RESUMO
The susceptibility patterns of gram-negative aerobic organisms to aminoglycosides differ widely from one European health care center to another and depend upon local antibiotic prescribing policies. Reports of the susceptibility of Pseudomonas aeruginosa to gentamicin and tobramycin have ranged from as low as 49.8 percent and 77.7 percent, respectively, in Greece, to as high as 96.6 percent and 99.2 percent, respectively, in the United Kingdom. The susceptibility of P. aeruginosa to gentamicin, tobramycin, and amikacin decreased in our hospital from 73.1 percent, 94.8 percent, and 95.6 percent, respectively, in 1982, to 43.1 percent, 70.6 percent, and 74.3 percent, respectively, in 1984. A prospective surveillance study of the susceptibility of gram-negative aerobic bacilli to four aminoglycosides (gentamicin, tobramycin, amikacin, and netilmicin) was performed over a period of 17 months. Gentamicin and tobramycin were freely used, while the use of amikacin was restricted throughout the hospital during a four-month baseline period (May through August 1984). Gentamicin and tobramycin accounted for 94 percent of the aminoglycoside use. During the following 13 months (September 1984 through September 1985), amikacin was used as the first-line aminoglycoside and accounted for more than 97 percent of the aminoglycoside usage. A total of 1,866 organisms were analyzed during the baseline period; 5,429 were analyzed during the amikacin-usage period. The overall susceptibility to gentamicin, tobramycin, amikacin, and netilmicin increased from 86.9 percent, 90.4 percent, 94.2 percent, and 88.3 percent, respectively, to 92.3 percent, 94.0 percent, 97.3 percent, and 92.3 percent, respectively. P. aeruginosa isolates had the most striking changes, with the susceptibility to gentamicin, tobramycin, amikacin, and netilmicin increasing from 43.1 percent, 70.6 percent, 74.3 percent, and 50.6 percent, respectively, during the baseline period, to 64.5 percent, 81.6 percent, 90.8 percent, and 65.1 percent, respectively, during the amikacin-usage period. The use of amikacin as a first-line aminoglycoside, while use of the other aminoglycosides was restricted, seemed to have a favorable influence on the susceptibility pattern of gram-negative aerobic isolates in our hospital.