Download Outline made by: Caleb Richards Checked by: (insert secondary

Outline made by: Caleb Richards
Checked by: (insert secondary author name after checking)
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Define commensal organisms, opportunistic pathogens, strict pathogens and the different types
of relationships that organisms have with their hosts.
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Normal flora are frequently found in the body of healthy persons, and while it tends to
remain constant for a given person, pretty much everybody has a different set of normal
flora
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Flora can be transient (deposited from environment or shed from mucous membranes
or residential
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Commensal intestinal bacteria are able to do: ( I.S.S.S.)
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I- Infection resistant (out- compete pathogenic bac. Due to size.
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S-source of nutrients ex. digest vitamin k, and help make vitamin B
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S- Stimulate tissue turnover ex. Help turn over gut epithelia.
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S- Stimulate immune system to produce antibiotic substances.
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Obligate pathogens are almost always associated with disease in humans
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Opportunistic pathogens are normally harmless, but can be dangerous if the pt is
immunocompromised (cancer tx, antibiotics, transplants)
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Most ideal type of symbiosis is mutualism
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Anaerobes typically outnumber aerobes by 100:1
Describe the normal flora that is present in the different parts of the human body.
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Normal flora are always present in skin, respiratory tract, digestive tract, urinary tract,
and reproductive tract ( weird memorize tip SUDRR-Mouth
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SUDRR-Mouth: Skin, Urinary tract, Dig. Tract, Respiratory Tract, Reproductive tract, &
Mouth)
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Internal flora is typically gram negative, while skin flora is usually gram positive (most
commonly coagulation-negative staphylococci)
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When you get old, the original skin bacteria gets replaced with yeasts
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Microbial density in skin goes: surface<intrafollicular<under occlusive dressing
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Skin microflora can make acids by metabolizing sebaceous secretions
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Most common vaginal bacteria: lactobacillus (post-menopausal, replaced by gramnegative bacilli)
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Most common large intestine bacteria: eschericha coli
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Propionibacteria is the flora present on our faces that caused most of us miserable acne
as teenagers.
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In the respiratory tract, the trachea, bronchi, and lungs have low or nonexistent flora
populations.
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Fetus is initially sterile; lactobacilli multiply in vagina before birth, and newborn
intestine is initially colonized with lactobacillus as well, and additional organisms are
introduced thru breathing and feeding
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Staphylococcus species are most common cause of skin and wound infections
Explain the qualities and roles of normal flora (location, infectious potential, contribution to
health of host through competition, maintenance of environmental conditions).
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Benefits of bacteria: germ-free animals have been found to have lower levels of Igs and
were more often overweight. Bacteria can also help us digest complex carbs.
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We have 10x more microorganism cells than human cells (10^13:10^14)
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Toxic compounds can be released if normal flora find their way into the wrong part of
our body by reacting dangerously with certain biochemical molecules.
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The heavy amount of anaerobic bacteria on our skin is encouraged by our hair follicles
and sebaceous fluids (it’s a good environment for them)
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Medical implant infections are most commonly caused by p. acnes and p. granulosum
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Tooth enamel is most often decayed by anaerobic bacteria metabolism going on
between your teeth (germ-free animals don’t get cavities)
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Oropharynx flora is most commonly found in teeth and gingivial surfaces, and less often
found in nasal washings.
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Trauma from oral cavity can cause s. sanguis to enter bloodstream, adhere to heart
valve, and cause endocarditis
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Helicobacter pylori can cause peptic ulcer disease, gastritis, and gastric cancer, although
most carriers are asymptomatic
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Largest intestinal flora categories are bacteroidetes (gram -) and firmicutes (gram +).
Bacteroidetes have been associated with weight loss.
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Flora are absent from brain, blood, lymph, muscles, cerebrospinal fluid, synovial fluid,
deep tissue, and solid organs (heart/kidney/liver)
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Small numbers of mostly transient microorganisms can be found in lungs, stomch/small
intestine, bladder, and uterus
Explain human defenses against infectious disease.
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The mucociliary system traps bacteria in mucus and uses cilia to push it into the throat
for swallowing.
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Alveolar macrophages guard the lower respiratory tract.
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Lysozyme degrades cell walls in nasal mucus
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The highest concentration of microbes in the entire body is found in the colon (the
ileum has similar types of bacteria, but less of them)
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The colon flora are mostly anaerobic, and almost all are either gram negative or
sporeforming gram positive
Describe the interaction of the bacterial cell with the immune system.
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Becomes Pathogenic in 3 ways: 1. Invasion, 2. Release Toxins, 3. Opportunistic infec.
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Local invasion can occur; for example, staph from skin can get in wound and cause
infection.
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Bacterial translocation occurs when viable bacteria from the GI tract pass to normally
sterile tissues.
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For example, if normal colonic bacteria invade the small intestine, you can get bowel
overgrowth syndrome.
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On mucous membranes, IgA can prevent attachment and opsonize bacteria
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Few bacteria leave the stomach due to its low pH
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Duodenum has few bacteria due to bile salts, pancreatic enzymes, and impact of low
stomach pH
Discuss methods of bacterial adaptation to host immunity.
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Gram + bacteria have lipotechoic acid wall and are immune to complement lysis
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Gram – bacteria have LPS/lipoprotein wall; the LPS is immunogenic, and complement
activation causes macrophage lysis
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Mycobacteria have a glycolipid wall and are eliminated via cell-mediated immunity
(CMI)
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Spirochetes have no organized cell wall, and are subject to elimination by complement
and antibodies
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Commensals limit pathogenic organisms by: displacement, mucin secretion to prevent
attachment, metabolic products (fatty acids, lower pH), compete for nutrients, and
create antibiotic substances
Explain the role of bacterial adaptation to host immunity in development of disease.
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In antigenic variation, a pt is infected, immune response clears the infection, then a
subsequent infection of a different type occurs, and the immune response clears this
one.
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To successfully infect, bacteria must gain entry, adhere, invade immunity, and cause
tissue damage
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Some bacteria can escape phagosomes and live safely in the cell cytosol.
Not included in outline: Lists of specific names/pathogenesis of normal flora typically found in each area
of the body. This seemed too detailed for this particular lecture, and I’m pretty sure this is discussed in
detail in another lecture…