Establishing streptomycin epidemiological cut-off values for Salmonella and Escherichia coli. Microbial Drug Resistance

L. Garcia-Migura, M. Sunde, S. Karlsmose, K.T. Veldman, A. Schroeter, B. Guerra, S.A. Granier, A. Perrin-Guyomard, M. Gicquel-Bruneau, A. Franco, S. Englund, C. Teale, H. Heiska, L. Clemente, P. Boerlin, M.A. Moreno, D. Daignault, D.J. Mevius, R.S. Hendriksen, F.M. Aarestrup

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21 Citations (Scopus)


This study was conducted to elucidate the accuracy of the current streptomycin epidemiological cut-off value (ECOFF) for Escherichia coli and Salmonella spp. A total of 236 Salmonella enterica and 208 E. coli isolates exhibiting MICs between 4 and 32¿mg/L were selected from 12 countries. Isolates were investigated by polymerase chain reaction for aadA, strA, and strB streptomycin resistance genes. Out of 236 Salmonella isolates, 32 (13.5%) yielded amplicons for aadA (n¿=¿23), strA (n¿=¿9), and strB (n¿=¿11). None of the 60 Salmonella isolates exhibiting MIC 4¿mg/L harbored resistance genes. Of the Salmonella isolates exhibiting MICs 8¿mg/L, 16¿mg/L, and 32¿mg/L, 1.6%, 15%, and 39%, respectively, tested positive for one or more genes. For most monitoring programs, the streptomycin ECOFF for Salmonella is wild type (WT) =32 or =16¿mg/L. A cut-off value of WT =32¿mg/L would have misclassified 13.5% of the strains as belonging to the WT population, since this proportion of strains harbored resistance genes and exhibited MICs =32¿mg/L. Out of 208 E. coli strains, 80 (38.5%) tested positive for aadA (n¿=¿69), strA (n¿=¿18), and strB (n¿=¿31). Of the E. coli isolates exhibiting MICs of 4¿mg/L, 8¿mg/L, 16¿mg/L, and 32¿mg/L, 3.6%, 17.6%, 53%, and 82.3%, respectively, harbored any of the three genes. Based on the European Committee on Antimicrobial Susceptibility Testing guidelines (ECOFF =16¿mg/L), 25% of the E. coli strains presenting MIC =16¿mg/L would have been incorrectly categorized as belonging to the WT population. The authors recommend an ECOFF value of WT =16¿mg/L for Salmonella and WT =8¿mg/L for E. coli.
Original languageEnglish
Pages (from-to)88-93
JournalMicrobial Drug Resistance-Mechanisms Epidemiology and Disease
Issue number1
Publication statusPublished - 2012


  • antimicrobial susceptibility
  • resistance genes
  • food animals
  • protein s12
  • integrons
  • bacteria
  • typhimurium
  • countries
  • products
  • class-1


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