lab notes 8 Flashcards
demonstration of antibiotic action results
isolate grows well
resistant bacterium
demonstration of antibiotic action results
isolate does not grow
susceptible bacterium
demonstration of antibiotic action results
single colonies grow along the inoculation line
a few cells are more resistant than the mainstream and may form colonies
Kirby-Bauer Assay Standardization
medium
mueller-hinton agar
Kirby-Bauer Assay Standardization
Petri dish
10 or 15cm diameter
Kirby-Bauer Assay Standardization
inoculum
suspension O.D.600=0.5
Kirby-Bauer Assay Standardization
disk placement
use a stencil
Kirby-Bauer Assay Standardization
incubation time and temperature
24hr at 37 Celsius
Kirby-Bauer Assay Standardization
paper disk quality
antibiotic concentration
Kirby-Bauer Assay determines
the choice of antibiotics to be used when treating an infection; relies on the inhibition of bacterial growth measured under standards conditions
antibiotic resistance
not resistant: no zones and easy to interpret
antibiotic resistant: “fussy” zones form; colony formation within the inhibition zone
Minimal Inhibitory concentration (MIC)
lowest concentration of the AB to result in no growth
determined in a serial dilution of the AB and inoculated with the target microorganism
Minimal Bactericidal Concentration (MBC)
lowest concentration of the AB to kill all the bacteria in the medium; inoculation from the serial dilution treated bacterial onto a solid medium
MIC vs MBC
MIC uses liquid serial dilution and wants a result of no growth MBC uses a solid medium and wants to kill all bacteria on the medium
Epsilometer Test (E Test) Method
diffusion of an antibiotic agent from a plastic strip onto an agar medium; quantitative, rapid and reproducible
service Laboratories
validation of service with a specific strain - has predetermined results and strain acquired from ATCC
WHO has the for the committee in 1961 to
develop a standardized procedure for antimicrobial testing
the Clinical Laboratory Standards Institute (CLSI)
is responsible for updating and modifying the original procedure of Kirby and Bauer through a global consensus process
