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

© 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

© 2004 Wadsworth – Thomson Learning 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

© 2004 Wadsworth – Thomson Learning Viral Infections Chickenpox and Shingles –Varicella Zoster virus herpesvirus most infected by adulthood –Pathogenesis upper respiratory tract dissemination throughout body incubation days rash –latency spinal ganglia –Treatment--acyclovir –Prevention--vaccine

© 2004 Wadsworth – Thomson Learning Varicella Zoster virus Day Infection of mucosa of upper respiratory tract Replication in regional lymph nodes Primary viremia Replication in liver, spleen and other organs Secondary viremia Infection of skin and appearance of vesicular rash Fever Incubation periodContagious 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

© 2004 Wadsworth – Thomson Learning Arthropod Infections Scabies –Sarcoptes scabiei (mite) –Transmission direct contact fomites –Pathogenesis epidermis of human skin skin burrows –Treatment arachnicide

© 2004 Wadsworth – Thomson Learning 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

© 2004 Wadsworth – Thomson Learning 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

© 2004 Wadsworth – Thomson Learning 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