Chromogenic detection of aminoglycoside phosphotransferases.

A coupled chromogenic reaction (based on an agar overlay combining NADH, pyruvate kinase, lactate dehydrogenase, phosphoenolpyruvate, ATP, and kanamycin sulfate with thiazolyl blue-phenazine methosulfate for detection of NADH consumption) was optimized for the detection of aminoglycoside phosphotransferases (APHs). When used after analytical isoelectrofocusing of bacterial extracts from APH-producing strains, this method revealed one band in each of two strains with a genetically confirmed APH (3') I and two bands in another strain with both APH (3') I and APH (3') VI, whereas no bands were detected in susceptible control strains or in aminoglycoside-resistant microorganisms without APH genes.