Fluorogenic substrates for .beta.-lactamase and methods of use

A method for detecting the presence of beta-lactamase activity in a sample, comprising:

• contacting the sample with at least one compound of general formula I ##STR29## wherein:
• one of X and Y is a fluorescent donor moiety or an ester said fluorescent donor moiety, and the other is a quencher or an ester derivative of said quencher;
• wherein said quencher quenches fluorescence of said fluorescent donor moiety;
• R' is selected from the group consisting of H, lower alkyl and (CH.sub.2).sub.n OH, in which n is 0 or an integer from 1 to 5;
• R" selected from the group consisting of H, physiologically acceptable metal and ammonium cations, --CHR.sub.2 OCO(CH.sub.2).sub.n CH.sub.3, --CHR.sup.2 OCOC(CH.sub.3).sub.3, -acylthiomthyl, -aeyloxy-alpha-benzyl, -delta-butyrolactonyl, -methoxycarbonyloxymethyl, -phenyl, methylsulphinylmethyl, -beta-morpholinoethyl, -dialkylaminoethyl, -acyloxyalkyl, -dialkylaminocarbonyloxymethyl and -alkyl, in which R.sup.2 is selected from the group consisting of H and lower alkyl and in which n is 0 or an integer from 1 to 5;
• A is selected from the group consisting of S, O, SO, SO.sub.2 and CH.sub.2 and Z' and Z" are linkers for the fluorescent donor and quencher moieties;
• and determining a fluorescence property or fluorescence spectrum of the sample.