Abstract:Background: Analysis of bivalves for microbial bacteria is a tool for sanitary control. Methodology: 104 samples of bivalves made up of smooth Venus (Callista chione) and red cockles (Acanthocardia tuberculatum) were analysed for Escherichia coli by using MPN technique and for Salmonella by method ISO 6579 and Vibrio parahaemolyticus, analysed biochemically and by multiplex PCR. Results and Conclusions:Seasonal variation of faecal contamination was observed between wet and dry periods in three locations. Prevalence of Salmonella was 8.6% and onto 47 strains isolated, three serotypes groups were identified as: S. Kentucky, S. Newport and S. Glostrup. Regarding Vibrio parahaemolyticus, prevalence was 8.6% with 24 isolates identified and confirmed by multiplex PCR as tdh and trh negatives.