Evaluation of culture, ELISA and PCR assays for the detection of Salmonella in seafood

Aims: The study evaluated the efficiency of culture, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) assays for the detection of Salmonella in naturally contaminated seafood. Methods and Results: In this study, 215 seafood samples comprising fish, shrimp, crab, clam, mussel, oyster, squid, cuttlefish and octopus from fish market of Cochin (India), were compared by culture, ELISA and PCR methods. Bacteriological Analytical Manual (BAM), U.S. Food and Drug Administration (USFDA) method was followed for culture assay, and Salmonella Tek, a commercial sandwich ELISA kit, was used for ELISA assay. Salmonella-specific PCR assay was developed for 284 bp Salmonella-specific invA gene amplicon. PCR assay exhibited 31.6% seafood positive for Salmonella followed by ELISA (23.7%) and culture method (21.3%). There was fair to excellent agreement between culture, ELISA and PCR assays (kappa coefficient values ranging from 0.385 to 1.0) for different seafood samples. Conclusion: The investigation revealed the greater concordance between culture and ELISA methods for seafood. Among the three methods, PCR assay was most sensitive. Lower detection rate with culture and ELISA assays could be attributed to greater sensitivity of the PCR method in the detection of Salmonella in seafood. Significance and Impact of the Study: We propose the incorporation of dual tests based on different principle and procedure for the routine analysis of Salmonella in seafood.