antimicrobial technique

MICROBIOLOGY

ANTIMICROBIAL TECHNIQUE

MEMBERS :IMRAN KHAN SULAIMAN

CHE ABDUL HALIMMUHD HUZAIFAH

NURUL ATIQA IBRAHIMNADHIRAHTUL HUSNA

NOR ZAFIFAHROSE AMALINA

• kills or inhibits the growth

of microorganism such

as bacteria , fungi, or protozoa

What is antimicrobial ?

kill microbes

(microbiocidal)

prevent growth of microbes

(microbiostatic).

 antimicrobial substances used on non-living objects or

outside the body.

Why antimicrobial technique is needed ?

• Bacteria have the ability to develop resistance following repeated or subclinical (insufficient) doses

• so more advanced antibiotics and synthetic antimicrobials are continually required to overcome them.

Technique in testing for Antibiotic sensitivity

• The method includes several steps including :• obtaining a bacterial sample• identifying the type of bacteria in the bacterial

sample• selecting a set of antibiotics based on the

identity of the bacteria in the bacterial sample• obtaining a control sample from the bacterial

sample

Antimicrobial technique . . .

Antimicrobial agent placed on the surface of an

agar plate

medium that has been inoculated with the disease

agent being tested, which will grow and

fill the disk.

killing some of the disease agent around where the

anitmicrobial agent was

innoculated

disease agent shows how

effective the antimicrobial

agent is.

It containing

Antimicrobial agent diffuse into medium

size of the area cleared

Disk diffusion

For example . . .

• Small wafers containing antibiotics are placed onto a plate which bacteria are growing.

• If the bacteria are sensitive to the antibiotic, a clear ring, or zone of inhibition, is seen around the wafer indicating poor growth

Antibiotic sensitivity testing

Zone sizes differ on sensitivity pattern

• It has been determined that zones of inhibition of a certain diameter (varies for antibiotic and to a lesser extent, bacterial species) correlate with sensitivity or resistance to the antibiotic tested

Steps for disk difussion method

• to determine whether or not a specific strain of bacterium or fungus is susceptible to the action of a specific antibiotic.

• commonly used in the setting of medicine, where a particular organism has been found to infect a patient, and the doctor treating the patient is seeking guidance on what concentration of antibiotic is suitable.

Epsilometer test

rectangular strip that has been

impregnated with the drug

A lawn of bacteria is spread and

grown on an agar plate

Etest strip is laid on topinto the agar

an exponential gradient of the drug

to be tested

Etest utilise by then

Drug diffuse out

andproducing

Epsilometer test

As a result . . .

• an exponential scale printed on the strip .

• After 24 hours of incubation, an elliptical zone of inhibition is produced

• the point at which the ellipse meets the strip gives a reading for the minimun inhibitory concentration (MIC) of the drug.

Dilution plating technique

• to reduce the concentration of microscopic organisms or cells in a sample

• A series of cultures is tested with various concentration pf an antibiotic to determine minimum inhibiting concentration of antibiotic

spread bacteria over a wide area

count the number of colonies that grow

bacterial cell in the original sample should produce a single colony

The numbers of bacteria colonies that grow on

each plate are counted

Stokes’ Method• In original Stokes’ method

the inoculum of the control strain is evenly spread over the upper and lower thirds of a plate

• the test strain over the central third,uninoculated (gaps 2 – 3 mm wide are left to test from the control areas.

For example . .

• In the Stokes controlled sensitivity test, a control organism is inoculated on part of a plate

• the test organism is plated on the remainder.

• Disks are placed at the interface and the zones of inhibition are compared.

• The use of a sensitive control shows that the antibiotic is active

• if the test organism grows up to the disk it may safely be assumed that the test organism is resistant to that drug.

Testing Minimum Inhibitory Concentration

• In alternative measure of susceptibility is to determine the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of a drug.

• Both are mixed with serially diluted antibiotic solutions and a standard inoculum is applied.

• After incubation, the MIC is the first broth in which growth of the organism has been

What is Minimum Inhibitory

concentration• Minimum inhibitory concentration (MIC), in is the lowest concentration of an antimicrobial that will inhibit the visible growth of a micro organism after overnight incubation.

• Minimum inhibitory concentrations are important in diagnostic laboratories to confirm resistance of micro organisms to an antimicrobial agent and also to monitor the activity of new antimicrobial agents.

The Antibiotics are diluted to various dilution to test the minimum inhibitory concentration