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1.
Carbohydr Polym ; 227: 115352, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590862

RESUMO

This study explores the influence of functionalization process of cellulosic structure on its mechanical and comfort properties. Chitosan hydrogel has been synthetized and applied on cellulosic fabric to impart pH-sensitivity and antimicrobial behavior. The hydrogel bounded rate onto the surface was enhanced by a previous chemical activation of cotton fabric. Antimicrobial behavior was confirmed by investigation of the antibacterial activities against Escherichia coli, Listeria monocytogene and Staphylococcus aureus bacteria. The pH stimuli-responsiveness behavior was also confirmed and the pH-dependency swelling of the chitosan hydrogel was successfully transformed into cellulosic sites. The resulting fabric was confirmed suitable for medical, surgical and also transdermal therapy applications. Meanwhile, these modifications have unexpectedly altered basic mechanical and comfort properties. It was established that the proposed antimicrobial treatment caused slight decrease in air permeability and made the support thickener. The obtained results revealed also that tensile behavior and the ultimate comfort properties were greatly influenced by the chemical activation.


Assuntos
Antibacterianos/química , Celulose/química , Quitosana/química , Hidrogéis/química , Têxteis , Escherichia coli/crescimento & desenvolvimento , Listeria monocytogenes/crescimento & desenvolvimento , Staphylococcus aureus/crescimento & desenvolvimento , Resistência à Tração
2.
Food Microbiol ; 85: 103282, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31500713

RESUMO

Two biopreservation approaches for fresh lettuce, rocket salad, parsley and spinach were studied. The potential of Pediococcus pentosaceus DT016, as a protective culture, to suppress Listeria monocytogenes in vegetables during storage was evaluated. The pathogen numbers in the vegetables inoculated with P. pentosaceus DT016 were significantly (p < 0.01) lower throughout the storage period and, at the last storage day, a minimum difference of 1.4 log CFU/g was reported when compared with the vegetables without the protective culture. Moreover, by using two levels of L. monocytogenes (about 6 and 4 log CFU/g), it was observed that the antagonist effect of P. pentosaceus was higher for the lower pathogen numbers. The second approach evaluated a pediocin DT016 solution to inactivate and control L. monocytogenes proliferation. The pathogen load was studied after washing with: water, chlorine and the pediocin solution and along storage at 4  °C. Comparing the various washing solutions, the vegetables washed with pediocin presented significantly (p < 0.01) lower pathogen numbers throughout storage, by a minimum of 3.2 and 2.7 log CFU/g, than in vegetables washed with water and chlorine, respectively. The proposed methodologies are promising alternatives to maintain the safety of fresh vegetables during extended storage at refrigeration temperature.


Assuntos
Antibiose , Microbiologia de Alimentos/métodos , Conservação de Alimentos/métodos , Listeria monocytogenes/fisiologia , Verduras/microbiologia , Carga Bacteriana , Cloro/farmacologia , Temperatura Baixa , Qualidade de Produtos para o Consumidor , Manipulação de Alimentos/métodos , Alface/microbiologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Pediocinas/farmacologia , Pediococcus pentosaceus/fisiologia , Petroselinum/microbiologia , Refrigeração , Spinacia oleracea/microbiologia , Água
3.
Int J Food Microbiol ; 313: 108390, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31678818

RESUMO

Growth of L. monocytogenes is among the most important factors affecting the risk of human listeriosis. In ready to eat leafy greens, the use of anti-Listeria treatments represents a good alternative to inhibit growth during storage. Several commercially available antimicrobial agents have been suggested as effective intervention strategies. Among them, phage preparations and bacteriocin-producing strains have shown promising results against L. monocytogenes. In this study, we investigate the efficacy of two commercially available surface treatments, the bacteriophage formulation PhageGuard Listex (Micreos Food Safety B.V., NL) and the bacteriocin-producing culture SafePro® (CHR Hansen, DK) to inactivate L. monocytogenes in fresh-cut curly endive after processing and during storage. Fresh-cut endive was inoculated with a cold-adapted L. monocytogenes cocktail of 6 strains (4.4 ±â€¯0.0 log cfu/g) and treated with the anti-Listeria treatments. The treatments were applied using a spray system at two different places within the processing line, on the conveyor belt and in the centrifuge. A total of 5 different treatments were applied: i) Untreated (CT); ii) PhageGuard Listex on the conveyor belt (Listex_Conveyor); iii) PhageGuard Listex during centrifugation (Listex_Centrifuge); iv) SafePro on the conveyor belt (SafePro_Conveyor); and v) SafePro during centrifugation (SafePro_Centrifuge). Samples were stored 3 days at 5 °C plus 5 days at 8 °C. PhageGuard Listex treatment reduced L. monocytogenes in fresh-cut endive by 2.5 logs, regardless of the place of treatment application (conveyor belt or centrifuge). On the other hand, SafePro only reduced L. monocytogenes by 0.2 and 0.4 logs, at the conveyor belt and centrifuge, respectively. Maximum L. monocytogenes reductions of about 3.5 log units were observed in fresh-cut endive treated with PhageGuard Listex after 3 days of storage. At the end of the shelf life (8 days), the initial trends were maintained and the fresh-cut curly endive treated with PhageGuard Listex showed the lowest L. monocytogenes concentration. However, by the end of the shelf-life, L. monocytogenes showed higher levels (1.3-fold) than immediately after the application of the treatment. One hypothesis could be that L. monocytogenes cells, which were able to survive the anti-Listeria treatments, were also able to proliferate under the specific storage conditions. Based on the obtained results, PhageGuard Listex seems to be a promising decontamination agent for leafy greens aiming to reduce growth of the bacteria but further work is needed.


Assuntos
Conservação de Alimentos/métodos , Listeria monocytogenes/crescimento & desenvolvimento , Verduras/microbiologia , Bacteriocinas/metabolismo , Bacteriófagos/fisiologia , Contagem de Colônia Microbiana , Microbiologia de Alimentos , Conservação de Alimentos/instrumentação , Inocuidade dos Alimentos , Humanos , Listeria monocytogenes/metabolismo , Listeria monocytogenes/virologia , Projetos Piloto , Folhas de Planta/microbiologia , Temperatura Ambiente
4.
Food Microbiol ; 86: 103335, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703853

RESUMO

The presence of eight common structural enterocin genes, singly or in varying combinations, in the genome of 15 antagonistic Enterococcus spp. previously isolated from artisan Greek Graviera and Galotyri retail cheeses was tested and associated with the mode of enterocin (Ent+) antilisterial activity of each isolate in three liquid culture media. The isolates were assigned to nine distinct strain genotypes of E. faecium (4 strains), E. durans (2) and E. faecalis (3). All strains were non-hemolytic, except for a cyl-positive E. faecalis genotype isolated from Galotyri cheese, which was strongly listericidal. All other strains varied from being listeriostatic to weakly listericidal in MRS and M17 broth, whereas all failed to inhibit listerial growth in skim milk. Two E. faecium strains retained strong Ent+ activity following neutralization and filter-sterilization of their MRS or M17 co-culture supernatants, whereas, all others required contact or proximity of their viable cells with L. monocytogenes cells in order to display activity. Additional studies to evaluate safety and potential synergistic effects of each strain genotype with starter LAB species in real milk environments will reveal the most active and truly harmless Enterococcus genotypes to be applied as co-starter or bioprotective adjunct cultures in traditional Greek cheese technologies.


Assuntos
Queijo/microbiologia , Enterococcus/química , Listeria monocytogenes/efeitos dos fármacos , Leite/microbiologia , Animais , Hidrocarbonetos Aromáticos com Pontes/química , Hidrocarbonetos Aromáticos com Pontes/metabolismo , Hidrocarbonetos Aromáticos com Pontes/farmacologia , Bovinos , Meios de Cultura/química , Meios de Cultura/metabolismo , Enterococcus/genética , Enterococcus/isolamento & purificação , Enterococcus/metabolismo , Grécia , Listeria monocytogenes/crescimento & desenvolvimento
5.
Food Microbiol ; 86: 103357, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703857

RESUMO

We investigated combinations of gaseous essential oils (EO gases) for their synergistic inhibitory activities against Listeria monocytogenes on a laboratory medium and radish sprouts. The minimum inhibitory concentrations and minimum lethal concentrations of oregano, thyme thymol, and cinnamon bark EO gases against L. monocytogenes were 0.0781 µL/mL on nutrient agar supplemented with glucose and bromocresol purple (NGBA). A checkerboard assay showed that combinations of oregano and thyme thymol EO gases and of oregano and cinnamon bark EO gases exert the strongest synergistic antilisterial activity (fractional inhibitory concentration index [FICI] = 0.3750). A combination of thyme thymol and cinnamon bark EO gases also had a synergistic effect (FICI = 0.5000) on L. monocytogenes on NGBA. Combinations of oregano and thyme thymol EO gases were tested for synergistic antimicrobial activity against L. monocytogenes on radish sprouts. A combination of these gases, each at 0.313 µL/mL, caused a significant (P ≤ 0.05) reduction in the number of L. monocytogenes on radish sprouts compared with reductions caused by treatment with oregano or thyme thymol EO gas alone at the same concentration. Our findings provide information that will be useful when developing antimicrobial applications using EO gases to control L. monocytogenes in the food industry.


Assuntos
Antibacterianos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Óleos Voláteis/farmacologia , Origanum/química , Raphanus/microbiologia , Timol/farmacologia , Thymus (Planta)/química , Antibacterianos/química , Cinnamomum zeylanicum/química , Meios de Cultura/química , Meios de Cultura/metabolismo , Sinergismo Farmacológico , Gases/farmacologia , Listeria monocytogenes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Óleos Voláteis/química , Óleos Vegetais/química , Óleos Vegetais/farmacologia , Raphanus/crescimento & desenvolvimento , Timol/química
6.
Food Microbiol ; 86: 103310, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703859

RESUMO

The objective of this study was to develop a qPCR method for specific enumeration of viable Listeria monocytogenes in food processing facilities and heat treated products. Primers specific for L. monocytogenes were designed to amplify a short (199 bp) or long (1561 bp) fragment of the listeriolysin (hly) gene. The short- and long-amplicon qPCR methods with and without propidium monoazide (PMA) treatment of the cells were tested for their ability to discriminate between viable (no heat) and heat-killed cells (90 °C, 10 min). The PMA-qPCR methods were subsequently used to assess the survival of L. monocytogenes during desiccation (33% RH, 15 °C) on stainless steel surfaces for ten days with and without prior biofilm formation. The long-amplicon qPCR method had a limit of quantification (LOQ) of 1.32 log CFU/reaction (efficiency 92%, R2 = 0.991), while the LOQ for the short-amplicon qPCR method was 1.44 log CFU/reaction (efficiency 102%, R2 = 0.991). PMA was essential for detection of viable cells, and the long-amplicon PMA-qPCR significantly (p < 0.05) reduced the signal from heat-killed cells compared to the short-amplicon method. L. monocytogenes survival during desiccation without biofilm formation was accurately enumerated with the long-amplicon PMA-qPCR method. However, when L. monocytogenes had formed biofilm prior to desiccation, the long-amplicon PMA-qPCR accurately measured the log fold inactivation but underestimated the number of viable cells even with use of an optimized DNA extraction method. This long-amplicon PMA-qPCR method can aid in the detection and enumeration of viable L. monocytogenes cells to further the understanding of its survival and persistence in food processing facilities. The developed method was demonstrated to work on both heat and desiccation treated cells and highlights the importance of amplicon size in viability-qPCR.


Assuntos
Antibacterianos/farmacologia , Azidas/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Propídio/análogos & derivados , Reação em Cadeia da Polimerase em Tempo Real/métodos , Primers do DNA/genética , DNA Bacteriano/genética , Dessecação , Temperatura Alta , Listeria monocytogenes/química , Listeria monocytogenes/genética , Viabilidade Microbiana/efeitos dos fármacos , Propídio/farmacologia
7.
Food Microbiol ; 86: 103312, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703872

RESUMO

Some Listeria monocytogenes strains are persistent in food processing environments, where this pathogen may be subjected to various stresses. This study aimed to elucidate the response of persistent strains of L. monocytogenes to low pH and H2O2 exposure. Almost all of the persistent strains examined were highly susceptible to low pH, whereas H2O2 susceptibility was comparable to that of control strains. Two persistent strains isolated from the same sample, however, exhibited lower susceptibility to low pH. These findings suggest an acid-susceptible phenotype predominates in the habitat, indicating that environmental conditions contribute to the establishment of persistence. Representative strains exhibiting acid-susceptible and less acid-susceptible phenotypes were further investigated regarding acid response characteristics. Less acid-susceptible strains exhibited increased survival in acidified brain heart infusion (BHI) broth compared with acidified phosphate-buffered saline (PBS). These strains also exhibited increased survival in acidified PBS containing glucose and glutamate, which are involved in acid response mechanisms, compared with acidified PBS alone. However, neither acidified BHI broth nor exogenous glucose and glutamate increased survival of acid-susceptible strains. An adaptive acid tolerance response of the acid-susceptible phenotype was observed, but this was limited compared with that of the less acid-susceptible phenotype.


Assuntos
Ácidos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Contagem de Colônia Microbiana , Meios de Cultura/química , Meios de Cultura/metabolismo , Microbiologia de Alimentos , Peróxido de Hidrogênio/farmacologia , Concentração de Íons de Hidrogênio , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo
8.
Food Microbiol ; 86: 103315, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703881

RESUMO

Non-thermal food processing and replacement of chemical additives by natural antimicrobials are promising trends in the food industry. The objective of the present work was to evaluate the effect of a process which combines mild high hydrostatic pressure - HHP (200 and 300 MPa, 5 min, 10 °C), phage Listex™ P100 and the bacteriocin pediocin PA-1 as a new non-thermal process for destruction of Listeria monocytogenes (104 CFU mL-1 or 107 CFU mL-1) in milk. For inoculum levels of 104 CFU mL-1, HHP combined with phage P100 eliminated L. monocytogenes immediately after pressurization. When L. monocytogenes was inoculated at levels of 107 CFU mL-1, a synergistic effect between phage P100, pediocin PA-1 and HHP (300 MPa) on the inactivation of L. monocytogenes was observed during storage of milk at 4 °C. For non-pressure treated samples inoculated with phage or pediocin or both, L. monocytogenes counts decreased immediately after biocontrol application, but regrowth was observed in a few samples during storage. Phage particles were stable during refrigerated storage for seven days while pediocin PA-1 remained stable only during three days. Further studies will have to be performed to validate the findings of this work in specific applications (e.g. production of raw milk cheese).


Assuntos
Bacteriófagos/fisiologia , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/virologia , Leite/microbiologia , Pediocinas/farmacologia , Animais , Bovinos , Contagem de Colônia Microbiana , Conservação de Alimentos/instrumentação , Pressão Hidrostática , Listeria monocytogenes/química , Listeria monocytogenes/crescimento & desenvolvimento
9.
Infect Immun ; 88(1)2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31685546

RESUMO

Listeria monocytogenes, a Gram-positive, facultative intracellular pathogen, survives and replicates in the cytosol of host cells. Synthesis of 1,4-dihydroxy-2-naphthoate (DHNA), an intermediate of menaquinone biosynthesis, is essential for cytosolic survival of L. monocytogenes independent from its role in respiration. Here, we demonstrate that DHNA is essential for virulence in a murine model of listeriosis due to both respiration-dependent and -independent functions. In addition, DHNA can be both secreted and utilized as an extracellular shared metabolite to promote cytosolic survival inside host macrophages. To understand the role(s) of DHNA in L. monocytogenes intracellular survival and virulence, we isolated DHNA-deficient (ΔmenD strain) suppressor mutants that formed plaques in monolayers of fibroblasts. Five ΔmenD suppressor (mds) mutants additionally rescued at least 50% of the cytosolic survival defect of the parent ΔmenD mutant. Whole-genome sequencing revealed that four of the five suppressor mutants had independent missense mutations in a putative transcriptional regulator, ytoI (lmo1576). Clean deletion and complementation in trans confirmed that loss of ytoI could restore plaquing and cytosolic survival of DHNA-deficient L. monocytogenes RNA-seq transcriptome analysis revealed five genes (lmo0944, lmo1575, lmo1577, lmo2005, and lmo2006) expressed at a higher level in the ΔytoI strain than in the wild-type strain, whereas two genes (lmo1917 and lmo2103) demonstrated lower expression in the ΔytoI mutant. Intriguingly, the majority of these genes are involved in controlling pyruvate flux. Metabolic analysis confirmed that acetoin, acetate, and lactate flux were altered in a ΔytoI mutant, suggesting a critical role for regulating these metabolic programs. In conclusion, we have demonstrated that, similar to findings in select other bacteria, DHNA can act as a shared resource, and it is essential for cytosolic survival and virulence of L. monocytogenes Furthermore, we have identified a novel transcriptional regulator in L. monocytogenes and determined that its metabolic regulation is implicated in cytosolic survival of L. monocytogenes.


Assuntos
Listeria monocytogenes/metabolismo , Listeriose/microbiologia , Proteínas Mutantes/metabolismo , Naftóis/metabolismo , Supressão Genética , Fatores de Transcrição/metabolismo , Animais , Citosol/química , Modelos Animais de Doenças , Listeria monocytogenes/genética , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/patogenicidade , Camundongos , Viabilidade Microbiana , Proteínas Mutantes/genética , Fatores de Transcrição/genética , Virulência , Vitamina K 2/análise , Sequenciamento Completo do Genoma
10.
J Agric Food Chem ; 67(38): 10774-10781, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31479258

RESUMO

The released milk N-glycome has been found to possess antipathogenic activity. Natively, they are covalently linked onto proteins. Whether the conjugated N-glycans still have antipathogenic properties and how the glycosylation influences the antipathogenic activity of proteins remain unclear. Herein, we compared the quantitative differences of milk protein N-glycosylation and the antilisterial differences of native milk proteins, released N-glycan pools, and deglycosylated proteins between human and bovine milk. N-glycosylation exhibited to be quantitatively species-specific. The entire growth inhibitory activity and the majority of the antiadhesive activity against Listeria monocytogenes of milk whey proteins, although not as high as the released N-glycans, are attributed to N-glycosylation. Moreover, all N-glycan-bearing samples from human milk showed better growth inhibitory activities than those from bovine milk. Generally, N-glycosylation significantly contributes to the antilisterial function of milk proteins and to the functional differences between species. This gives novel insights into the role of these glycoconjugates in nature.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Proteínas do Leite/química , Proteínas do Leite/farmacologia , Leite Humano/química , Animais , Aderência Bacteriana/efeitos dos fármacos , Células CACO-2 , Bovinos , Glicosilação , Humanos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/fisiologia , Polissacarídeos/química , Especificidade da Espécie
11.
J Dairy Sci ; 102(11): 9674-9688, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31477293

RESUMO

Listeria monocytogenes can survive and grow in a variety of environments, including refrigeration, making it difficult to control and highlighting the importance of optimizing control strategies against this pathogen. Listeria phages are attractive biocontrol agents because phages bind to specific wall teichoic acids (WTA) on the bacterial cell wall, inhibiting pathogens without disrupting the normal microbiota or structure of the food. Common stresses found on dairy products can affect cell wall composition and structure and subsequently affect the efficiency of control strategies that target the cell wall. The goal of this study was to determine the effect of a range of pH and temperatures on the effectiveness of a commercial phage cocktail treatment against several strains of L. monocytogenes in a cheese matrix. We developed a laboratory-scale cheese model that was made at different pH, treated with phage, and then inoculated with L. monocytogenes. Cheeses were incubated at 6, 14, or 22°C for 14 d, and bacterial counts were determined on d 1, 7, and 14. Our data show that phage treatment has a limited ability to reduce L. monocytogenes counts at each temperature tested; however, it was more effective on specific strains of L. monocytogenes when cheese was stored at higher temperatures. More specifically, the average counts of L. monocytogenes on phage-treated cheese stored at 22°C were significantly lower than those on phage-treated cheese stored at 6 or 14°C. Similarly, phage treatment was significantly more effective at inhibiting L. monocytogenes on cheese made at higher pH (6 and 6.5) compared with counts on cheese made at pH 5.5, where L. monocytogenes did not grow. Furthermore, serotype was found to affect the susceptibility of L. monocytogenes to phage treatment; serotype 1/2 strains showed significantly higher susceptibility to phage treatment than serotype 4b strains. Overall, our results suggest the importance of considering the efficacy of phage under conditions (i.e., temperature and pH) specific to a given food matrix when applying interventions against this important foodborne pathogen.


Assuntos
Bacteriófagos , Queijo/microbiologia , Microbiologia de Alimentos , Listeria monocytogenes/virologia , Animais , Carga Bacteriana , Humanos , Concentração de Íons de Hidrogênio , Análise dos Mínimos Quadrados , Listeria monocytogenes/classificação , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Sorogrupo , Temperatura Ambiente , Fatores de Tempo
12.
J Dairy Sci ; 102(10): 8721-8733, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31400901

RESUMO

Bloomy rind cheeses, including Brie, Camembert, and related varieties, are at high risk of contamination by environmental pathogens during manufacture and ripening. This risk is particularly high during ripening due to open-air exposure of the product. Currently, no kill step is applied after manufacture or post ripening to control food safety risks associated with Listeria monocytogenes contamination. Instead, cheesemakers must rely on sanitation and environmental monitoring to reduce this risk. High-pressure processing (HPP) is a nonthermal food-processing technology that can effectively reduce bacterial contaminants with minimal impact on the organoleptic properties of various foods. The objective of this study was to evaluate HPP as a potential intervention to maintain Camembert cheese quality and reduce risk associated with L. monocytogenes. Timing of HPP treatments (3, 11, and 45 d after manufacture) was based on the growth of L. monocytogenes during Camembert cheese ripening. High-pressure processing treatment of fully ripened cheeses (45 d) resulted in destruction of the surface mold, which caused browning and yellowing of the cheese rind. Applying HPP treatment earlier in the ripening process (11 d) resulted in a similar degradation of cheese appearance, which did not improve with continued ripening. Applying HPP treatment shortly after production (3 d; before the surface flora developed) delayed the development of the cheese rind and the textural ripening of the cheese. This early treatment time also resulted in free whey being expelled from the cheese, creating a firmer body. Applying HPP 11 d after manufacture resulted in >5 log reduction of L. monocytogenes at 450 and 550 MPa with holding times of 10 min. Although HPP was effective at reducing L. monocytogenes associated with bloomy rind cheeses, the quality deterioration would be unacceptable to consumers. Cheesemakers must continue to emphasize sanitation and environmental monitoring to reduce the risk of L. monocytogenes in bloomy rind cheeses.


Assuntos
Queijo , Manipulação de Alimentos/métodos , Qualidade dos Alimentos , Animais , Bovinos , Queijo/microbiologia , Microbiologia de Alimentos , Inocuidade dos Alimentos , Fungos/isolamento & purificação , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/isolamento & purificação , Pressão
13.
J Appl Microbiol ; 127(5): 1391-1402, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31386785

RESUMO

AIMS: This work aimed to evaluate the antimicrobial activity of pure (ZnO) and doped (ZnMgO) zinc oxide (ZnO) nanoparticles on bacterial pathogens and Saccharomyces cerevisiae to confirm their applicability as an alternative to antibiotics and to estimate their biocompatibility. METHODS AND RESULTS: Microbial growth inhibition on agar plates, microbial viability and adaptation tests in broth with ZnO nanoparticles, spore germination, random amplified polymorphic DNA and SDS-PAGE analysis were conducted to evaluate the effects of ZnO nanoparticles on cell morphology, viability, DNA damage and protein production. For this purpose, Escherichia coli, Salmonella, Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis and S. cerevisiae were studied after the addition of ZnO nanoparticles to the growth media. The contact with ZnO nanoparticles produced changes in morphology, shape, viability, DNA arrangement (DNA fingerprints) and protein content (SDS-PAGE) in treated cells. CONCLUSIONS: As reported in this study, ZnO nanoparticles have an antimicrobial effect on both prokaryotic and eukaryotic cells. Before using ZnO nanoparticles as antimicrobial agents, it is important to evaluate the target because their effect depends on their composition, size and dose. SIGNIFICANCE AND IMPACT OF THE STUDY: We believe that the results obtained can help to optimize manufactured metal oxide nanoparticles in terms of their composition, size and working concentration. The parameters obtained directly define the applicability and biocompatibility of ZnO nanoparticles and thus are essential for any utilization in food, medicine and industry where pathogen control is crucial.


Assuntos
Anti-Infecciosos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Nanopartículas/toxicidade , Saccharomyces cerevisiae/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Óxido de Zinco/farmacologia , Anti-Infecciosos/química , Bacillus subtilis/crescimento & desenvolvimento , Escherichia coli/crescimento & desenvolvimento , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Nanopartículas/química , Saccharomyces cerevisiae/crescimento & desenvolvimento , Staphylococcus aureus/crescimento & desenvolvimento , Óxido de Zinco/química
14.
J Microbiol Biotechnol ; 29(8): 1240-1247, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31370118

RESUMO

This study was conducted to examine the inactivation effect of the combined treatment of high hydrostatic pressure (HHP; 400 MPa for 1, 3, and 5 min) and cationic surfactant washing (0.05% benzethonium chloride, BEC) against Listeria monocytogenes inoculated on fresh-cut broccoli (FCB). Washing with BEC at concentrations exceeding 0.05% resulted in 2.3 logreduction of L. monocytogenes counts on FCB, whereas HHP treatment had approximately 5.5- 5.6 log-reductions regardless of the treatment time. Scanning electron microscopy corroborated microbial enumeration, revealing that the combined treatment was more effective in removing L. monocytogenes from FCB than individual treatment with HHP or BEC. Color and total glucosinolate content were maintained after the combined treatment, although the hardness of the FCB slightly decreased. The results clearly suggest that the combined treatment of HHP and BEC washing has potential value as a new sanitization method to improve the microbial safety of FCB.


Assuntos
Brassica/microbiologia , Conservação de Alimentos/métodos , Listeria monocytogenes/efeitos dos fármacos , Tensoativos/farmacologia , Benzetônio/farmacologia , Contagem de Colônia Microbiana , Cor , Contaminação de Alimentos/prevenção & controle , Microbiologia de Alimentos , Qualidade dos Alimentos , Inocuidade dos Alimentos , Pressão Hidrostática , Listeria monocytogenes/crescimento & desenvolvimento
15.
Lett Appl Microbiol ; 69(4): 252-257, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31429475

RESUMO

Alfalfa sprouts have been implicated in multiple foodborne disease outbreaks. This study evaluated the growth of Listeria monocytogenes during sprouting of alfalfa seeds and the effectiveness of daily chlorine dioxide & ozone rinsing in controlling the growth. Alfalfa seeds inoculated with L. monocytogenes were sprouted for 5 days (25°C) with a daily aqueous ClO2 (3 ppm, 10 min) or ozone water (2 ppm, 5 min) rinse. Neither treatment significantly reduced the growth of L. monocytogenes on sprouting alfalfa seeds. The initial level of L. monocytogenes was 3·44 ± 0·27, which increased to c. 7·0 log CFU per g following 3 days of sprouting. There was no significant difference in the bacterial population between the treatment schemes. Bacterial distribution in roots (7·63 ± 0·511 log CFU per g), stems (7·51 ± 0·511 log CFU per g) and leaves (7·41 ± 0·511 log CFU per g) were similar after 5 days. Spent sanitizers had significantly lower levels of bacterial populations compared to the spent distilled water control. The results indicated that sprouting process provides a favourable condition for the growth of L. monocytogenes and the sanitizer treatment alone may not be able to reduce food safety risks. SIGNIFICANCE AND IMPACT OF THE STUDY: Sprouts are high-risk foods. Consumption of raw sprouts is frequently associated with foodborne disease outbreaks. Optimum sprouting procedure involves soaking seeds in water followed by daily water rinsing to maintain a moist environment that is also favourable for the growth of pathogenic micro-organisms. The present study emphasized the potential food safety risks during sprouting and the effect of applying daily sanitizer rinsing in the place of water rinsing to reduce those risks. The finding of this study may be useful in the development of pre-harvest and post-harvest risk management strategies.


Assuntos
Compostos Clorados/farmacologia , Doenças Transmitidas por Alimentos/prevenção & controle , Listeria monocytogenes/crescimento & desenvolvimento , Medicago sativa/microbiologia , Óxidos/farmacologia , Água/farmacologia , Contagem de Colônia Microbiana , Microbiologia de Alimentos/métodos , Inocuidade dos Alimentos/métodos , Ozônio/farmacologia , Raízes de Plantas/microbiologia , Sementes/microbiologia , Verduras/microbiologia , Água/química
16.
Molecules ; 24(16)2019 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-31426583

RESUMO

The principle of animal wellbeing, which states that animals should be free from pain, injury, and disease, is difficult to maintain, because microorganisms are most frequently found to be resistant or multi-resistant to drugs. The secondary metabolites of plants are an alternative for the treatment of these microorganisms. The aim of this work was to determine the antibacterial effect of Salix babylonica L. hydroalcoholic extract (SBHE) against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes, and identify the compounds associated with the activity. The SBHE showed activity against the three strains, and was subjected to a bipartition, obtaining aqueous fraction (ASB) with moderate activity and organic fraction (ACSB) with good activity against the three strains. The chromatographic separation of ACSB, allowed us to obtain ten fractions (F1AC to F10AC), and only three showed activity (F7AC, F8AC and F10AC). In F7AC, five compounds were identified preliminary by GC-MS, in F8AC and F10AC were identified luteolin (1) and luteolin 7-O-glucoside (2) by HPLC, respectively. The best antibacterial activity was obtained with F7AC (Listeria monocytogenes; MIC: 0.78 mg/mL, MBC: 0.78 mg/mL) and F8AC (Staphylococcus aureus; MIC: 0.39 mg/mL; MBC: 0.78 mg/mL). The results indicated that the compounds obtained from SBHE can be used as an alternative treatment against these microorganisms and, by this mechanism, contribute to animal and human health.


Assuntos
Antibacterianos/química , Flavonoides/química , Luteolina/química , Salix/química , Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Cromatografia Líquida de Alta Pressão , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Etanol/química , Flavonoides/isolamento & purificação , Flavonoides/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Luteolina/isolamento & purificação , Luteolina/farmacologia , Testes de Sensibilidade Microbiana , Extratos Vegetais/química , Solventes/química , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Água/química
17.
Food Microbiol ; 84: 103255, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421751

RESUMO

The aim of this study was to develop and validate a growth and growth boundary model with terms for melting salts to predict growth of Listeria monocytogenes in spreadable processed cheese. Cardinal parameter terms for phosphate salts and citric acid were developed in broth studies and used to expand an available growth and growth boundary model. The expanded model includes the effect of nine environmental factors (temperature, pH, aw, lactic acid, acetic acid, citric acid, orthophosphate, di-phosphate and tri-phosphate). To generate growth data for model evaluation challenge tests with inoculated commercial (n = 10) and customized (n = 10) spreadable processed cheeses were performed. Evaluation of the new model by comparison of observed and predicted µmax-values resulted in a bias factor of 1.12 and an accuracy factor of 1.33 (n = 42). Prediction of growth and no-growth responses in processed cheese (n = 60) were 89% correct with 11% fail-safe and 0% fail-dangerous predictions. The developed model can be used to support product development, reformulation or risk assessment for spreadable processed cheese.


Assuntos
Queijo/microbiologia , Microbiologia de Alimentos/métodos , Listeria monocytogenes/crescimento & desenvolvimento , Sais/farmacologia , Ácido Acético/farmacologia , Ácido Cítrico/farmacologia , Contagem de Colônia Microbiana , Concentração de Íons de Hidrogênio , Ácido Láctico/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Modelos Biológicos , Sais/química , Temperatura Ambiente
18.
Food Microbiol ; 84: 103267, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421789

RESUMO

The development of more accurate predictive models that describe the microbial kinetics of mild thermal treatments of foods requires knowledge concerning the influence of food microstructure and initial cell conditions on foodborne pathogens' inactivation kinetics. The effect of food microstructure and initial cell conditions on thermal inactivation kinetics and sublethal injury (SI) of Listeria monocytogenes was investigated at 59, 64 and 69°C. Fish-based food model systems with different microstructures, possessing minimal compositional and physicochemical variations, were used. L. monocytogenes growth morphology had no significant influence on thermal inactivation kinetics. A gelled matrix resulted in a lower specific inactivation rate kmax and a higher residual cell population Nres, while the presence of fat droplets resulted in a higherkmaxand did not influenceNres. SI was higher in viscous than in gelled systems and more prominent for cells that were grown inside the matrix. Hence, predictive thermal inactivation models could benefit from the inclusion of factors related to the nature of the food matrix and fat properties. Starting inactivation from cells that were grown inside the matrix, resulted in lower (i.e., fail-safe)kmaxvalues and more uncertainty onNres as compared to starting from cells grown at optimal conditions.


Assuntos
Peixes/microbiologia , Microbiologia de Alimentos/métodos , Conservação de Alimentos , Listeria monocytogenes/fisiologia , Viabilidade Microbiana , Temperatura Ambiente , Animais , Contagem de Colônia Microbiana , Contaminação de Alimentos/prevenção & controle , Manipulação de Alimentos , Cinética , Listeria monocytogenes/crescimento & desenvolvimento , Modelos Biológicos , Alimentos Marinhos/microbiologia
19.
Int J Food Microbiol ; 306: 108272, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31376617

RESUMO

In this study, zein coatings containing Lauroyl-l-arginine ethyl ester monohydrochloride (LAE) were developed to be applied on polypropylene films and manufacture an active food packaging. The concentration of LAE and the addition of a suitable plasticizer (glycerol or oleic acid (OA)) were the main variables considered. Active plasticized zein films, with glycerol or oleic acid were characterized in terms of release kinetics, mechanical, barrier, optical, and antimicrobial properties. Results showed that active agent concentration, (5 and 10%), had no-significant effect on mechanical and WVP properties of the plasticized films. Films plasticized with OA presented greater water resistance, UV-light opacity, and water barrier properties than glycerol-plasticized films. On the contrary, the latter had better antimicrobial properties. The analysis of LAE release kinetics from films to different food simulants revealed different behaviours, depending on both film formulation and food simulant. Despite the lower water resistance of coatings containing glycerol, bags based on polypropylene/glycerol plasticized zein containing 10% of LAE presented a great antimicrobial activity in tests with chicken soup (real food system) contaminated with pathogen bacteria, concretely, the films showed 3.21 Log reduction against Listeria monocytogenes and 3.07 log reductions against Escherichia coli. These results suggest a promising strategy on the use of LAE-containing zein in active food packaging to control foodborne pathogens.


Assuntos
Antibacterianos/farmacologia , Arginina/análogos & derivados , Escherichia coli/crescimento & desenvolvimento , Embalagem de Alimentos/métodos , Listeria monocytogenes/crescimento & desenvolvimento , Zeína/farmacologia , Animais , Arginina/farmacologia , Galinhas , Escherichia coli/efeitos dos fármacos , Listeria monocytogenes/efeitos dos fármacos , Água
20.
J Med Microbiol ; 68(9): 1359-1366, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31364964

RESUMO

Methodology. Biochemical and molecular methods were used to identify 100 lactobacilli isolated from rectal swabs. Among these, L. paracasei ssp. paracasei LP5 and L. brevis LP9 showed significant antibacterial activity against S. agalactiae and L. monocytogenes. Accordingly, characterization of their bacteriocins, BacLP5 and BacLP9, was conducted to obtain information on their kinetic production, sensitivity to chemico-physical parameters and molecular weight. To investigate the possible use of the two Lactobacillus strains as probiotics, their gastrointestinal resistance, cellular adhesiveness and sensitivity to antibiotics were also studied.Results. The obtained data show that BacLP5 and BacLP9 most likely belong to class II bacteriocins and both have a molecular weight of approximately 3 kDa. The production of BacLP5 and BacLP9 started after 4 h (40 and 80 AU ml-1), respectively. Both of the Lactobacillus strains survived gastric and intestinal juices well and showed adhesive capability on HEp-2 cells.Conclusion. Due to their peculiar antimicrobial characteristics, L. paracasei ssp. paracasei LP5 and L. brevis LP9 are suitable for use in the treatment of vaginal disorders, through both oral and transvaginal administration.


Assuntos
Antibacterianos/metabolismo , Bacteriocinas/metabolismo , Lactobacillus brevis/metabolismo , Lactobacillus paracasei/metabolismo , Antibacterianos/química , Antibacterianos/isolamento & purificação , Aderência Bacteriana , Bacteriocinas/química , Bacteriocinas/isolamento & purificação , Ácidos e Sais Biliares/farmacologia , Linhagem Celular , Fenômenos Químicos , Suco Gástrico/metabolismo , Humanos , Lactobacillus brevis/classificação , Lactobacillus brevis/isolamento & purificação , Lactobacillus paracasei/classificação , Lactobacillus paracasei/isolamento & purificação , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Peso Molecular , Probióticos , Reto/microbiologia , Streptococcus agalactiae/efeitos dos fármacos , Streptococcus agalactiae/crescimento & desenvolvimento
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