• Sonuç bulunamadı

Prof. Dr. Sevgi ERTUĞRUL KARATAY

N/A
N/A
Protected

Academic year: 2021

Share "Prof. Dr. Sevgi ERTUĞRUL KARATAY"

Copied!
8
0
0

Yükleniyor.... (view fulltext now)

Tam metin

(1)

Prof. Dr. Sevgi ERTUĞRUL KARATAY

(2)

Antibiogram Tests

Antibiogram tests are often used to determine antibiotics and effect doses that can be used to prevent the growth or growth of pathogenic

microorganisms.

It is important to know the following terms when performing antibiogram tests.

Antibiotic: Natural chemicals produced by microorganisms to prevent growth or kill the other microorganisms. There are also semi-natural derivatives of

these antibiotics produced with laboratory facilities.

Antibacterial: Chemical agent acting against bacteria.

Antifungal: A substance that acts against eukaryotic yeast and fungi.

MIC (MIC / Minimum inhibition concentration): The lowest concentration of antibiotic at which a microorganism dies or stops its development.

(3)

Antibiogram Tests

McFarland Standard: Microorganisms must be at a certain concentration and turbidity before antibiogram testing. This value

is usually set to 0.5 McFarland density. Values below and above this value are not studied.

Bacteriocidal: The substance that kills bacterial cells.

Bacteriostatic: The substance that stops the growth of bacterial cells.

CLSI: Clinical Laboratory Standards Institute. An organization in the US where antibiogram tests are standardized.

ATCC: American Type Culture Collection.

DSMZ: Microbial culture collection which located in Germany.

Microorganisms of these centers are used as control strains when antibiogram tests are applied.

(4)

Antibiogram Tests

Antibiogram tests can be performed by various

methods. Disc diffusion (Kirby Bauer Method) is one of the most important ones. Although this method is a

semi-quantitative method, serial dilution is

advantageous and easy to interpret. Its sensitivity is slightly lower than other methods.

1) Disc diffusion method

In this method antibiotic impregnated discs are used in certain doses of antibiotics. After incubation, the sensitivity or resistance to the antibiotic is determined

by looking at the zone value around the disc.

(5)

Antibiogram Tests

Application of Disc Diffusion Method:

Antibiotic susceptibility is prepared for the

microorganism suitable solid medium (Mueller Hinton Agar-MHA) is prepared and poured into petroleum.

The turbidity of the 18-24 hours liquid microorganism culture is adjusted to 0.5 McFarland.

The liquid culture is immersed in the swab and waited until it is absorbed. The process is repeated at least 6

times to spread the microorganisms to the whole agar

medium.

(6)

Antibiogram Tests

The antibiotic discs whose effect will be determined are placed on the surface of the inoculated petri dish according

to the size of the petri dish and gently pressed on it with forceps.

The petri dish with antibiotic discs is incubated at the temperature and time (37 ºC, 18-24 hours) at which the

microorganism will develop.

After incubation, transparent zones of inhibition around the disc on the surface of the petri dish are measured in

millimeters, and the measured value is compared to the standard criteria reported by CLSI or EUCAST to determine whether the microorganism is susceptible or

resistant to that antibiotic.

(7)

Antibiogram Tests

Inhibition zone Inhibition zone

Inhibition zone No inhibition zone

(8)

Antibiogram Tests

If there is not visible zone, the zone diameter should be given as 6 mm. (Diameter of the disks)

Observation a zone in a microorganism does not mean that the microorganism is resistant or susceptible to that antibiotic. Here you need to compare data from the guidelines of organizations such as CLSI, EUCAST.

In readings exceeding 18-24 hours, microorganisms may develop at the site of the antibiotic. This results in false negative results. Therefore, it is very important

to carry out the experiment on time.

Referanslar

Benzer Belgeler

Selective Media: A medium that promotes the development of a particular microorganism and prevents the growth of others. Differential Media: A medium used to distinguish differences

crystal violet in the medium prevent the growth of Gram (+) bacteria and are used as selective indicator in the medium. When lactose is used, a red color is formed due to the pH

1) For fermentation test, phenol red is placed on four nutrient broth media containing glucose, sucrose,. lactose

Fermentation Tests - Triple Sugar Iron (TSI) Agar Test.. TSI agar is especially used to identify Gram (-) bacteria such as

At the end of the experiment, it is obtained whether glucose is used in fermentative way, organic acids are.. formed in the medium and

If the microorganism has the amylase activity, it will break down starch molecules and use glucose when added to starchy agar medium. In this case,

If microorganism having the gelatinase enzyme forms a gelatinase zone in the gelatin nutrient medium. If there is liquefaction in the medium:

Normally, the agar content of 1.5%, but in the case of mobility test agar concentration adjusted to 0.4% to.. allow