(529.10) Comparative evaluation of methods for determining sensitivity to colistin in E. coli isolates

Poster Board Number: D58

Georgy Nikitin (Saint Petersburg State University of Veterinary Medicine), Ophelia Sulyan (Saint Petersburg State University of Veterinary Medicine, Pediatric Research and Clinical Center for Infectious Diseases under the Federal Medical Biological Agency), Alexander Sukhinin (Saint Petersburg State University of Veterinary Medicine)

The study aims to compare two colistin susceptibility measurement approaches: by disk diffusion test and using VITEK® 2 Compact instrument. We collected 103 E.coli isolates from 7 livestock farms in St. Petersburg and the Leningrad region. Minimum inhibitory concentration (MIC) of colistin was determined using disk diffusion test and VITEK® 2 Compact instrument and then compared with the reference broth microdilution method results. The processing of the results was based on the EUCAST recommendations. Eight E. coli isolates proved to be resistant to colistin when determining MIC in broth microdilutions. Two isolates (eco-103 and eco-151) carried the MCR-1 gene. The identical isolates were tested by other methods to determine the MIC. The data obtained by the three methods were identical. This suggests that the disc diffusion test can be used to determine the MIC of colistin on E.coli. This method has several advantages over the reference method and VITEK-2 Compact use since it is simultaneously cheap, fast, and accurate for determining the MIC of colistin.