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Microbiology and Parasitology (Lab) > Microbial Growth & Culture and Sensitivity > Flashcards

Microbial Growth & Culture and Sensitivity Flashcards

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Biology 101 flashcards
1
Q

bacterial growth is an increase in

A

number

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2
Q

during Stationary phase there is a net increase in cell numbers

A

false

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3
Q

growth of bacteria on solid agar media
typically results in:

A

colony

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4
Q

one factor that will slow down rapid growth of bacteria in broth is
A. Increase in waste products
B. Decrease in nutrients
C. Decrease in oxygen availability
D. All of these

A

D

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5
Q

which stage of growth would we expect to see the highest concentration of bacterial cells in broth?
A. Lag phase
B. Log phase
C. Stationary phase
D. Death phase

A

stationary

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6
Q

why is the study of bacterial growth important?

A

to utilize or inoculate known numbers of the bacterial isolate and to assess whether a particular strain of bacteria are adapted to a particular medium

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7
Q

how is microbial growth measured?

A

either directly or indirectly

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8
Q

CFU or bacterial cell counts are…

A

direct measures

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9
Q

turbidity, metabolic products, and oxygen consumption are…

A

indirect measures

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10
Q

consists of diluting the sample several times and transferring of specific volume of the sufficiently diluted sample onto agar plate using either pour plate or spread plate method

A

Standard Plate Count

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11
Q

Colonies which have grown on the subsurface of the agar are counted and reported as…

A

colony forming units (CFU)

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12
Q

used in the preparation of the serial dilution of the sample

A

sterile saline solution or phosphate buffer diluent

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13
Q

number of colonies that can be counted in a plate

A

25 to 250

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14
Q

assumptions that are based around the method

A

(1) the culture is homogenous; (2) the colonies to be counted are between 25 to 250 colonies; and (3) each colony has risen from a viable bacterial cell that has divided several times to produce distinct growth on the agar.

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15
Q

labels for the test tubes and plates of SPC

A

1:10, 1:100, 1:1000. 1:10000, 1:100000

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16
Q

incubation temperature and duration

A

35C and 24 hours

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17
Q

> 250 colonies

A

Too Many To Count (TMTC)

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18
Q

< 25 colonies

A

Too Few To Count (TFTC)

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19
Q

formula for SPC

A

CFU/ml = no. of colonies x reciprocal of dilution / volume of culture plate

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20
Q

an indirect method of determining bacterial population.

A

Turbidimetric Method

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21
Q

formula for SPC

A

CFU/ml = no. of colonies x reciprocal of dilution / volume of culture plate

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22
Q

measures (turbidity) cloudiness

A

turbidimetric method

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23
Q

used for turbidimetric method

A

Colorimeter and UV-Vis Spectrophotometer

24
Q

turbidimetric method is expressed as

A

% transmittance (amount of light passing through)

25
Q

absorbance in plotting the bacterial growth

A

Optical Density (OD)

26
Q

formula for optical density

A

OD = 2-log(%T)

27
Q

a statistical method used to estimate the viable numbers of bacteria in a sample by inoculating broth in 10-fold dilutions and is based on the principle of extinction dilution

A

most probably number (MPN)

28
Q
  • carbon dioxide
  • ATP
  • DNA
A

metabolic activity

29
Q
  1. standard plate count
  2. filtration
  3. MPN
  4. direct microscopic count
A

direct methods

30
Q
  1. Turbidimetric
  2. Metabolic Activity
  3. Dry Weight
A

indirect methods

31
Q

specifically target bacteria and are used to treat bacterial infections

A

antibiotics

32
Q

encompass a broader range of products that act on microbes in general

A

antimicrobials

33
Q

The determination of antibiotic susceptibility
of a particular pathogen to antimicrobial
agents.

A

culture and sensitivity

34
Q

a laboratory procedure performed by medical technologists (clinical laboratory scientists) to identify which antimicrobial regimen is specifically effective for individual patients

A

antimicrobial susceptibility testing (AST)

35
Q

culture media for AST?

A

mueller-hinton agar (MHA)

36
Q
  • Agar diffusion method or the disc diffusion method
    *In this test, a number of small, sterile filter paper disks of uniform size
A

kirby-bauer disc method

37
Q

sizes of paper disks in the kirby-bauer disc method

A

6 mm

38
Q

used to standardize the approximate number of bacteria in a liquid suspension by comparing the turbidity of the test suspension with that of the McFarland Standard.

A

mcfarland standard

39
Q

preparation of mcfarland standard

A

ass 0.05 ml of 1% Barium chloride to 9.5 of 1% Sulfuric acid

40
Q

how long and at what temperature should you store the mcfarland standard?

A

up to 6 months in the dark at room temp (20 to 25C)

41
Q

how would you check the accuracy of the density prepared mcfarland standard using a…

A

spectrophotometer with a 1-cm light path

42
Q

absorbance at 625 nm should be

A

0.08 to 0.1 for 0.5 mcfarland standard

43
Q

If the saline with the inoculum is more turbid than the standard,

A

dilute with more sterile saline solution until equally turbid

44
Q

If the saline with the inoculum is less turbid than the standard,

A

add more inoculum, mix and then compare until equally turbid

45
Q

If the saline with the inoculum is less turbid than the standard,

A

add more inoculum, mix and then compare until equally turbid

46
Q

a circular area around the spot of the antibiotic in which the bacteria colonies do not grow

A

zone of inhibition (ZOI)

47
Q

<10 mm and 10-13

A

resistant zoi

48
Q

14-19 mm

A

intermediate zoi

49
Q

<10 mm and 10-13

A

resistant zoi

50
Q

> 19 mm

A

susceptible zoi

51
Q

Determines the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism.

A

minimum inhibitory concentration (MIC)

52
Q

methods for MIX

A

oAgar Dilution
oBroth Dilution
Macrodilution
Microdilution

53
Q

antimicrobial resistance happens when microorganisms change when they are exposed to antimicrobial drugs

A

– World Health Organization

54
Q

Antibiotic resistance happens when the germs no longer respond to the antibiotics designed to inhibit the growth (-static) or directly kill them (-cidal)

A

– Centers for Disease Control and
Prevention

55
Q

origins of resistance

A
  • natural resistance
  • acquired resistance
56
Q

mechanisms of resistance

A
  1. limiting drug uptake
  2. drug efflux
  3. β - lactamases
  4. Modification of Drug Targets
57
Q

β – lactamase Inhibitors

A

*Amoxicillin + Clavulanic acid (Co-amoxiclav)
*Ticarcillin + Clavulanic acid
*Ampicillin + Sulbactam
*Piperacillin + Tazobactam

Microbiology and Parasitology (Lab) (6 decks)

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