In vitro susceptibility to aminoglycoside antibiotics in blood and urine isolates consecutively collected in twenty-nine European laboratories

Abstract

The in vitro susceptibilities to gentamicin, tobramycin, amikacin and netilmicin were determined by a standardized microdilution method in unsupplemented Mueller-Hinton broth using blood and urine isolates from hospitalized patients in 29 laboratories in 12 European countries. The distribution of bacteria was similar in each laboratorys,Escherichia coli and staphylococci predominating. While resistance rates varied between laboratories (e.g., rates of 1.1–34% were reported for gentamicin), they were consistently higher in southern Europe for all four antibiotics. Production of aminoglycoside-modifying enzymes was observed among resistant strains, ANT(2′), AAC(3)-V and AAC(6')-II predominating in gram-negative bacilli and APH(2)′ + AAC(6')-I in staphylococci.