The use of bacteriophages for killing pathogenic bacteria is seen as feasible alternative to antibiotics. In this scenario, large quantity of phages will be required and their production must be optimized. This study’s aim was to define conditions that maximize the final phage titre (phage yield) in broth of the virulent and polyvalent bacteriophage vB_SauM-phiIPLA-RODI. This phage has been isolated from sewage and further characterized in our lab. It belongs to the Myoviridae family, and is able to infect strains of Staphylococcus aureus, S. epidermidis, S. xylosus, and S. sciuri, among other staphylococcal strains.
The strain S. xylosus CTC1642, isolated from a fermented meat product (IRTA, Spain), was used instead of S. aureus since the use of non-pathogenic hosts facilitates the preparation of safe phage products. The influence of initial bacterial concentration (5-8 log10 CFU/mL), initial phage concentration (5-8 log10 PFU/mL), temperature (21-40°C) and agitation (50-250 rpm) on the phage yield (response) was modelled using response surface methodology.
From the results of four successive experimental designs, it was concluded that agitation did not significantly influenced the phage titre while the optimum temperature was 38 °C. The phage yield can be described by a model (based on all the information available) which is a function of the initial bacterial (6-7 log10 CFU/mL) and phage (around 6 log10 PFU/mL) concentrations, with an agitation of 135 rpm and at a temperature of 38°C. Phage titres up to 8.8 log10 PFU/mL were reached which are in the same order of magnitude as when propagated on its original host.