Characterising phages for the control of pathogenic bacteria associated with bivalve consumption

In the present study, five new bacteriophages (or phages) were characterized, and their efficacy in controlling pathogenic bacteria—Escherichia coli, Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Enteritidis, Aeromonas hydrophila, and Vibrio parahaemolyticus—associated with bivalve consumption was evaluated. The isolated phages include both siphovirus [vB_EcoS_UALMA_PCEc3 (PCEc3), vB_SeTS_UALMA_PCST1 (PCST1), and vB_VpaS_UALMA_PCVp3 (PCVp3)] and myovirus [vB_SeEM_UALMA_PCSE1 (PCSE1) and vB_AhyM_UALMA_PCAh2 (PCAh2)] morphotypes. Four phages are safe for bacterial control, with only one (PCAh2) showing potential lysogenic characteristics. All phages exhibited a narrow host range, capable of infecting up to six additional bacterial strains besides their original host, and four could infect the host bacteria of other phages. Adsorption rates ranged from 24% and 98% within 1 h. One-step growth assays revealed different latent periods, ranging from 10 to 120 min, and low to average burst sizes, ranging from 7.60 to 83.97 PFU/mL. Generally, increasing the multiplicity of infection (MOI) enhanced phage efficiency significantly. All phages effectively reduced the bacterial load of their respective hosts, achieving maximum reductions between 3.73 and 5.57 log CFU/mL within 10 h of treatment. These results suggest that phage biocontrol can be an effective alternative to combat pathogenic bacteria associated with bivalve consumption.