unit 3 study guide

• Pathogenesis: The process by which a disease is caused.
• Microbial competition: When two or more microbes compete for the same resources, they can either coexist or one will be eliminated.
• Virulence: the ability of a pathogen to cause disease in a host
• Opportunistic pathogen: A pathogen that can cause disease in a host only when the host is weakened
• Steps of pathogenesis:

  1.) Portals of entry

  2.) Adherence

  3.) Penetration or evasion of host defenses.

  3.5) Damage to host cells

  4.) Portals of exit
• Once a microbe has gained entry to the body, it does NOT mean it causes disease. Host defenses, microbiota and the ID50 dictate whether infection or disease occur.
• Bacteria use adhesins to attach to cells. Gram (-) use fimbrae. Gram (+) use polysaccharides to attach.
• MOST bacteria invade tissue NOT cells
• Exoenzymes: substances that help the bacteria penetrate into tissues.
• Coagulase: Promotes blood clotting
• kinases: dissolve clots
• Hyaluronidase: hydrolyzes hyaluronic acid (in connective tissue)
• collagenase: hydrolyzes collagen (major protein in collective tissue)
• invasins: rearrange the host cell cytoskeleton to cradle bacterium into the cell.
• Toxigenicity: the ability of a microorganism to produce toxins that can cause disease in a host
• Exotoxins: proteins secreted into host tissues. There are 3 targets.

  1.) Intracellular targeting

  2.) Membrane disruption

  3.) Superantigens
• 3 types of exotoxins:

  1.) Cytotoxins (hemolysins and leukocidins)

  2.) neurotoxins

  3.) enterotoxins (causes cell membrane to rupture or leak)
• Endotoxins cause; fever production, inflammation, tissue damage, tissue disruption, intravascular coagulation, and capillary damage.
• Endotoxins: toxins produced by gram-negative bacteria that are released into the environment. These are released when organisms die.
• Endotoxins indirectly harm the body when massive amounts are released, causes cytokine response.
• Fungi: absorb nutrients, when pathogenic the toxins/enzymes can cause allergic reactions.
• When protozoa cause disease it's from invasion of RBC, WBC, nervous tissue, brain, major organs, etc.
• helminths cause disease by releasing toxic waste, clogging blood, crushing tissue, burrowing into tissue, etc.
• Broad spectrum: antibiotics that kill a wide range of bacteria, including bacteria that are resistant to other antibiotics
• Narrow spectrum: antibiotics that only kill bacteria of a specific type
• Bactericidal: kills bacteria
• Bacteriostatic: slows growth of bacteria but does not kill them.
• synergy: the combination of two or more factors that work together to produce a greater effect.
• antagonism: when antibiotics interfere with each other.
• 5 ways antibiotics attack pathogens. Inhibit cell wall synthesis, inhibit protein synthesis, inhibit nucleic acid synthesis, inhibit cell membrane synthesis, and interfere with metabolic reactions.
• Antibiotic resistance.

  1.) Alteration of target (change the target so antimicrobial agent can't bind)

  2.) Alteration of transport systems (alteration of proteins in cell membranes and does not allow antibiotics to enter the cell)

  3.) Drug destroying enzymes

  4.) Efflux (pumps it out when enters the cell)
• Normal flora is the first line of defense
• Lungs produce mucous to pump into the trachea for the human to swallow microbes to the stomach.
• M-protein is a VF. It inhibits phagocytosis.