Quantitative Analysis of Pathogenic and Nonpathogenic V ibrio parahaemolyticus in Shrimp Derived from Industrial Processing

Abstract

Vibrio parahaemolyticus is an important seafood-borne pathogen. V. parahaemolyticus carrying either tdh or trh or both genes is considered a pathogenic strain. The objectives of this study were to examine the prevalence and concentration of V. parahaemolyticus in shrimp processed in a factory using most probable number (MPN) combined with either polymerase chain reaction (PCR) or loop-mediated isothermal amplification (LAMP) techniques. The pathogenic group (pathogenic Vp) is composed of strains carrying tdh (tdh+ Vp) and/or trh (trh+ Vp) and nonpathogenic group (total Vp) is consisted of both pathogenic and nonpathogenic strains. There was no difference in the total Vp detection by PCR and LAMP techniques. However, combined MPN with LAMP techniques, an increase in detection of pathogenic Vp in samples was identified and the concentrations of pathogenic Vp in shrimp from the first five processing steps were 3.2, 3.0, 3.1, 3.5 and 4.3 MPN/g and were below the detection level (<3 MPN/g) in shrimp from the last three steps. LAMP technique estimated significantly higher positive samples and MPN values for pathogenic V. parahaemolyticus than PCR technique. Practical Applications Loop-mediated isothermal amplification technique is more sensitive than polymerase chain reaction at determining low numbers of pathogenic Vibrio parahaemolyticus in seafood. Decreased temperature in the peeling step as well as frequent change in dipping water in the grazing step will reduce the total numbers of V. parahaemolyticus contaminated in shrimp.