Aminoglycosides are commonly used antibiotics especially in hospital-acquired infections. As a result of their widespread usage, resistance to these antibiotics is increasing. Isepamicin is a newly developed aminoglycoside and it is claimed that resistance to this antibiotic will develop in lower frequency in comparison with other aminoglycosides. This study was conducted to evaluate the resistance patterns of Gram-negative isolates to aminolycosides and to compare isepamicin with other aminoglycosides. All Gram-negative bacteriae isolated from blood and other cultures during the years 2000-2001 were tested against gentamicin, tobramycin, netilmicin, amikacin and isepamicin. The in-vitro susceptibility tests were performed by disk diffusion method. In total 3683 Gram-negative isolates were studied. According to our results, netilmicin (66.4%) was the most effective aminoglycoside. It was followed by isepamicin (64%), amikacin (63%), tobramicin (55.9%) and gentamicin (51.9%). Netilmicin was also the most effective aminoglycoside against Gram-negative bacteriae isolated from blood culture. Amikacin (62.6%) and isepamicin (62.5%) were equally effective against these isolates. In conclusion, netilmicin was the most effective aminoglycoside against Gram negative bacteriae. The resistance to isepamicin was significant
