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1.
Food Chem ; 366: 130599, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34298392

RESUMO

Nisin was encapsulated in silica through sol-gel process by acid-catalyzed routes. The silica xerogels were characterized through nitrogen adsorption isotherms, small-angle X-ray scattering (SAXS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy (FTIR). SAXS results showed that the particle diameters in a second level of aggregation varied from 4.78 to 5.86 nm. Zeta potential of silica particles were from -9.6 to -25.3 mV, while the surface area and pore diameters ranged from 216 to 598 m2 g-1 and 2.53 to 2.90 nm, respectively, indicating the formation of mesoporous nanostructures. Nisin retained the antimicrobial activity against all microorganisms tested after encapsulation in silica materials. These novel silica-based structures can be valuable carriers for nisin delivery in food systems.


Assuntos
Bacteriocinas , Nisina , Espalhamento a Baixo Ângulo , Dióxido de Silício , Difração de Raios X
2.
Food Chem ; 369: 130956, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34479016

RESUMO

Biodegradable active packaging was produced by compounding nisin (3, 6 and 9%) and nisin-ethylenediaminetetraacetic acid (EDTA) (3 and 6%) mixtures with poly(butylene adipate terephthalate) and thermoplastic starch blends (PBAT/TPS) by blown-film extrusion. Nisin and EDTA interacted with polymers, involving CO stretching of ester bonds and increased compatibility. This plasticized the films and modified the crystallinity, surface roughness and thermal relaxation behavior. Barrier properties were improved due to modified hydrophilic-hydrophobic properties, compact structures and crystallites that restricted vapor and oxygen permeation. PBAT/TPS films containing EDTA and nisin effectively inhibited lipid degradation in pork tissues corresponding with stabilizing the CO ester bond of triacylglycerol. Microbial growth was also inhibited, particularly in EDTA-containing films up to 1.4 log. Inactivation of microorganisms stabilized redness and delayed meat discoloration, preserving the quality of packaged pork. Interaction between nisin, EDTA and polymers modified the morphology and film properties and functionalized biodegradable food packaging to inactivate microorganisms.


Assuntos
Nisina , Carne de Porco , Ácido Edético , Poliésteres , Amido
3.
An Acad Bras Cienc ; 93(suppl 4): e20210550, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34730626

RESUMO

The aim of this study was to investigate the combined effect of carvacrol, thymol and nisin against Staphylococcus aureus and the combined effect of carvacrol and thymol against Salmonella Enteritidis. Minimum inhibitory concentrations (MIC) of carvacrol, thymol, and nisin for S. aureus were 200, 150 and 30 µg/mL, respectively. MIC of carvacrol and thymol for Salmonella Enteritidis was 200 µg/mL. A factorial method of independent variables was then used to study the combined effect of antimicrobials. Results showed that combinations of carvacrol-thymol-nisin (reduction of 1.2 log CFU/mL for MIC and 4.98 log CFU/mL for 2MIC), carvacrol-thymol (reduction of 1.33 log CFU/mL for 2MIC), nisin-thymol (reduction of 3.52 log CFU/mL for 2MIC) and nisin-carvacrol (reduction of 3.41 log CFU/mL for 2MIC) attained a significant inhibition of S. aureus. Similarly, there was significant reduction of Salmonella Enteritidis due to combined effect of thymol-carvacrol (reduction of 4.5 log CFU/mL for MIC and inhibition below detection limit for 2MIC). Therefore, the combinations of natural antimicrobials described in this work showed potential to be used as an additional barrier for food safety.


Assuntos
Nisina , Timol , Antibacterianos/farmacologia , Cimenos , Testes de Sensibilidade Microbiana , Monoterpenos/farmacologia , Nisina/farmacologia , Salmonella enteritidis , Staphylococcus aureus , Timol/farmacologia
4.
Colloids Surf B Biointerfaces ; 208: 112121, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34600362

RESUMO

Some removable medical devices such as catheters and cardiovascular biomaterials require antiadhesive properties towards both prokaryotic and eukaryotic cells in order to prevent the tissues from infections upon implantation and, from alteration upon removal. In order to inhibit cell adhesion, we developed ultrathin hydrated Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes. In order to confer antibacterial activity to the coatings, we proceeded to the electrostatically-driven immobilization of nisin Z, an antimicrobial peptide (AMP) active against gram-positive bacteria. The nisin-enriched coatings had a significantly increased anti-proliferative impact on fibroblasts, as well as a strong contact-killing activity against Staphylococcus aureus in the short and long term.


Assuntos
Anti-Infecciosos , Nisina , Antibacterianos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Nisina/farmacologia , Staphylococcus aureus
5.
Molecules ; 26(18)2021 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-34577022

RESUMO

Conventional thermal and chemical treatments used in food preservation have come under scrutiny by consumers who demand minimally processed foods free from chemical agents but microbiologically safe. As a result, antimicrobial peptides (AMPs) such as bacteriocins and nisin that are ribosomally synthesised by bacteria, more prominently by the lactic acid bacteria (LAB) have appeared as a potent alternative due to their multiple biological activities. They represent a powerful strategy to prevent the development of spore-forming microorganisms in foods. Unlike thermal methods, they are natural without an adverse impact on food organoleptic and nutritional attributes. AMPs such as nisin and bacteriocins are generally effective in eliminating the vegetative forms of spore-forming bacteria compared to the more resilient spore forms. However, in combination with other non-thermal treatments, such as high pressure, supercritical carbon dioxide, electric pulses, a synergistic effect with AMPs such as nisin exists and has been proven to be effective in the inactivation of microbial spores through the disruption of the spore structure and prevention of spore outgrowth. The control of microbial spores in foods is essential in maintaining food safety and extension of shelf-life. Thus, exploration of the mechanisms of action of AMPs such as nisin is critical for their design and effective application in the food industry. This review harmonises information on the mechanisms of bacteria inactivation from published literature and the utilisation of AMPs in the control of microbial spores in food. It highlights future perspectives in research and application in food processing.


Assuntos
Nisina , Proteínas Citotóxicas Formadoras de Poros , Manipulação de Alimentos , Microbiologia de Alimentos , Conservação de Alimentos , Esporos Bacterianos/efeitos dos fármacos
6.
Food Chem ; 365: 130535, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34256226

RESUMO

Nisin and potassium sorbate as preservatives are used in a broad range of meat. A lipidomic evaluation was performed on Tan sheep meat treated by two types of preservatives. The addition of potassium sorbate resulted in higher lipid losses compared with nisin treatment. Furthermore, 106 significant lipids of 12 lipid classes (PC, PS, LPS, LPC, PE, PI, LPE, TG, Cer, DG, SM, Sph) with variable importance in projection scores greater than 1.0 were detected and qualified to distinguish different preservatives added meat using UHPLC-Q-Orbitrap MS/MS. LOD and LOQ were 0.12-0.32 µg kg-1 and 0.35-0.89 µg kg-1, indicating high sensitivity and excellent analytical characteristics in the study. Nisin was confirmed to be the better preservative for prolonging the shelf life of Tan sheep meat while reducing the loss of nutrients. These results could provide a strong cornerstone for future research on preservatives in meat products.


Assuntos
Nisina , Animais , Cromatografia Líquida de Alta Pressão , Conservantes de Alimentos , Lipídeos/análise , Carne/análise , Valor Nutritivo , Ovinos , Ácido Sórbico , Espectrometria de Massas em Tandem
7.
Colloids Surf B Biointerfaces ; 206: 111965, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34237525

RESUMO

Wound infection is a serious threat to patients, in particular those with septic wound infections, which result in high mortality rates. Moreover, the treatment of wound infections with antimicrobial-resistant and/or biofilm-forming pathogens can be challenging. Nisin, a potent antimicrobial against Gram-positive bacterial pathogens, has been used in the food industry as a preservative for decades. Silver has been approved by the FDA as a topical antimicrobial. Here, we show that silver-nisin nanoparticles (Ag-nisin NP), with an average diameter of 60 nm, can be quickly synthesized with the assistance of a simple microwave. Ag-nisin NP act as bactericidal antibiotics against the tested pathogens. In contrast, resistance was observed in S. aureus and A. baumannii that were treated with silver nitrate alone. In addition, Ag-nisin NP showed potent antibiofilm activity against S. aureus, P. aeruginosa, A. baumannii, K. pneumoniae, and E. coli, which are pathogens occurring in wound infections. Notably, the synthesized Ag-nisin NP showed lower cytotoxicity than silver nitrate to human cells. This formulation provides an alternative and safe measurement for biofilm-infected wound control.


Assuntos
Nanopartículas , Nisina , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Biofilmes , Escherichia coli , Humanos , Staphylococcus aureus
8.
Curr Microbiol ; 78(9): 3430-3438, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34255153

RESUMO

An attempt was made, to characterize natural antibiotics or lantibiotics from unconventional sources and its antibacterial spectrum against food borne pathogens and drug resistant bacteria. Six different traditional fermented foods i.e., fermented fish, fermented soybeans, Soibum (fermented bamboo shoots), milk, idly and dosa batter were used for the isolation of bacteriocin producing Lactic acid bacteria (LAB). Among all bacterial cultures isolated from the various sources, 129 cultures have found to produce antimicrobial compounds. Nisin specific reporter bacteria was utilized as biosensor to identify the Nisin like bacteriocin, where 10 cultures found to be positive Nisin producer. Identified Nisin like bacteriocin was partially concentrated by using ammonium sulphate followed by butanol extraction. Minimum inhibitory concentration (MIC) was analyzed against food borne pathogen and drug resistant bacteria. MIC of partially purified Nisin (pp-Nisin) of all the LAB isolates against food-borne pathogens are ranged between 0.5 and 92 µg/ml respected to various Gram-positive bacteria. Similarly, the drug resistant bacteria were also inhibited by pp-Nisin (MIC ranged between 15 and 175 µg/ml). All samples of ppnisin exhibited auto induction ability. Taxonomic identification of the nisin producers was done by whole genome sequencing which reveals that cultures belongs to Lactococcus lactis ssp. lactis. Also it was found that Lactococcus lactis ssp. lactis C2d and Lactococcus lactis ssp. lactis SP2C4 harbor nisA gene and Lactococcus lactis ssp. lactis FS2 (L. lactis FS2) harbor nisQ gene. The finding of this study highlights the first case of L. lactis FS2 isolated from fermented fish harbor nisQ gene. Antibacterial activity of pp-Nisin against drug resistant LAB is also reported.


Assuntos
Bacteriocinas , Alimentos e Bebidas Fermentados , Lactobacillales , Lactococcus lactis , Nisina , Animais , Bacteriocinas/genética , Fermentação , Lactobacillales/genética , Lactobacillales/metabolismo , Lactococcus lactis/genética , Lactococcus lactis/metabolismo , Nisina/metabolismo
9.
ACS Appl Mater Interfaces ; 13(27): 32058-32066, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34197071

RESUMO

Exploration of novel material platforms to protect biological preservatives and realize intelligent regulation during fermentation is of great significance in industry. Herein, we established an intelligent responsive platform by introducing antimicrobial biomolecules (nisin) into rationally designed covalent organic frameworks (COFs), resulting in a new type of "smart formulation", which could responsively inhibit microbial contamination and ensure the orderly progression of the fermentation process. The encapsulated biomolecules retained their activity while exhibiting enhanced stability and pH-responsive releasing process (100% bacteriostatic efficiency at a pH of 3), which can ingeniously adapt to the environmental variation during the fermentation process and smartly fulfill the regulation needs. Moreover, the nisin@COF composites would not affect the fermentation strains. This study will pave a new avenue for the preparation of highly efficient and intelligent antimicrobial agents for the regulation of the fermentation process and play valuable roles in the drive toward green and sustainable biomanufacturing.


Assuntos
Fermentação/efeitos dos fármacos , Estruturas Metalorgânicas/química , Nisina/química , Nisina/farmacologia , Desenho de Fármacos , Concentração de Íons de Hidrogênio
10.
Food Microbiol ; 99: 103835, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34119119

RESUMO

In this study, we examined the ability of nisin A and a rationally assembled bank of 36 nisin derivative producing Lactococcus lactis strains to inhibit Listeria. A broth-based bioluminescence assay for screening single and combinations of bioengineered nisin derivatives using cell-free supernatants (CFS) from nisin derivative producing strains was developed. In this way, we screened 630 combinations of nisin derivative producing strains, identifying two (CFS from M17Q + N20P and M17Q + S29E) which exhibited enhanced anti-listerial activity when used together compared to when used alone, or to the nisin A producing strain. Minimal inhibitory concentration assays performed with purified peptides revealed than when used singly, the specific activities of M17Q, N20P and S29E (3.75-7.5 µM) against L. innocua were equal to, or less than that of nisin A (MIC of 3.75 µM). Broth-based growth curve assays using purified peptides demonstrated that use of the double peptide combinations and a triple peptide combination (M17Q + N20P + S29E) resulted in an extended lag phase of L. innocua, while kill curve assays confirmed the enhanced bactericidal activity of the combinations in comparison to the single derivative peptides or nisin A. Furthermore, the enhanced activity of the M17Q + N20P combination was maintained in a model food system (frankfurter homogenate) at both chill (4 °C) and abusive (20 °C) temperature conditions, with final cell numbers significantly less (1-2 log10 CFU/ml) than those observed with the derivative peptides alone, or nisin A. To our knowledge, this study is the first investigation that combines bioengineered bacteriocins with the aim of discovering a combination with enhanced antimicrobial activity.


Assuntos
Antibacterianos/metabolismo , Antibacterianos/farmacologia , Lactococcus lactis/metabolismo , Listeria/efeitos dos fármacos , Nisina/metabolismo , Nisina/farmacologia , Antibacterianos/química , Bioengenharia , Lactococcus lactis/genética , Listeria/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Nisina/química , Nisina/genética
11.
Appl Environ Microbiol ; 87(16): e0039121, 2021 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-34105992

RESUMO

Antimicrobial peptides are evolving as novel therapeutic options against the increasing problem of multidrug-resistant microorganisms, and nisin is one such avenue. However, some bacteria possess a specific nisin resistance system (NSR), which cleaves the peptide reducing its bactericidal efficacy. NSR-based resistance was identified in strains of Streptococcus uberis, a ubiquitous pathogen that causes mastitis in dairy cattle. Previous studies have demonstrated that a nisin A derivative termed nisin PV, featuring S29P and I30V, exhibits enhanced resistance to proteolytic cleavage by NSR. Our objective was to investigate the ability of this nisin derivative to eradicate and inhibit biofilms of S. uberis DPC 5344 and S. uberis ATCC 700407 (nsr+) using crystal violet (biomass), 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) (viability) assays, and confocal microscopy (viability and architecture). When preestablished biofilms were assessed, both peptides reduced biofilm biomass by over 60% compared to that of the untreated controls. However, a 42% higher reduction in viability was observed following treatment with nisin PV compared to that of nisin A. Accordingly, confocal microscopy analysis revealed significantly more dead cells on the biofilm upper surface and a reduced thickness following treatment with nisin PV. When biofilm inhibition was assessed, nisin PV inhibited biofilm formation and decreased viability up to 56% and 85% more than nisin A, respectively. Confocal microscopy analysis revealed a lack of biofilm for S. uberis ATCC 700407 and only dead cells for S. uberis DPC 5344. These results suggest that nisin PV is a promising alternative to effectively reduce the biofilm formation of S. uberis strains carrying NSR. IMPORTANCE One of the four most prevalent species of bovine mastitis-causing pathogens is S. uberis. Its ability to form biofilms confers on the bacteria greater resistance to antibiotics, requiring higher doses to be more effective. In a bid to limit antibiotic resistance development, the need for alternative antimicrobials is paramount. Bacteriocins such as nisin represent one such alternative that could alleviate the impact of mastitis caused by S. uberis. However, many strains of S. uberis have been shown to possess nisin resistance determinants, such as the nisin resistance protein (NSR). In this study, we demonstrate the ability of nisin and a nisin derivative termed PV that is insensitive to NSR to prevent and remove biofilms of NSR-producing S. uberis strains. These findings will add new information to the antimicrobial bacteriocins and control of S. uberis research fields specifically in relation to biofilms and nsr+ mastitis-associated strains.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Nisina/química , Nisina/farmacologia , Streptococcus/efeitos dos fármacos , Bioengenharia , Farmacorresistência Bacteriana , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Nisina/genética , Streptococcus/crescimento & desenvolvimento , Streptococcus/fisiologia
12.
J Dairy Sci ; 104(9): 9556-9569, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34147226

RESUMO

ComX can improve bacterial competence by modulating global gene expression. Although competence induction may also be a protective mechanism under stress, this has not been investigated in detail. Here, we demonstrated that ComX improved the acid tolerance and nisin yield of Lactococcus lactis, which is an important gram-positive bacterium increasingly used in modern biotechnological applications. We found that overexpression of comX could improve the survival rate up to 36.5% at pH 4.0, compared with only 5.4% and 1.1% with the wild-type and comX knockout strains, respectively. Moreover, quantitative real-time PCR results indicated that comX overexpression stimulated the expression of late competence genes synergistically with exposure to acid stress. Finally, electrophoretic mobility shift assay demonstrated the binding of purified ComX to the cin-box in the promoters of these genes. Taken together, our results reveal a regulation mechanism by which ComX and acid stress can synergistically modulate the expression of late competence genes to enhance cells' acid tolerance and nisin yield.


Assuntos
Lactococcus lactis , Nisina , Ácidos/metabolismo , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Lactococcus lactis/genética , Lactococcus lactis/metabolismo , Nisina/genética
13.
Acta Trop ; 220: 105945, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33945825

RESUMO

Schistosomiasis continues to pose significant public health problems in many developing countries. Mass drug administration (MDA) is the most adopted control option but there is increasing evidence for the development of praziquantel-resistant Schistosoma strains. This shortcoming has necessitated the search for other effective methods for the control of schistosomiasis. The breaking of Schistosoma transmission cycles through the application of molluscicides into snail infested freshwater bodies has yielded positive outcomes when integrated with MDA in some countries. However, few of such effective molluscicides are currently available, and where available, their application is restricted due to toxicity concerns. Some nanotized particles with molluscicidal activities against the different stages of snail intermediate hosts of schistosomes have been reported. Importantly, the curcumin-nisin nanoparticle synthesized by our group was very effective and it showed no significant toxicity in a mouse model and brine shrimps. This, therefore, offers the possibility of developing a molluscicide that is not only safe for man but also is environmentally friendly. This paper reviews nanoparticles with molluscicidal potential. The methods of their formulation, activities, probable mechanisms of actions, and their toxicity profiles are discussed. More research should be made in this field as it offers great potential for the development of new molluscicides.


Assuntos
Moluscocidas/química , Moluscocidas/farmacologia , Nanopartículas/química , Esquistossomose/transmissão , Caramujos/efeitos dos fármacos , Animais , Curcumina/química , Curcumina/farmacologia , Composição de Medicamentos , Humanos , Camundongos , Nisina/química , Nisina/farmacologia , Esquistossomose/prevenção & controle , Caramujos/fisiologia
14.
Res Microbiol ; 172(4-5): 103836, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34029676

RESUMO

Salmonella enterica is a pathogen that induces self-limiting gastroenteritis and is of worldwide concern. Nisin, an antimicrobial peptide, has emerged as an alternative for the control of microbial growth but its effect on the virulence of pathogenic bacteria is not yet well-explored. This work aimed to evaluate the virulence of S. enterica in the presence of sub-inhibitory nisin using the experimental model Galleria mellonella. Sub-inhibitory concentrations of nisin of 11.72 and 46.88 µM did not affect the cellular viability of S. enterica but promoted changes in gene expression within 1 h of treatment, with increases of up to 3-fold of pagC, 1.8-fold of invA and 2.3-fold of invF. Larvae of G. mellonella inoculated with S. enterica combined with nisin at 46.88 µM presented mortality, and TL50 noticeably increased to 50% and 80% at 24 and 48 h post-infection, respectively. Defence responses, such as melanisation, nodulation, pseudopodia, immune response, and expression of defence proteins of the larvae G. mellonella were enhanced when the treatments with S. enterica were combined with 11.72 or 46.88 µM nisin. These results show an increase in virulence of S. enterica by sub-MIC concentration of nisin that needs to be explored.


Assuntos
Antibacterianos/administração & dosagem , Larva/microbiologia , Mariposas/microbiologia , Nisina/administração & dosagem , Salmonella enterica/efeitos dos fármacos , Animais , Antibacterianos/farmacologia , Nisina/farmacologia , Salmonella enterica/patogenicidade , Virulência
15.
Int J Food Microbiol ; 349: 109227, 2021 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-34022613

RESUMO

The present work mainly investigated the effects of prepared chitosan­sodium alginate-nisin (CS-SA-N) preservatives on the quality and bacterial phase of Penaeus vannamei shrimp during cold storage. Results showed that CS-SA-N preservatives treated samples had the lower pH, total volatile basic nitrogen (TVB-N), total viable count (TVC), and freeness (K) values than those of untreated ones during cold storage. The sensory evaluation results indicated that CS-SA-N preservatives treated shrimps had the higher comprehensive scores than those of untreated ones during whole storage. Microbial community of all samples was dominated by Proteobacteria. The initial predominant bacteria of fresh shrimps were Sphingomonas, Carnobacterium and Psychrobacter. Psychrobacter, Pseudomonas, and Shewanella, Acinetobacter and Vibrio were the predominant bacteria of untreated samples. CS-SA-N preservatives significantly decreased predominant microbial numbers by inhibiting the growth of Psychrobacter, Vibrio, Acinetobacter and Carnobacterium during cold storage. Therefore, the CS-SA-N preservatives could be used to prolong the shelf life of shrimp and guarantee its quality.


Assuntos
Conservantes de Alimentos/farmacologia , Armazenamento de Alimentos/métodos , Microbiota/efeitos dos fármacos , Penaeidae/microbiologia , Alimentos Marinhos/microbiologia , Alginatos/farmacologia , Animais , Bactérias/classificação , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Quitosana/farmacologia , Nisina/farmacologia , Nitrogênio/análise , Alimentos Marinhos/análise
16.
Microbiol Res ; 249: 126772, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33930841

RESUMO

Enterococcus faecalis, a severe nosocomial and community opportunistic pathogen, is difficult to control due to its multidrug resistance. Through heredity and the recombination of intrinsic resistance genes and horizontally acquired resistance genes, E. faecalis can rapidly evolve drug resistance. Nisin, an important antimicrobial peptide, is extensively employed in the healthcare and food industries to inhibit Gram-positive bacteria and may induce the emergence of nisin-resistant bacteria worldwide. However, the mechanism governing nisin resistance in E. faecalis has not been fully elucidated. This study utilizes transposon insertion sequencing (TIS) to comprehensively explore novel genes related to nisin resistance. According to the analysis of TIS results, hundreds of genes appear to be essential for nisin resistance in E. faecalis. The phosphate transport system (OG1RF_10018-10021, named PTS), which is screened by TIS results, enhances the resistance of E. faecalis to nisin, the mechanism of which may be involved in potA and/or OG1RF_10526 (hypothetical gene). Meanwhile, PTS also strongly represses the biosynthesis of ribosomes to increase the sensitivity of E. faecalis to gentamycin. In addition, the overexpression of PTS increases the sensitivity of E. faecalis to daptomycin, the mechanism of which is independent of the LiaFSR system. This study first demonstrated that E. faecalis utilizes PTS to mediate the resistance to multidrug, which may help to elucidate the mechanism governing drug resistance and to establish guidelines for the treatment of infectious diseases caused by E. faecalis.


Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla , Enterococcus faecalis/efeitos dos fármacos , Nisina/farmacologia , Fosfatos/metabolismo , Transporte Biológico , Elementos de DNA Transponíveis , Daptomicina/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Enterococcus faecalis/genética , Enterococcus faecalis/metabolismo , Genes Bacterianos , Ribossomos/metabolismo , Análise de Sequência de DNA , Transcrição Genética
17.
Sci Rep ; 11(1): 7915, 2021 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-33846473

RESUMO

White button mushrooms are greatly high perishable and can deteriorate within a few days after harvesting due to physicomechanical damage, respiration, microbial growth of the delicate epidermal structure. For that reason, the present research work was applied to evaluate the effect of chitosan combination with nano-coating treatments on physicochemical parameters and microbial populations on button mushrooms at chilling storage. Nano coating with the addition of nisin 1% (CHSSN/M) established the minimum value for weight loss 12.18%, maintained firmness 11.55 N, and color index profile. Moreover, O2% rate of (CHSSN/M) mushrooms was the lowest at 1.78%; while the highest rate was reported for CO2 24.88% compared to the untreated samples (Control/M) on day 12. Both pH and total soluble solid concentrations increased during storage. Results reported that the (CHSS/M) mushroom significantly (P < 0.05) reduced polyphenol oxidase activity (24.31 U mg-1 Protein) compared with (Control/M) mushrooms that increased faster than the treated samples. (CHSSN/M) treatment was the most efficient in the reduction of yeast and mold, aerobic plate microorganisms (5.27-5.10 log CFU/g), respectively. The results established that nano-coating film might delay the aging degree and accompany by marked prolongation of postharvest mushroom freshness.


Assuntos
Agaricus/química , Bactérias/metabolismo , Fenômenos Químicos , Nanopartículas/química , Ácidos/análise , Dióxido de Carbono/análise , Catecol Oxidase/metabolismo , Quitosana/química , Cor , Eletrólitos/análise , Nisina/química , Oxigênio/análise , Solubilidade
18.
J Appl Microbiol ; 131(5): 2223-2234, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33876507

RESUMO

AIMS: Increases in antimicrobial resistance have meant that the antimicrobial potential of lantibiotics is now being investigated irrespective of the nature of the producing organism. The aim of this study was to investigate whether natural nisin variants produced by non-Generally Recognized as Safe (GRAS) strains, such as nisin H, nisin J and nisin P, could be expressed in a well-characterized GRAS host. METHODS AND RESULTS: This study involved cloning the nisin A promoter and leader sequence fused to nisin H, nisin J or nisin P structural gene sequences originally produced by Streptococcus hyointestinalis DPC 6484, Staphylococcus capitis APC 2923 and Streptococcus agalactiae DPC 7040, respectively. This resulted in their expression in Lactococcus lactis NZ9800, a genetically modified strain that does not produce nisin A. CONCLUSIONS: Induction of the nisin controlled gene expression system demonstrates that these three nisin variants could be acted on by nisin A machinery provided by the host strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Describes the first successful heterologous production of three natural nisin variants by a GRAS strain, and demonstrates how such systems could be harnessed not only for lantibiotic production but also in the expansion of their structural diversity and development for use as future biotherapeutics.


Assuntos
Bacteriocinas , Lactococcus lactis , Nisina , Antibacterianos/farmacologia , Nisina/genética , Nisina/farmacologia , Staphylococcus/genética , Streptococcus , Streptococcus agalactiae
19.
Toxicon ; 197: 1-5, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-33838179

RESUMO

Staphylococcus aureus is one of the commonest food-borne pathogens that can cause gastroenteritis owing to having several enterotoxins. Also, biofilm formation can complicate infections caused by this microorganism. Nisin is a safe food bio preservative which is usually used as an agent to prevent pathogen growth; however, it is important to identify the exact impact of nisin on the growth of S. aureus and to determine the suitable concentration needed for elimination of this pathogen in food. In this study, after MIC determination of nisin against S. aureus ATCC 29213, this strain was treated with sub-MIC (1/2) of nisin (4 µg/ml) and transcript levels of toxin-encoding (hla, SEA, SEB, and SED) and biofilm-associated (fnb, ebpS, eno, and icaA) genes were determined using Quantitative Real-time PCR at 2, 8, and 24 h post exposure. All toxin genes were down-regulated following exposure to sub-MIC of nisin, whereas biofilm-associated genes were up-regulated. The expression levels of fnb and icaA in S. aureus were highest after 8 h (4.5-fold and 6.8-fold increase, respectively), while the expression levels of eno and ebpS genes were highest after 2 h (3.3 and 4.5-fold increase, respectively). According to these results, although transcriptional levels of toxin genes were reduced, sub-MIC concentrations of nisin could trigger the expression of biofilm-associated genes in S. aureus. This can further lead to bacteriocin tolerance such that even its higher concentrations cannot kill bacterial cells after exposure to sub-lethal doses. Therefore, it is pivotal to add appropriate concentrations of nisin to food products for preservation purposes.


Assuntos
Nisina , Infecções Estafilocócicas , Antibacterianos/farmacologia , Biofilmes , Enterotoxinas , Humanos , Nisina/farmacologia , Staphylococcus aureus
20.
Int J Mol Sci ; 22(7)2021 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-33801752

RESUMO

Bovine mastitis is a significant economic burden for dairy enterprises, responsible for premature culling, prophylactic and therapeutic antibiotic use, reduced milk production and the withholding (and thus wastage) of milk. There is a desire to identify novel antimicrobials that are expressly directed to veterinary applications, do not require a lengthy milk withholding period and that will not have a negative impact on the growth of lactic acid bacteria involved in downstream dairy fermentations. Nisin is the prototypical lantibiotic, a family of highly modified antimicrobial peptides that exhibit potent antimicrobial activity against many Gram-positive microbes, including human and animal pathogens including species of Staphylococcus and Streptococcus. Although not yet utilized in the area of human medicine, nisin is currently applied as the active agent in products designed to prevent bovine mastitis. Over the last decade, we have harnessed bioengineering strategies to boost the specific activity and target spectrum of nisin against several problematic microorganisms. Here, we screen a large bank of engineered nisin derivatives to identify novel derivatives that exhibit improved specific activity against a selection of staphylococci, including mastitis-associated strains, but have unchanged or reduced activity against dairy lactococci. Three such peptides were identified; nisin A M17Q, nisin A T2L and nisin A HTK.


Assuntos
Antibacterianos/farmacologia , Bacteriocinas/farmacologia , Lactococcus/efeitos dos fármacos , Mastite Bovina/microbiologia , Nisina/química , Staphylococcus/efeitos dos fármacos , Animais , Bioengenharia/métodos , Bovinos , Feminino , Testes de Sensibilidade Microbiana , Leite/microbiologia , Peptídeos/química , Engenharia de Proteínas/métodos
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