Diseases of the Skin Normally skin is protected

Diseases of the Skin Normally skin is protected by perspiration, which produces an acidic p. H- 4 -5, which denatures the protein coat of some bacteria n Perspiration also contains lysozyme, which is a protease, and salt, which creates an osmotic imbalance for some bacteria n

Diseases Staphylococci and streptococci are particularly guilty in skin diseases n Staphylococci are divided into those that produce coagulase, and those that do not n Coagulase clots fibrin in the blood, and enhances the isolation of B n The coagulase- negative strains form 90 % of all B on the skin n

Diseases S. epidermidis is the most common species on the skin- Gram + n S. aureus is the most pathogenic n One strain has no known cure n All S. aureus are coagulase- positive n Fibrin clots protect the bacteria from the immune system of the organism n Kinase gets rid of the clots n

Diseases S. aureus is particularly dangerous in hospital environments n Patients can pass on the infection n The bacteria can become resistant to many antibiotics n Can cause pimples, sties, and boils n Also causes toxic shock syndrome- caused by some tampons n

Streptococcus Gram + n Many inhabit the mouth, GI tract, and respiratory system n Some produce hemolysins, which damage blood cells n

Viral Diseases Warts- benign tumors- caused by papillomoviruses- transmitted by personal contact n Smallpox-during the middle ages, 80 % of the population contracted smallpox n Caused by the variola virus n Transmitted by the respiratory routeviruses infect many internal organs, as well as the skin n

Viruses Chickenpox- Most common infectious disease, after gonorrhea n Passes through the respiratory tract- skin fills with vessicles filled with pus, which rupture and form scabs n Lesions form on the chest, back, and face n

Viruses Herpes Simplex- 90% of the population has been infected with herpes simplex virus- usually in infancy n Sometimes this causes cold sores or fever sores n Herpes Simplex Virus 2 is sexual herpestransmitted by sexual contact n

Viruses Measles- extremely contagious- passed through the respiratory route n Only humans catch measles n There is a vaccine which is 95 % effective but can only be given at one year of age n Infection comes through the respiratory tract, and incubates 10 - 12 days n Symptoms are a sore throat, headache, cough, rash, and lesions n

German Measles Also called rubella n Milder version of measles n Extremely dangerous when a pregnant woman gets it in the first trimester n Then there is a 35 % chance of serious fetal damage, including deafness, eye cataracts, heart defects, death n

Conjunctivitis Inflammation of the conjunctiva- a membrane which covers the eyeball and inner eyelid n Often caused by contact lenses n Trachoma is caused by chlamydia, and is the greatest single infectious cause of blindness in the world- especially in Africa and Asia n