Strain effect on the heterogeneity of individual-cell growth kinetics of Salmonella Typhimurium

The present study showed that the variability of individual-cell growth kinetics may differ among strains of S. Typhimurium. The results provide useful quantitative information for incorporating strain variability and heterogeneity in individual-cell behavior in stochastic growth models and risk assessment studies

Acquired acid adaptation of Listeria monocytogenes during its planktonic growth enhances subsequent survival of its sessile population to disinfection with natural organic compounds

In this study, the possible influence of acid adaptation of L. (monocytogenes cells during their planktonic growth on their subsequent resistance against some such compounds (i.e. lactic acid, essential oil or hydrosol of Mediterranean spice Satureja( thymbra) nupon their attachment to SS, was evaluated by simultaneously using the bead vortexing technique and a conductance method

P3-21 Comparative Proteomic Analysis of Salmonella enterica serovar Enteritidis PT4 Planktonic and Sessile Cells on Stainless Steel Surface Provides New Insights in Protein Determinants Involved in the Maintenance of a Biofilm community

In order to better understand the cellular mechanisms sustaining a surface-associated lifestyle of S. Enteritidis in food related environments, the differential protein patterns of this bacterium cultivated as biofilm on SS versus planktonic mode were comparatively studied in the present work

Population dynamics of Staphylococcus aureus and Salmonella Typhimurium in a laboratory medium and rocket extract

In the present study, the growth of Staphylococcus aureus and Salmonella Typhimurium on different growth media was studied. For this purpose, a growth medium (Luria – Bertani broth, LB) and extract from rocket, were inoculated with Staphylococcus aureus strain COL (MRSA) and Salmonella Typhimurium (CDC 6516-60). After the inoculation, the samples were incubated at 20°C

Quorum Sensing in the Context of Food Microbiology

Food spoilage may be defined as a process that renders a product undesirable or unacceptable for consumption and is the outcome of the biochemical activity of a microbial community that eventually dominates according to the prevailing ecological determinants. Although limited information are reported, this activity has been attributed to quorum sensing (QS). Consequently, the potential role of cell-to-cell communication in food spoilage and food safety should be more extensively elucidated. Such information would be helpful in designing approaches for manipulating these communication systems, thereby reducing or preventing, for instance, spoilage reactions or even controlling the expression of virulence factors. Due to the many reports in the literature on the fundamental features of QS, e.g., chemistry and definitions of QS compounds, in this minireview, we only allude to the types and chemistry of QS signaling molecules per se and to the (bioassay-based) methods of their detection and quantification, avoiding extensive documentation. Conversely, we attempt to provide insights into (i) the role of QS in food spoilage, (ii) the factors that may quench the activity of QS in foods and review the potential QS inhibitors that might “mislead” the bacterial coordination of spoilage activities and thus may be used as biopreservatives, and (iii) the future experimental approaches that need to be undertaken in order to explore the “gray” or “black” areas of QS, increase our understanding of how QS affects microbial behavior in foods, and assist in finding answers as to how we can exploit QS for the benefit of food preservation and food safety

Identification of meat spoilage gene biomarkers in Pseudomonas putida using gene profiling

While current food science research mainly focuses on microbial changes in food products that lead to foodborne illnesses, meat spoilage remains as an unsolved problem for the meat industry. This can result in important economic losses, food waste and loss of consumer confidence in the meat market. Gram-negative bacteria involved in meat spoilage are aerobes or facultative anaerobes. These represent the group with the greatest meat spoilage potential, where Pseudomonas tend to dominate the microbial consortium under refrigeration and aerobic conditions. Identifying stress response genes under different environmental conditions can help researchers gain an understanding of how Pseudomonas adapts to current packaging and storage conditions. We examined the gene expression profile of Pseudomonas putida KT2440, which plays an important role in the spoilage of meat products. Gene expression profiles were evaluated to select the most differentially expressed genes at different temperatures (30 °C and 10 °C) and decreasing glucose concentrations, in order to identify key genes actively involved with the spoilage process. A total of 739 and 1269 were found to be differentially expressed at 30 °C and 10 °C respectively; of which 430 and 568 genes were overexpressed, and 309 and 701 genes were repressed at 30 °C and 10 °C respectively

Assessment of the effect of a Salmonella enterica ser. Typhimurium culture supernatant on the single-cell lag time of foodborne pathogens

The objective of this study was the in vitro evaluation of the effect of a cell-free microbial supernatant, produced by a luxS-positive Salmonella enterica ser. Typhimurium strain, on the single-cell growth kinetic behavior of two strains of S. enterica (serotypes Enteritidis and Typhimurium) and a methicillin-resistant Staphylococcus aureus strain. The single-cell lag time (λ) of the pathogens was estimated in the absence and presence (20% v/v) of microbial supernatant based on optical density measurements. As demonstrated by the obtained results, the tested microbial supernatant had a strain-specific effect on the single-cell λ and its variability. Although the mean λ values were similar in the absence and presence of microbial supernatant in the case of Salmonella Enteritidis, a significant (P ≤ 0.05) reduction and increase in the mean value of this parameter in the presence of microbial supernatant were observed for Salmonella Typhimurium and St. aureus, respectively. With regard to the effect of the tested microbial supernatant on the single-cell variability of λ, similar λ distributions were obtained in its absence and presence for S. Enteritidis, while considerable differences were noted for the other two tested organisms; the coefficient of variation of λ in the absence and presence of microbial supernatant was 41.6 and 69.8% for S. Typhimurium, respectively, with the corresponding values for St. aureus being 74.0 and 56.9%. As demonstrated by the results of bioassays, the tested microbial supernatant exhibited autoinducer-2 activity, indicating a potential association of such quorum sensing compounds with the observed effects. Although preliminary in nature, the collected data provide a good basis for future research on the role of quorum sensing in the single-cell growth behavior of foodborne pathogens

Ability of Salmonella enterica and Staphylococcus aureus to develop biofilm community on stainless steel and colonize rocket tissue

In the present study, the ability of S. Typhimurium (CDC 6516-60) and S. aureus strain COL (MRSA) to both develop a biofilm community on stainless steel (SS) and colonize rocket tissue was investigated (incubation at 20°C for 144 h). In parallel, the planktonic growth of these pathogens in Brain Heart Infusion (BHI) broth, was followed