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Microbiology

QuestionAnswer
Normal Microbiota Microbes regularly found at an anatomical site
How does our skin prevent overgrowth of microorganisms? Skin prevents microorganism overgrowth by being slightly acidic and salty.
How does propionibacterium acnes cause pimples? P. acnes are normal residents of the skin but when pores become engorged with excess oil and sebum fluid that is secreted by oil glands, it creates an anaerobic environment where P. acnes can live.
How does propionibacterium acnes cause body odor? When oil glands secrete complex lipids, they can be partially degraded by enzymes from certain gram positive bacteria. Secreted lipids then change to unsaturded fatty acids. Some fatty acids are volatile and may be associated with a strong odor.
Why is there no normal microbiota in the lower respiratory tract? We want to avoid getting it into the lungs.
What happens if normal microbiota is in the lower respiratory tract? Can cause pneumonia or TB
How do we avoid normal microbiota in the lower respiratory tract? 1. Ciliated epithetal cells move mucous upward away from the lower part. 2. Phagocytic action of alveolar macrophages (white blood cells); cells catch other cells, eat and kill them. 3. Lysozyme in mucus
Streptococcus sobrinus causes Dental plaque
Streptococcus mutans causes teeth with strands of dextran
Why do the stomach and small intestine have a lower number of microorganisms than the large intestine? In the stomach, most are killed by acidic conditions. In the large intestine, there's a high reproductive rate; mostly anaerobic and facultative anaerobic microbes growing anaerobically.
Do kidneys, ureters, or bladders have normal microbiota? Nope, microbiota free.
Do male/female genetalia have normal microbiota? Female: cmopex microbiota in flux due to menstrual cycle.
What bacteria is predominant in female genetalia? Lactobacilli; it is acid tolerant so it contributes to low vaginal pH. (A high pH leads to a yeast infection)
Mutually beneficial effects between normal microbiota: 1. Prevent pathogen attachment 2. Consume available nutrients so bad things can't eat them. 3. Produce toxic compounds that in hibit other microbes 4. Prime the immune system.
Opportunistic pathogen Organism that exists harmlessly as part of the body's normal environment but becomes a threat when body's immune system fails.
Normal microbiota changes because of: Hormonal changes, type of food consumed, ethnicity, antibiotics.
How can a woman get a yeast infection? If pH gets too high. Or if a woman takes an antibiotic which kills off lactose bacillus, the pH increases in the vagina and a yeast infection is caused.
Factors impacting the final outcome of host-pathogen relationships 1. Number of organisms present 2. Virulence of pathogen 3. Host's defenses and degree of resistance
Virulence Degree or intensity of pathogenicity
Virulence is determined by 1. Infectivity 2. Invasiveness 3. Pathogenic potential
Define infectivity Ability to establish focal point of infection
Define invasiveness Ability to spread to adjacent tissues
Define pathogenic potential Degree to which pathogen can cause damage to host
Virulence is measured by Lethal and infectious dose
Define lethal dose number that kills 50% of experimental host
Define infectious dose number that infects 50% of experimental host
Steps of pathogenesis of diseases 1. Maintain a reservoir 2. Be transported to host 3. Adhere to, colonize and/or invade host 4. Multiply or complete life cycles on or in host 5. Initially evade host defenses 6. Damage host 7. Leave host (Return to reservoir/enter new host)
Define reservoir Place to live before/after causing an infection
Reservoirs for human pathogens Other humans, animals, or the environment
How are diseases transported? (Two ways) Direct or Indirect contact
Define direct contact cough, sneeze, body contact, etc.
Define indirect contact Vehicles: soil, water, food Vectors: living organisms that transmit pathogen Formites: Inanimate objects that harbor/trasmit
Define adherence process Adhesins recognize specific receptors on the host cells surface
Define colonization process Establishment of a site of microbial reproduction on or within a host
Invasions can be passive or active, define both Active: penetration of mucous membrane and epithelium Passive: Entering through skin lesions, wounds
When does multiplication in the host occur? When pathogen finds appropriate environment within the host
Define bacteremia viable bacteria in blood
Define Septicemia bacteria AND toxins in the bloodstream
Must occur if microbe is to be perpetuated; and be done by passive mechanisms Leave the host
Virulence genes Could be in plasmids or lysogenic phages which can be integrated into chromosomes.
Most bacteria have a lot or a few clonal types? A few
Define pathogenicity islands large segments of DNA that carry cirulence genes
When are pathogenicity islands acquired? During evolution of pathogen by horizontal gene transfer
What regulates bacterial virulence factors Environmental factors (control gene expression)
What are virulence factors made of? Proteins with various properties
Define Intoxication disease resulting from entry of a specific preformed toxin into host
Define toxin Specific substance that damages host
Define toxemia Condition caused by toxins in blood of host
What is an AB toxin? 2 cell units bound together on exotoxin. Made up of an A and B subunit.
Role of the A subunit Reponsible for toxic effect; does the damage
Role of the B subunit Binds to the target cell that enables A subunit to enter
How do Cytolytic toxins work? Membrane disrupting
Two forms of cytolytic toxins? Poreforming adn Phospholipase
Process of poreforming toxin Forms a hole in the membrane, Water enters and the cell dies
Leukocidins Kill phagocytic leukocytes
Hemoysins Kill erythrocytes, leukocytes and many others
Neurotoxins Act directly on neurons by interfering with membrane protein and ion channels
Endotoxins Interacts with host molecules and cells, activates host enzymes
Systematic effects of endotoxins Fever, shock, blood coagulation, weakness, diarrhea, inflmmation
Barriers of nonspecific resistance Cells, tissues, chemicals, physical
Define nonspecific Prevent colonization of the host by most pathogens
Where do cells involved in immunity originate from? Stem cells in the bone marrow
T & B cells are activated by.. the innate immune system
T cells' job Perform specific cellular immune responses like assisting B cells and killing foreign cells
B cells' job Differentiate into plasma cells and form antibodies
PAMP Pathogen Associated Molecular Patterns
PRR Patern Recognition Receptors
Process of innate immune response Phagocytes recognize PAMPs via a family of membrane bound PRRs. Phagocytes are activated to produce metabolic products that kill the pathogen and limit its effects
Inflammation signs Pain, swelling, heat, redness
First half of Inflammation 1. Bac/path enter wound 2. Injured tissues/macrophages @ site release chemokines which recruit immune system cells to site
Define antigen molecule on an invader
Second half of Inflammation 3. Mast cells at site secrete factors that constrict blood vessel at wound, dilate blood vessel near wound 4. Neutrophils arrive, remove pathogens by phagocytosis
How do dendritic cells start adaptive immune response? By degrading foreign proteins and presenting them on MHC class II proteins
CD8+ cells function Induce death of cells that are infected with viruses or are damaged.
CD4+ cells function Activate B cells that become plasma cells, which make antibodies
Innate immune system: provides immediate defense against infections and are found in all classes of plant and animal life
Anatomical barriers of innate immune system Skin, gastrointestinal tract, airways, lungs, eyes, nasopharynx
Adaptive immune system Highly specialized; systemic cells and processes to eliminate and prevent pathogenic growth; activated by innate immune system
Cells used during adaptive immune system Lymphocytes T & B cells
How do immunological memory cells prevent future disease? Cells "remember" pathogens by their signature antigen. If the pathogen infects the body more than once, the cells are used to quickly eliminate it.
Vaccinations work by: When a person becomes exposed to a pathogen, use the vaccine to destroy/cut virus into small pieces. Antibodies are produced and find virus cells to gather for macrophages to destroy.
Vaccinations use active immunity to: "turn on" B cell for body to be ready when real sickness comes
Created by: rtate17