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

Abstract

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.

Deniz Ürünlerinde Salmonella spp. ve Listeria monocytogenes Varlığının Kültürel Metotlar ve PCR İle Araştırılması

“…was isolated [21] . Contrary to this, the studies which had higher results (90.0%, 43.8% and 30.5%) than ours were reported by Jegadeeshkumar et al [22] , Budiati et al [23] and Kumar et al [6] respectively. The reason for high contamination rate should be due to the use of contaminated raw materials, detection methods and the geographical conditions.…”

“…The prevalence of Salmonella spp. in shrimp samples tested in this study was lower in comparison to those detected by Kumar et al [6] (29.0%), Kumar et al [24] (26.7%) and Hatha & Lakshmanaperumalsamy [20] (%15.2). On the other hand, Koonse et al [25] reported the prevalence rate of Salmonella spp.…”

“…Salmonella-specific invA primers (5'-GTGAAATTATCGCC ACGTTCGGGCAA-3' and 5'-TCATCGCACCGTCAAAGGAACC-3') were used for the detection of Salmonella in this study [6,16] . The PCR program consisted of an initial denaturation step at 95°C for 2 min, followed by 35 cycles of DNA denaturation at 95°C for 30 s, primer annealing at 64°C for 30 s, and primer extension at 72°C for 30 s. After the last cycle, a final extension step at 72°C for 5 min was added.…”

“…in Morocco [3] , in Spain [4] , in Vietnam [5] , in India [6] ; L. monocytogenes in Spain [7] , in USA [8] , in India [9] , in Denmark [10] , in Iran [11] . In Turkey the prevalence of these pathogens has not been extensively investigated.…”

Detection of Salmonella spp. Presence in Food

“…The specificity of these phages is partly mediated by tail-associated proteins that distinctively recognize surface molecules of susceptible bacteria (Kretzer et al, 2007). Bacteriophages or proteins of bacteriophages have been included in various ways in detection methods for pathogens (Favrin et al, 2003) Although there is a need to perform a collaborative study to further evaluate the methods before it can be concluded that their performances are equal, both the PCR and the ELFAbased assay could provide a rapid and user-friendly screening method for detection of Salmonella in food (Uyttendaele et al, 2003;Priego et al, 2009;Kumar et al, 2008;Szabo et al, 2008) …”