The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity.

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

Acid-Heat-Induced Fabrication of Nisin-Loaded Egg White Protein Nanoparticles: Enhanced Structural and Antibacterial Stability.

As a natural cationic peptide, Nisin is capable of widely inhibiting the growth of Gram-positive bacteria. However, it also has drawbacks such as its antimicrobial activity being susceptible to environmental factors. Nano-encapsulation can improve the defects of nisin in food applications. In this study, nisin-loaded egg white protein nanoparticles (AH-NEn) were prepared in fixed ultrasound-mediated under pH 3.0 and 90 °C. Compared with the controls, AH-NEn exhibited smaller particle size (112.5 ± 2.85 nm), smaller PDI (0.25 ± 0.01), larger Zeta potential (24 ± 1.18 mV), and higher encapsulation efficiency (91.82%) and loading capacity (45.91%). The turbidity and Fourier transform infrared spectroscopy (FTIR) results indicated that there are other non-covalent bonding interactions between the molecules of AH-NEn besides the electrostatic forces, which accounts for the fact that it is structurally more stable than the controls. In addition, by the results of fluorescence intensity, differential scanning calorimetry (DSC), and X-ray diffraction (XRD), it was shown that thermal induction could improve the solubility, heat resistance, and encapsulation of nisin in the samples. In terms of antimicrobial function, acid-heat induction did not recede the antimicrobial activity of nisin encapsulated in egg white protein (EWP). Compared with free nisin, the loss rate of bactericidal activity of AH-NEn was reduced by 75.0% and 14.0% following treatment with trypsin or a thermal treatment at 90 °C for 30 min, respectively.

Effects of Lactococcus lactis on colorectal cancer in various terms: a narrative review.

Introduction: Colorectal cancer is one of the most common cancers with an increasing number of cases. Various studies have found an association between the gut microbiota balance and colorectal cancer incidence. Lactococcus lactis is a probiotic bacterium found in fermented foods, particularly yogurt and cheese. This probiotic has been shown to reduce various anti-inflammatory and pro-inflammatory agents that trigger cancer, such as interleukin (IL)-6, IL-18, tumour necrosis factor-alpha (TNF-α), and natural killer (NK) cells. Methods: Full-text articles and original research published in the last ten years were used as references, and "Lactococcus and colorectal cancer" as keywords. The reference search is on several databases, such as PubMed, ScienceDirect, ProQuest, and Nature. Searching results obtained eleven articles. Discussion: Lactococcus lactis does have a perfect role in suppressing cancer cells. Lactococcus lactis has anti-proliferative effects associated with decreased cyclin D1 expression in SW480 cell lines, decreased NK cells, reduced cancer cell viability, decreased IL-8 levels, and decreased IL-6. Conclusion: Lactococcus lactis contains nisin, which can suppress various gene, protein, and cytokine expressions that play a role in cancer cell growth. Probiotics can inhibit colorectal cancer without significant side effects.

Co-encapsulation of Shirazi thyme (Zataria multiflora) essential oil and nisin using caffeic acid grafted chitosan nanogel and the effect of this nanogel as a bio-preservative in Iranian white cheese.

The current study aims to co-encapsulate Shirazi thyme (Zataria multiflora) essential oil (ZEO) and nisin into chitosan nanogel as an antimicrobial and antioxidant agent to enhance the shelf-life of cheese. Chitosan-caffeic acid (CS-CA) nanogel was produced to co-encapsulate Zataria multiflora essential oil and nisin. This nanogel was characterized by dynamic light scattering (DLS), Fourier Transform Infrared (FTIR) spectroscopic analysis, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) images. The effect of free (TFZN) and encapsulated ZEO-nisin in chitosan nanogel (TCZN) on the chemical and microbiological properties of Iranian white cheese was assessed. The particle size, polydispersity index value (PDI), zeta potential, antioxidant activity, and encapsulation efficiency of the optimal chitosan-ZEO-nisin nanogel were 421.6 nm, 0.343, 34.0 mV, 71.06%-82.69%, and 41.3 ± 0.5%, 0.79 ± 0.06 mg/mL. respectively. FTIR and XRD approved ZEO and nisin entrapment within chitosan nanogel. The chitosan nanogel showed a highly porous surface with an irregular shape. The bioactive compounds of ZEO and nisin decreased the pH changes in cheese. On the 60th day of storage, the acidity of treated samples was significantly lower than that of control. Although the lowest anisidine index value was observed in samples treated with sodium nitrate (NaNO3) (TS), there was no significant difference between this sample and TCZN. The lowest microbial population was observed in TCZN and TS. After 60 days of ripening, Coliforms were not detected in the culture medium of TCZN and TS. The results can contribute to the development of a natural preservative with the potential for application in the dairy industry.

Microfluidic preparation and optimization of (Kollicoat ® IR-b-PCL) polymersome for co-delivery of Nisin-Curcumin in breast cancer application.

This work aimed to develop amphiphilic nanocarriers such as polymersome based diblock copolymer of Kollicoat ® IR -block-poly(ε-caprolactone) (Kollicoat ® IR-b-PCL) for potential co-delivery of Nisin (Ni) and Curcumin (CUR) for treatment of breast cancer. To generate multi-layered nanocarriers of uniform size and morphology, microfluidics was used as a new technology. In order to characterise and optimize polymersome, design of experiments (Design-Expert) software with three levels full factorial design (3-FFD) method was used. Finally, the optimized polymersome was produced with a spherical morphology, small particle size (dH < 200 nm), uniform size distribution (PDI < 0.2), and high drug loading efficiency (Ni 78 % and CUR 93 %). Furthermore, the maximum release of Ni and CUR was found to be roughly 60 % and 80 % in PBS, respectively. Cytotoxicity assays showed a slight cytotoxicity of Ni and CUR -loaded polymersome (N- Ni /CUR) towards normal cells while demonstrating inhibitory activity against cancer cells compared to the free drugs. Also, the apoptosis assays and cellular uptake confirmed the obtained results from cytotoxic analysis. In general, this study demonstrated a microfluidic approach for preparation and optimization of polymersome for co-delivery of two drugs into cancer cells.

Nisin-preconditioned mesenchymal stem cells combatting nosocomial Pseudomonas infections.

Background: Nosocomial infections caused by multidrug-resistant Pseudomonas aeruginosa are a considerable public health threat, requiring innovative therapeutic approaches. Objectives: This study explored preconditioning mesenchymal stem cells (MSCs) with the antimicrobial peptide Nisin to enhance their antibacterial properties while maintaining regenerative capacity. Methods: Human MSCs were preconditioned with varying concentrations of Nisin (0.1-1000 IU/mL) to determine an optimal dose. MSCs preconditioned with Nisin were characterized using microscopy, flow cytometry, gene expression analysis, and functional assays. The effects of preconditioning on the viability, phenotype, differentiation capacity, antimicrobial peptide expression, and antibacterial activity of MSCs against Pseudomonas aeruginosa were tested in vitro. The therapeutic efficacy was evaluated by topically applying conditioned media from Nisin-preconditioned versus control MSCs to infected wounds in a rat model, assessing bacterial burden, healing, host response, and survival. Results: An optimal Nisin dose of 500 IU/mL was identified, which increased MSC antibacterial gene expression and secretome activity without compromising viability or stemness. Nisin-preconditioned MSCs showed upregulated expression of LL37 and hepcidin. Conditioned media from Nisin-preconditioned MSCs exhibited about 4-fold more inhibition of P. aeruginosa growth compared to non-preconditioned MSCs. In the wound infection model, the secretome of Nisin-preconditioned MSCs suppressed bacterial load, accelerated wound closure, modulated inflammation, and improved survival compared to standard MSC treatments. Conclusion: This study explores the effect of preconditioning MSCs with the antimicrobial peptide Nisin on enhancing their antibacterial properties while maintaining regenerative capacity. Secreted factors from Nisin-preconditioned MSCs have the potential to attenuate infections and promote healing in vivo. The approach holds translational promise for managing antibiotic-resistant infections and warrants further development. Preconditioned MSCs with Nisin may offer innovative, multifaceted therapies for combating nosocomial pathogens and promoting tissue regeneration.

Screening, characterization and mechanism of a potential stabiliser for nisin nanoliposomes with high encapsulation efficiency.

The encapsulation efficiency (EE%) reflects the amount of bioactive components that can be loaded into nanoliposomes. Obtaining a suitable nanoliposome stabiliser may be the key to improving their EE%. In this study, three polyphenols were screened as stabilisers of nanoliposomes with high nisin EE%, with curcumin nanoliposomes (Cu-NLs) exhibiting the best performance (EE% = 95.94%). Characterizations of particle size, PDI and zeta potential indicate that the Cu-NLs had good uniformity and stability. TEM found that nisin accumulated at the edges of the Cu-NLs' phospholipid layer. DSC and FT-IR revealed that curcumin was involved in the formation of the phospholipid layer and altered its structure. FT-IR and molecular docking simulations indicate that the interactions between curcumin and nisin are mainly hydrogen bonding and hydrophobic. In whole milk, Cu-NLs effectively protected nisin activity. This study provides an effective strategy for improving the EE% of nanoliposomes loaded with nisin and other bacteriocins.

Activity and safety evaluation of natural preservatives.

Synthetic preservatives are widely used in the food industry to control spoilage and growth of pathogenic microorganisms, inhibit lipid oxidation processes and extend the shelf life of food. However, synthetic preservatives have some side effects that can lead to poisoning, cancer and other degenerative diseases. With the improvement of living standards, people are developing safer natural preservatives to replace synthetic preservatives, including plant derived preservatives (polyphenols, essential oils, flavonoids), animal derived preservatives (lysozyme, antimicrobial peptide, chitosan) and microorganism derived preservatives (nisin, natamycin, ε-polylysine, phage). These natural preservatives exert antibacterial effects by disrupting microbial cell wall/membrane structures, interfering with DNA/RNA replication and transcription, and affecting protein synthesis and metabolism. This review summarizes the natural bioactive compounds (polyphenols, flavonoids and terpenoids, etc.) in these preservatives, their antioxidant and antibacterial activities, and safety evaluation in various products.

A crosslinked and percolation network alginate coating for litchi prevention.

The short shelf life of Litchi is due to its rapid metabolism after being harvested. Refrigeration is not a suitable method for preserving litchi, as the browning process of litchi that has been cryogenic will accelerate when it is brought to room temperature. This study introduces an alginate-based coating as a solution to control the post-harvest metabolism of litchi. The coating achieves this by simultaneously establishing crosslink and percolation networks, both of which act as barriers. The percolation network is created using rod-like cellulose nanocrystals, which possess excellent percolation properties. This network effectively reduces moisture loss. Compared to the control group, the coated litchi exhibited a 38.1 % lower browning index and a 62.5 % lower decay rate. Additionally, the soluble solid content increased by 107.1 %. The inclusion of cellulose nanocrystals and the crosslinking of calcium ions enhanced the mechanical properties of the composite membrane. Specifically, the tensile strength and elongation at break increased by 70 % and 366 % respectively. As all the components in the coating are edible, it is environmentally friendly and safe for human consumption.

Nisin Inhibition of Gram-Negative Bacteria.

Aims: This study investigates the activity of the broad-spectrum bacteriocin nisin against a large panel of Gram-negative bacterial isolates, including relevant plant, animal, and human pathogens. The aim is to generate supportive evidence towards the use/inclusion of bacteriocin-based therapeutics and open avenues for their continued development. Methods and Results: Nisin inhibitory activity was screened against a panel of 575 strains of Gram-negative bacteria, encompassing 17 genera. Nisin inhibition was observed in 309 out of 575 strains, challenging the prevailing belief that nisin lacks effectiveness against Gram-negative bacteria. The genera Acinetobacter, Helicobacter, Erwinia, and Xanthomonas exhibited particularly high nisin sensitivity. Conclusions: The findings of this study highlight the promising potential of nisin as a therapeutic agent for several key Gram-negative plant, animal, and human pathogens. These results challenge the prevailing notion that nisin is less effective or ineffective against Gram-negative pathogens when compared to Gram-positive pathogens and support future pursuits of nisin as a complementary therapy to existing antibiotics. Significance and Impact of Study: This research supports further exploration of nisin as a promising therapeutic agent for numerous human, animal, and plant health applications, offering a complementary tool for infection control in the face of multidrug-resistant bacteria.

Antimicrobial peptides and proteins as alternative antibiotics for porcine semen preservation.

BACKGROUND: Antimicrobial resistance (AMR) is nowadays a major emerging challenge for public health worldwide. The over- and misuse of antibiotics, including those for cell culture, are promoting AMR while also encouraging the research and employment of alternative drugs. The addition of antibiotics to the cell media is strongly recommended in sperm preservation, being gentamicin the most used for boar semen. Because of its continued use, several bacterial strains present in boar semen have developed resistance to this antibiotic. Antimicrobial peptides and proteins (AMPPs) are promising candidates as alternative antibiotics because their mechanism of action is less likely to promote AMR. In the present study, we tested two AMPPs (lysozyme and nisin; 50 and 500 µg/mL) as possible substitutes of gentamicin for boar semen preservation up to 48 h of storage. RESULTS: We found that both AMPPs improved sperm plasma membrane and acrosome integrity during semen storage. The highest concentration tested for lysozyme also kept the remaining sperm parameters unaltered, at 48 h of semen storage, and reduced the bacterial load at comparable levels of the samples supplemented with gentamicin (p > 0.05). On the other hand, while nisin (500 µg/mL) reduced the total Enterobacteriaceae counts, it also decreased the rapid and progressive sperm population and the seminal oxidation-reduction potential (p < 0.05). CONCLUSIONS: The protective effect of lysozyme on sperm function together with its antimicrobial activity and inborn presence in body fluids, including semen and cervical mucus, makes this enzyme a promising antimicrobial agent for boar semen preservation.

Development of transcriptional factor-based whole-cell biosensors to monitor and degrade antibiotics using mutant cells obtained via adaptive laboratory evolution.

With the widespread use of antibiotics and increasing environmental concerns regarding antibiotic abuse, the detection and degradation of antibiotic residues in various samples has become a pressing issue. Transcriptional factor (TF)-based whole-cell biosensors are low-cost, easy-to-use, and flexible tools for detecting chemicals and controlling bioprocesses. However, because of cytotoxicity caused by antibiotics, the application of such biosensors is limited in the presence of antibiotics. In this study, we used antibiotic-tolerant mutants obtained via adaptive laboratory evolution (ALE) to develop TF-based whole-cell biosensors for antibiotic monitoring and degradation. The biosensors had high performance and stability in detecting relatively high concentrations of tetracycline (Tc) and nisin. The ALE mutant-based Tc biosensor exhibited a 10-fold larger linear detection range than the wild-type strain-based biosensor. Then, the Tc biosensor was employed to detect residual amounts of Tc in mouse stool, serum, and urine samples and facilitate Tc biodegradation in mouse stool, demonstrating its high utility. Considering that ALE has been demonstrated to enhance cell tolerance to various toxic chemicals, our strategy might facilitate the development of whole-cell biosensors for most antibiotics and other toxic ligands.

Assessing the synergistic potential of bacteriophage endolysins and antimicrobial peptides for eradicating bacterial biofilms.

Phage-encoded endolysins have emerged as a potential substitute to conventional antibiotics due to their exceptional benefits including host specificity, rapid host killing, least risk of resistance. In addition to their antibacterial potency and biofilm eradication properties, endolysins are reported to exhibit synergism with other antimicrobial agents. In this study, the synergistic potency of endolysins was dissected with antimicrobial peptides to enhance their therapeutic effectiveness. Recombinantly expressed and purified bacteriophage endolysin [T7 endolysin (T7L); and T4 endolysin (T4L)] proteins have been used to evaluate the broad-spectrum antibacterial efficacy using different bacterial strains. Antibacterial/biofilm eradication studies were performed in combination with different antimicrobial peptides (AMPs) such as colistin, nisin, and polymyxin B (PMB) to assess the endolysin's antimicrobial efficacy and their synergy with AMPs. In combination with T7L, polymyxin B and colistin effectively eradicated the biofilm of Pseudomonas aeruginosa and exhibited a synergistic effect. Further, a combination of T4L and nisin displayed a synergistic effect against Staphylococcus aureus biofilms. In summary, the obtained results endorse the theme of combinational therapy consisting of endolysins and AMPs as an effective remedy against the drug-resistant bacterial biofilms that are a serious concern in healthcare settings.

Effect of Soy Protein Products on Growth and Metabolism of Bacillus subtilis, Streptococcus lactis, and Streptomyces clavuligerus.

Microbial nitrogen sources are promising, and soy protein as a plant-based nitrogen source has absolute advantages in creating microbial culture medium in terms of renewability, eco-friendliness, and greater safety. Soy protein is rich in variety due to different extraction technologies and significantly different in the cell growth and metabolism of microorganisms as nitrogen source. Therefore, different soy proteins (soy meal powder, SMP; soy peptone, SP; soy protein concentrate, SPC; soy protein isolate, SPI; and soy protein hydrolysate, SPH) were used as nitrogen sources to culture Bacillus subtilis, Streptococcus lactis, and Streptomyces clavuligerus to evaluate the suitable soy nitrogen sources of the above strains. The results showed that B. subtilis had the highest bacteria density in SMP medium; S. lactis had the highest bacteria density in SPI medium; and S. clavuligerus had the highest PMV in SPI medium. Nattokinase activity was the highest in SP medium; the bacteriostatic effect of nisin was the best in SPI medium; and the clavulanic acid concentration was the highest in SMP medium. Based on analyzing the correlation between the nutritional composition and growth metabolism of the strains, the results indicated that the protein content and amino acid composition were the key factors influencing the cell growth and metabolism of the strains. These findings present a new, high-value application opportunity for soybean protein.

AcrR1, a novel TetR/AcrR family repressor, mediates acid and antibiotic resistance and nisin biosynthesis in Lactococcus lactis F44.

Lactococcus lactis, widely used in the manufacture of dairy products, encounters various environmental stresses both in natural habitats and during industrial processes. It has evolved intricate machinery of stress sensing and defense to survive harsh stress conditions. Here, we identified a novel TetR/AcrR family transcription regulator, designated AcrR1, to be a repressor for acid and antibiotic tolerance that was derepressed in the presence of vancomycin or under acid stress. The survival rates of acrR1 deletion strain ΔAcrR1 under acid and vancomycin stresses were about 28.7-fold (pH 3.0, HCl), 8.57-fold (pH 4.0, lactic acid) and 2.73-fold (300 ng/mL vancomycin) as that of original strain F44. We also demonstrated that ΔAcrR1 was better able to maintain intracellular pH homeostasis and had a lower affinity to vancomycin. No evident effects of AcrR1 deletion on the growth and morphology of strain F44 were observed. Subsequently, we characterized that the transcription level of genes associated with amino acids biosynthesis, carbohydrate transport and metabolism, multiple drug resistance and DNA repair proteins significantly upregulated in ΔAcrR1 using transcriptome analysis and quantitative reverse transcription-PCR (qRT-PCR) assays. Additionally, AcrR1 could repress the transcription of nisin post-translational modification gene, nisC, leading to a 16.3% increase in nisin yield after AcrR1 deletion. Our results not only refined the knowledge of the regulatory mechanism of TetR/AcrR family regulator in L. lactis, but presented a potential strategy to enhance industrial production of nisin.

Antifungal activity of nisin against clinical isolates of azole-resistant Candida tropicalis.

The rapid emergence of invasive infections caused by azole-resistant Candida tropicalis has become a public health concern, and there is an urgent need for alternative treatment strategies. Studies have demonstrated the antibacterial effects of nisin, a well-known peptide naturally produced by Lactococcus lactis subsp. lactis. However, there is scant information about the antifungal effect of nisin against C. tropicalis. The present study aims to investigate the in vitro antifungal activity of nisin against clinical isolates of azole-resistant C. tropicalis strains, as well as its inhibitory effect on biofilm formation. A total of 35 C. tropicalis strains isolated from patients with invasive fungal infections were divided into the azole-resistant group and the azole-sensitive group, containing 21 and 14 strains, respectively. The relative expression levels of the ERG11 and UPC2 genes in the azole-resistant group were higher than those in the azole-sensitive group (p < 0.0001), while no significant differences were observed in the expression levels of the MDR1 and CDR1 genes. The minimum inhibitory concentration of nisin against C. tropicalis ranged from 2 to 8 µg/mL. Nisin treatment inhibited the growth of azole-resistant C. tropicalis, with over a four-fold reduction in OD600 nm values observed at the 8-h time point, while it promoted the transition of C. tropicalis from the spore phase to the hyphal phase, as observed on cryo-scanning electron microscopy. The results of biofilm quantification using crystal violet staining indicated a significant decrease in OD570 nm values in the nisin-treated group compared to the controls (p < 0.0001). Among the 21 azole-resistant C. tropicalis strains, the biofilm formation was inhibited in 17 strains (17/21, 81%), and more than 85% inhibition of biofilm formation was observed in the representative strains. With regard to the molecular mechanisms, the expression of the BCR1 and UPC2 genes in the azole-resistant strains was down-regulated on nisin treatment (p < 0.05). In conclusion, we demonstrated, for the first time, that nisin has antifungal activity and significant anti-biofilm activity against clinical isolates of azole-resistant C. tropicalis strains. Based on the findings, nisin could be a promising alternative antifungal agent for combating azole-resistant C. tropicalis infections.

Sensitivity of Salmonella Typhimurium to nisin in vitro and in orange juice under refrigeration.

The influence of environmental factors on Salmonella sensitivity to nisin in vitro and in refrigerated orange juice were investigated. Nisin activity was observed in the different conditions, but the highest efficiency was achieved at lower pH (4.0) and with higher bacteriocin concentration (174 µM). Moreover, the bactericidal action was directly proportional to the incubation period. When tested in orange juice, nisin caused a reduction of up to 4.05 logarithm cycles in the Salmonella population. So, environmental factors such as low pH and low temperature favored the sensitization of Salmonella cells to the bactericidal action of nisin. Therefore, this may represent an alternative to control Salmonella in refrigerated foods.

The Spx stress regulator confers high-level ß-lactam resistance and decreases susceptibility to last-line antibiotics in methicillin-resistant Staphylococcus aureus.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a leading cause of mortality worldwide. MRSA has acquired resistance to next-generation ß-lactam antibiotics through the horizontal acquisition of the mecA resistance gene. Development of high resistance is, however, often associated with additional mutations in a set of chromosomal core genes, known as potentiators, which, through poorly described mechanisms, enhance resistance. The yjbH gene was recently identified as a hot spot for adaptive mutations during severe infections. Here, we show that inactivation of yjbH increased ß-lactam MICs up to 16-fold and transformed MRSA cells with low levels of resistance to being homogenously highly resistant to ß-lactams. The yjbH gene encodes an adaptor protein that targets the transcriptional stress regulator Spx for degradation by the ClpXP protease. Using CRISPR interference (CRISPRi) to knock down spx transcription, we unambiguously linked hyper-resistance to the accumulation of Spx. Spx was previously proposed to be essential; however, our data suggest that Spx is dispensable for growth at 37°C but becomes essential in the presence of antibiotics with various targets. On the other hand, high Spx levels bypassed the role of PBP4 in ß-lactam resistance and broadly decreased MRSA susceptibility to compounds targeting the cell wall or the cell membrane, including vancomycin, daptomycin, and nisin. Strikingly, Spx potentiated resistance independently of its redox-sensing switch. Collectively, our study identifies a general stress pathway that, in addition to promoting the development of high-level, broad-spectrum ß-lactam resistance, also decreases MRSA susceptibility to critical antibiotics of last resort.

Natural approach of using nisin and its nanoform as food bio-preservatives against methicillin resistant Staphylococcus aureus and E.coli O157:H7 in yoghurt.

BACKGROUND: Natural antimicrobial agents such as nisin were used to control the growth of foodborne pathogens in dairy products. The current study aimed to examine the inhibitory effect of pure nisin and nisin nanoparticles (nisin NPs) against methicillin resistant Staphylococcus aureus (MRSA) and E.coli O157:H7 during the manufacturing and storage of yoghurt. Nisin NPs were prepared using new, natural, and safe nano-precipitation method by acetic acid. The prepared NPs were characterized using zeta-sizer and transmission electron microscopy (TEM). In addition, the cytotoxicity of nisin NPs on vero cells was assessed using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The minimum inhibitory concentrations (MICs) of nisin and its nanoparticles were determined using agar well-diffusion method. Further, fresh buffalo's milk was inoculated with MRSA or E.coli O157:H7 (1 × 106 CFU/ml) with the addition of either nisin or nisin NPs, and then the inoculated milk was used for yoghurt making. The organoleptic properties, pH and bacterial load of the obtained yoghurt were evaluated during storage in comparison to control group. RESULTS: The obtained results showed a strong antibacterial activity of nisin NPs (0.125 mg/mL) against MRSA and E.coli O157:H7 in comparison with control and pure nisin groups. Notably, complete eradication of MRSA and E.coli O157:H7 was observed in yoghurt formulated with nisin NPs after 24 h and 5th day of storage, respectively. The shelf life of yoghurt inoculated with nisin nanoparticles was extended than those manufactured without addition of such nanoparticles. CONCLUSIONS: Overall, the present study indicated that the addition of nisin NPs during processing of yoghurt could be a useful tool for food preservation against MRSA and E.coli O157:H7 in dairy industry.

Addition of nisin to high-viscosity glass-ionomer cement: a comparative in vitro study on antibacterial and physical properties.

PURPOSE: Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength. METHODS: 1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student's t test, one-way ANOVA with Tamhane's post hoc test, and repeated-measures ANOVA. RESULTS: As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control. CONCLUSION: The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength.