Detection of Pathogenic Bacteria, Viruses, and Parasitic Protozoa in Shellfish

Abstract

Many types of methodologies have been used for the detection of pathogenic bacteria, viruses, and parasitic protozoa from bivalve molluscs. This chapter presents general processing methodologies, including conventional detection approaches such as microscopic or cultural methods, as well as the molecular approaches that are increasingly being applied to the detection of these pathogens in the bivalve mollusc food matrix. For viruses and parasitic protozoa, the approach used for pathogen extraction and concentration not only affects the efficiency of recovery of targeted pathogens but also influences the sample-associated toxicity or inhibition of the assay. Although efforts to detect protozoan parasites in shellfish have lagged behind those for virus detection, like viruses, it is recommended that parasitic protozoa be concentrated from shellfish tissues prior to the application of detection methods. Most of the molecular approaches applied to the detection of pathogens in shellfish originated from the clinical literature and were first applied to pure cultures (bacteria) or to purified cell culture lysates or fecal suspensions (parasitic protozoa and viruses). The practical application of real-time PCR and reverse transcription-PCR (RT-PCR) for quantification also needs to be investigated further. With consistent developmental effort, much as has been experienced over the last decade, even better methods for the rapid detection of human pathogenic microorganisms in shellfish at naturally occurring levels of contamination should be available in the future.