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Food Microbiology Jun 2022The behaviour of Listeria monocytogenes was investigated in soft pasteurized milk cheese elaborated with different salt concentrations (1.17 and 0.30% w/w) and in cured...
The behaviour of Listeria monocytogenes was investigated in soft pasteurized milk cheese elaborated with different salt concentrations (1.17 and 0.30% w/w) and in cured raw sheep milk cheese over storage up to 189 days at different isothermal conditions. Commercial 25-g cheese samples were inoculated with a 4-strain cocktail of L. monocytogenes (serovars 4b, 1/2a, 1/2b and 1/2c) at approximately 10 CFU/g. The inoculated samples were stored at 4 and 22 °C and withdrawn at proper intervals for L. monocytogenes enumeration. The prevalence of the different serovar strains of L. monocytogenes was characterized on soft cheese samples over storage at 4 °C using multiplex PCR. Salt reduction did not affect the survival of L. monocytogenes in soft cheeses and a maximum of 1-log reduction was observed in both regular and low-salt cheeses after 189 days of storage at 4 °C. The pathogen showed greater survival capacity in both soft and cured cheeses during storage at 4 °C compared to the storage at 22 °C, where more than 2.5 log reductions were computed. The fate of L. monocytogenes was described through a Weibull model fitted to survival data. The time required for a first tenfold reduction of the L. monocytogenes population (δ) at 4 °C is around 150 days in soft and 72 days in cured cheeses. At 22 °C, the estimated δ values are at least 60% lower in both cheese types. Among the four L. monocytogenes serovars present in the inoculated cocktail, the serovar 4b strain was the most sensitive to refrigerated storage, while the prevalence of serovar 1/2c strain increased over time in soft cheeses. Overall, the data obtained in this study help to deepen knowledge into factors affecting L. monocytogenes behaviour on cheeses and evidenced the variability between serovars in terms of survival capacity, which may be considered when performing microbial risk assessments.
Topics: Animals; Cheese; Food Microbiology; Food Storage; Listeria monocytogenes; Sheep; Temperature; Time Factors
PubMed: 35287808
DOI: 10.1016/j.fm.2022.103979 -
Cellular Microbiology Apr 2020Decades of breakthroughs resulting from cross feeding of microbiological research and technological innovation have promoted Listeria monocytogenes to the rank of model... (Review)
Review
Decades of breakthroughs resulting from cross feeding of microbiological research and technological innovation have promoted Listeria monocytogenes to the rank of model microorganism to study host-pathogen interactions. The extraordinary capacity of this bacterium to interfere with a vast array of host cellular processes uncovered new concepts in microbiology, cell biology and infection biology. Here, we review technological advances that revealed how bacteria and host interact in space and time at the molecular, cellular, tissue and whole body scales, ultimately revolutionising our understanding of Listeria pathogenesis. With the current bloom of multidisciplinary integrative approaches, Listeria entered a new microbiology era.
Topics: Animals; Bacterial Proteins; Biotechnology; Gene Expression Regulation, Bacterial; Host-Pathogen Interactions; Humans; Listeria monocytogenes; Listeriosis; Mice; Virulence; Virulence Factors
PubMed: 32185895
DOI: 10.1111/cmi.13183 -
Food Microbiology Oct 2021Genomic diversity of Listeria monocytogenes isolates from the deboning and slicing areas of three dry-cured ham processing plants was analysed. L. monocytogenes was...
Genomic diversity of Listeria monocytogenes isolates from the deboning and slicing areas of three dry-cured ham processing plants was analysed. L. monocytogenes was detected in 58 out of 491 samples from the environment and equipment surfaces, all from the deboning area, with differences in prevalence among facilities. The most frequent PCR-serogroup was IIa (74.1%) followed by IIb and IIc, and only one isolate was serogroup IVb. Twenty different pulsotypes and 11 sequence types (STs) grouped into 10 clonal complexes (CCs) were determined. ST121 (CC121) and ST9 (CC9) were the most abundant. Premature stop codons (PMSC6 and PMSC19) associated with attenuated virulence were found in the inlA sequence in 7 out of 12 selected strains. CC121 strains were strong biofilm formers and some harboured the transposon Tn6188, related with increased tolerance to quaternary ammonium compounds. L. monocytogenes clones considered hypovirulent resulted predominant in the deboning areas. The clonal structure and potential virulence of the isolates could help to establish adequate control measures and cleaning protocols for the comprehensive elimination of the pathogen in dry-cured ham processing environment.
Topics: Animals; Bacterial Proteins; Bacterial Typing Techniques; Biofilms; Equipment Contamination; Equipment and Supplies; Food Handling; Food Microbiology; Genetic Variation; Genomics; Listeria monocytogenes; Meat Products; Pork Meat; Swine
PubMed: 34119091
DOI: 10.1016/j.fm.2021.103779 -
Cellular Microbiology Apr 2020By modifying the host cell transcription programme, pathogenic bacteria disrupt a wide range of cellular processes and take control of the host's immune system.... (Review)
Review
By modifying the host cell transcription programme, pathogenic bacteria disrupt a wide range of cellular processes and take control of the host's immune system. Conversely, by mobilising a network of defence genes, the host cells trigger various responses that allow them to tolerate or eliminate invaders. The study of the molecular basis of this crosstalk is crucial to the understanding of infectious diseases. Although research has long focused on the targeting of eukaryotic DNA-binding transcription factors, more recently, another powerful way by which bacteria modify the expression of host genes has emerged: chromatin modifications in the cell nucleus. One of the most prolific bacterial models in this area has been Listeria monocytogenes, a facultative intracellular bacterium responsible for serious food-borne infections. Here, we aim to highlight the contribution of this model to the field of bacteria-mediated chromatin modifications. We will first recall the general principles of epigenetic regulation and then illustrate five mechanisms that mobilise the epigenetic machinery in response to Listeria factors, either through bacterial molecular patterns, a toxin, an invasion protein, or nucleomodulins. Strategies used by Listeria to control the expression of host genes at the chromatin level, by activation of cytosolic signalling pathways or direct targeting of epifactors in the nucleus, have contributed to the emergence of a new discipline combining cellular microbiology and epigenetics: "patho-epigenetics."
Topics: Animals; Bacterial Proteins; Chromatin; Epigenesis, Genetic; Host-Pathogen Interactions; Humans; Listeria monocytogenes; Listeriosis; Mice; Protein Binding; Protein Processing, Post-Translational; Virulence Factors
PubMed: 32185898
DOI: 10.1111/cmi.13169 -
MicrobiologyOpen Nov 2021Listeria monocytogenes is a human pathogen. It is the causative agent of listeriosis, the leading cause of bacterial-linked foodborne mortality in Europe and elsewhere.... (Review)
Review
Listeria monocytogenes is a human pathogen. It is the causative agent of listeriosis, the leading cause of bacterial-linked foodborne mortality in Europe and elsewhere. Outbreaks of listeriosis have been associated with the consumption of fresh produce including vegetables and fruits. In this review we summarize current data providing direct or indirect evidence that plants can serve as habitat for L. monocytogenes, enabling this human pathogen to survive and grow. The current knowledge of the mechanisms involved in the interaction of this bacterium with plants is addressed, and whether this foodborne pathogen elicits an immune response in plants is discussed.
Topics: Disease Outbreaks; Food Microbiology; Foodborne Diseases; Host Microbial Interactions; Humans; Listeria monocytogenes; Listeriosis; Microbial Interactions; Microbial Viability; Microbiota; Plant Immunity; Plants; Vegetables
PubMed: 34964288
DOI: 10.1002/mbo3.1255 -
FEMS Microbiology Letters Nov 2019The aims of this study were to evaluate the occurrence of Listeria monocytogenes and Salmonella spp. in sliced cheese and ham from retail markets in southern Brazil, as...
The aims of this study were to evaluate the occurrence of Listeria monocytogenes and Salmonella spp. in sliced cheese and ham from retail markets in southern Brazil, as well as to perform molecular characterization and to assess the antimicrobial resistance profile of the isolates. Samples (n = 160) of sliced cheese and ham were collected at retail level from the city of Pelotas, Brazil. The isolation of L. monocytogenes and Salmonella spp. was performed and the isolates were confirmed by PCR, submitted to antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE). Listeria monocytogenes was found in 9.4% (15/160) of the samples. All L. monocytogenes isolates were positive for the prs, inlA, inlC and inlJ genes. Salmonella spp. was not isolated. Regarding the antimicrobial susceptibility, one (6.6%) L. monocytogenes isolate was resistant to streptomycin and four (26.6%) to clindamycin. Macrorestriction analysis with ApaI and AscI enzymes yielded two major PFGE groups I and II. All L. monocytogenes isolates showed virulence genes, and some of them were resistant to clinically used antimicrobials, representing a risk to public health. Moreover, PFGE patterns with high similarity were visualized in L. monocytogenes isolates at different times, demonstrating adaptability of the pathogen at retail level in the region.
Topics: Anti-Bacterial Agents; Brazil; Cheese; Cities; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Genes, Bacterial; Genotype; Genotyping Techniques; Listeria monocytogenes; Meat Products; Microbial Sensitivity Tests; Phenotype; Polymorphism, Restriction Fragment Length; Salmonella; Virulence Factors
PubMed: 31834356
DOI: 10.1093/femsle/fnz249 -
Food Microbiology Sep 2021Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on...
Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on predictive models, ListWare, is being developed. The aim of this study was to develop and validate a predictive model for the growth of Listeria monocytogenes in sliced roast beef. A challenge study was performed comprising 51 different combinations of variables. The growth curves followed the Baranyi and Roberts model with no clear lag phase and specific growth rates in the range <0.005-0.110 hr. A linear regression model was developed based on 528 observations and had an adjusted R-square of 0.80. The significant predictors were storage temperature, sodium lactate, interactions between sodium acetate and temperature, and MAP packaging and temperature. The model was validated in four laboratories in three countries. For conditions where the model predicted up to + log 2 cfu/g Listeria concentration, the observed concentrations were true or below the predicted concentration in 90% of the cases. For the remaining 10%, the roast beef was coated with spices and therefore different from the others. The model will be implemented in ListWare web-application for calculation of "Listeria shelf life".
Topics: Animals; Cattle; Fast Foods; Food Contamination; Food Safety; Food Storage; Kinetics; Listeria monocytogenes; Meat Products; Models, Biological; Regression Analysis; Temperature
PubMed: 33875206
DOI: 10.1016/j.fm.2021.103770 -
Applied and Environmental Microbiology Apr 2021is a deadly intracellular pathogen mostly associated with consumption of ready-to-eat foods. This study investigated the effectiveness of total beef fat (BF-T) from...
is a deadly intracellular pathogen mostly associated with consumption of ready-to-eat foods. This study investigated the effectiveness of total beef fat (BF-T) from flaxseed-fed cattle and its fractions enriched with monounsaturated fatty acids (BF-MUFA) and polyunsaturated fatty acids (BF-PUFA), along with commercially available long-chain fatty acids (LC-FA), as natural antimicrobials against BF-T was ineffective at concentrations up to 6 mg/ml, while was susceptible to BF-MUFA and BF-PUFA, with MICs at pH 7 of 0.33 ± 0.21 mg/ml and 0.06 ± 0.03 mg/ml, respectively. The MIC of C14:0 was significantly lower than those of C16:0 and C18:0 (0.05). Fatty acids 9-C16:1, C18:2n-6, and C18:3n-3 showed stronger inhibitory activity than 9-C18:1 and conjugated C18:2, with MICs of <1 mg/ml. Furthermore, global transcriptional analysis by transcriptome sequencing (RNA-seq) was performed to characterize the response of to selected fatty acids. Functional analysis indicated that antimicrobial LC-UFA repressed the expression of genes associated with nutrient transmembrane transport, energy generation, and oxidative stress resistance. On the other hand, upregulation of ribosome assembly and translation process is possibly associated with adaptive and repair mechanisms activated in response to LC-UFA. Virulence genes and genes involved in bile, acid, and osmotic stresses were largely downregulated, and more so for 9-C16:1, C18:2n-6, and C18:3n-3, likely through interaction with the master virulence regulator PrfA and the alternative sigma factor σ is a bacterial pathogen known for its ability to survive and thrive under adverse environments and, as such, its control poses a significant challenge, especially with the trend of minimally processed and ready-to-eat foods. This work investigated the effectiveness of fatty acids from various sources as natural antimicrobials against and evaluated their potential role in pathogenicity modulation, using the strain ATCC 19111. The findings show that long-chain unsaturated fatty acids (LC-UFA), including unsaturated beef fat fractions from flaxseed-fed cattle, could have the potential to be used as effective antimicrobials for through controlling growth as well as virulence attenuation. This not only advances our understanding of the mode of action of LC-UFA against but also suggests the potential for use of beef fat or its fractions as natural antimicrobials for controlling foodborne pathogens.
Topics: Animals; Anti-Bacterial Agents; Cattle; Fats; Fatty Acids; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Listeria monocytogenes; Red Meat
PubMed: 33608290
DOI: 10.1128/AEM.03027-20 -
International Journal of Food... Jun 2021Listeria monocytogenes is a foodborne human pathogen that causes systemic infection, fetal-placental infection in pregnant women causing abortion and stillbirth and...
Listeria monocytogenes is a foodborne human pathogen that causes systemic infection, fetal-placental infection in pregnant women causing abortion and stillbirth and meningoencephalitis in elderly and immunocompromised individuals. This study aimed to analyse L. monocytogenes from different sources from New Zealand (NZ) and to compare them with international strains. We used pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and whole-genome single nucleotide polymorphisms (SNP) to study the population structure of the NZ L. monocytogenes isolates and their relationship with the international strains. The NZ isolates formed unique clusters in PFGE, MLST and whole-genome SNP comparisons compared to the international isolates for which data were available. PFGE identified 31 AscI and 29 ApaI PFGE patterns with indistinguishable pulsotypes being present in seafood, horticultural products and environmental samples. Apart from the Asc0002:Apa0002 pulsotype which was distributed across different sources, other pulsotypes were site or factory associated. Whole-genome analysis of 200 randomly selected L. monocytogenes isolates revealed that lineage II dominated the NZ L. monocytogenes populations. MLST comparison of international and NZ isolates with lineage II accounted for 89% (177 of 200) of the total L. monocytogenes population, while the international representation was 45.3% (1674 of 3473). Rarefaction analysis showed that sequence type richness was greater in NZ isolates compared to international trend, however, it should be noted that NZ isolates predominantly came from seafood, horticulture and their respective processing environments or factories, unlike international isolates where there was a good mixture of clinical, food and environmental isolates.
Topics: Environmental Microbiology; Food Handling; Food Microbiology; Genetic Variation; Genome, Bacterial; Horticulture; Humans; Listeria monocytogenes; New Zealand; Seafood
PubMed: 33838478
DOI: 10.1016/j.ijfoodmicro.2021.109166 -
International Journal of Food... Oct 2021Among pathogens, L. monocytogenes has the capability to persist on Food Processing Environment (FPE), first of all posing safety issues, then economic impact on...
Among pathogens, L. monocytogenes has the capability to persist on Food Processing Environment (FPE), first of all posing safety issues, then economic impact on productivity. The aim of this work was to determine the influence of biofilm forming-ability and molecular features on the persistence of 19 Listeria monocytogenes isolates obtained from FPE, raw and processed products of a cold-smoked salmon processing plant. To verify the phenotypic and genomic correlations among the isolates, different analyses were employed: serotyping, Clonal Complex (CC), core genome Multi-Locus Sequence Typing (cgMLST) and Single Nucleotide Polymorphisms (SNPs) clustering, and evaluation of the presence of virulence- and persistence-associated genes. From our results, the biofilm formation was significantly higher (*P < 0.05) at 37 °C, compared to 30 and 12 °C, suggesting a temperature-dependent behaviour. Moreover, the biofilm-forming ability showed a strain-specific trend, not correlated with CC or with strains persistence. Instead, the presence of internalin (inL), Stress Survival Islet (SSI) and resistance to erythromycin (ermC) genes was correlated with the ability to produce biofilms. Our data demonstrate that the genetic profile influences the adhesion capacity and persistence of L. monocytogenes in food processing plants and could be the result of environmental adaptation in response to the external selective pressure.
Topics: Animals; Biofilms; Food Handling; Food Industry; Food Microbiology; Listeria monocytogenes; Multilocus Sequence Typing; Salmon
PubMed: 34411997
DOI: 10.1016/j.ijfoodmicro.2021.109353