The prevalence of high-level aminoglycoside resistance among enterococci isolated from blood cultures during 1980–1988

Two hundred and eighty-one strains of enterococci isolated from blood cultures of 281 consecutive patients during 1980-1988 and 108 strains of enterococci isolated from miscellaneous clinical materials during 1988 were studied for high-level resistance (MIC greater than 2000 mg/l) to amikacin, kanamycin, streptomycin, gentamicin, tobramycin and netilmicin. Before 1985 there was no enterococcal strain with high-level resistance to amikacin, gentamicin, tobramycin or netilmicin, but 14% were resistant to kanamycin and 21% to streptomycin. For strains isolated from blood cultures during 1985-1988, the prevalence of high-level resistance was as follows: amikacin, less than 1%; kanamycin, 35%; streptomycin, 26%; gentamicin, 9%; tobramycin, 9%, netilmicin, 4%. Prevalence of high-level aminoglycoside resistance of enterococci isolated from miscellaneous sources during 1988 was higher (amikacin, 5%; kanamycin, 37%; streptomycin, 31%; gentamicin, 24%, tobramycin, 27%; netilmicin, 10%). Among strains isolated from blood cultures between 1980-1984, 24% (30 of 126 strains) and among 1985-1988 strains, 40% (62 of 155 strains) were resistant to at least one of the aminoglycosides tested. Similarly, among the miscellaneous strains, 40% (43 of 108 strains) had high-level resistance to at least one of the aminoglycosides tested.