Aminoglycoside resistance patterns in Turkey.

Resistance of gram-negative aerobic bacteria to aminoglycoside antibiotics differs by region and country. It is known that 54% of gram-negative bacilli in Turkey are resistant to gentamicin, 32% to netilmicin, 35% to tobramycin, and only 0.9% to amikacin. Resistance to these antibiotics is generally caused by aminoglycoside-modifying enzymes. The resistance mechanisms of 300 aminoglycoside-resistant gram-negative bacteria were evaluated by determination of susceptibility to selected aminoglycosides. Comparison of strains isolated from community acquired infections and hospital acquired infections was made. Of the strains from community, 45.4% had an aminoglycoside resistance pattern indicative of 2''-adenyltransferase [ANT(2'')]. This was found in 44.4% of the hospital isolates. In both groups the second common enzyme was the 3-acetyltransferase [AAC(3)-II], in 20.8% and 23.3% respectively. Overall, most strains had an aminoglycoside resistance pattern indicative of ANT(2''), followed by AAC(3)-II and AAC(3)-I. Among bacteria tested, AAC(3)-II was the most common enzyme in Pseudomonas aeruginosa. The results of this study suggest that local antibiotic prescribing patterns play an important role in regional resistance mechanisms.