Developing application and detection methods for Listeria monocytogenes and fish extract on open surfaces in order to optimize cleaning protocols

© 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Surfaces in the food industry are often fouled with bacteria and organic materials. A range of fouling and testing methods using two Listeria monocytogenes strains (Scott A and N53-1) and organic material (0.4 g/ml fish extract) were designed to determine the efficacy of two different cleaning methods (spray and wipe) in 1% sodium hypochlorite. The optimum method for applying the cells and organic material to substrata occurred when the cells and organic material were mixed together, dried onto the surface and stained. As the number of cleaning and re-foulings increased, cells were removed from the surfaces but the organic material remained. The pattern of organic material retention was different on the surfaces with the different cleaning protocols, but neither method was better at removing the retained organic material. More cells were removed from the surfaces by the spray than the spray with wipe clean. There was no difference in cell number retention for either of the L. monocytogenes strains. These findings are valid for a 'dirty material' as classified in BS EN1276. To determine cleaning method efficacy, the application of cells and organic material to a surface is important, as is the detection methods used

Adhesion and biofilm formation by Staphylococcus aureus from food processing plants as affected by growth medium, surface type and incubation temperature

This study assessed the effect of different growth media [BHI broth, BHI broth plus glucose (10 g/100 mL) and BHI broth plus NaCl (5 g/100 mL)] and incubation temperatures (28 or 37 ºC) on the adherence, detachment and biofilm formation on polypropylene and stainless steel surfaces (2 x 2 cm coupons) for a prolonged period (24-72 h) by some strains of Staphylococcus aureus (S3, S28 and S54) from food processing plants. The efficacy of the sanitizers sodium hypochlorite (250 mg/mL) and peracetic acid (30 mg/mL) in reducing the number of viable bacterial cells in a preformed biofilm was also evaluated. S. aureus strains adhered in highest numbers in BHI broth, regardless of the type of surface or incubation temperature. Cell detachment from surfaces revealed high persistence over the incubation period. The number of cells needed for biofilm formation was noted in all experimental systems after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered onto polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacities to adhere and form biofilms on polypropylene and stainless steel surfaces under the different growth conditions, and the cells in biofilm matrixes were resistant to total removal when exposed to the sanitizers sodium hypochlorite and peracetic acid.Este estudo teve como objetivo avaliar o efeito de diferentes meios de crescimento [caldo BHI, caldo BHI adicionado de glucose (10 g/100 mL) e caldo BHI adicionado de NaCl (5 g/100 mL)] e temperaturas de incubação (28 e 37 ºC) sobre a adesão, separação e formação de biofilme sobre superfícies (2 x 2 cm) de polipropileno e aço inoxidável durante longo tempo de incubação (24-72 h) por parte de cepas de Staphylococcus aureus (S3, S58 e S54) isoladas de plantas de processamento de alimentos. Também foi avaliada a eficácia dos sanitizantes hipoclorito de sódio (250 mg/mL) e ácido peracético (30 mg/mL) na redução do número de células bacterianas viáveis presentes em um biofilme pré-formado. As cepas de S. aureus aderiram em número mais elevado quando incubadas em caldo BHI em ambos os tipos de superfícies e temperaturas de incubação testadas. A separação das células das superfícies revelou alta persistência ao longo do período de incubação. Número de células necessário para a formação do biofilme foi detectado depois de três dias de incubação em todos os sistemas experimentais. O ácido peracético e o hipoclorito de sódio não foram eficientes em remover completamente a células de S. aureus aderidas sobre as superfícies de polipropileno e aço inoxidável. Os resultados obtidos revelaram alta capacidade das cepas ensaiadas em aderir e formar biofilme sobre superfícies de polipropileno e aço inoxidável sobre diferentes condições de crescimento e que as células na matriz do biofilme apresentaram-se resistentes à total remoção quando expostas aos sanitizantes hipoclorito de sódio e ácido peracético

Culture Conditions of Roseobacter Strain 27-4 Affect Its Attachment and Biofilm Formation as Quantified by Real-Time PCR

The fish probiotic bacterium Roseobacter strain 27-4 grows only as rosettes and produces its antibacterial compound under static growth conditions. It forms three-dimensional biofilms when precultured under static conditions. We quantified attachment of Roseobacter strain 27-4 using a direct real-time PCR method and demonstrated that the bacteria attached more efficiently to surfaces during static growth than under aerated conditions

Social Theory

This textbook offers a new approach to understanding social theory. Framed around paired theoretical perspectives on a series of sociological problems, the book shows how distinctive viewpoints shed light on different facets of social phenomena. The book includes sociology’s “founding fathers”, major 20th-century thinkers and recent voices such as Butler and Zizek. Philosophically grounded and focused on interpretation and analysis, the book provides a clear understanding of theory’s scope while developing students’ skills in evaluating, applying and comparing theories.</p