Can anybody explain: Is the RND efflux pump genes MexAB-oprM present in all the Grm Negatives , but hyperexpressed only in repressor mutant strains?
Presence of MexAB-oprM, MexCD-oprJ, MexXY-oprN Genes may vary from strain to strain ?
Or the expression purely based on the repressors activity?
Since, I found some P aeruginosa expressed (QR-RTPCR) and PCR for MexA, but MexB negative.
nfxB is present in most of the strains, but still some strains (10/85) were negative for nfxB. (Can you justify for this result)
Thanks in Advance.
Hello Murugan
MexAB transporter is a intrinsic gene which is present in psedo and some gram negative bacteria's. So their is no possibility of getting MexB negative(given MexA positive). Recheck your primer and your pcr reaction.
For your better understanding go through this article.
http://www.ncbi.nlm.nih.gov/pubmed/24878531
Am aware that it is an intrinsic gene which is basal expression in wild type strains, but practically i felt absence of this gene in multiple strains. Thats why i have queried, so, i checked the primers and other conditions, even i have changed primer sets too. Still, I couldnt get it. Let me try other options.
Thanks for your suggestions Mr. Nithin
in some instances mutations can be responsible. I agree you check your PCR and primers for more stringent conditions. However it will be good to investigate the possibility of mutations. I hope this helps.
Can u sent me your primer sequence i will have a look on it. Thank you.
For your kind information, kindly go through the below article attached, they published a data stating,
Table 3 The presence of antibiotic resistance genes in Pseudomonas
aeruginosa by multiplex PCR method
Genes (bp) Isolate number (%)
nfxB (164) 32 (64)
oprN (235) 26 (52)
mexE (114) 26 (52)
mexC (164) 24 (48)
ampC (218) 21 (42)
oprD (232) 21 (42)
mexR (150) 17 (34)
mexC (344) 12 (24)
oprJ (305) 11 (22)
oprD (156) 9 (18)
mexA (316) 7 (14)
mexT (216) 5 (10)
mexX (326) 2 (4)
Kindly suggest the meaning for this.
hello Murugan
i went through the paper and the table. The table says some isolates did not have some genes which are intrinsic to the organism, which is little tough for me to digest.
I have done pcr for same gene and never got negative results. one thing i have noticed in the paper was the author used a single annealing temperature for all the isolates.
If you have already done gradient PCR and confirmed negative band then i have no clue of what is happening. but if u have not tried gradient pcr to find the annealing temperature you can try that. iam sure same gene of same organism can have different annealing temperature.
If you ever solved the problem please notify, iam curious to know about it. Thank you
I tried of different gradient PCRs also. Let me try some other options,
But i feel not all strains will carry all the efflux genome, as i have worked on NGS datas too.
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