Chapter 27HostmicrobeMed micro13th ed2


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Unformatted text preview: s enter host: Most through breaks or How Microbes enter host: Most through breaks or wounds in skin or invasion of mucous membranes of respiratory, digestive, or genitourinary tract Mucuous Membranes: Respiratory track: microbes inhaled into nose or mouth in drops of moisture or dust particles (Exhalation Droplets) GI track: food, water, and contaminated fingers (Food & Water Bourne) Ex. Cholera, dysentery, typhoid, Salmonella food poisoning Genourinary: Typically sexually transmitted (Direct contact) Ex. Common cold, influenza, pneumonia, measles Ex: HIV, syphillis, gonorrhea, herpes Skin: hair follicles and sweat glands (hookworm); also broken skin due to injury or puncture. See parenteral. Parenteral: directly into tissues beneath skin or into mucus membranes when barriers penetrated Punctures, bites, injections, wounds, surgery Ex. Tetanus, gangrene, e.t.c. o . o Entry of Pathogen into the Host, I Entry of Pathogen into the Host, I II. Adherence Bacteria or viruses usually initiate infection by adhering specifically to epithelial cells through interactions between macromolecules on surfaces of the pathogen and host. Infections often begin at sites in mucous membranes, which consist of single or multilayers of epithelial cells, tightly packed cells that interface with environment Tissue Selective: Neisseria gonorrhoeae adheres more strongly to urogenital epithelium (tissue specificity). Opa surface protein binds with host CD66 protein. II. Adherence Continued II. Adherence Continued o Host Selectivity: a microorganism that normally infects humans binds to human epithelial cells better than those of a rat o Capsules (well defined layer), glycocalyx or slime layer (loose network of polymer fibers) may be involved in adherence. o Fimbriae & Pili are bacterial surface protein structures that also function in attachment (bind host cell glycoproteins). Enterotoxic strains of Escherichia coli express fimbrial proteins called CFA (Colonization factor antigens) that adhere specifically to cells in small intestine. Produce enterotoxins. Bacterial Interactions with Mucous Bacterial Interactions with Mucous Membranes: a. Loose Association b. Adhesion or Adherence c. Invasion into submucosal epithelial cells (III) o o Invasion & Colonization Invasion & Colonization and Growth When a pathogen gains access to tissues, it may multiply; a pathogen must grow within host tissues to produce disease ie. After Adherence (II) to epithelial cells, microbe may penetrate through small breaks or lesions or even an intact mucosal surface (III: Invasion), especially if normal flora is altered. Then microbe may establish itself, grow, and multiply (IV: Colonization and Growth). Disease results when anatomical and/or physiological damage occurs due to Virulence of microbe: (includes Toxigenicity and Invasiveness) Microorganisms and Mechanisms Microorganisms and Mechanisms of Pathogenesis: Overview of Steps Virulence of Microorganism Virulence of Microorganism versus Resistance of Host THE BATTLE AND THE BALANCE Virulence of Microorganism Virulence of Microorganism versus Resistance of Host Virulence: Invasiveness: grow in large numbers and may spread thr...
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