Requirements for the urease assay of aminoglycoside antibiotics.

The hydrolysis of urea by N.C.I.B. 10823 has been investigated and found to be independent of bacterial growth up to 90 minutes incubation and to require only a source of readily available amino acids. Evidence is presented which indicates that the urease of N.C.I.B. 10823 is an inducible enzyme. The induction time of the urease in stationary phase organisms is 20-30 minutes and only those antibiotics which can inhibit protein synthesis within this time (aminoglycosides, tetracycline, chloramphenicol and spectinomycin) have an inhibitory effect on the hydrolysis of urea. N.C.I.B. 10823 is found to be 8-10 times more sensitive to gentamicin at low NaCl concentrations. The significance of these findings in relation to the urease assay for aminoglycoside antibiotics is discussed.