Antibiotic use and development of resistance in blood culture isolates: 8 years of experience from a cancer referral center

The consumption of antimicrobial agents in a Slovakian national cancer inst itute from 1989-1996 was compared with resistance rates in clinically signi ficant blood culture isolates. We observed an increase in resistance of vir idans streptococci to penicillin and of enterococci to ampicillin, Resistan ce to vancomycin and teicoplanin was stable over the entire period despite a 20-fold increase in vancomycin consumption. Nor did we observe increased resistance to ofloxacin despite a 10-fold increase in consumption. Consumpt ion of aminoglycosides and resistance levels were both stable. A different situation was observed with third-generation cephalosporins, where resistan ce of Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacte r spp, to ceftazidime and cefotaxime increased with increasing consumption. Resistance of Enterobacteriaceae to cefotaxime and ceftazidime was stable. Resistance to imipenem did not change significantly. However, the number o f Stenotrophomonas maltophilia bacteremias increased significantly after im ipenem was introduced in 1991, Because of improved outcome in bacteremia, a n increased incidence of both Gram-negative and Gram-positive bacteremia le d to only a slight increase in associated mortality.