The flashcards below were created by user victimsofadown on FreezingBlue Flashcards.

  1. How much normal flora is associated with the human body?  Where is it located?  When is it acquired?
    • ~1014 bacteria associated with the ~1013 body cells (the majority in the large bowel)
    • Viruses, fungi, and protozoa form only a minor component
    • Internal organs and tissues are normally sterile
    • Acquired rapidly during and shortly after birth
    • Continuously changes throughout life
    • Normal flora occur in parts that are exposed to the environment (skin, nose, mouth, intestinal tract, urinogenital tract)
  2. Why are exposed areas of the skin a bad environment for microbes?
    • pH is 4-6 due to organic acids
    • Low moisture content
    • High salt levels
    • Rapidly changing conditions due to external environment
    • Moist areas (sweat glands in underarm, genitals, nipples, and umbilicus) are colonized
  3. Describe the two types of sweat glands
    • Eccrine glands: main sweat glands, concentrated in certain areas (feet, hands), but distributed over the entire body.
    • Thermoregulation
    • Not many bacteria associated with these glands (dermcidin)
    • dermcidin: anti-microbial peptide secreted by eccrine glands as part of innate immunity
    • Apocrine glands: found primarily in the underarms, genitals, nipples, and umbilicus and WHEREVER THERE IS BODY HAIR
    • Microbial growth in the secretions from these glands = reason for deodorant
    • Develop during the early to mid-puberty ages
    • Reason why food preparers are required to use hair nets
  4. What are the two types of skin normal flora?
    • Transients: organisms that don't grow, but appear as contaminants
    • Can be almost anything
    • E. coli is one of the most common transients (hands, door knobs, faucets, etc)
    • Residents: able to survive/grow on the skin
    • Almost all are gram+ (Staphylococcus[aerobic] and Corynebacterium [anaerobic])
    • Secretion changes during puberty result in an increase of Propionibacterium acnes
    • Yeasts aren't usually found on the skin, but a number of fungi (Candida) occur on the scalp/around the nails
  5. What are the factors that affect skin normal flora in an individual?
    • Weather (heat, humidity, sweat, etc)
    • Age
    • Hospitalization (exposure)
    • Personal hygiene
  6. General information about the normal flora of nose and mouth
    • Majority of bacteria in the nose and mouth are anaerobes
    • Common species include Streptococci, Staphylococci, diptheroids, and gram- cocci
    • Some aerobic bacteria found in normal flora are potentially pathogenic (S. aureus, S. pneumonia, S. pyogenes, Neisseria meningitidis)
    • Candida is also a potential pathogen (mouth thrush)
    • Mucous membranes in the mouth have ~the same microbial density of the large intestines
  7. Positive and negative reasons for growing bacteria in the mouth?
    • Mouth is constantly getting nutrient for the bacteria
    • Saliva: furnishes moisture and nutrients, but has toxic proteins
    • Lysozyme- responsible for most antimicrobial action, breaks glycosidic linkages in peptidoglycan
    • Lactoperoxidase- Enzyme that generates a singlet oxygen (toxic)
  8. How does the normal flora change as the teeth grow in?
    • Before teeth: primarily Streptococci and Lactobacilli (aerotolerant anaerobes)
    • After teeth: surfaces of teeth/gingival crevices are colonized by anaerobic bacteria
  9. What is dental plaque? Dental caries?
    • A thick layer of a mixture of bacteria and polymers
    • Dental caries (cavities): demineralization and destruction of the tooth hard tissues (enamel, dentin, and cementum)
  10. Describe dental plaque development
    • Deposition of acidic glycoproteins from saliva
    • Attachment of facultative S. sanguis, S. sobrinus, S. mutans, and S. mitis on those layers
    • Heavy growth of the above organisms results in colonization of the dental plaque and consumes all the oxygen
    • Secondary growth of filamentous fusobacterium (anaerobic bacteria that produce lactic acid from sugars) and Actinomyces (obligate anaerobes)
    • As dental plaque accumulates the resident microflora produce high concentrations of lactic acid which cause decalcification of the tooth enamel (dental caries)
  11. Give information about S. mutans and S. sobrinus in detail
    • Primarily responsible for dental caries
    • Produce lactic acid by fermenting SUCROSE
    • Lactic acid dissolves CaPO4 in enamel leaving the tooth open to bacterial attack
    • Grow in cracks/crevices between teeth
    • Produces dextran (very thick and sticky glucose polymer) only when growing on SUCROSE via dextransucrase (enzyme)
    • S. mutans is not part of the oral normal flora in populations with no sucrose in the diet
    • ~90% of the US population has S. mutans
  12. Describe the normal flora of the upper respiratory tract
    • Throat, nasal passages, nasopharynx
    • Most of the microbes live in the mucus linings of these areas
    • The flora is highly variable
    • Some can carry pathogenic bacteria as part of the normal flora such as...
    • S. pyogenes: strep throat, flesh eating bacterium
    • S. aureus: staph infection, boils, etc
    • Corynebacterium diphtheriae: diptheria
    • Streptococcus pneumoniae: bacterial pneumonia
  13. Describe the normal flora of the lower respiratory tract
    • Trachea, bronchi, lungs
    • Quite sterile due to...
    • filtration in nasal passages
    • Air slowing as it passes into the lungs
    • Ciliated epithelium push particulate matter up/out of the lungs
    • Many clinically normal individuals may have the fungus Pneumocystis jiroveci in their lungs
  14. What is smoker's cough?
    • Paralysis of the ciliated epithelial cells of the lower respiratory tract by nicoctine and other cytotoxins in tobacco smoke
    • Causes accumulation of mucus, particles, and bacteria (bronchitis)
  15. Describe the normal flora in the gastrointestinal tract
    • Stomach harbors only transient organism (high pH)
    • Gastric mucosa may be colonized by acid-tolerant lactobacilli and streptococci
    • H. pylori is carried by many without gastric ulcer symptoms
    • The upper small intestine is only lightly colonized
    • Populations increase markedly in the ileum where streptococci, lactobacilli, enterobacteriaceae, and Bacteroides may all be present
    • Bacterial numbers are very high in the large bowel (a large fermentor)
    • The vast majority are obligate anaerobes
    • Bacteroides, Clostridium sp, and filamentous fusiform (G- rods w/ tapering ends) are common and major components of feces
    • Relatively small # of facultative anaerobes (E. coli, Enterococcus faecalis)
    • Harmless protozoans can occur, but are not frequent
  16. Describe the bioconversions in the large intestine
    • Gas: by the metabolism of fermentative and methangoenic microorganisms
    • H2 and CO2 by fermentative bacteria
    • CH4 from H2 and CO2 by methanogenic bacteria
    • Odor products: H2S, NH3, amines, indole...
    • Vitamin B12 & K: essential vitamins for humans made by intestine flora
    • Steroids: produced in the liver, but modified/activated by the gut microbes, then reabsorbed
  17. What are the three dominant phyla of fecal microbiota
    • Bacteroidetes: Gram-, nonspore-forming, anaerobic, rod-shaped
    • Includes genus Bacteroides and Porphyromonas
    • Not particularly harmful
    • Firmicutes: Gram+, spore-forming, anaerobic/facultative/obligate anaerobic
    • Includes genus Clostridium and Bacillus
    • Can cause health issues
    • Actinobacteria:
    • The Firmicutes to Bacteroidetes ratio is of significant relevance in human micriobiota composition
    • Obese mice in a study have 50% fewer bacteroidetes and more Firmicutes
  18. Describe the normal microbial flora in the Urogenital tract
    • Bladder: normally sterile
    • Urethra: lightly colonized with Staphylococcus epidermidis, Streptococcus faecalics, and Gram- enterics (E. coli and Proteus mirabilis).
    • These opportunistic pathogens can cause bladder infections (cystitis)
  19. Describe the age-related normal flora changes in the vagina
    • Before puberty: mildly alkaline, predominated by Staphyococci, Streptococci, E. coli
    • Puberty+: mildy acidic, Lactobacillus aerophilus predominates secreting lactic acid while fermenting glycogen
    • Prevents overgrowth by other vaginal organisms
    • Menopause+: secretion of glycogen stops, flora returns to pre-puberty condition
  20. Describe the fungi of the vagina
    • A number of fungi occur
    • Candida can overgrow to cause thrush if vaginal pH rises and competing bacteria diminish
  21. What are the advantages of normal flora?
    • Skin bacteria produce fatty acids which discourage potential pathogens
    • Gut bacteria release a number of antibacterials (bacteriocins, colicins)
    • Vaginal lactobacilli maintain an acidic environment, which suppresses growth of other organisms
    • The sheer number of bacteria in the intestine out-compete potential pathogens for living space
    • Gut bacteria produce B and K vitamins in substantial amounts if diet is deficient
  22. What are the disadvantages of normal flora?
    • The potential for spread of microorganisms into sterile parts of the body...
    • 1. Intestine is perforated
    • 2. Skin is broken
    • 3. Extraction of teeth
    • 4. honeymoon cystitis- perinatal organisms ascent the urethra causing UTI
    • Members of the normal flora often cause nosocomial infection during invasive treatments
    • Overgrowth can occur when...
    • 1. Composition of flora changes (after antibiotics)
    • 2. Local environment changes (increases in stomach or vaginal pH)
    • 3. Immune system become ineffective (AIDS, clinical immunosuppression)
  23. What are the types of symbiotic relationships?
    • commensalism: one species gets shelter/food without harming the other
    • mutualism: mutually beneficial
    • Many cases are interdependent
    • Parasitism: only the parasite benefits
    • There are "blurred lines" and overlap for each type of symbiosis - not clearly defined
  24. Describe commensalism in detail w/ examples
    • One species gets shelter/food without harming the other species
    • Extensive commensal microbial flora on skin, in mouth, and in GI tract
    • Can become harmful (parasitic) if environmental conditions change (eg - Bacteroides, E. coli, Staphylococcus aureus)
    • Can benefit the host (mutual) by preventing colonization of others (intestinal flora) and producing metabolites for host (bacteria/protozoa in ruminant stomach)
  25. Describe mutualism in detail w/ examples
    • Mutually beneficial relationship
    • Bacteria/protozoa in stomachs of domestic ruminants play essential role in digestion/utilization of cellulose and receive environment and nutrition for survival
    • Line between commensalism and mutualism can be hard to draw (enteric bacteria in humans are good for health, but not REQUIRED for survival)
  26. Describe parasitism in detail w/ examples
    • Parasite benefits (environment, nutrients, metabolic needs, regulatory signals, etc) at determinant of host (All pathogens are parasites)
    • Many parasites establish innocuous (commensal) associations with their natural host, but may become pathogenic if there are changes in host's health OR infect an unnatural host
    • eg- rabies virus coexists harmlessly with many wild mammals, but causes fatal disease in human
    • eg- Yersinia pestis (the plague)
  27. Describe the advantages of parasitism (to the parasite) (detailed)
    • Metabolic advantages: host provides a variety of metabolic requirements so the parasite can devote its resources to replication
    • Nutritional advantages: host provides nutrition to parasite, but the extent varies between groups
    • Some use macromolecular material from the host and digest it with their own enzymes
    • Others rely on pre-digestion of the host and take up only low MW molecules
    • Reproductive advantages: evident from metabolic and nutritional advantages
    • HOWEVER- development may be controlled by the host if the host loses the ability to regulate its own development (evolution)
    • This disadvantage forces the parasite to have a host, and will result in death if none are available
  28. Describe the parasite dependency spectrum
    • Viruses (complete dependence): host provides basic building blocks, AND synthetic machinery and energy required
    • Non-viral parasites (partial dependence): have genetic/cellular machinery for independent metabolic activity
Card Set:
2013-09-13 04:03:21

Show Answers: