Two-dimensional thin-layer chromatography for simultaneous detection of bacterial beta-lactam acylases and beta-lactamases

Abstract

A rapid and specific procedure was developed for the simultaneous detection of bacterial acylases and P-lactamases, using ampicillin and cephalexin as substrates. Bacterial suspensions from agar plates were incubated separately with each l-lactam substrate for 1 h at 37°C. The supernatant of the reaction mixture was dansylated, and the dansyl derivatives were separated by two-dimensional thin-layer chromatography on polyamide sheets. The end products resulting from acylase hydrolysis, including the intact ,-lactam nucleus, 6-aminopenicillanic acid or 7-aminodeacetoxycephalosporanic acid, and the acyl side chain acid, D-(-)-aaminophenylacetic acid, and the end product resulting from P-lactamase hydrolysis (D-phenylglycylpenicilloic acid or D-phenylglycyldeacetoxycephalosporoic acid) were separated from each unhydrolyzed substrate and amino acids by this procedure. The presence of the intact P-lactam nucleus in the reaction mixture is the indication of acylase activity. This method is sensitive and reproducible and has been successfully applied to screening for acylase activity in a variety of bacteria. It may be pharmaceutically useful for identifying organisms capable of removing the acyl side chain from naturally occurring ,l-lactam antibiotics such as penicillin G, penicillin V, and cephalosporin C for production of the l-lactam nuclei which serve as the starting materials for semisynthetic ,l-lactam antibiotics.