Investigation of plasmid mediated colistin resistance phenotypically and genotypically in Salmonella and E. coli isolates in Turkey

Tok, Seray
Today, colistin is used as the last resort antimicrobial against Gram-negative bacteria. Excessive use of colistin caused resistance among bacteria. Recent studies showed presence of plasmid mediated mcr genes, encoding colistin resistance that can be transferred horizontally between different bacterial species. In this study, it was aimed to investigate colistin resistance and change in colistin resistance rate in E. coli and Salmonella isolates over time from different cities in Turkey. For this aim, we used 2 groups of isolates as recent (collected in 2018-2019) and historical (collected in 2010-2015). E. coli and Salmonella isolates, were isolated from 238 chicken meat samples collected between 2018-2019 in Ankara in this study. 36 E. coli and 16 Salmonella were isolated. All strains were tested for antimicrobial resistance for colistin and 18 antimicrobial agents other than colistin. 197 Salmonella isolates, representing historical isolates collected between 2010-2015 from human, animal and food samples and 48 E. coli isolates collected in 2011-2015 from food samples were investigated for colistin resistance. Phenotypic resistance was observed using disc diffusion and MIC test. Genotypic resistance characterization was investigated using PCR. 25 % and 53 % of recent, 0 % and %8 of historical E. coli and Salmonella isolates showed evidence of colistin resistance. Colistin resistance was seen to be increased over time among both Salmonella and E. coli isolates. We investigated that colistin resistance in isolates used in this study was not due to plasmid mediated genes, but most likely due to the chromosomal mutations. This assumption should be further investigated.


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Citation Formats
S. Tok, “Investigation of plasmid mediated colistin resistance phenotypically and genotypically in Salmonella and E. coli isolates in Turkey,” M.S. - Master of Science, Middle East Technical University, 2022.