Lecture 23Outline of Last Lecture 1. Antimicrobial Compounds2. ResistanceOutline of Current Lecture Current LectureChapter 14—Host-Microbe InteractionsWe 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 DefenseTypes of host-microbe interactionsMicrobial AssociationsSymbiotic: 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 togetherdo more- Antogonism: Some members are inhibited or destroy by others. Penicilium & BacteriaMany interactions between human body & microorganisms involve the development of biofilmsMajor Factors in the Development of an InfectionPathogen: Infectious agent; Parasite… Penetrate host defense & multiplyTrue Pathogen: Capable of producing infection in a normal functioning host (immune system) BSC 160 1nd Edition- Influenza virus, plague bacillus, malarial protozoanOpportunistic Pathogens: When host defense (immune system) is compromised, or grown in body when it’s not its natural location- Pseudomonas sp & Candida albicansSeverity of the disease depends on…Virulence Factor: Characteristic or structure that contributes to the ability of a microbe to cause diseaseBringing Microbes inside Cells- Encytosis- Phagocytosis Causing Disease-Virulence Factors- Trait used to invade & establish themselves in the host, also determine degree of tissue damage that occurs –severity of diseaseExoenzymes- Dissolve extracellular barriers & penetrate through or between cellsToxigenicity- Capacity to produce toxins at site of multiplication2 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 tissueo Strong specificity for target cell, Hemolysins, A-B toxins (A-active, B-binding)Host Immune Response-- Release cytokines- Fever- Complement- Clotting- Ab & Immune
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