Decreased Incidences of Resistance to Antimicrobial Agents Among Escherichia coli and Klebsiella-Enterobacter

Antibiograms were reviewed of all strains of Escherichia coli and Klebsiella-Enterobacter isolated from lesions of patients at the University of Washington Hospital, Seattle, from mid-1959 through 1968. No trend to increasing resistance to any of the chemotherapeutics tested was noted among the isolates of E. coli or Klebsiella-Enterobacter, and declining resistance was evident. E. coli showed an increase of strains resistant to none or only one of the seven agents and a decrease in multiply resistant strains. The frequency of E. coli bacteremia has not increased since 1959-1960 and 1961, and the antibiograms of organisms isolated from the blood generally coincided with the antibiograms of the total population. The incidences of Klebsiella-Enterobacter strains resistant to the seven chemotherapeutic agents also diminished as did that of multiply resistant strains. In contrast to E. coli, the frequency of klebsiella-enterobacter bacteremia did not diminish during the first 7 years; during the subsequent 3 years there was a marked decrease in frequency of positive blood cultures. The incidences of resistance to tetracycline and streptomycin may be associated with the amounts used per patient.