Progressive increase in antibiotic resistance of gram-negative bacterial isolates. Walter Reed Hospital, 1976 to 1980: specific analysis of gentamicin, tobramycin, and amikacin resistance.

During a five-year period at Walter Reed Army Hospital, Washington, DC, the frequency of aminoglycoside resistance among clinical bacterial isolates increased from less than 1% in 1976 to 13% of all isolates in later years. This resistance was seen among frequently isolated species of gram-negative bacilli isolated from patients throughout the hospital and from all anatomical sites, including blood. The incidence of gentamicin and amikacin resistance rose with increased administration of these antibiotics; however, the incidence of tobramycin resistance increased despite its minimal usage. From 1977 to 1978 and from 1979 to 1980, there was a decrease in the conjugal transmissibility of resistance to gentamicin and tobramycin. There was no detectable transmissible amikacin resistance. These findings suggest that high priority must be given to strategies that limit the emergence and dissemination of organisms resistant to these important antibiotics.