Application of bacteriophages during depuration reduces the load of Salmonella Typhimurium in cockles

Carla Pereira; Catarina Moreirinha; Rui J M Rocha; Ricardo Calado; Jesús L Romalde; Maria L Nunes; Adelaide Almeida

doi:10.1016/j.foodres.2016.10.031

Application of bacteriophages during depuration reduces the load of Salmonella Typhimurium in cockles

Food Res Int. 2016 Dec:90:73-84. doi: 10.1016/j.foodres.2016.10.031. Epub 2016 Oct 26.

Authors

Carla Pereira¹, Catarina Moreirinha¹, Rui J M Rocha¹, Ricardo Calado¹, Jesús L Romalde², Maria L Nunes³, Adelaide Almeida⁴

Affiliations

¹ Department of Biology, CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
² Departamento de Microbiología e Parasitología, CIBUS, Facultad de Biologia, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
³ CIIMAR/CIMAR - Centro de Investigação Marinha e Ambiental, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
⁴ Department of Biology, CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal. Electronic address: aalmeida@ua.pt.

PMID: 29195893
DOI: 10.1016/j.foodres.2016.10.031

Abstract

As bivalve molluscs are filter feeder, often consumed raw or lightly cooked and are frequently cultivated in contaminated waters, they are implicated in food-borne disease transmission to human. The present study investigated the potential application of bacteriophage (or phage) phSE-2, phage phSE-5 and phage cocktail phSE-2/phSE-5 to decrease the concentration of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) during the depuration of natural and artificially contaminated cockles (Cerastoderma edule). Cockles were artificially infected with 10⁵ and 10⁶colony-forming units (CFU)/mL of S. Typhimurium in static seawater and infected group were treated with phages at four different MOI values: 0.1, 1, 10 and 100. Depuration in static seawater at multiplicity of infection (MOI) of 0.1 with single phage suspensions of phSE-2 and phSE-5 provided the best results, as it decreased by ~1.3 and 1.7 logCFU/g, respectively, the concentration of Salmonella spp. after a 4h treatment. At a MOI of 0.1, the rate of inactivation with single phage suspensions was higher when compared with the results obtained using the phage cocktail. However, in naturally contaminated cockles treated in static seawater with single phage suspensions and phage cocktail phSE-2/phSE-5, similar decreases in cultivable bacteria concentration (~0.7-0.9 logCFU/g) were achieved after 6h of treatment. When artificially contaminated cockles were depurated with phage phSE-5 in a recirculated seawater system (mimicking industrial depuration conditions), a 0.9 and 2.0 logCFU/g reduction of Salmonella spp. was reached after 4 and 6h treatment. Once the depuration process was performed without phage, a 6h treatment was needed to obtain a 1.1 logCFU/g reduction of Salmonella spp. Results indicated that combining phage biocontrol with depuration procedures enhance bivalve microbial safety for human consumption by improving decontamination efficiency, proving that this technology can be transposed to the bivalves industry. Moreover, this approach also displays the advantage of reducing the time required for depuration and consequently its associated costs.

Keywords: Bacteriophage; Cerastoderma edule; Cockles; Food safety.