The aim of this study was to determine the prevalence of aminoglycosides antibiotic resistance in Salmonella spp. and E. coli strains. 32 E. coli, and 47 Salmonella spp., isolated from cases of enteritis in growers and fatteners from 1998 to 2002 in Umbria and Marche regions, were tested. Susceptibility to gentamicin, tobramycin and streptomycin was determined by Kirby-Bauer method, apramycin by microdilution method. 92,4 % of the strains tested were susceptible to apramycin, 77,2 % to gentamicin, 67,1 % to tobramycin and 35,4 % to streptomycin. A positive statistical association between gentamicin and apramycin (RR = 7,63; p = 0,014), tobramycin and apramycin (RR = 9,22; p = 0,027) was demonstrated. There is no difference between the association apramycin-streptomycin, suggesting a mechanism of resistance related to the presence of the aminoglycoside acetyltranspherase IV enzyme. The trend based on estimated OR from the resistance of the strains for every year considered was significant (p = 0,00049), showing a progressive decrease from 1998 (OR = 1) to 2002 (OR = 0,3)
