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Microbiology > Quiz 2 > Flashcards

Quiz 2 Flashcards

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Biology 101 flashcards
1
Q

antibiotic

A

a chemical synthesized by a microbe that will kill or inhibit other microbes

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2
Q

important producers of antibiotics

A

streptomyces, bacillus, penicillum, and cephalosporium

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3
Q

tube dilution antibiotic sensitivity assay

A

a known concentration of antibiotic is diluted in a twofold tube dilution series and a drop of test organism is added to each tube to observe if good growth will occur. The antibiotic in the highest dilution tube that shows no culture growth is called the minimum inhibitory concentration (MIC)

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4
Q

kirby-bauer or disc method of determining antibiotic sensitivity

A

paper discs containing antibiotic are used to test for inhibition of bacterial growth in the vicinity of the disc on an agar plate. For standardization of the technique, a type agar called Mueller-Hinton is used for the plates. To determine if an isolate is resistant or sensitive to an antibiotic, the growth inhibition zone diameter (including disc diameter) is compared with values produced by reference organisms of the same species on a standard table. Two antibiotics that produce the same inhibition zone diameter do not have the same efficacy because of many factors, such as diffusion rates effects results.

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5
Q

organism used for antibiotic disc assay

A

escherichia coli & staphylococcus epidermidis

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6
Q

disc assay: CAR 100

A

concentration: 100
inhibition zones:
e. coli:
s. epidermidis:

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7
Q

disc assay: C30

A

concentration: 30
inhibition zones:
e. coli:
s. epidermidis:

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8
Q

disc assay: Te30

A

concentration: 30
inhibition zones:
e. coli:
s. epidermidis:

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9
Q

disc assay: K30

A
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10
Q

disc assay: Did the two organisms tested show the same sensitivity pattern? Why?

A

No, because bacteria react differently to different antibiotics

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11
Q

Minimum Inhibitory Concentration (MIC)

A

least amount of antibiotic to stop bacteria

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12
Q

bactericidal antibiotic

A

antibiotic that kills microorganism

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13
Q

bacteriostatic antibiotic

A

antibiotic that prevents growth

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14
Q

penecillinase

A

hydrolyzes penicillin

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15
Q

How are plasmids associated w/ the efficacy of antibiotic therapy?

A

they decrease the efficacy of antibiotic therapy because they introduce genes that are resistant to the antibiotics

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16
Q

serum titer

A

the greatest dilution of serum which causes agglutination

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17
Q

acute serum

A

a sample taken from a patient at the onset of an illness

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18
Q

convalescent serum

A

a sample taken from a patient during recovery of an illness or several days after the onset

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19
Q

identification of etiological agent

A

if the microorganism being tested as an antigen results in the observation of an increase in convalescent titer at least 4 fold greater than the acute titer, it is likely to be the infectious agent

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20
Q

explain the methods for the experiment

A
  1. placed PBS in each of the 9 tubes
  2. place 1 ml of the serum(aby) in position 1
  3. place .5 of serum in tube 2 which is one to two dilution
  4. take .5 from tube 2 and put in tube 3 this is one to four dilution
  5. continue two-fold dilution for all tubes and discard 0.5 ml from last tube
  6. add 0.5 of washed cells (sheep red blood cells -> antigen) to all 10 tubes
  7. incubate
  8. determine the titer
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21
Q

what was the serum titer

A

-the 1/32 dilution which was tube 6
-serum titer because it’s the greatest dilution that causes agglutination
-serum titer is usually 1/16 or 1/32

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22
Q

what is agglutination

A

-when antigen combines with its antibody
-causes clumping of cells

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23
Q

what happens in agglutination reaction when there is an excess of antibodies and what is it called

A

-called prozone
-agglutination will not occur
-antibodies will bind to antigens univalently instead of multivalently
-antibodies that bind univalently cant crosslink one antigen to another

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24
Q

what occurs in agglutination when there is excess of antigens and what is it called

A

-agglutination will not occur
-called post-zone
-not enough aby and too many ag
-no crossbridging

25
Q

what is required for agglutination rxn to work optimally

A

specific ratio of aby:ag

26
Q

how does an antibody affect a germ/bacteria

A
  1. aby doesnt kill
  2. aby just signals
  3. wbc comes to kill
  4. complement binds and starts series of rxns
  5. complement proteins put holes in cell membrane
  6. water rushes into cell -> hemolysis
27
Q

what creature makes the best complement

A

guinea pig

28
Q

major illnesses caused by staphylococci

A

boils, scalded skin syndrome, toxic shock syndrome, food poisoning (staphylococcus aureus)

29
Q

major diseases caused by streptococci

A

contagious skin disease, sore throat, rheumatic fever, glomerulonephritis (streptococcus pyogenes: the flesh eating bacteria); Pneumonia (streptococcus pneumoniae)

30
Q

beta-hemolysis in staphylococci

A

this activity produces the lysis of red blood cells in agar plate medium. Blood agar is prepared by mixing 5% sterile defibrinated sheep blood with a nutritional blood agar that has been cooled to aboute 45 degree C after autoclaving. The medium is then dispensed into tubes or plates

31
Q

hemolysis in streptococci

A

lysis of red blood cells in agar (beta-hemolysis), conversion of red blood cells to green (alpha-hemolysis), no effect on blood cells (gamma-hemolysis)

32
Q

selective medium

A

medium to prevent growth of some species but permitting others to thrive

33
Q

differential medium

A

medium that enables the investigator to distinguish one species from another. This is usually done through use of a chemical reaction which causes the color of the medium or colonies to change

34
Q

gram stain results

A

S. aureus: gram positive, coccus, cluster
S. epidermidis: gram positive, coccus, cluster
S. faecalis: gram positive, coccus, chain
G. tetragena: gram positive, coccus, tetrad

35
Q

catalase reaction

A

S. aureus: +
S. epidermidis: +
S. faecalis: -
G. tetragena: -

36
Q

staphylococci

A

S. aureus: positive for all tests (hemolysis on blood agar, mannitol fermentation, gelatinase, coagulase)
S. epidermidis: negative for all tests(hemolysis on blood agar, mannitol fermentation, gelatinase, coagulase)

37
Q

bile esculin azide agar

A

s. faecalis: good growth and blackening of medium
g. tetragena: no growth

38
Q

Under the microscope, how can staphylococcus be differentiated from gaffkya tetragena?

A

Staph has grape-like clusters and g. tetragena is in tetrad

39
Q

What is the chemical reaction mediated by the enzyme catalase?

A

2H2O2 > O2 + 2H2O
hydrogen peroxide to water and oxygen

40
Q

What simple test can differentiate staph from strep

A

Catalase

41
Q

Describe the mechanism by which staphylococcal coagulase causes plasma to clot?

A

conversion of fibrinogen to fibrin
-s. aureus produces bound & free coagulase (bound directly to fibrinogen)

42
Q

major intestinal diseases

A

typhoid (salmonella typhi), dysentery (shigella dysenteriae), cholera (vibrio cholerae), travelers diarrhea (escherichia coli)

43
Q

enterobacteria

A

gram-negative rods that are frequently found in the intestinal tract

44
Q

facultative anaerobe

A

a bacterium that can grow in the anaerobic intestinal tract but also in the presence of oxygen

45
Q

selective medium

A

medium to prevent growth of some species but permitting others to thrive

46
Q

differential medium

A

medium that enables the investigator to distinguish one species from another. This is usually done through use of a chemical reaction which causes the color of the medium or colonies to change

47
Q

macconkey agar

A

lactose fermenting organisms produce red colonies on this plate medium. Gram-positive bacteria are inhibited. The ingredients include lactose, bile salts and neutral red (pH indicator)

48
Q

XLD

A

organisms that ferment the constituent carbohydrates produce yellow or red colonies on this plate medium. If lysine decarboxylase is produced colonies are red. Colonies may be black if H2S is produced. The medium contains xylose, lactose, sucrose, phenol red (pH indicator), bile salts, lysine, and ferric ammonium citrate (H2S detection)

49
Q

TSI

A

triple sugar iron agar is used in the form of a slant tube. If an organism can use lactose or sucrose, the entire tube will turn yellow (acid). Gas may push the agar up the tube or form large bubbles. If only glucose is used, the base (butt) of the agar slant will turn yellow but the slant itself will remain red. An organism that produces H2S will cause the formation of a black pigment in the tube. Besides the sugars, the medium containts phenol red (pH indicator) and iron salts (H2S)

50
Q

Simmons Citrate

A

this medium will turn blue if inoculated organism can use citrate. The medium includes citrate and thymol blue (pH indicator) and is prepared as an agar slant.

51
Q

urea agar

A

organisms that can break down urea can be recognized by changing the color of this medium. Phenol red is used as an indicator.

52
Q

iron Agar

A

this medium is for the detection of H2S produced by some species

53
Q

Fermentation Broth

A

this is a test to determine if an organism can use a specific carbohydrate. The broth includes phenol red to test for acid produced from the carbohydrate.
A tiny inverted tube (durham tube) is present to assay production of gas

54
Q

Decarboxylase Broth

A

this medium can detect the ability to produce decarbyoxylases by a color change of the tube

55
Q

Motility Medium

A

if growth spreads from a straight vertical stab line of inoculation, the bacterium may be motile

56
Q

enterotube II

A

this is a multiple test medium made by Roche diagnostics that can assay for several qualities at once

57
Q

organisms used for biochemical characterization of enteric bacteria

A

e. coli
klebsiella pneumoniae
proteus vulgaris
pseudomonas aeruginosa

58
Q
A

Microbiology (6 decks)

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