The use of bacteria producing the aminoglycoside inactivating enzyme ANT-(2") in an in-vitro model

A series of transconjugants of Escherichia coli W3110 containing different plasmids coding for the aminoglycoside inactivating enzyme ANT-(2") were tested in an in-vitro model simulating the concentration time curves of aminoglycosides after intramuscular administration of 80 or 120 mg. There was good correlation of the MIC, which ranged from 2 to 32 mg/l, with the killing ability of the drugs. A second dose had no or only little effect on ANT-(2") producing strains. All strains, although of 'intermediate' sensitivity were found to be resistant in the in-vitro model. Only netilmicin could eliminate some of the strains but its activity on ANT-(2")-positive strains was not as good as on ANT-(2")-negative ones.