[2S] Exp 8 & 9 AT & Test for AR Flashcards
AST : KIRBY-BAUER DISK DIFFUSION
T/F: Once agent has been identified & deemed as clinically significant = proper selection of antimicrobial agents is performed
T
Provide MIC (minimum inhibitory concentration) values or zones of inhibition established using cut-off
points/break off
Kirby-Bauer Disk Method
AST : KIRBY-BAUER DISK DIFFUSION
Spreading of bacteria on an agar plate and placing paper discs impregnated with antibiotics on the plate
Disk Diffusion
AST : KIRBY-BAUER DISK DIFFUSION
Area around antibiotic disk where no bacterial growth can be seen
Zone of Inhibition
AST : KIRBY-BAUER DISK DIFFUSION
Zone indicates?
antibiotic is successful in stopping bacterial growth or killing bacteria
AST : KIRBY-BAUER DISK DIFFUSION
Diameter is measured to?
compare efficacy of antibiotics and monitor antimicrobial resistance
AST : KIRBY-BAUER DISK DIFFUSION
Specimen used
< 24 hour-old test culture on BAP, TSA or NAP
AST : KIRBY-BAUER DISK DIFFUSION
Turbidity of suspension is visually compared to
0.5 McFarland standard
AST : KIRBY-BAUER DISK DIFFUSION
Turbidity of inoculum is adjusted by
Adding sufficient sterile saline or adding more colonies
AST : KIRBY-BAUER DISK DIFFUSION
Desired turbidity of the inoculum
same turbidity with McFarland Standard
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Material used to dip in standardized inoculum suspension
Sterile cotton swab
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Excess fluid in cotton swab
Pressed and rotated multiple times against wall of test tube
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Manner of streaking (surface medium)
Inoculated by overlap method of streaking
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Rotate plate ___ each time for even distribution
60°
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
T/F: After streaking, rim-edge the medium
T
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Number of times plate is rotated
3-4x to ensure that it’s confluent
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Inoculation is done [time] from time of standard inoculum was prepared
<15 minutes
AST : KIRBY-BAUER DISK DIFFUSION - INOCULATION OF MHA PLATE
Place ___ then apply antibiotic disks
3-5 minutes
AST : KIRBY-BAUER DISK DIFFUSION - APPLICATION OF ANTIBIOTIC DISKS
Place disks evenly distributed
o At least ____ from each other
o At least ____ from edge of the plate
24mm
10mm
AST : KIRBY-BAUER DISK DIFFUSION - APPLICATION OF ANTIBIOTIC DISKS
Plates are inverted and placed in incubator set at ____ for _____
35-37C; 16-18 hours
Uses standardized amount of test inoculum present in Mueller Hinton Broth (MHB) and a selected antimicrobial agent
Broth Dilution
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Medium used
Mueller Hinton Broth (MHB)
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Antimicrobial agent is diluted ___-fold
two
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Lowest concentration of antimicrobial agent that
completely inhibits visible growth
MIC
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Interpretative categories
o Susceptible (S)
o Intermediate (I)
o Resistant (R)
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
2 categories
Broth microdilution & Broth macrodilution
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Main difference of the 2 categories
volume of the MHB used
AST : BROTH MACRODILUTION OR
MACROBTROTH DILUTION
Specimen used
Culture on BAP
AST : BROTH MACRODILUTION
Final Bacterial Concentration
5x10^5 CFU/mL
AST : BROTH MACRODILUTION
Adjusted inoculum is diluted _____ by adding 0.1mL of standardized inoculum in 19.9 mL MHB
1:200
AST : BROTH MACRODILUTION
Test tube 1-10 is for
actual test
AST : BROTH MACRODILUTION
How many test tubes are needed?
13 sterile test tubes