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30 Cards in this Set
- Front
- Back
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Sites where bacteria are normally found
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•Skin
•Oral cavity •Gastrointestinal tract •Respiratory tract (no normal flora in lungs themselves) •Urogenital tract (bladder is sterile) |
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Reasons Skin is Difficult to Colonize
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•Dry
•Salty •Acidic (pH 4-6) •Protective oils > Microbes prefer moist environments |
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Bacterial Species commonly associated with the Skin
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Most Gram (+) due to harsh conditions
> Staphylococcus - Gram+; aerobic cocci > Propionibacterium- Gram +; anaerobic rods (acne) > Acinetobacter- Gram- rods |
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Factors that affect types of Normal Flora
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•Weather
•Age •Personal hygiene |
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Bacterial genera commonly found in the mouth
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> Streptococcus
> Lactobacillus |
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Attachment site for microbes in the mouth
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Acidic glycoproteins produced by saliva
+ microbes = dental plaque Dextran produced by Streptococcus mutans |
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Dental Plaques
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produce acid which decalcify tooth enamel
> lactic acid produced by bacteria fermenting sucrose |
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Dextran
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polysaccharide used for attachment to tooth surface
produced by Streptococcus mutans only when sucrose is present |
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Microflora of the Stomach
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• pH about 2
• Only acid-tolerant bacteria can colonize stomach wall Ex. Helicobacter pylori • Very few bacteria are found in stomach fluids |
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Microflora in Small Intestines
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increases as move through intestines due to increasing pH
• Duodenum: few due to stomach acids; Gram + cocci and bacilli • Jejunum: Enterococcus, Lactobacillus • Ileum: similar to large intestine; Bacteroides & facultative aerobes (E. coli) |
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Microflora in Large Intestines
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> 300 species (10^11 cells/g contents)
> mostly anaerobes, small # facultative aerobes > Diet affects (↑ meat = ↑ Bacteroides) > vitamins produces (B12, K, riboflavin, thiamine) > Methanogens (H2+CO2->methane) > Growth rate = 1-2 doublings/day |
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Genera of Common Anaerobic Flora found in the Large Intestines
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> Bacteroides
> Clostridium > Enterococcus |
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Bacterial Genera considered Probiotics
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> Lactobacillus
> Bifidobacterium |
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Microflora in Respiratory Tract
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UPPER - trapped in mucus
LOWER - lined with cilia to push bacteria and dust upwards into upper |
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Opportunist Pathogens in Nasopharynx
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• Staphylococcus aureus: sinus and ear infections
• Streptococcus pneumonia: sinus infections and bronchitis • Streptococcus pyogenes: sinus infections & “strep” throat • Corynebacterium diphtheriae: diphtheria |
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Genitourinary Microflora
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Urethra-
(1) Escherichia (2) Klebsiella (3) Proteus (4) Neisseria Vagina - Lactobacillus acidophilus |
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Benefits and Risks of Human Microflora
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Benefits
(1) Makes vitamins (2) Digests food (3) Prevents colonization by pathogens Risks (1) Opportunistic pathogens - surface breach, immunocompromised |
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Innate Immunity vs. Adaptive Immunity
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Innate: barriers, nonspecific reaction to invaders
Adaptive: response to antigens and retains "memory" |
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Cells of the Immune System
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WHITE BLOOD CELLS
(1) Neutrophils & Monocytes: phagocytosis (monocytes-> microphages & dendritic cells) (2) Basophils & Eosinphils: release toxins to poison microbes (3) Lymphocytes > T cells: cell mediated immunity (tumor and virus) > B cells: antibody mediated immunity |
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Barriers to Infection
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(1) PHYSICAL Barriers
> Skin > Mucous > Cilia in Lungs > Receptor proteins on tissues (M cells in gut, Langerhas cells on skin) (2) CHEMICAL Barriers > Acidic pH (skin, vagina, stomach) > Lysozymes (skin, tears): destroys peptidoglycan |
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Innate Host Defenses to Infection
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(1) Physical and Chemical Barriers
(2) Inflammation (3) Fever (4) Phagocytosis (5) Defense by Interferon (6) Natural Killer Cells |
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Role of Inflammation in Immunity
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> Redness, swelling, pain, heat
> Clot forms to localize pathogen Septic shock- infection & inflammation spread throughout the whole body |
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Role of Fever in Immunity
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> Some products of pathogens (endotoxin) are pyrogenic (fever-inducing)
> Endogenous pyrogens produced by leukocytes to ↑ body temp – ↑ antibody and phagocyte production – Slows bacterial growth – BUT very high temps damage host tissue |
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Acute Inflammatory Response
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(1) Macrophages: phagocytosis, release vasofactors & cytokines = capillaries dilate
(2) WBC leak into wound (3) Damaged tissue>bradykinin- stimulates mast cells (4) Mast cells degranulate> release histamine (vessels dilate further) (5) Platelets & plasma enter area (6) Prostaglandin released> nerve cells signal pain, itching |
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Chronic Inflammation
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Some pathogens resist host defenses; remain in body
Body walls off site in granuloma; fibrotic lesion around bacteria Ex. Crohn’s disease |
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Autoimmune Response
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Immune system responds to body cells as if foreign; host tissue destroyed
Ex. Lupus erythematosus, rheumatoid arthritis, Crohn’s disease |
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Phagocytes
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WBC that engulf & digest bacteria
– Produce lysozyme & antimicrobial peptides – Kill with reactive oxygen species Ex. superoxide ions |
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Interferons
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proteins made and released by infected cells; nearby cells respond
Type I- bind to uninfected, make resistant to infection (cleave viral RNA or prevent transcription) Type II- activate macrophage, natural killer T-cells |
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Natural Killer Cells
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destroy infected or cancerous host cells
> Infected & cancerous cells stop producing MHCI > Antibodies bind viral proteins on infected cell surfaces NK cells secrete perforin, create pores to lyse cells |
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Factors Affecting Host's Ability to Resist Infection
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(1) Age
(2) Stress (3) Diet (4) Lifestyle - smoking, drugs, alcohol, lack of sleep (5) Prior or concurrent disease (6) Genetic conditions (Ex. autoimmune) |
