Introduction: Listeria monocytogenes is a gram positive bacteria, frequently found in the environment and is responsible for food-borne disease such as perinatal infections, septicameia and meningeonceohalitis in human and animals. Material and Methods: For this reason, distribution of the ctpA determinate among L. monocytogenes isolated from clinical environment, diry and poultry samples were investigated. Then, ctpA gene was tranfered into E.coil DH5-alfa. This investigation was carried out in 2 steps (ctpA was found Listeria monocytogenes isolated from different sources, which was kept in culture collection of Adelaiede University, Australia. Then ctpA gene was transferred into E.coil DH5-alfa). CtpA DNA from Listeria monocytogenes was ampilified by PCR, identified on agarose gel, purified by phenol, and ligated into pGEM-T vector. Then transferred on X-gal plate contaning ampicilin. The sequencing of ctpA DNA in with colonies was determined by using by terminator kit and sequencing machine. Results: Using PCR to identify the homologous DNA in 69 isoltes, 38% of isolates tested contained the ctpA determinate. Our results showed that 90% of clinical and dairy isolates, 85% of environmental isolates and 7% of poultry isolates of L. monocytogenes into E.coil DH5-alfa was successful. Conclusion: Since, the existence of ctpA in clinical, dairy and environmental samples was 90% and in poultry was 7%, so, the virulence of all of strains of this bacteria are not the same, by introducing of such (ctpA gene) into suitable carrier strains, could be expected to producted to produce a good oral immunogen against L. monocytogenes.