Beta Lactamase Test: Result, Principle, Procedure, and Reagents

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Beta Lactamase Test Introduction

Biochemical tests are generally used to determine the ability of the microorganism to be stable in the enzymatic field. Beta Lactamase Test also helps us to determine the characteristics of the microbe in the medium.

However, these tests are usually preferred for identifying the different species of bacteria based on their ability to differentiate the biochemical and enzymatic activities of the chosen species in the culture. Basically, Bacterial physiology varies from one type of organism to the other.

This ability of the bacteria to form an organic compound by metabolizing the certain forms of carbohydrates and compounds related to it are performed by biochemical tests.

Beta lactamase test is one such biochemical test which is used for differentiating the bacteria based on the characteristic, that can produce an enzyme known as beta-lactamases which are mediated by the genes that are being present on plasmids and chromosomes.

Beta Lactamase Test

As mentions above, different bacteria produce different and an important class of enzymes known as beta-lactamases, that are being mediated by the genes that are present of the plasmids or in the chromosomes.

Generally, these enzymes confer a resistance against several penicillin antibiotics by cleaving action of the beta-lactam ring of the penicillin and cephalosporin antibiotics, which results in inactivating the drugs.

These are then capable of inactivating the penicillinase-labile penicillin. Such as amoxicillin, ampicillin, Penicillin, Mezlocillin and carbenicillin.

Beta-lactamases thus plays an important role in resisting the bacteria against the agents of Beta-lactam and ring of the penicillin’s and the cephalosporin antibiotics, which results in inactivating the drugs, now a day’s various assays are available to detect the presence of Beta-lactamases such as iodometric method, acidimetric method by using the chromogenic substrates.

Beta Lactamase Test Objective

The main aim of the test is to detect the ability of the enzyme beta-lactamase, that confers the penicillin resistance to the various bacterial organisms.

Beta Lactamase Test Principle

The most useful tests in the clinical laboratories for the detecting the beta-lactamase is chromogenic cephalosporinase test.

This test disk is usually consisting of a chromogenic cephalosporin that is being used as a substrate.

Organism that contains Beta-lactamases when applied to the disk for exerting the effect by opening their Beta-lactam ring present in the substrate.

This process thus results in formation of a coloured product that is conspicuous, and it also allowed the detection.

On hydrolysing the bacterial inoculum, it produces a deep pink colour. If there is no formation of any of the colours, then it indicates the absence of a Beta-lactamase.

Beta Lactamase Test Disk

Cefinase disk is considered as one of the best examples for the commercially available chromogenic tests. This disk helps in incorporating the nitrocefin as the basic substrate.

It also exhibits a rapid colour change from yellow to red due to the presence of amide bond in the beta lactam ring which hydrolyses the ring with the helps of the enzyme, Beta-lactamase.

When the bacterium produces this enzymes, Beta-lactamase in the significant quantity the coloured disc turns red in the specific areas where the isolated area is being smeared.

Beta Lactamase Test Procedure

Initially the disk is dispensed from the cartridge into an empty petri dish using a single disk dispenser. In some cases, instead of petri dish, microscopic slides can also be used.

Then the disc is moistened with one drop of the sterile distilled water.

Then with the help of a sterile loop or an applicator stick several well-isolated colonies are removed and the surface of the disks are smeared. Then the change in colour of the disk can be observed.

Beta Lactamase Test Results

Positive Results: If the result is positive then there will be a change in colour from yellow to pink-red colour on the area particularly where culture is spread.

Negative Results: If the results are negative there will be no colour change in the medium.

Beta Lactamase Test Uses

 Beta Lactamase Test helps us to detect the whether the certain species are resistance to drugs such as penicillin or ampicillin. Few examples are that

 N. gonorrhoea is resistance towards penicillin.

 H. influenzae is resistance to ampicillin.

 Staphylococcal is resistance to penicillin.

Beta Lactamase Test Limitation

 Beta Lactamase Test is limited for using it directly for detecting the Beta-lactamase production in the organisms that produces the enzyme those activities are known already. This also includes the Beta-lactams that are more commonly used for the therapeutic eradication of the organisms.

 Beta Lactamase Test is not supposed to replaced entirely by the convectional susceptibility because the other factors cannot be participated here for influencing the other results of the tests.

 Whereas the detection of the activity of the Beta-lactamase in the species of Staphylococci takes a longer period than others, up to one hour.

 Only one disk can be used at a time to detect the bacterial strain for determining the presence or absence of a Beta-lactamase.

Beta Lactamase Test Citations


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