Is it safe to eat raw seafood? Prevalence of Salmonella in some seafood products sold in Alexandria markets

Abstract

Salmonella is a significant microbial hazard in seafood. Salmonella-contaminated seafood usually looks and smells normal; it is therefore essential that every effort is made toward the rapid detection of Salmonella as an important criterion in quality control of seafood. This study aims to determine the percentage of Salmonella in some Egyptian seafood sold in Alexandria markets and to study the validity of Chromagar Salmonella Plus (CASP) agar versus xylose lysine desoxycholate and Salmonella-Shigella agar for the isolation and identification of Salmonella in seafood. Two hundred and twenty-five samples of three seafood types, shrimp, gandofli, and river mussel (om-elkhloul) were studied. Samples were selectively enriched in Rappaport-Vassiliadis and tetrathionate broth, and then plated onto the aforementioned plating media for the detection of Salmonella. In total, Salmonella was detected in 9.8% of the samples. The sensitivity and specificity of the media used varied according to the media and enrichment broth combinations used. The CASP and Rappaport-Vassiliadis combination yielded the best sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 95.45, 100, 100, 99.5, and 99.5%, respectively. CASP was more accurate than xylose lysine desoxycholate and Salmonella-Shigella in the detection of Salmonella from seafood samples. We recommend that CASP medium should be tested against more Salmonella-positive samples before it is used as a screening plating medium for Salmonella in seafood.