Lab Practical 2

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Lab Practical 2
2013-05-01 16:44:17
BI 301 Lab

Lab practical questions
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  1. In most labs, the effect of antibiotics on bacteria is determined by what test?
    Standardized Disk Susceptibility Test
  2. Describe the Kirby-Bauer method.
    • Bacteria are swabbed on Mueller-Hinton agar
    • Disks containing known amts of antibiotic are added
    • Plate incubated
    • Observe for clear zones of inhibition surrounding disks
  3. How can the results of the Kirby-Bauer method be used to help treat a bacterial infection?
    By comparing the results to a standardized chart a physician can be reasonably certain that if the stated dose on an antibiotic is in tissue then inhibition will take place
  4. Mueller-Hinton agar gives ___ results and does not inhibit ___.
    • Reproducible 
    • Sulfonamides
  5. Zones that represent areas where bacterial growth was inhibited are known as a ___ of ___.
    Zones of inhibition
  6. How is a zone of inhibition measured?
    With a mm ruler measure the diameter of the zone including the disk
  7. What are the 4 steps in the antibiotic susceptibility test?
    • Inoculate plate of test med w/bacteria
    • Place antibiotic disks on the surface
    • Incubate
    • Observe & measure zones of inhibition
  8. The genus ___ includes a broad grp of gram-pos, facultatively anaerobic cocci that form chains of varying length.
  9. What are some common places where species of streptococci are located on human skin?
    • Mouth
    • URT
    • Intestine
    • Human skin
  10. Why is it that streptococcus must be cultivated on a rich medium such as blood agar?
    B/c the organisms lack certain enzymes systems for nutrician
  11. Streptococci are an important component of the microbiota of the ___ ___ ___.
    Upper respiratory Tract
  12. Streptococci organisms may be cultivated on an enriched medium that contains blood & is incubated in an environment rich in ___ & low in ___.
    • Carbon dioxide
    • Oxygen
  13. Streptococci that destroy RBCs completely and form a clear zone around the colonies are known as ___-___ streptococci.
  14. What is an example of a Beta Hemolytic streptococci we encountered?
    Streptococcus pyogenes
  15. Streptococci that cause incomplete destruction of blood cells and their colonies are surrounded by an olive green or brown discoloration of the medium are ___-___ streptococci
  16. Two examples of Alpha-hemolytic streptococci that we discussed are what?
    • S. mitis
    • S. pneumoniae
  17. Nonhemolytic streptococci cause no ___ of RBCs.  ___ that organism in yogurt is a member of this grp.
    • Hemolysis
    • S. lactis
  18. A 5% blood agar medium can be prepared with what 2 components?
    • Trypticase soy agar
    • Defibrinated whole sheep blood
  19. S. mitis (___-hemolytic) and S. salivarius (___-hemolytic) are dominant species in the microbiota of the ___ ___.
    • Alpha
    • Non
    • Oral cavity
  20. S.mitis and S. salivarius in the oral cavity are found where?
    Between teeth and under gums
  21. What nonhemolytic species of streptococci ferments sucrose to acid and is an important cause of tooth decay?
    S. mutans
  22. A selective medium that contains crystal violet, potassium tellurite and trypan blue, which inhibit most gram-neg bacilli and gram-pos bacteria other than streptococci is known as ___ ___ agar.
    Mitis Salivarius agar
  23. ___ ___ broth is an enriched medium containing glucose buffers, sodium carbonate & disodium phosphate which favor growth of hemolytic streptococci.
  24. When Streptococcus mitis grows on a mitis salavarius plate the streptococcal colonies look how?
    Blue dome shaped colonies with a gum drop appearance 
  25. When Streptococcus salivarius grows on a mitis salavarius plate the streptococcal colonies look how?
    Domed colonies having a domed brown center
  26. Mitis salivarius agar inhibits the growth of what bacterial growth? 
    Gram neg and nonstreptococcal Gram pos bacteria
  27. When growing streptococcal bacteria in Todd Hewitt broth what do are we looking for to indicate that growth has actually occurred?
    Sediment at the bottom of the tube
  28. A broth used primarily to enrich the growth of pathogenic (beta-hemolytic) streptococci is called what?
    Todd Hewitt broth
  29. Streptococci grown in Todd Hewitt broth grown in what form and look like what when Gram stained.
    • Long chains
    • Characteristic streptococcal formations
  30. Members of the genus ____ are Gram pos spherical organisms about 1 micrometer in diameter
  31. Staphylococcus grow in what 3 forms?
    • Singly 
    • Pairs 
    • Irregular clusters
  32. What members of the genus Staphylococcus grow on agar media they appear how? 
    Yellow, orange or white colonies
  33. Staphylococcus bacteria are ___ tolerant and can grow on ordinary bacteriological media or on which selective media?
    • Salt
    • Mannitol Salt agar
  34. Certain strains of ___ ___ cause food poisoning, toxic shock syndrome (TSS) or boils and carbuncles.
    Staphylococcus aureus
  35. The species of Staphylococcus that is usually a saprobe of the skin and is rarely involved in human infection is known as ___ ___.
    Staphylococcus epidermidis
  36. A species of staphylococcus, ___ ___, is an opportunistic species that may cause UTIs in women of child bearing years
    Staphylococcus saprophyticus
  37. An alcohol derivative of the hexose mannose is known as ____. 
  38. ___ ___ is a species of staphylococcus that ferments mannose while ___ ___ and ___ ___ do not.
    • Staphylococcus aureus
    • Staphylococcus epidermidis 
    • Staphylococcus saprophyticus
  39. Why would we want to grow bacteria on a differential media?
    In order to rule out certain bacteria
  40. We used mannitol salt agar, a medium that is both ___ and ___.  The ___ concentration is high and the mannitol is available for ___ to ___.
    • Selective and differential
    • Salt
    • Fermentation to acid
  41. The indicator ___ ___ is included in mannitol salt agar to detect acid production.
    Phenol Red
  42. Phenol red will change from ___ to ___ in the presence of acid producing S. aureus.
    Red to yellow
  43. After obtaining a swab, inoculating mannitol salt agar plates and incubating, what should be seen on the plate if Staphylococcus species are present?
    Round, opaque colonies that are white or pigmented
  44. S. aureus produces what type of colonies on mannitol salt agar?
    Golden yellow pigmented colonies
  45. Colonies grown on mannitol salt agar that are surrounded by a yellow halo contain bacteria that did what and probably contain what species?
    Fermented the mannitol and probably contain S. aureus
  46. What do Micrococcus luteus colonies look like on an agar plate?
    Bright yellow, round colonies 
  47. S. aureus has the ability to produce ____, an enzyme that clots blood plasma and enhances its virulence by providing resistance to ___.
    • Coagulase
    • Phagocytosis
  48. S. aureus produces ___ to digest DNA and is also sensitive to the antibiotic ___.
    • DNase
    • Novobiocin
  49. Some of the bacteria normally found inhabiting the animal or human intestinal tract are Gram neg nonspore-forming rods called ____ ___.
    Enteric bacteria
  50. What family do enteric bacteria belong too?
  51. Many enteric bacteria species are ___ anaerobic, and certain species cause human diseases such as what? 
    • Typhoid fever
    • Shigellosis
    • Infantile/travelers diarrhea
  52. How can enteric bacteria species be isolated?
    By cultivating fecal samples on differential media containing lactose
  53. What 2 agars did we use to isolate enteric bacteria?
    • MacConkey agar
    • Levine eosin methylene blue (EMB) agar
  54. ___ agar is a differential medium containing bile salts to inhibit non-enteric bacteria.
    McaConkey agar
  55. MacConkey agar contains 2 dyes, ___ and ___, which are taken up by lactose fermenting bacteria.
    Neutral red and crystal violet
  56. Crystal violet inhibits the growth of what?
    Gram pos bacteria
  57. When grown on MacConkey agar, enteric bacteria form ___ colonies whereas nonlactose fermenters form ___ colonies
    • Pigmented colonies
    • Colorless colonies
  58. EMB agar is a ___ medium that does not support the growth of Gram-___ bacteria.
    • Differential
    • Postitve
  59. On MacConkey agar lactose fermenting bacteria will appear as ___ colonies.
  60. Escherichia coli will usually be ___ ___ colonies while Enterobacter, Kliebsiella and other lactose fermenters will be ___ to ___ with a ___ texture when grown on MacConkey agar.  
    • Brick red
    • Pink to red with mucoid texture
  61. On EMB agar, E. coli colonies appear how?
    Blue-Black with a green metallic sheen.
  62. On EMB agar, Enterobacter aerogenes colonies appear how?
    Convex & mucoid with dark centers & creamy pink borders
  63. Non-lactose fermenters grown on EMB agar look how?
    Transparent, colorless colonies
  64. What is another valuable medium for differentiating enteric bacteria?
    Triple sugar iron (TSI) agar
  65. What is the name given to a growth medium that contains glucose, lactose and sucrose as well as the pH indicator phenol red?
    Triple sugar iron (TSI) agar
  66. If a bacteria ferments ONLY glucose what will happen in TSI agar?
    The slant & butt will turn yellow aft several hrs but the slant will soon revert back to red & butt will stay yellow
  67. In bacteria the ferments ONLY glucose grown on TSI agar, what causes the red to return to the slant over time?
    Reappearance of alkaline conds fr digestion of peptones & production of ammonium compounds
  68. If bacteria ferments lactose, sucrose or both, then what will happen on TSI agar?
    Sufficient acid will be produced to cause the slant and butt to remain yellow
  69. What will happen on TSI agar if no carbohydrates are fermented?
    Slant and butt will remain red alkaline color
  70. Gas production from carbohydrates may be determined in TSI agar by noting the presence of what?
    Cracks/fissures in the medium after the incubation period
  71. Why is it that hydrogen sulfide production can be tested with TSI agar?
    B/c TSI agar contains iron ions and sodium thiosulfate
  72. Certain bacteria use thiosulfate in their metabolism and release hydrogen sulfide which reacts w/iron yielding iron sulfide which appears how in TSI agar?
    As a black precipitate
  73. What is the primary purpose of the IMViC test?
    To differentiate between E. coli & Enterobacter  aerogenes.
  74. What are the 4 tests that make up an IMViC series?
    • Methyl Red test
    • Vogues-Proskauer test
    • Citrate test
    • Indole test
  75. The ___ test IDs species that can digest tryptophan to ___ and other products.
    • Indole
    • Indole
  76. The ___ ___ test depends on an organism's ability to ferment glucose and produce acid.
    Methyl Red
  77. Methyl red indicator, added at the end of an incubation period remains ___ in acid solution but becomes ___ in alkaline or neutral solution.
    • Red
    • Yellow
  78. The ___-___ test uses the digestion of glucose to acetylmethylcarbinol to differentiate between enteric species.
    Vogues-Proskauer test
  79. If acetylmethylcarbinol fr the digestion of glucose is present it will react w/alpha napthol & potassium hydroxide to form what?
    Red Chemical compound
  80. The ___ test is based on the ability of certain bacteria to use ___, a salt citric acid, as a sole carbon source in growth.
    • Citrate
    • Citrate
  81. What is the pH indicator in a citrate test?
    Bromthymol Blue
  82. What happens to pH when a bacteria uses citrate as a sole carbon source in growth?
    pH of medium rises 
  83. What happens to bromthymol blue when pH rises?  What happens when pH doesn't change?
    • pH rises = becomes deep blue
    • pH remains = original green remains
  84. What agar is used for the citrate test?
    Simmons citrate agar
  85. What reagent is used for the indole test?
    Kovacs reagent
  86. When doing an indole test what indicates a positive result?
    Presence of a red surface layer on the trypticase soy or tryptone broth tube
  87. What reagent is used when doing a methyl red test?
    Methyl red indicator
  88. Explain the results of the methyl red test.
    • Red = pos for acid production
    • No color change = neg for acid production
  89. What are the 2 reagents used for the Vogues-Proskauer test?
    • Alpha naphthol
    • Potassium hydroxide
  90. What indicates a positive Vogues-Proskauer test?
    Development of a red color aft several mins indicating the production of acetylmethylcarbinol
  91. A ___ color indicates an ability of a bacteria to to use citrate and constitutes a pos test.
  92. What is seen on Simmons citrate agar that indicates a negative for citrate result?
    A green color
  93. Describe an Enterotube.
    Self-contained, sterile, compartmentalized plastic tube containing 12 different media complete with enclosed inoculating wire
  94. What are the 15 tests done utilizing an Enterotube?
    • Acid fr Glucose
    • Gas fr glucose
    • Lysine decarboxylated
    • Ornithine
  95. What is Bacillus subtilis is used as a source of enzymes in ___.
  96. The agent of anthrax is ___ ___.
    Bacillus anthracis
  97. The organisms of the Bacillus species are gram-___, sporeforming ___ that produce catalase, are motile and digest ___ & ___.
    • Positive
    • Rods
    • Starch & DNA
  98. We isolated Bacillus species from where?
  99. Why did we heat the soil samples prior to taking samples?
    In order to destroy soilborne, aerobic organisms leaving only spores behind
  100. What reagent do we use to test for catalase production?
    Hydrogen peroxide
  101. What do we add to colonies in order to test for starch digestion?
  102. What should we observe around a colony if starch has been digested?
    Clear areas around the colonies
  103. What are 4 important human diseases caused by Clostridium?
    • Botulism
    • Food poisoning
    • Tetanus
    • Gas Gangrene
  104. What do species of Clostridium do in soil?
    • Decay organic matter and release carbon back into the environment
    • Fix atmospheric nitrogen & make it available to plants
  105. Clostridium are Gram-___, sporeforming ___that grow under ___ conditions.
    • Positive
    • Bacilli
    • Anaerobic
  106. Name several places where anaerobic conditions exist and Clostridium can be found.
    • Dead tissue
    • Vacuum sealed, contaminated food
    • Sanitary landfills
    • Swamps 
    • Marshes
  107. Thioglycolate medium contains ___ thioglycolate, a reducing agent the removes ____ from the environment.
    • Sodium
    • Oxygen
  108. Describe stormy fermentation.
    In litmus milk when acid clots milk and gas produced shreds the clot
  109. What does Clostridium do when placed in cooked meat medium?
    Digest meat particles to fine sediment causing an odor of Hydrogen sulfide & blackening of the medium
  110. What is an advantage to using the pour plate technique with brain heart infusion agar?
    Dilution of the soil suspension gives Clostridium species more opportunity to form wide spaced colonies
  111. SPS agar contains ___ ___ which is reduced by certain Clostridia to form sulfide
    Sodium sulfide
  112. SPS agar contains ___ & ___ two antimicrobial agents that inhibit organisms other than Clostridium.
    • Polymyxin
    • Sulfadiazine
  113. Blood in blood agar is ___ by clostridia to form the characteristic ___ zone of ___.
    • Hemolyzed
    • Double zone of hemolysis
  114. Explain the double zone of hemolysis created by clostridia on blood agar.
    • Inner zone of Beta hemolysis
    • Outer area of alpha hemolysis
  115. What should be observed in a thioglycolate medium inoculated with Clostridium species?
    Cloudiness below methylene blue indicator 
  116. A Gram stain of a Clostridium species should reveal what?
    Gram pos sporeforming rods
  117. What are 3 eukaryotic organisms in the microbial world?
    • Fungi
    • Protozoa
    • Multicellular parasites
  118. ____ grow as long, tangled filaments of cells.
  119. Each filament of a mold is known as a ___.
  120. A mass of mold filaments is called a ___.
  121. Spores eventually form on the specialized hypha that form reproductive structures called ___ ___.
    Fruiting Bodies
  122. ____ are unicellular microorganisms whose colonies on agar resemble bacterial colonies.
  123. What do yeast colonies look like when grown on agar?
    Cream colored or another light color
  124. What is the primary mode of reproduction in yeasts?
  125. Explain the process of budding.
    A new cell form at the periphery of the parent then grows and breaks free to assume an independent existence
  126. ___ ___ agar contains acidity & added carbohydrate favored by molds.
    Sabouraud dextrose
  127. Broad spectrum antibiotics
  128. Narrow spectrum antibiotics