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

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

Primary processing and storage affect the dominant microbiota of fresh and chill-stored sea bass products

The cultivable microbiota isolated from three sea bass products (whole, gutted, and filleted fish from the same batch) during chilled storage and the effect of primary processing on microbial communities in gutted and filleted fish were studied. Microbiological and sensory changes were also monitored. A total of 200 colonies were collected from TSA plates at the beginning and the end of fish shelf-life, differentiated by High Resolution Sequencing (HRM) and identified by sequencing analysis of the V3–V4 region of the 16S rRNA gene. Pseudomonas spp. followed by potential pathogenic bacteria were initially found, while Pseudomonas gessardii followed by other Pseudomonas or Shewanella species dominated at the end of fish shelf-life. P. gessardii was the most dominant phylotype in the whole sea bass, P. gessardii and S. baltica in gutted fish, while P. gessardii and P. fluorescens were the most dominant bacteria in sea bass fillets. To conclude, primary processing and storage affect microbial communities of gutted and filleted fish compared to the whole fish. HRM analysis can easily differentiate bacteria isolated from fish products and reveal the contamination due to handling and/or processing, and so help stakeholders to immediately tackle problems related with microbial quality or safety of fish. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Correlation between chemical composition of Greek essential oils and their antibacterial activity against food-borne pathogens

The compositions of forty-nine essential oils obtained from plants growing in areas of biodiversity in Greece were determined by means of gas chromatography and gas chromatography-mass spectrometry. The in vitro antibacterial activities of the oils were evaluated against a panel of five common food-borne bacteria (Escherichia coli 0157:H7 NCTC 12900, Salmonella Enteritidis PT4, Staphylococcus aureus ATCC 6538, Listeria monocytogenes Scott A and Bacillus cereus FSS 134). Monoterpene hydrocarbons, phenolic monoterpenes and alcohols were the major constituents of the oils, but their concentrations varied greatly between the samples examined. The essential oils obtained from the species endemic to Greece (Satureja and Origanum) had the most potent bactericidal properties. The chemical composition data were statistically processed through Principal Component Analysis (PCA) and correlated with the antibacterial activities, allowing a rough estimation of the potential of the essential oils antibacterial activity. © 2007 Natural Product Incorporation. All Rights Reserved

Quest of intelligent research tools for rapid evaluation of fish quality: FTIR spectroscopy and multispectral imaging versus microbiological analysis

The aim of the present study was to assess the microbiological quality of farmed sea bass (Dicentrarchus labrax) fillets stored under aerobic conditions and modified atmosphere packaging (MAP) (31% CO2, 23% O2, 46% N2,) at 0, 4, 8, and 12◦ C using Fourier transform infrared (FTIR) spectroscopy and multispectral imaging (MSI) in tandem with data analytics, taking into account the results of conventional microbiological analysis. Fish samples were subjected to microbiological analysis (total viable counts (TVC), Pseudomonas spp., H2 S producing bacteria, Brochothrix thermosphacta, lactic acid bacteria (LAB), Enterobacteriaceae, and yeasts) and sensory evaluation, together with FTIR and MSI spectral data acquisition. Pseudomonas spp. and H2 S-producing bacteria were enumerated at higher population levels compared to other microorganisms, regardless of storage temperature and packaging condition. The developed partial least squares regression (PLS-R) models based on the FTIR spectra of fish stored aerobically and under MAP exhibited satisfactory performance in the estimation of TVC, with coefficients of determination (R2) at 0.78 and 0.99, respectively. In contrast, the performances of PLS-R models based on MSI spectral data were less accurate, with R2 values of 0.44 and 0.62 for fish samples stored aerobically and under MAP, respectively. FTIR spectroscopy is a promising tool to assess the microbiological quality of sea bass fillets stored in air and under MAP that could be effectively employed in the future as an alternative method to conventional microbiological analysis. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Microbiota Succession of Whole and Filleted European Sea Bass (Dicentrarchus labrax) during Storage under Aerobic and MAP Conditions via 16S rRNA Gene High-Throughput Sequencing Approach

In the present work, the profiles of bacterial communities of whole and filleted European sea bass (Dicentrarchus labrax), during several storage temperatures (0, 4, 8 and 12 °C) under aerobic and Modified Atmosphere Packaging (MAP) conditions, were examined via the 16S rRNA High-Throughput Sequencing (HTS) approach. Sensorial attributes were also assessed to determine products’ shelf-life. Results indicated that shelf-life was strongly dependent on handling, as well as on temperature and atmosphere conditions. HTS revealed the undisputed dominance of Pseudomonas from the very beginning and throughout storage period in the majority of treatments. However, a slightly different microbiota profile was recorded in MAP-stored fillets at the middle stages of storage, which mainly referred to the sporadic appearance of some bacteria (e.g., Carnobacterium, Shewanella, etc.) that followed the dominance of Pseudomonas. It is noticeable that a major difference was observed at the end of shelf-life of MAP-stored fillets at 12 °C, where the dominant microbiota was constituted by the genus Serratia, while the relative abundance of Pseudomonas and Brochothrix was more limited. Furthermore, at the same temperature under aerobic storage of both whole and filleted fish, Pseudomonas almost co-existed with Acinetobacter, while the presence of both Erwinia and Serratia in whole fish was noteworthy. Overall, the present study provides useful information regarding the storage fate and spoilage status of whole and filleted European sea bass, suggesting that different handling and storage conditions influence the shelf-life of sea bass by favoring or delaying the dominance of Specific Spoilage Organisms (SSOs), affecting in parallel to some extent the formation of their consortium that is responsible for products’ sensorial deterioration. Such findings enrich the current knowledge and should be used as a benchmark to develop specific strategies aiming to delay spoilage and thus increase the products’ added value. © 2022 by the authors