A NEW SIMPLE ASSAY FOR DETERMINING AMINOGLYCOSIDE INACTIVATION IN INTACT-CELLS OF PSEUDOMONAS-AERUGINOSA

Intact cells of aminoglycoside (AG) antibiotic-resistant Pseudomonas a eruginosa usually do not inactivate AG, even though they possess the A G-modifying enzyme. An assay method for determining the activity of in activating enzyme in intact cells of streptomycin-resistant P. aerugin osa was previously reported. Although this assay method was applied to the determination of the activity of kanamycin (KM)-inactivating enzy mes, it could not apply to some of the KM-resistant strains. A new sim pe assay method has now been investigated for determining the activity of KM-inactivating enzyme in intact cells of clinically isolated KM-r esistant FI aeruginosa. The determination of AG-inactivating enzyme ac tivity was attempted using lysozyme for release of the inactivating en zymes in washed cells, and both DNase and RNase were added to digestio n of the nucleic acids released by bacteriolysis. This lysozyme-DNase- RNase (LDR) method has facilitated the confirmation of the presence of AG-inactivating enzyme in the strains used. In addition, the LDR tech nique was applicable to the determination of inactivating enzyme activ ity for various AGs other than KM. Since this simple assay method can determine any type of AG-inactivating enzyme activity of various P. ae ruginosa strains, it may contribute significantly to the rapid selecti on of drugs in clinical use.