Article

Research Note: Efficacy of Phageguard L (PGL) on shrimp

Roy Andries
17-04-2019
Reading time 2 min
Related bacteria
Listeria
Publishing date April 17th, 2019

Objective

Study the efficacy of phages applied on cooked, unpeeled shrimp that have been contaminated with Listeria monocytogenes.

Protocol

Shrimp samples of 25 grams each were treated with a dip application using two Phageguard L (PGL) concentrations: 1% and 5%. After this, they were artificially contaminated at two different bacterial concentrations. Samples were stored for 24 hours at 4°C, time after which the bacteria were retrieved and plated on ALOA selective agar plates.

Results

  • Samples analyzed on day 0, showed expected contamination levels, which were similar after 24 hours.

  • When a 1% treatment was applied, it was possible to observe a bacterial reduction of 1.1 – 1.6 logs after 24 hours.

  • When a 5% treatment was applied, the observed bacterial reduction was of about 2.4 -2.8 log after 24 hours.

Conclusions

These results demonstrate that phage effectively controls Listeria on cooked, unpeeled shrimp contaminated with L. monocytogenes and stored at low temperatures. The effect of PGL on Listeria is dose dependent, with bigger reductions (2.4 – 2.8 logs) when higher treatment concentrations are used (5%). At a treatment concentration of 1%, bacterial reductions were of 1.1 – 1.6 logs.