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Transcript
Infection Chapter 9 1 Microorganism/Human Relationship Mutual relationship Normal flora Relationship can be breached by injury Leave their normal sites and cause infection elsewhere Opportunistic microorganisms 2 Mosby items and derived items © 2006 by Mosby, Inc. Stages of Infection Colonization Invasion Multiplication Spread 3 Mosby items and derived items © 2006 by Mosby, Inc. Factors for Infection Mechanism of action Infectivity Pathogenicity Virulence Immunogenicity Toxigenicity Portal of entry 4 Mosby items and derived items © 2006 by Mosby, Inc. Classes of Infectious Microorganisms Virus Chlamydia Rickettsia Mycoplasma Bacteria Fungi Protozoa Helminths 5 Mosby items and derived items © 2006 by Mosby, Inc. Pathogen Defense Mechanisms Surface coats Inhibit phagocytosis, surface receptors to bind host cells, and toxins Antigenic variation Mutation Recombination Antigenic drift Antigenic shifts Gene switching 6 Mosby items and derived items © 2006 by Mosby, Inc. Bacterial Virulence and Infectivity Bacteria must have iron to multiply Siderophores (iron receptors) Presence of polysaccharide capsules Suppression of complement activation Bacterial proliferation rates can surpass protective response 7 Mosby items and derived items © 2006 by Mosby, Inc. Bacterial Virulence and Infectivity Toxin production Exotoxins Enzymes released during growth causing specific responses Immunogenic Antitoxin production Endotoxins Lipopolysaccharides contained in the cell walls of gram-negative organisms Pyrogenic effects 8 Mosby items and derived items © 2006 by Mosby, Inc. Toxin Production 9 Mosby items and derived items © 2006 by Mosby, Inc. Bacterial Virulence and Infectivity Bacteremia or septicemia Presence of bacteria in the blood due to a failure of the body’s defense mechanisms Usually caused by gram-negative bacteria Toxins released in the blood cause the release of vasoactive peptides and cytokines that produce widespread vasodilation 10 Mosby items and derived items © 2006 by Mosby, Inc. Viral Infection and Injury Obligate intracellular parasites Dependent on host cells No metabolism or incapable of independent reproduction Permissive host cell Virion binds to receptors on the plasma membrane Usually a self-limiting infection Spreads cell to cell 11 Mosby items and derived items © 2006 by Mosby, Inc. Viral Replication DNA or RNA Single or double stranded Protein receptor–binding site Virus uncoats Most RNA viruses directly produce mRNA DNA “provirus” enters nucleus is are transcribed into mRNA 12 Mosby items and derived items © 2006 by Mosby, Inc. Viral Replication Translation of mRNA results in the production of viral proteins New virions are released through budding Viral DNA that is integrated in host cell DNA is transmitted to daughter cells by mitosis 13 Mosby items and derived items © 2006 by Mosby, Inc. Viral Replication 14 Mosby items and derived items © 2006 by Mosby, Inc. Cellular Effects of Viruses Inhibition of host cell DNA, RNA, or protein synthesis Disruption of lysosomal membranes Promotion of apoptosis Fusion of infected, adjacent host cells Alteration of antigenic properties Transformation of host cells into cancerous cells Promotion of secondary bacterial infections 15 Mosby items and derived items © 2006 by Mosby, Inc. Fungal Infection and Injury Large microorganisms with thick cell walls Eukaryotes Exist as single-celled yeasts, multicelled molds, or both Pathogenicity Adapt to host environment Wide temperature variations, digest keratin, low oxygen Suppress the immune defenses 16 Mosby items and derived items © 2006 by Mosby, Inc. Fungal Infection and Injury Diseases caused by fungi are called mycoses Superficial, deep, or opportunistic Fungi that invade the skin, hair, or nails are known as dermatophytes The diseases they produce are called tineas (ringworm) Tinea capitis, tinea pedis, and tinea cruris Deep fungal infections are life threatening and are commonly opportunistic 17 Mosby items and derived items © 2006 by Mosby, Inc. Fungal Infection and Injury 18 Mosby items and derived items © 2006 by Mosby, Inc. Clinical Manifestations of Infectious Disease Variable depending on the pathogen Directly caused by the pathogen or indirectly caused by its products Fever Resetting the hypothalamus Exogenous pyrogens Endogenous pyrogens 19 Mosby items and derived items © 2006 by Mosby, Inc. Countermeasures Vaccines Induction of long-lasting protective immune responses that will not result in disease in a healthy recipient Attenuated organism Killed organisms Recombinant viral protein Bacterial antigens Toxins 20 Mosby items and derived items © 2006 by Mosby, Inc. Countermeasures Antimicrobials Inhibit synthesis of cell wall Damage cytoplasmic membrane Alter metabolism of nucleic acid Inhibit protein synthesis Modify energy metabolism 21 Mosby items and derived items © 2006 by Mosby, Inc. Pathogenic Adaptations Suppression of immune response Antigenic changes Development of resistance 22 Mosby items and derived items © 2006 by Mosby, Inc.
