The prevalence of gentamicin resistance among clinical isolates of enterobacteria in a Danish region

The susceptibility of enterobacteria to gentamicin was studied in the County of North Jutland during 1993–1998. A total of 378 patients had a first‐time gentamicin‐resistant isolate. The annual number rose from 34 patients in 1993 to 89 in 1998. The prevalence of resistance per 1000 patients with isolates examined was 13.5 for Escherichia coli, 15.8 for Klebsiella pneumoniae, 26.1 for Klebsiella oxytoca, and 150.4 for Citrobacter freundii. E. coli accounted for 67% of gentamicin‐resistant isolates. K. oxytoca was probably associated with a nosocomial epidemic, whereas a source for C. freundii remained unresolved. An analysis confined to E. coli identified specimens other than urine as risk factors for gentamicin resistance. Likewise, resistance to sulfonamides and to fluoroquinolones were strong risk factors for gentamicin resistance among urinary isolates of E. coli. Thus, it is likely that aminoglycoside resistance may be promoted by other antibiotic groups due to co‐resistance. The therapeutic and prophylactic uses of aminoglycosides have as yet not been undermined, but continuous population‐based surveillance and vigilance are recommended.