Establishing Streptomycin Epidemiological Cut-Off Values for Salmonella and Escherichia coli
Investigation published in Microbial Drug Resistance (Larchmont, N.Y.)
February 1st, 2012
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
Garcia-Migura L., Sunde M., Karlsmose S., Veldman K., Schroeter A., Guerra B., Granier SA., Perrin-Guyomard A., Gicquel-Bruneau M., Franco A., Englund S., Teale C., Heiska H., Clemente L., Boerlin P., Moreno MA., Daignault D., Mevius DJ., Hendriksen RS. and Aarestrup F.
 | Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
| Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM). |
 | National Food Institute (DTU Food). Technical University of Denmark (DTU). |
| Seksjon for Bakteriologi. Veterinærinstituttet. | |
 | Central Veterinary Institute. Wageningen University (UR). |
 | Federal Institute for Risk Assessment (BfR). |
 | Agence Nationale de Sécurité Sanitaire de l´alimentation, de l´environnement et du travail (ANSES). |
| AFSSA—LERMVD. | |
 | Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana (IZSLT). |
 | Department of Animal Health and Antimicrobial Strategies. National Veterinary Institute (SVA). |
 | Veterinary Laboratories Agency. Department for Environment, Food and Rural Affairs (Defra). |
 | Finnish Food Safety Authority (EVIRA). |
| Laboratório Nacional de Investigação Veterinária (LNIV). Instituto Nacional de Recursos Biologicos (INRB). | |
| Ontario Veterinary College. University of Guelph. | |
 | Laboratory for Foodborne Zoonoses. Public Health Agency of Canada (PHAC). |
