title: Control of Listeria monocytogenes growth in soft cheeses by bacteriophage P100.
abstract: The purpose of this study was to determine the effect of bacteriophage P100 on strains of Listeria monocytogenes in artificially inoculated soft cheeses. A mix of L. monocytogenes 1/2a and Scott A was inoculated in Minas Frescal and Coalho cheeses (approximately 10(5) cfu/g) with the bacteriophage added thereafter (8.3 × 10(7) PFU/g). Samples were analyzed immediately, and then stored at 10 °C for seven days. At time zero, 30 min post-infection, the bacteriophage P100 reduced L. monocytogenes counts by 2.3 log units in Minas Frescal cheese and by 2.1 log units in Coalho cheese, compared to controls without bacteriophage. However, in samples stored under refrigeration for seven days, the bacteriophage P100 was only weakly antilisterial, with the lowest decimal reduction (DR) for the cheeses: 1.0 log unit for Minas Frescal and 0.8 log units for Coalho cheese. The treatment produced a statistically significant decrease in the counts of viable cells (p < 0.05) and in all assays performed, we observed an increase of approximately one log cycle in the number of viable cells of L. monocytogenes in the samples under refrigeration for seven days. Moreover, a smaller effect of phages was observed. These results, along with other published data, indicate that the effectiveness of the phage treatment depends on the initial concentration of L. monocytogenes, and that a high concentration of phages per unit area is required to ensure sustained inactivation of target pathogens on food surfaces.
authors.affiliation: Departamento de Análises Bromatológicas Faculdade de Farmácia Universidade Federal da Bahia SalvadorBA Brazil.
authors.forename: Elaine Nóbrega Gibson
authors.initials: EN
authors.lastname: Silva
authors.affiliation: Departamento de Ciência dos Alimentos Escola de Nutrição Universidade Federal da Bahia SalvadorBA Brazil.
authors.forename: Ana Cláudia Leite
authors.initials: AC
authors.lastname: Figueiredo
authors.affiliation: Departamento de Ciência dos Alimentos Escola de Nutrição Universidade Federal da Bahia SalvadorBA Brazil.
authors.forename: Fernanda Araújo
authors.initials: FA
authors.lastname: Miranda
authors.affiliation: Departamento de Ciência dos Alimentos Escola de Nutrição Universidade Federal da Bahia SalvadorBA Brazil.
authors.forename: Rogeria Comastri
authors.initials: RC
authors.lastname: de Castro Almeida
mesh_terms: D058491:Bacterial Load; D001435:Bacteriophages / Q000254:growth & development*; D002611:Cheese / Q000382:microbiology* / Q000821:virology*; D005516:Food Microbiology / Q000379:methods*; D008089:Listeria monocytogenes / Q000254:growth & development* / Q000821:virology*; D050296:Microbial Viability; D010572:Pest Control, Biological / Q000379:methods*; D013696:Temperature; D013997:Time Factors
keywords: Listeria; bacteriophage; biocontrol; cheese; food safety