AMINOGLYCOSIDE RESISTANCE AMONG DANISH BLOOD CULTURE ISOLATES OF COAGULASE-NEGATIVE STAPHYLOCOCCI

A sample of 137 coagulase-negative staphylococci isolated from blood c ultures in Denmark over a 4-month period during 1992-1993 were tested for aminoglycoside resistance and for the presence of aminoglycoside-m odifying enzymes. This was done on the basis of minimum inhibitory con centrations (MICs) measured by agar dilution, inhibition zone diameter by disk diffusion, and DNA dot blot analysis. Using the National Comm ittee for Clinical Laboratory Standards (NCCLS) MIC breakpoints, 5%, 4 6%, 57% and 63% of the strains were resistant to netilmicin, amikacin, gentamicin and tobramycin, respectively. The large majority of resist ant staphylococci strains produced the bifunctional AAC(6')-III+APH(2 '') enzyme. The presence of AAC(6')-III+APH(2 '') explains the high le vel of resistance to gentamicin, kanamycin and tobramycin. In contrast to our results, Staphylococcus haemolyticus strains are usually repor ted to be more resistant than Staphylococcus epidermidis strains.