International journal of food microbiology最新文献

Campylobacter was considered asaccharolytic, but is now known to carry saccharide metabolization pathways for L-fucose and d-glucose. We hypothesized that these clusters are beneficial for Campylobacter niche adaptation and may help establish human infection.

We investigated the distribution of d-glucose and L-fucose clusters among ∼9600 C. jejuni and C. coli genomes of different isolation sources in the Netherlands, the United Kingdom, the United States of America and Finland. The L-fucose utilization cluster was integrated at the same location in all C. jejuni and C. coli genomes, and was flanked by the genes rpoB, rpoC, rspL, repsG and fusA, which are associated with functions in transcription as well as translation and in acquired drug resistance. In contrast, the flanking regions of the d-glucose utilization cluster were variable among the isolates, and integration sites were located within one of the three different 16S23S ribosomal RNA areas of the C. jejuni and C. coli genomes. In addition, we investigated whether acquisition of the L-fucose utilization cluster could be due to horizontal gene transfer between the two species and found three isolates for which this was the case: one C. jejuni isolate carrying a C. coli L-fucose cluster, and two C. coli isolates which carried a C. jejuni L-fucose cluster. Furthermore, L-fucose utilization cluster alignments revealed multiple frameshift mutations, most of which were commonly found in the non-essential genes for L-fucose metabolism, namely, Cj0484 and Cj0489. These findings support our hypothesis that the L-fucose cluster was integrated multiple times across the C. coli/C. jejuni phylogeny.

Notably, association analysis using the C. jejuni isolates from the Netherlands showed a significant correlation between human C. jejuni isolates and C. jejuni isolates carrying the L-fucose utilization cluster. This correlation was even stronger when the Dutch isolates were combined with the isolates from the UK, the USA and Finland. No such correlations were observed for C. coli or for the d-glucose cluster for both species. This research provides insight into the spread and host associations of the L-fucose and d-glucose utilization clusters in C. jejuni and C. coli, and the potential benefits in human infection and/or proliferation in humans, conceivably after transmission from any reservoir.

The aim of this study was to characterize the pulp of Rheum ribes L. and to determine the effect of the pulp enriched with eugenol (1 %) or thymol (1 %) on the microbiological and physico-chemical quality of chicken breast fillets. Chicken breast fillets, inoculated with Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium, and Escherichia coli O157:H7 (~6.0 log₁₀), were marinated for 24 h in a mixture prepared from a combination of Rheum ribes L. pulp with eugenol or thymol. The quality parameters were analyzed for 15 days at +4 °C. The Rheum ribes L. pulp was found to have high antioxidant activity, high total phenolic content and contained 22 different phenolic substances, among which rutin ranked first. The pulp contained high levels of p-xylene and o-xylene as volatile substances and citric acid as an organic acid. The combination of Pulp + Eugenol + Thymol (PET) reduced the number of pathogens in chicken breast fillets by 2.03 to 3.50 log₁₀ on day 0 and by 2.25 to 4.21 log₁₀ on day 15, compared to the control group (P < 0.05). The marinating treatment significantly lowered the pH values of fillet samples on the first day of the study, compared to the control group (P < 0.05). During storage, TVB-N levels showed slower increase in the treatment groups compared to the control group (P < 0.05). In addition, the marinating process led to significant changes in physicochemical parameters such as water holding capacity, color, texture, cooking loss, and drip loss compared to the control group (P < 0.05). In conclusion, the results of this study showed that the pulp of Rheum ribes L., which has a high antioxidant capacity and contains various bioactive compounds. Furthermore, S. Typhimurium, E. coli O157:H7 and L. monocytogenes were inhibited considerably by marinating Rheum ribes L. pulp with a combination of eugenol and thymol.

Salmon aquaculture is the fastest growing food production system in the world. Deficiencies in the quality or safety of salmon can have global repercussions. Controlling food safety aspects during production is therefore essential. Here, we investigate the state of hygiene in a salmon processing plant using next generation sequencing and classical culture-dependent methods to characterize the surface microbiota before and after cleaning and disinfection (C&D) at ten surface sampling points. Total aerobic counts revealed an average reduction in the bacterial loads of 1.1 log CFU/cm² by C&D. The highest relative abundance in the core microbiota before C&D was assigned to Acinetobacter, Mycoplasmataceae, Pseudomonas and Enterobacteriaceae in descending order. After C&D, we observed a significant increase in the relative abundance of Pseudomonas (p < 0.05). However, variations were found between conveyors, processing machines and drains. To assess the efficacy of commercial disinfectants, we performed susceptibility assays using advanced robotic high-throughput technologies and included foodborne bacteria which may affect food safety and spoilage. These included 128 Pseudomonas isolates, 46 Aeromonas isolates and 59 Enterobacterales isolates sampled from the salmon processing plant. Generally, minimum inhibitory concentrations (MICs) of the disinfectants were below the user concentration recommended by the producer for most isolates. BacTiter-Glo biofilm assays revealed that 30 min exposure to six out of eight commercial disinfectants resulted in an average reduction of relative luminescence >95 % in 59 single-species biofilms selected for screening. However, disinfection alone may not always be sufficient to eradicate biofilms completely. C&D routines must therefore be continuously assessed to maintain food safety and quality. The results from this study can contribute to understand and improve the state of hygiene in salmon processing environments.

The frozen fruit sector has experienced significant growth due to improved product quality as well as the advantage of long-term preservation. However, freezing alone does not eliminate foodborne viruses, a major public health concern and considerable economic burden. One promising disinfecting treatment is pulsed light, shown previously to inactivate hepatitis A virus (HAV) and murine norovirus-1 (MNV-1) on the surface of fresh berries. Viral loads were reduced by 1–2 log, with minor visual quality deterioration observed. In this study, an FDA-compliant pulsed light treatment (11.52 J/cm²) was applied to frozen fruits and berries. Infectious MNV-1 and HAV titers were reduced by 1–2 log on most frozen fruits. A noteworthy finding was that reductions of both viruses on cranberries exceeded 3.5 log cycles. Although pulsed light caused a measurable rise in temperature on the product surface, no visible physical changes (e.g., color) were observed, and the fruit pieces were still frozen after treatment. Although the reduction of infectious titer by pulsed light alone was not large (1–2 log), considering the low amount of virus typically found on fruit, it may be beneficial in the frozen fruit sector. It would be easy to combine with other treatments, and synergic interactions might increase virus inactivation.

Escherichia coli is one of the most prevalent foodborne pathogens, frequently found in meat and dairy products. Current decontamination methods are often associated with changes in organoleptic characteristics, nutrient loss, and potentially harmful side effects. Furthermore, despite the array of available methods, foodborne outbreaks still frequently occur. For this reason, bacteriophages (or simply phages) emerged as a natural alternative for the biocontrol of bacterial contamination in food without altering their organoleptic properties. In this study, the potential of phage phT4A was assessed in the biocontrol of E. coli in liquid (milk) and solid (ham) food matrices. Firstly, as foods have different pH and temperature values, the influence of these parameters on phage phT4A viability was also assessed to develop an effective protocol. Phage phT4A proved to be stable for long storage periods at pH 7–8 (56 days) and temperatures of 4–37 °C (21 days). Before application of phages to inactivate pathogenic bacteria in food, previous assays were carried out in Tryptic Soy Broth (TSB) to study the dynamics of phage-bacteria interaction. Then, the antibacterial potential of phage phT4A was evaluated in the two food matrices at different temperatures (4, 10 and 25 °C). This phage was more efficient at 25 °C in all tested matrices (maximum inactivation of 6.6, 3.9 and 1.8 log CFU/mL in TSB, milk and ham, respectively) than at 10 °C (maximum decrease of 4.7, 2.1 and 1.0 log CFU/mL in TSB, milk and ham, respectively) and 4 °C (maximum reduction of 2.6 and 0.7 log CFU/mL in TSB and milk, respectively). However, the decrease of temperature from 25 °C to 10 and 4 °C prevented bacterial regrowth. The results suggest that during phage treatment, a balance between an incubation temperature that provide effective results in terms of bacterial inactivation by the phages and at the same time prevents or delays bacterial regrowth, is needed. The application of phage phT4A at a temperature of 10 °C can be an effective strategy in terms of bacterial inactivation, delaying bacterial regrowth and also reducing energy costs.

Antimicrobial resistance represents a global health emergency, necessitating the introduction of novel antimicrobial agents. In the present study, lysozyme and holin from Shigella flexneri 1.1868 phage SGF2, named LysSGF2 and HolSGF2, respectively, were cloned, expressed, and characterized. LysSGF2 and HolSGF2 showed lytic activities against S. flexneri 1.1868 cells at 4–55 °C and pH 3.1–10.3. LysSGF2 exhibited antimicrobial activity against five gram-negative and two gram-positive bacteria. HolSGF2 showed antimicrobial activity against four gram-negative and one gram-positive species. The antibacterial activities of LysSGF2 and HolSGF2 were determined in liquid beverages, including bottled water and milk. The relative lytic activity of LysSGF2 combined with HolSGF2 against the tested bacteria was approximately 46–77 % in water. Furthermore, the combination markedly decreased the viable counts of tested bacteria by approximately 3–5 log CFU/mL. LysSGF2 and HolSGF2 could efficiently remove biofilms on polystyrene, glass, and stainless-steel. The efficacy of the LysSGF2 and HolSGF2 combination against the tested bacteria on polystyrene was 58–71 %. Combination treatment effectively killed biofilm cells formed on stainless-steel and glass by 1–4 log CFU/mL. ese results indicate that LysSGF2 and HolSGF2 can successfully control both the planktonic and biofilm cells of common pathogenic bacteria, suggesting that the combined or single use of LysSGF2 and HolSGF2 may be of great value in food processing.

The biosynthetic machinery for cell wall polysaccharide (CWPS) formation in Lactococcus lactis and Lactococcus cremoris is encoded by the cwps locus. The CWPS of lactococci typically consists of a neutral rhamnan component, which is embedded in the peptidoglycan, and to which a surface-exposed side chain oligosaccharide or polysaccharide pellicle (PSP) component is attached. The rhamnan component has been shown for several lactococcal strains to consist of a repeating rhamnose trisaccharide subunit, while the side chain is diverse in glycan content, polymeric status and glycosidic linkage architecture. The observed structural diversity of the CWPS side chain among lactococcal strains is reflected in the genetic diversity within the variable 3′ region of the corresponding cwps loci. To date, four distinct cwps genotypes (A, B, C, D) have been identified, while eight subtypes (C₁ through to C₈) have been recognized among C-genotype strains. In the present study, we report the identification of three novel subtypes of the lactococcal cwps C genotypes, named C₉, C₁₀ and C₁₁. The CWPS of four isolates representing C₇, C₉, C₁₀ and C₁₁ genotypes were analysed using 2D NMR to reveal their unique CWPS structures. Through this analysis, the structure of one novel rhamnan, three distinct PSPs and three exopolysaccharides were elucidated. Results obtained in this study provide further insights into the complex nature and fascinating diversity of lactococcal CWPSs. This highlights the need for a holistic view of cell wall-associated glycan structures which may contribute to robustness of certain strains against infecting bacteriophages. This has clear implications for the fermented food industry that relies on the consistent application of lactococcal strains in mesophilic production systems.

Biofilm formation in natural environments involving complex multi-structural arrangements hinders challenges in antimicrobial resistance. This study investigated the antimicrobial resistance potential of grapefruit seed extract (GSE) by examining the formation of mono-, dual-, and multi-species biofilms. We also explored the counterintuitive effect in response to GSE at various concentrations, including minimum inhibitory concentration (MIC) and sub-MIC (1/2 and 1/4 MIC). The results of the swimming and swarming motility tests revealed increased motility at the sub-MIC of GSE. The crystal violet assay demonstrated increased biofilm formation in multi-species biofilms, highlighting the synergistic effect of Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes. At the MIC concentration of GSE, field emission scanning electron microscopy (FE-SEM) revealed cell morphology damage, while sub-MIC increased biofilm formation and architectural complexity. Multi-species biofilms demonstrated greater biofilm-forming ability and antimicrobial resistance than mono-species biofilms, indicating synergistic interactions and enhanced resilience. These findings highlight the importance of understanding biofilm dynamics and antimicrobial resistance to ensure environmental safety.

The primary objective of this study was to characterize lactic acid bacteria (LAB) strains derived from sourdough for possible utilization as functional starters to produce sourdough and various cereal-based fermented foods. A total of 350 autochthonous LAB strains were isolated from 65 Type I sourdough samples and characterized using six random amplified polymorphic DNA (RAPD) primers at intra- and interspecific levels. Species identification of selected strains representing distinct clusters from RAPD analysis was performed based on the 16S rRNA region. The LAB strains were identified as Companilactobacillus crustorum (n = 135), Levilactobacillus brevis (n = 125), Latilactobacillus curvatus (n = 40), Companilactobacillus paralimentarius (n = 32), and Lactiplantibacillus plantarum (n = 18). A total of 66 LAB strains were selected for technological characterization along with two commercial strains. The characterization involved acidity development, EPS production potential, leavening activity, and growth abilities under harsh conditions. Principle component analysis (PCA) identified 2 Lp. plantarum and 14 Lev. brevis strains as the most relevant technologically. Among them, Lp. plantarum L35.1 and Lev. brevis L37.1 were resistant to tetracycline. Evaluation of probiotic characteristics (survival in pH 2.5 and bile presence, auto aggregation capacity, hydrophobic activity, antioxidant activity, antimicrobial activity) by PCA identified four strains with relevance to Lactobacillus rhamnosus GG (LGG), which were further selected for in vitro digestion assays. Lactiplantibacillus plantarum L7.8, Lev. brevis L55.1, and L62.2 demonstrated similar viability indices to LGG, along with increased auto aggregation capacity and antioxidant activity. These strains are promising as candidate starters for producing sourdough and sourdough-related fermented food products.