Antibiotic susceptibility testing (Bmlt mumbai)..... Microbiology

1.  ANTIBIOTICSUSCEPTIBILITYTESTING
PRESNETED BY: Needa Zaveri
MGM School of biomedical sciences.
(department of microbiology)

2. DEFINITION:
Antibiotic sensitivity testing or
antibiotic susceptibility testing is
the measurement of the
susceptibility of bacteria to
antibiotics .It is essential to
determine the susceptibility of
isolates of pathogenic bacteria to
antibiotics that are likely to be
used in treatment.

3. ◉Types of antibiotic
susceptibility test1
DiffusionTests-
◉Kirby-Bauer disc
diffusion
◉-This is the most commonly used
method._Filter paper discs impregnated
with a known concentration of
antimicrobials are placed on an agar
plate that has been inoculated with a
culture of the bacterium to be tested.
◉-Inoculate the Muller Hinton agar
plate by streaking the swab over the
entire agar surface.Antibiotic discs are
placed in the plate as shown in fig.

4. KIRBY-
BAUER
DIFFUSION
METHOD

5. ◉Stroke disc
diffusion method-
In this method
◉-In this method ; bacterium is inoculated
over the upper and lower one third of the
plate and control on central one third .
Antibiotics discs are applied between the
control and test inoculum.-The plated are
incubated at 35-37⁰C for 16-18 hours .If the
organism is susceptible to a particular agent
;there will be a zone of inhibition of growth
around the disc.If it is resistant;there will be
a smaller zone of inhibition.-And then the
results are reported as

6. STOKES
DISC
METHOD

7. AND THERESULTSARE
REPORTEDAS:
(1)Susceptible:Zone size of the test
strain is larger than or equal to
control strain
(2)Intermediate:Zone size of the test
strain is 2-3mm smaller than control
strain.
(3)Resistant:Zone of the test strain is
smaller than 2mm

8. ◉E-Test
(Epsilometer test)>
-It uses an absorbent
strip with a known
gradient of drug
concentration along
its length.-When the
strip is placed on the
agar plate seeded
with the test
bacterium;
the antibiotic spreads
into the medium.-
And then MIC
(minimum inhibitory
concentration)is
determined.

9. ◉DilutionTests-
Dilution tests
◉maybe done by the tube dilution or
agar dilution methods.(1)Tube
dilution-Serial dilutions of the drug in
broth are made in tubes and a
suspension of the test bacterium is
inoculated.After overnight
incubation;the MIC(minimum
inhibitory concentration)is read.-Abd
minimum bactericidal concentration
(MBC)is the lowest concentration of
the drug that kills the bacterium.

10. BROTH
DILUTION
METHOD

11. ◉Agar dilution-
The agar
dilution>>
◉The agar dilution method is
more easily carried out when
several strains are to be tested at
the same time.-In this method;
serial dilutions of the drug are
prepared in agar and poured into
plates.
-Dilution tests are generally
more accurate.

12. THANKYOU~