BSC 160 1nd Edition Lecture 23 Outline of Last Lecture 1 Antimicrobial Compounds 2 Resistance Outline of Current Lecture Current Lecture Chapter 14 Host Microbe Interactions We Are Not Alone The human body exists in a state of dynamic equilibrium with regard to microbes Microbes get nutrients good environment for growth reproduction Microbes can be free living or on a host Correct host communication Colonization of the body involves a constant give take Host Defense Types of host microbe interactions Microbial Associations Symbiotic Very close nutritional relationship requiring both members Mutualism Obligatory dependent Both members benefit Commensalism 1 benefits other not impacted Parasitism 1 benefits host is harmed Pathogenesis Nonsymbiotic Free living Doesn t require relationship but can have Synergism Members cooperate share nutrients Active together do more Antogonism Some members are inhibited or destroy by others Penicilium Bacteria Many interactions between human body microorganisms involve the development of biofilms Major Factors in the Development of an Infection Pathogen Infectious agent Parasite Penetrate host defense multiply True Pathogen Capable of producing infection in a normal functioning host immune system Influenza virus plague bacillus malarial protozoan Opportunistic Pathogens When host defense immune system is compromised or grown in body when it s not its natural location Pseudomonas sp Candida albicans Severity of the disease depends on Virulence Factor Characteristic or structure that contributes to the ability of a microbe to cause disease Bringing Microbes inside Cells Encytosis Phagocytosis Causing DiseaseVirulence Factors Trait used to invade establish themselves in the host also determine degree of tissue damage that occurs severity of disease Exoenzymes Dissolve extracellular barriers penetrate through or between cells Toxigenicity Capacity to produce toxins at site of multiplication 2 Types of Bacteria Toxins Endotoxins Toxin that is not secreted but is released after the cell is damaged o Composed of lipopoly saccharide LPS part of the outer membrane of gram cell walls Exotoxins Toxin molecule secreted by a living bacterial cell into the infected tissue o Strong specificity for target cell Hemolysins A B toxins A active B binding Host Immune Response Release cytokines Fever Complement Clotting Ab Immune activiation
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