27 Normal Human Microbe Interactions Vocabulary Colonization the growth of microbes found at any anatomical site Mucus membranes outer layer of epithelial cells surface of many tissues Epithelial cells cells on surface of many tissues Sebaceous glands exocrine glands that secrete oily matter sebum to waterproof mammal s hair and skin Gingival crevis area between the tooth and gingiva where microbes can colonize Dextran a growing glucose polymer that helps in attachment of biofilm Dextransucrase bacterial enzyme that breaks down sucrose and throws away fructose to make dextran one glucose molecule larger Carriers form of spreading pathogens where organism can spread to others but don t get sick themselves Lactobacillus acidophilus beneficial bacteria in the vagina that ferments glycogen and produces acid making the low pH difficult for most bacteria and pathogens to survive pH 5 Pathogenicity ability of a microorganism to cause a disease Opportunistic pathogen causes disease because the normal resistance mechanisms of a host are weakened Adherence factors aids adherence Tissue tropism some pathogens have molecules on their surface that recognize and tightly bind molecules on host tissues Concepts 1 Colonization growth of microbes occurs in three steps a Loose association microbes are in close proximity to the epithelial b Adhesion microbes have various fimbrae cells that attach to epithelial cells cells c Colonization organisms grow and buildup at the particular site on epithelial cells 2 Many factors affect microbial population on skin a Age b Overall personal hygiene c Moisture 3 There are two anti bacterial enzymes that inhibit bacteria but there is still 600 700 phylotypes in the oral cavity typically form biofilm on surface a Lactoperoxidase makes a reactive oxygen species as a product which kills bacteria prevents pathogen colonization b Lysozyme Cleaves peptidoglycan 4 Plaque and tartar are forms of biofilm that form in stages facilitated by dietary sucrose to make dextran a First begin as layer of glycoprotein on the surface of a clean tooth b Then bacteria attach and colonize c Plaque then forms with continued growth to form a thick layer d Tartar forms when plaque becomes calcified i Biofilm plaque tartar 5 1 Dental caries are when anaerobic microbes in an oral biofilm ferment dietary sugars and produce acids e The acid demineralizes the tooth enamel f Fermentation acids dental caries 5 2 Gingivitis is an infection of the gingival crevis that leads to tissue inflammation and bone loss 6 1 The gastrointestinal tract includes stomach small intestine large intestine 6 2 The pH and oxygen in gastrointestinal tract changes to cause changing microbial communities 6 2 1 pH changes from acidic to neutral 6 2 2 Oxygen quickly consumed and anaerobic for the rest of the tract small and large intestines 6 3 Stomach acts as a barrier to microbes because not many microbes can survive a pH of 2 exposure best to kill pathogens 7 Beneficial effects of intestinal microbes all anaerobic in large intestine a Vitamin synthesis and K i Make vitamins that can t make in body or get from food B12 ii Glycosidase helps with digestion that can t usually get broken down stimulates immune system and helps break down steroids 8 The respiratory tract and urogenital tracts are lined with mucus membranes colonized by microbes that maintain normal microflora and stop pathogens from growing pathogens could be present but don t cause disease 9 Pathogenesis has several steps a Exposure to pathogen b Adherence to skin mucosa Invades through epithelium c d Infects inside body e Because invasive and toxic f Damage and disease occurs 10 Virulence is the measure of pathogenicity and can be quantitated by using ID50 and LD50 measures by exposing test subjects to increasing doses of pathogen ID50 infective does that makes 50 sick a b LD50 lethal does that kills 50 11 Adherence factors aid pathogenesis because they re usually specific where pathogens have molecules on surface that tightly bind to molecules on host tissues a Glycocalyx polysaccharide surrounding some bacterial cells and help attach and form biofilm i Slime layers host cells tissues b Adherence proteins on fimbrae pili bind to proteins on surfaces of 28 Virulence and Pathogenesis Vocabulary invasion of pathogen Virulence factors disrupt connective tissues destroy host cells to aid o Produced by pathogen protein enzyme adherence factor that help establish pathogenesis of an infectious disease Hyaluronidase enzyme that breaks down hyaluronic acid polymer that glues host cells together o Holds them together for invasion o Virulence factor Collagenase enzyme that breaks down collagen in connective tissue o Virulence factor Streptokinase destroys fibrin of blood clots o Encloses infection site but with enzyme can break through in invasion o Virulence factor Coagulase creates a fibrin layer around the cell that prevents immune system from detecting the bacteria o Forms clotting o On exterior of pathogenic Staphylococcus aureus cells o Virulence factor Enterotoxins subset of exotoxins that affect the small intestine Exotoxin proteins exported outside of bacterial cell o Endotoxin inside cytoplasm cell of bacterial cell Diarrhea osmosis resulting in large fluid loss from the victim Compromised host one in which mechanisms of resisting pathogens is weakened increased risk of infection by injury illness Immunocompromised weakened immune system Probiotics friendly bacteria that occupy sites on body to inhibit pathogens from gaining access Concepts 1 Tissue specific infections invasion and disruption to connective tissues while systemic infections bacteria have access to the blood system a Bacteremia when bacteria are in circulating blood b Septicemia inflammatory response to bacteremia bacteria in blood 2 Three common types of exotoxins a Cytotoxins cause damage to host cell membranes and can cause cell lysis and death b AB toxins have two subunits i B subunit binds to surface of specific host cells ii A subunit enters host cell where it acts as an enzyme to damage host cell c Superantigens proteins that cause a hyper stimulated immune response resulting in excessive inflammation and tissue damage 3 a three types of cytolytic exotoxins i Hemolysins red blood lysins that have ability to lyse red blood ii Phospholipases enzymes that cut phospholipids and destroy cells host cell membranes iii Staphylococcal alpha toxin cause hole in host cell membrane b We can
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