Aminoglycoside resistance among blood culture isolates.

A total of 633 blood culture isolates were collected from 1981 to 1982 from seven major Finnish hospitals, including all university central hospitals. Susceptibility of the strains to gentamicin, tobramycin, amikacin, and netilmicin was determined by the Sensititre microtiter procedure. Resistance against any of these agents occurred in 1.3 to 6.5% of all strains studied. In the Turku University Central Hospital, an increased number of tobramycin- and gentamicin-resistant Staphylococcus epidermidis were found; the frequency of strains resistant to tobramycin was 57% and to gentamicin was 29% versus frequencies of 16 and 18%, respectively, which were observed in the other hospitals. An explanation for this might be a change in the use of aminoglycosides in the Turku University Central Hospital; within 3 years, 1979 to 1981, the consumption of tobramycin and amikacin had increased 330 and 290%, respectively, whereas the use of gentamicin had decreased to 24% of that in the beginning of the period. Resistance against tobramycin was mediated by enzymes APH(2")-AAC(6') and ANT(4').