Introduction: Listeria monosytogenes is a Gram-positive organism, frequently found in the environment and is responsible for serious food-born diseases such as perinatal infections, septicaemia and meningoencephalitis in humans and animals. Materials & Methods: Distribution of the CTPA determinant among L. monosytogenes isolated from environmental and clinical samples was investigated using PCR to identify the homologous DNA in 69 isolates, 38% of tested isolates contained the CTPA determinant. Results: DNA homologous to CTPA was not detected in all strains. Our results showed that 90% of clinical and dairy isolates, 85% of environmental isolates and 7% of poultry isolates op L. monocytogenes contained CTPA in chromosomal DNA. Conclusion: It is possible that the increased incidence of CtpA in strains contributes to their association with clinical infection. The occurrence of CtpA was less frequent in poultry isolates and may explain why these strains are not associated with clinical case.