Occurrence and molecular identification of Vibrio parahaemolyticus in retail shellfish in Mansoura, Egypt

In the present work, we examined 120 shellfish samples (40 each of shrimp, crab and cockle) collected from different fish shops in Mansoura city, Egypt, for the presence of potentially pathogenic strains of Vibrio parahaemolyticus. The conventional method as exemplified by biochemical means indicated that 40 (33.3%) of samples were positive for V. parahaemolyticus. Molecular means as represented by PCR, however, verified that only 20 (16.7%) shellfish samples were positive for V. parahaemolyticus. These 20 positive samples were distributed as 9, 8 and 3 of shrimp, crab and cockle, respectively. Biochemical analyses of the recovered 143 presumptive V. parahaemolyticus colonies indicated that 89 isolates were identified as V. parahaemolyticus. PCR analysis, for the presence of the species-specific toxR gene, indicated that only 27 (30.34%) out of these 89 isolates were verified as V. parahaemolyticus. These molecularly verified 27 strains were distributed as 14, 10 and 3 isolates from the examined shrimp, crab and cockle samples, respectively. Out of the 27 molecularly identified isolates, three (11%) strains were verified to be potentially pathogenic based on detection of tdh and/or trh virulent genes. One of these 3 strains that derived from shrimp was positive for both tdh and trh. The second strain (derived from cockle) was positive for tdh only, while the third one (derived from shrimp) was positive for trh only. The two strains that were positive for tdh, were also verified to be positive for Kanagawa reaction. This study concluded that the examined shellfish may carry the potential human health risk associated with the presence of pathogenic V. parahaemolyticus and that the reliable molecular detection methods should be included in the routine seafood examination in addition to the conventional bacteriological methods.