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  <head>
    <title>095-02 Microbial evolution, horizontal gene transfer, virulence, and antimicrobial resistance</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Microbial evolution and resistance">
      <outline text="Rapid evolution, variation, and selection">
        <outline text="Change visible within one infection or outbreak"/>
        <outline text="Large populations and short generation times"/>
        <outline text="Evolution is not intentional">
          <outline text="Random or imported variants persist if they reproduce more"/>
        </outline>
        <outline text="Mutation from replication or damage repair">
          <outline text="Most changes neutral or harmful"/>
          <outline text="A few alter targets, permeability, regulation, host range"/>
          <outline text="Antibiotics do not direct the useful mutation"/>
        </outline>
        <outline text="Selection enriches existing or new variants">
          <outline text="Subtherapeutic concentration at one site selects resistance"/>
        </outline>
      </outline>
      <outline text="Fitness cost and reversibility">
        <outline text="Costs from slow enzymes, transport, energy burden"/>
        <outline text="Compensatory mutations cut cost without restoring susceptibility"/>
        <outline text="Without drug pressure resistance may fall or persist"/>
        <outline text="Reducing use does not guarantee rapid reversal"/>
      </outline>
      <outline text="Horizontal gene transfer mechanisms">
        <outline text="Transfer independent of parent-to-offspring inheritance"/>
        <outline text="Transformation takes up naked environmental DNA"/>
        <outline text="Transduction moves genes by bacteriophage"/>
        <outline text="Conjugation transfers plasmids through cell contact"/>
      </outline>
      <outline text="Mobile genetic elements">
        <outline text="Plasmids are extrachromosomal replicons">
          <outline text="Persist via partitioning, addiction systems, selection"/>
          <outline text="Multi-resistance plasmids give co-selection"/>
        </outline>
        <outline text="Transposons move using transposases"/>
        <outline text="Integrons capture cassettes and express from a promoter"/>
      </outline>
      <outline text="Phage and microbial defence">
        <outline text="Phage act by predation, lysogeny, gene transfer"/>
        <outline text="Temperate phage integrate as prophage">
          <outline text="Confer toxins in diphtheria, cholera, Shiga systems"/>
        </outline>
        <outline text="CRISPR-Cas stores invader fragments">
          <outline text="RNA-guided nucleases cut matching nucleic acid"/>
          <outline text="Mobile elements evolve anti-CRISPR mechanisms"/>
        </outline>
      </outline>
      <outline text="Resistance mechanisms by drug class">
        <outline text="Destruction, target change, efflux, reduced entry, bypass"/>
        <outline text="Phenotype emerges from expression, permeability, inoculum, assay"/>
        <outline text="Beta-lactams inhibit penicillin-binding proteins">
          <outline text="Beta-lactamases, altered targets, porins, efflux"/>
          <outline text="Extended-spectrum enzymes versus carbapenemases"/>
          <outline text="Enzyme name alone cannot predict every drug"/>
        </outline>
        <outline text="Methicillin resistance uses a low-affinity binding protein"/>
        <outline text="Enterococcal vancomycin resistance replaces target chemistry"/>
        <outline text="Staphylococcal intermediate resistance thickens cell wall">
          <outline text="Same phenotype from distinct biology"/>
        </outline>
        <outline text="Aminoglycosides: modifying enzymes, methylation, uptake, efflux"/>
        <outline text="Fluoroquinolones: target mutation plus efflux and permeability"/>
        <outline text="Rifampicin: RNA polymerase change, rapid under monotherapy">
          <outline text="Link genotype to validated phenotype"/>
        </outline>
      </outline>
      <outline text="Tolerance, persistence, and testing">
        <outline text="Tolerance: survival without raised inhibitory concentration"/>
        <outline text="Persistence: small subpopulation surviving transient exposure"/>
        <outline text="Heteroresistance: resistant minority in a susceptible isolate">
          <outline text="These states cause relapse and buy evolutionary time"/>
        </outline>
        <outline text="Minimum inhibitory concentration under standard conditions"/>
        <outline text="Breakpoints use pharmacology, outcomes, distributions, standards">
          <outline text="Susceptible result does not guarantee success"/>
        </outline>
        <outline text="Method limits: diffusion, dilution, automated, molecular">
          <outline text="Molecular finds known determinants, not expression"/>
          <outline text="Genome prediction weakest for novel combinations"/>
        </outline>
      </outline>
      <outline text="Virulence and host damage">
        <outline text="Virulence is capacity to damage in a host context">
          <outline text="Adhesion, invasion, capsule, toxins, secretion systems"/>
          <outline text="A virulence gene does not prove current causation"/>
        </outline>
        <outline text="Pathogenicity islands show horizontal acquisition"/>
        <outline text="Secretion systems inject effectors"/>
        <outline text="Capsules block phagocytosis and complement"/>
        <outline text="Quorum sensing coordinates collective behaviour"/>
        <outline text="Damage is toxin, invasion, or immune mediated">
          <outline text="Superantigens broadly activate T cells"/>
          <outline text="Low-toxin organisms can still destroy tissue"/>
        </outline>
      </outline>
      <outline text="Within-host evolution, transmission, stewardship">
        <outline text="Within-host selection by immunity and drugs">
          <outline text="Parallel lineages adapt to biofilm and low oxygen"/>
          <outline text="One colony misrepresents diversity"/>
          <outline text="Relapse versus reinfection distinguished imperfectly"/>
        </outline>
        <outline text="Transmission adds a selection layer">
          <outline text="No universal trend toward benignity"/>
        </outline>
        <outline text="Stewardship keeps treatment effective, cuts needless selection">
          <outline text="Narrowest effective agent, optimised dose, source control"/>
          <outline text="Review at a set time and shorten duration"/>
          <outline text="Withholding needed early therapy is not stewardship"/>
        </outline>
        <outline text="One Health links humans, animals, water, soil">
          <outline text="Control needs many sectors together"/>
        </outline>
        <outline text="Evolution predictable in principle, contingent in detail">
          <outline text="Measure phenotype rather than trusting a name"/>
        </outline>
      </outline>
    </outline>
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