ch 23 lecture

ch 23 lecture - Chapter 23 Human Microflora and Nonspecific...

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Chapter 23 – Human Microflora and Nonspecific Host Defenses Human Microflora Humans colonized by many microbes Normal flora “Commensal” (mutualistic) organisms Microbe populations change constantly Vary with type of tissue, conditions pH, moisture, other microbes present Intestinal flora varies with food eaten Can cause disease if reach abnormal location Normal Human Flora There are Sites where bacteria are normally found: Skin Oral cavity Gastrointestinal tract Respiratory tract Urogenital tract See Fig 23.1 Human Microflora: Skin Skin is difficult to colonize Dry, salty, acidic , protective oils Microbes grow mostly in moist areas – underarms, genitals, etc. Associated with sebaceous (oil) glands and apocrine (sweat) glands (pH 4-6) Factors that affect types of normal flora – weather, age, personal hygiene Bacterial species commonly associated with the skin: Most are Gram positive Staphylococcus Gram positive, aerobic cocci Propionibacterium Gram positive, anaerobic rods Propionibacterium acnes can cause acne Acinetobacter Gram negative rods Few Gram negative bacteria found on skin Human Microflora: Mouth Bacteria in the mouth prior to tooth formation are mainly aerotolerant anaerobes such as Streptococcus and Lactobacillus Acidic glycoproteins in saliva form a layer on teeth providing a firm attachment site for microbes, usually Streptococcus species Extensive growth of these microbes results in thick bacterial layers called dental plaque Microflora of dental plaques make acids that decalcify tooth enamel; results in dental caries (tooth decay, cavities)
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Tooth surfaces in and near the gingival crevice where food particles remain are common sites of tooth decay. Floss!!! Diets high in sucrose are cariogenic – cavity causing Lactic acid bacteria ferment the sucrose to lactic acid Streptococcus mutans produces dextran (polysaccharide used for attachment to tooth surface) only when sucrose is present Diets containing fluoride during formation of tooth enamel make teeth more resistant to tooth decay Incorporation of fluoride into the calcium phosphate crystal matrix increases resistance to decalcification. Normal flora of the gastrointestinal tract
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This note was uploaded on 03/30/2010 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

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ch 23 lecture - Chapter 23 Human Microflora and Nonspecific...

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