Selected Dieases - Contact Diseases Leprosy Caused by...

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Contact Diseases Leprosy Caused by Mycobacteria leprae that are acid fast and have a 12 day division cycle. Transmission is through contamination of nasal mucosa or skin lesions with secretions from lepromatous leprosy. Clinical forms vary: a. Tuberculoid - The skin looses pigment and sensation with destructions of nerves. The incubation period is 2 - 5 years. There is cell mediated immune response, but the disease progresses slowly and there is healing. b. Lepromatous - There are granulomas in skin, nerves and bones causing disfigurements. There is no cell mediated immunity. Organisms can be found in respiratory secretions and pus discharged from lesions. Treatment - Dapsone and rifampin for tuberculoid leprosy. For lepromatous leprosy a third agent, clofazimine or thalidomide is added. ii. Staphylococcal Skin Infection Staphylococcus is a gram positive coccus S. aureus causes abscesses, boils, furuncles, carbuncles, impetigo and scaled skin syndrome. Virulence Factors - Alpha toxin (hemolysin), pyrogenic exotoxin, enterotoxin, surface protein A (antiphaocytic), coagulase, leukocidin, hyaluronidase and staphylokinase. Treatment - For superficial infections drain pus and apply moist heat. For deep infections use multidrug treatment. Cephalosporin and vancomycin.
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Sexually Transmitted Diseases (STD) i. Syphilis The agent is a motile spirochete, Treponema pallidum , that is microaerophilic. The organism is easily demonstrated by silver impregnation technique. Treponemes are killed by drying and disinfectants. The disease occurs in stages: a. Primary Syphilis - A lesion occurs on the skin or mucous membrane of the genitals and a chancre develops in 2-3 weeks. b. Secondary Syphilis - There is systemic dispersal of organisms. Symptoms -Lesions on mucous membranes, fever, patchy loss of hair or a rash. Primary and Secondary stages are very infectious. c. Latent Syphilis - Characterized by a positive serological test but there is absence of symptoms. d. Tertiary Syphilis - Gummas (soft tumors) are characteristic of this stage and are due to hypersensitive responses. Organisms can be found anywhere in the body damaging tissues. In a pregnant woman with syphilis organisms can penetrate the placenta after the fourth month and cause congenital syphilis to the fetus. Before the fourth month adequate treatment of the mother prevents fetal damage. Fluorescent Treponemal Antibody (FTA) and Rapid Plasma Reagin (RPR) are tests sensitive in the late primary and secondary stages. Treatment - Penicillin is the drug of choice in all stages. ii. Gonorrhea Neisseria gonorrhoeae is the agent. It is facultative gram negative diplococci and oxidase positive. It causes genitourinary tract infection and also extragenital infections depending on the mode of contact. Gonococcus with pili is virulent, antiphagocytic and produces IgA protease that inactivates IgA. It removes iron from the host and defends against oxidative killing by an increase of catalase production. Adherence to host cells is by pili
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Selected Dieases - Contact Diseases Leprosy Caused by...

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