What can be the possible reason for not getting mcr genes in colistin resistant bacteria?
i checked colistin resistivity through broth micro dilution method and agar micro dilution method. Phenotypically all isolates were colistin resistant with mics 4 to 16 ug/ml. Alkaline lysis method was used for plasmid extraction. PCR was done but except few isolates show presence of mcr 1 gene while all other genes were absent.
Hello Waqas,
when I look for mcr in my isolates I don´t use a protocol that isolates only the plasmids but that isolates whole cell DNA. That usually works well.
Best regards
yup sir you are right but in case of plasmid mediated resistant genes it is recommended to use the protocol which only isolate plasmid.
I think what Dirk Schmidt is saying that it might not be on a plasmid, phages and transposons can be pretty good at carrying antibiotic resistance genes and are likely to be integrated into the chromosome so they wouldn't show up on a plasmid prep.
However, it might also just be that they aren't using any of the typical mcr genes for resistance. Colistin/polymyxin B resistance, like most antibiotic resistance, has a lot of potential mechanisms.
Waqas, I know that this resistance is located on the plasmid. But it works anyway. You could give it a try 👍
Colilstin resistance in Enterobacteriaceae is mostly chromosomally determined by various mutations in the two component regulatory systems - pmrABC, phoPQ genes and insertions in mgrB or its promotor. See for example Article Molecular Epidemiology and Colistin Resistant Mechanism of m...
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