomy of the Skin Figure 26.1

3. 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 Bacterial Skin Infections

4. 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

5. 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

6. 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

7. 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)

8. 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

9. 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

10. Varicella Zoster virus Infection of mucosa of upper respiratory tract Replication in regional lymph nodes Replication in liver, spleen and other organs Infection of skin and appearance of vesicular rash Fever Primary viremia Secondary viremia 0 5 10 15 20 Day Incubation period Contagious period

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. Fungal Infections • Candidiasis • Candida albicans • opportunistic pathogen • infants and elderly • vagina • mouth • diaper area

18. Arthropod Infections • Scabies • Sarcoptes scabiei (mite) • Transmission • direct contact • fomites • Pathogenesis • epidermis of human skin • skin burrows • Treatment • arachnicide

19. 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

20. Anatomy of the Eye Figure 26.2

21. Eye infections • Chlamydia trachomatis • Inclusion Conjunctivitis • infects genital tract • transmitted during birth • Trachoma • keratoconjunctivitis • blindness • inflammation resulting in scarring • Prevention • sensitive to antibiotics

22. 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

23. Eye infections • Onchocerciasis (River blindness) • Africa and Latin America • Onchocerca volvulus • Loaiasis (Loa Loa) • Africa • nematode infection of eye