I prepare the CHROMagar Col-APSE (for selection of colistin resistant gram-negative bacteria) exactly to manufacturers guidelines. I have E. coli isolates that grow perfectly well on this media, but when I try to grow these same isolates on MacConkey agar supplemented with 2mg/L colistin sulphate (EUCAST guidelines) or 4mg/L (CSLI Guidelines) there is no growth.
Hi dear;
As the bacterium grown on chrom agar supplemented with colistin, so the bacterium under the selection pressure of colistin, soon will express resistance phenotype when further culturing with other media supplemented with colistin.
regards
Hi dear;
As the bacterium grown on chrom agar supplemented with colistin, so the bacterium under the selection pressure of colistin, soon will express resistance phenotype when further culturing with other media supplemented with colistin.
regards
It's possible, I have had the same results when testing for carbapenemase. You should always isolate on free antibiotic medium as a control.
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