A Sensitive Procedure for Screening Microorganisms for the Presence of Penicillin Amidase

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Abstract
A procedure for screening bacteria for the presence of penicillin amidase was described. Cells, grown in the presence of phenylacetic acid, were incubated with phenoxymethylpenicillin (type I), benzylpenicillin (type II) or ampicillin, and the 6-aminopenicillanic acid formed was detected and quantitatively estimated by its strong reaction with fluorescamine at pH 4. There is no requirement for separation of the penicillin substrate from the product but when .alpha.-aminobenzylpenicillin derivatives were used as enzyme substrates the amount of 6-aminopenicillanic acid formed must be determined by calculation. The procedure allowed positive and reliable identification of penicillin amidases in 6 organisms known to produce the enzyme and indicated that some of these enzymes had different properties in reactivity towards .alpha.-aminobenzylpenicillin derivatives.