Journal
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Volume 76, Issue 18, Pages 6038-6046Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/AEM.00613-10
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Funding
- Ministerio de Educacion, Spain [AGL2006-03659/ALI]
- Plan de Ciencia, Tecnologia e Innovacion, Principado de Asturias, Spain [IB08-052]
- CSIC
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The use of bacteriophages provides an attractive approach to the fight against food-borne pathogenic bacteria, since they can be found in different environments and are unable to infect humans, both characteristics of which support their use as biocontrol agents. Two lytic bacteriophages, vB_SauS-phiIPLA35 (phiIPLA35) and vB_SauS-phiIPLA88 (phiIPLA88), previously isolated from the dairy environment inhibited the growth of Staphylococcus aureus. To facilitate the successful application of both bacteriophages as biocontrol agents, probabilistic models for predicting S. aureus inactivation by the phages in pasteurized milk were developed. A linear logistic regression procedure was used to describe the survival/death interface of S. aureus after 8 h of storage as a function of the initial phage titer (2 to 8 log(10) PFU/ml), initial bacterial contamination (2 to 6 log(10) CFU/ml), and temperature (15 to 37 degrees C). Two successive models were built, with the first including only data from the experimental design and a global one in which results derived from the validation experiments were also included. The temperature, interaction temperature-initial level of bacterial contamination, and initial level of bacterial contamination-phage titer contributed significantly to the first model prediction. However, only the phage titer and temperature were significantly involved in the global model prediction. The predictions of both models were fail-safe and highly consistent with the observed S. aureus responses. Nevertheless, the global model, deduced from a higher number of experiments (with a higher degree of freedom), was dependent on a lower number of variables and had an apparent better fit. Therefore, it can be considered a convenient evolution of the first model. Besides, the global model provides the minimum phage concentration (about 2 x 10(8) PFU/ml) required to inactivate S. aureus in milk at different temperatures, irrespective of the bacterial contamination level.
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