i wanted to know whether i can trust to my gapdh band? because i can not have any bands from my genes of interest. my primers have been worked in previous study.
Well, I'm not an expert in PCR. But i think it depends on the protocol you used for the reverse transcription. If you used random hexamer primers, bacterial RNA maybe was transcribed to cDNA and maybe yields false positive results in PCR. But as bacterial RNA is not polyadenylated, you should be fine, if you are using oligo(dT) primers for RT.
if your specific primers used to work but no longer work it may be that the primers are degraded.This sometimes happens if they are dissolved in water not TE for storage. I would try a pcr with the primers on a control target which always works and possibly using more primer than usual in case of degradation. If this does not work order new primers. Borrow a different set of primers from a colleague to amplify to test your cDNA if the cDNA was made with random hexanucleotides or oligodT