Beta Strips

Rapid diagnostic test for penicillin resistant bacteria.

Beta Strips rapidly detect the presence of β-lactamase enzymes produced by strains of Staphylococcus aureus, Neisseria gonorrhoeae, Branhamella catarrhalis and Haemophilus influenzae. These enzymes confer resistance to a number of penicillin antibiotics by attacking the common β-lactam ring structure in these drugs, and thus inactivating them. This reaction provides the basis for Beta Strips. Each Beta Strip is impregnated with benzylpenicillin and the pH indicator, bromocresol purple. β-lactamase positive organisms produce an enzyme which hydrolyses the benzylpenicillin to form penicilloic acid. This in turn lowers the pH, causing the bromocresol purple to change rapidly in colour from purple to yellow. Beta Strips require only a few organisms, and can be used as soon as there is visible growth on the primary culture medium.

Description: Paper strip impregnated with benzylpenicillin and indicator. Changes colour on contact with material containing β-lactamase.

Method of use: Using wire or plastic loop, touch 2 or 3 colonies of test organism on agar medium. Smear organism onto strip. Positive reaction shown by smeared zone changing from purple to yellow within 5 minutes.

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