ANTIMICROBIAL SUSCEPTIBILITY TESTING Flashcards
13, 17, 18
diameter of inhibition of erythromycin
9, 11, 12
diameter of inhibition of vancomycin
antimicrobial susceptibility testing
Is a laboratory procedure in which it determines the susceptibility pattern of an isolate
ANTIBIOTIC
products of microorganisms that react with and inhibit the growth of another microorganism
antimicrobial susceptibility testing
is performed on bacteria causing an individual’s infection after they have been recovered in a culture of the specimen
antimicrobial susceptibility testing
It is used to determine the potential effectiveness of specific antibiotics on the bacteria and/or to determine if the bacteria have developed resistance to certain antibiotics
antimicrobial susceptibility testing
- The results of this test can be used to help select the drug(s) that will likely be most effective in treating an infection
diffusion method and dilution method
give the 2 METHODS OF AST
kirby-bauer diffusion method
the most common method in AST
broth media, sterile saline or NSS
in pure inoculum, We can use ________, ________, or ________
barium chloride, sulfuric acid
McFarland Standard is prepared by adding ______ to ____ to obtain a barium sulfate precipitate
barium sulfate precipitate
0.5 McFarland standard combined the 2 reagents to form _______
1.5 x 10^8 colony-forming unit/mL
what is the recommended population density of organism in a pure inoculum
0.5 mL of 1.175% barium chloride
the 0.5 McFarland standard solution has how many ml and percent of barium chloride
99.5 mL of 1% sulfuric acid
the 0.5 McFarland standard solution has how many ml and percent of sulfuric acid
0.5 McFarland standard
what is the comparator used for a pure inoculum
KIRBY-BAUER METHOD
Also known as Agar Diffusion Method or Disk Diffusion Method
MHA (Mueller-Hinton Agar)
in kirby-bauer method, A standardized suspension of organism is inoculated into what agar?
lawn culture method
inoculation of the bacteria to the whole surface of the culture media without space.
zone of inhibition
the area surrounding the antibiotics that doesn’t have an indication of the growth of bacteria
6
the lowest measurement for a zone of inhibition
Mueller-Hinton Broth
Trypticase Soy Broth
Sterile Distilled Water
Natural Saline Solution
Brain Heart Infusion Broth
Preparation of pure inoculum, using any of the following:
add colonies to inoculum or incubate inoculum
2 ways we can do when the standard is more turbid than the inoculum
add distilled water
what we can to when the inoculum is much turbid than the standard
smaller
a heavy inoculum will result to a (larger, smaller) zone of inhibition
larger
a light inoculum will result to a (larger, smaller) zone of inhibition
sterile cotton swab
tool/equipment/apparatus used in streaking the inoculum to a plate
sterile forceps
tool/equipment/apparatus used in putting disk into plate
25 mm
in putting disks the Space must be at least _______ of each antibiotic
Normally 35°C for 16/18-20 hours
the proper temperature and duration of incubating organism is _______
ruler or microcaliper
tool/equipment/apparatus used in measuring zone of inhibition
S for susceptible or sensitive
in the interpretation of results it indicates that the organism is inhibited by the recommended dose, at the infection site of an antimicrobial agent
S for susceptible or sensitive
bacteria are being killed fast
I for intermediate
in the interpretation of results it indicates that an organism may require a higher dose of antibiotic for a longer time period to be inhibited
R for resistant
in the interpretation of results it indicates that an organism is not inhibited by recommended dose and the Antibiotics are not effective for that particular bacteria
20, 28, 29
diameter of inhibition of penicillin to staphylococcus
7.2 - 7.4
pH level of growth medium
3-5 mm
agar depth
4 example of DIFFUSION METHOD
- Kirby-Bauer Diffusion Method (most common)
- Agar Cup Diffusion Method
- Agar Cylinder Diffusion Methods
- Epsilometer or Gradient Diffusion Method
Used to standardize the approximate number of bacteria in a liquid suspension by visually comparing the turbidity of a test suspension with the turbidity of a McFarland standard
Pure inoculum
After __ lhours of incubation, the diameters of the zone of inhibitions are measured
16-20
8 steps of capsular staining
- Place a loopful of saline on a labelled slide.
- Emulsion a single colony.
- Place a loopful of serum and spread to make a thin smear.
- Air dry and heat fix gently.
- Cover smear with Crystal Violet. Hold over flame for a few seconds
- Wash excess stain with 20% Aqueous CuSO4 (Copper(II) sulfate)
- Blot dry and view under OIO
reagents in capsular staining
crystal violet and 20% aqueous CuSO4 (copper II sulfate)
- A standardized suspension of an organism is inoculated into MHA (Mueller-Hinton Agar)
- Paper disk impregnated with specific antibiotics concentration are placed into the agar
- After 16-20 hours of incubation, the diameters of the zone of inhibitions are measured
- Results are compared to determine susceptibility or resistance
principle of kirby-bauer method
- It is used to determine the potential effectiveness of specific antibiotics on the bacteria and/or to determine if the bacteria have developed resistance to certain antibiotics
Antimicrobial suscpetibility testing is for?
- Macrobroth Method or Tube Dilution Method
- Microtube Dilution Method
give the 2 example of dilution method
1a suspension of bacteria that has been isolated from a patient. Only one type of bacteria is perent, and it can be a NSS, a saline, or broth media
define what is pure inoculum
- preparation of pure inoculum using any of the acceptable medium
- standardize pure inoculum usng 0.5 mcfarland standard
- streak the pure inoculum into the medium (MHA)
- apply antibiotics
- incubate
- measure the zone of inhibition
steps by step procedure in kirby-bauer method
if the medium is too thick the zones will be
falsely small
if the medium is too thin the zone will be falsely
larg
- growth medium
-pH level (7.2 - 7.4)
-agar depth (3-5mm) - inoculum (density)
- temperature and atmospheric condition
- choice of antibiotic panel
- reading and interpreting results
considerations in AST
