Cryptophytes as potential source of natural antimicrobials for food preservation.

Cryptophytes are a promising source of bioactive compounds that have not been fully explored. This research investigated the antimicrobial activity of total phenolic compounds (TPC) and exopolysaccharides (EPS) extracted from several cryptophytes against a range of harmful foodborne bacteria and fungi. To measure the minimum inhibitory concentration (MIC) value, the broth microdilution method was used. In the antibacterial evaluation of TPC, the MIC ranged between 31.25 and 500 µg/mL, while for the antifungal activity test, it varied from 31.25 to 125 µg/mL. In the antibacterial activity test of EPS, the MIC values ranged from 125 to 1,000 µg/mL, whereas in the antifungal susceptibility test, it ranged between 62.5 and 1,000 µg/mL. The most resistant pathogen against TPC was Escherichia coli, while Campylobacter jejuni was the most susceptible. In the case of EPS, the most resistant pathogen was Salmonella Typhimurium, while Aspergillus versicolor exhibited the highest susceptibility. Overall, in terms of antimicrobial activity, TPC was more effective than EPS. Finally, the tolerance level (TL) for TPC and EPS was ≤4 in all tested samples, indicating their bactericidal/fungicidal mechanism of action. In conclusion, TPC and EPS isolated from cryptophytes demonstrated remarkable antimicrobial properties and ability to fully eradicate pathogens, and could be considered as natural preservatives in the food industry.

The applicability of the SERS technique in food contamination testing - The detailed spectroscopic, chemometric, genetic, and comparative analysis of food-borne Cronobacter spp. strains.

Microorganisms assigned as Cronobacter are Gram-negative, facultatively anaerobic, bacteria widely distributed in nature, home environments, and hospitals. They can also be detected in foods, milk powder, and powdered infant formula (PIF). Additionally, as an opportunistic pathogen, Cronobacter may cause serious infections, sometimes leading to the death of neonates and infants. Thus, it is essential to test food products for the presence of Cronobacter spp. The currently used standard described in ISO 22964:2017 is a laborious method that could be easily replaced by surface-enhanced Raman scattering (SERS). Here, we demonstrate that SERS allows the identification of food-borne bacteria belonging to Cronobacter spp. based on their SERS spectra. For this purpose, twenty-six Cronobacter strains from different food samples were analyzed. Additionally, it was shown that it is possible to differentiate them from other closely related pathogens such as Salmonella enterica subsp. enterica, Escherichia coli, or Enterobacter spp. The SERS results were supported by principal component analysis (PCA), as well as and sequencing of 16S rRNA, rpoB and fusA genes. Last but not least, it was demonstrated that the cells of Cronobacter sakazakii may be easily separated from PIF using an appropriate filter, microfluidic chip, and dielectrophoresis (DEP) technique.

Hybrid chain reaction-based and Au/Bi4NbO8Cl/In2S3 layer-by-layer assembled dual-mode photoelectrochemical-electrochemical aptasensor for the detection of Salmonella enteritidis.

Salmonella enteritidis (SE) is a food-borne pathogens that can cause acute gastroenteritis. With the increasing social attention to food safety, the detection method of SE has attracted wide attention. In response to the demand for efficient detection methods of SE, this study constructed a novel dual-mode photoelectrochemical-electrochemical (PEC-EC) aptamer-based biosensor. The sensor was constructed using Bi4NbO8Cl/In2S3 heterojunction as the electrode substrate material, the hybridization chain reaction (HCR) and dye sensitization were used as the signal amplification strategies. Bi4NbO8Cl/In2S3 heterojunction could provide an excellent initial photocurrent response for the sensing platform, and the HCR was opened by the end of complementary DNA (cDNA) and generated an ultra-long DNA double-stranded (dsDNA) "super structure" on the surface of the electrode, which could be embedded with a large number of methylene blue (MB) as the bifunctional probes. Thus, dual-mode output was achieved via the PEC and EC activity of MB. Under the optimized conditions, the PEC and EC signal responses of the system were linear to the logarithm of SE concentration in a range from 1.5 × 102 CFU/mL to 1.5 × 107 CFU/mL. The detection limits were found to be 12.9 CFU/mL and 12.3 CFU/mL using the PEC and EC methods, respectively. The constructed dual-mode biosensor exhibited good performance for real sample analysis, and demonstrated great application potential in the field of SE rapid detection. Moreover, this dual-mode detection strategy provided more accurate and reliable results than the single-mode output.

Epiphytic Yeasts from South Romania for Preventing Food Microbial Contamination.

Epiphytic yeasts represent an important source for the development of novel strategies aiming to combat food microbial contamination. The present study deals with the characterization of nine yeast strains belonging to Starmerella, Candida, Metschinikowia, Lachancea, Kodamaea and Pichia genera, isolated from the surface of plants from the Botanical Garden "Dimitrie Brandza" (Bucharest, Romania) for use as antimicrobial and probiotic agents. The tests involved the determination of the safe status, cell growth under stress conditions, and activity against pathogenic Candida and bacteria strains, respectively, as well as phytopathogenic filamentous fungi and lipolytic activity. None of the nine strains showed all the characteristics for virulence and pathogenicity, with the rare positive results being explained rather by their adaptability to the habitats of origin. The strains Lachancea thermotolerans CMGB-ST12 and Kodamaea ohmeri CMGB-ST19 grew at 37 °C; Metschnikowia reukaufii CMGB-ST21.2, M. reukaufii CMGB-ST.8.1 and M. reukaufii CMGB ST10 grew in the presence of 10% NaCl, while L. thermotolerans CMGB-ST12 and K. ohmeri CMGB-ST19 tolerated both acidic and alkaline pH values well (3.0 to 12.0). The studied yeast strains showed good antimicrobial activity against Candida krusei, Candida albicans and Gram-negative bacterial strains, with K. ohmeri CMGB-ST19 and Pichia membranaefaciens CMGB-ST53 inhibiting up to 100% the development of filamentous fungi. All the strains produced lipases for tributyrin hydrolysis, the best producer being Starmerella bombi CMGB-ST1, and only Candida magnoliae CMGB-ST8.2 tested positive against other probiotic yeasts. Overall, our nine yeast strains show high potential for industrial applications, for obtaining probiotic products and for preventing the development of a wide range of microbial food contaminants.

Impact of Veterinary Feed Directive Rules Changes on the Prevalence of Antibiotic Resistance Bacteria Isolated from Cecal Samples of Food-Producing Animals at US Slaughterhouses.

This study examined the impact of the 2017 Veterinary Feed Directive (VFD) rule changes on the prevalence of tetracycline-resistant and erythromycin-resistant bacteria (Salmonella spp., Campylobacter spp., and Escherichia coli) in cecal samples of food animals (cattle, swine, chicken, and turkey) at US slaughterhouses. Multivariable logistic regression was used to analyze 2013-2019 cecal samples of food-producing animals surveillance data from the National Antimicrobial Resistance Monitoring System (NARMS) in the U.S. The variables included year (used to evaluate VFD rule changes), host, and quarter of year. The analysis of surveillance data showed that the VFD rule changes have varying effects on tetracycline-resistant and erythromycin-resistant bacteria in food animals. For example, the odds of detecting tetracycline-resistant Salmonella spp. decreased in cattle but increased in chickens following the implementation of the VFD rule changes. Similarly, the odds of detecting tetracycline-resistant Escherichia coli decreased in chickens but increased in swine after the VFD rule changes. The odds of detecting erythromycin-resistant Campylobacter spp. increased in cattle but decreased in chickens after the VFD rule changes. In conclusion, the implementation of VFD rule changes has been beneficial in reducing the odds of detecting tetracycline-resistant Escherichia coli and erythromycin-resistant Campylobacter spp. in chickens, as well as tetracycline-resistant Salmonella spp. in cattle at US slaughterhouses.

Characterization of highly pathogenic avian influenza virus in retail dairy products in the US.

In March 2024, clade 2.3.4.4b H5N1 highly pathogenic avian influenza virus (HPAIV) was detected in dairy cattle in the US, and it was discovered that the virus could be detected in raw milk. Although affected cow's milk is diverted from human consumption and current pasteurization requirements are expected to reduce or eliminate infectious HPAIV from the milk supply, a study was conducted to characterize whether the virus could be detected by quantitative real-time RT-PCR (qrRT-PCR) in pasteurized retail dairy products and, if detected, to determine whether the virus was viable. From 18 April to 22 April 2024, a total of 297 samples of Grade A pasteurized retail milk products (23 product types) were collected from 17 US states that represented products from 132 processors in 38 states. Viral RNA was detected in 60 samples (20.2%), with qrRT-PCR-based quantity estimates (non-infectious) of up to 5.4log1050% egg infectious doses per mL, with a mean and median of 3.0log10/mL and 2.9log10/mL, respectively. Samples that were positive for type A influenza by qrRT-PCR were confirmed to be clade 2.3.4.4 H5 HPAIV by qrRT-PCR. No infectious virus was detected in any of the qrRT-PCR-positive samples in embryonating chicken eggs. Further studies are needed to monitor the milk supply, but these results provide evidence that the infectious virus did not enter the US pasteurized milk supply before control measures for HPAIV were implemented in dairy cattle.IMPORTANCEHighly pathogenic avian influenza virus (HPAIV) infections in US dairy cattle were first confirmed in March 2024. Because the virus could be detected in raw milk, a study was conducted to determine whether it had entered the retail food supply. Pasteurized dairy products were collected from 17 states in April 2024. Viral RNA was detected in one in five samples, but infectious virus was not detected. This provides a snapshot of HPAIV in milk products early in the event and reinforces that with current safety measures, infectious viruses in milk are unlikely to enter the food supply.

Draft genome sequences of two wide-host-range phages of Listeria monocytogenes from food processing environments in the United States.

Listeria monocytogenes is notorious for persistence in food facilities. Phages can significantly impact the ecology of Listeria, but there is a dearth of genome sequence data for Listeria phages from food processing ecosystems. We report the genome sequences of two Listeria phages from turkey processing facilities in the USA.

Draft genome sequence of a Shiga toxin-producing Escherichia coli strain from deer meat showing an IS-element integration in the B-subunit of the Shiga toxin Stx2b gene.

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens. Here we report sequence data of the STEC strain BfR-EC-18960, which has integrated IS elements in the B-subunit of the Shiga toxin Stx2b gene. The strain was isolated from deer meat at a local butchery in Germany in 2021.

D-tryptophan, an eco-friendly natural, safe, and healthy compound with antimicrobial activity against food-borne pathogens: A systematic review.

Recently, the use of D-amino acids as food preservatives has attracted considerable attention because these natural compounds do not have adverse effects on human health. In addition, D-amino acids such as D-tryptophan can reduce the harmful effects of other treatments. For instance, the use of D-tryptophan in food reduces the requirement for high temperatures and their damaging effects on nutrients such as proteins and vitamins. The purpose of this systematic review was to investigate the antimicrobial effect of D-tryptophan on food-borne pathogens in vitro and in food models. To identify related studies, scientific digital databases such as PubMed, Science Direct, and Google Scholar were searched from January 2000 to February 2023. The results of the studies showed that when D-tryptophan was used with other stresses such as using different salt concentrations, refrigeration, or high temperatures, it showed significant antimicrobial effects on Gram-positive and Gram-negative food-borne pathogens, and antibiofilm impacts were also observed with D-tryptophan. Since studies have shown that the antimicrobial activity of D-tryptophan depends on several factors, including the pathogen strain, the type of stress, and the concentration of D-tryptophan, and every article has focused on one of these factors, there is a need for a systematic review that summarizes and concludes the effect of all these factors on the antimicrobial activity of D-tryptophan against food-borne pathogens.

Developmental Formulation Principles of Food Preservatives by Nanoencapsulation-Fundamentals, Application, and Challenges.

The role of food additives is to preserve food by extending shelf life and limiting harmful microorganism proliferation. They prevent spoilage by enhancing the taste and safety of food by utilizing beneficial microorganisms and their antimicrobial metabolites. Current advances in food preservation and processing utilize green technology principles for green preservative formulation, enhancing nutrition and supplying essential micronutrients safely, while also improving quality, packaging, and food safety. Encapsulation is gaining attention for its potential to protect delicate materials from oxidative degradation and extend their shelf life, thereby ensuring optimal nutrient uptake. Nanoencapsulation of bioactive compounds has significantly improved the food, pharmaceutical, agriculture, and nutraceutical industries by protecting antioxidants, vitamins, minerals, and essential fatty acids by controlling release and ensuring delivery to specific sites in the human body. This emerging area is crucial for future industrial production, improving the sensory properties of foods like color, taste, and texture. Research on encapsulated bioactive compounds like bacteriocins, LAB, natamycin, polylysine, and bacteriophage is crucial for their potential antioxidant and antimicrobial activities in food applications and the food industry. This paper reviews nanomaterials used as food antimicrobial carriers, including nanoemulsions, nanoliposomes, nanoparticles, and nanofibers, to protect natural food antimicrobials from degradation and improve antimicrobial activity. This review discusses nanoencapsulation techniques for biopreservative agents like nisin, poly lysine, and natamycin, focusing on biologically-derived polymeric nanofibers, nanocarriers, nanoliposomes, and polymer-stabilized metallic nanoparticles. Nanomaterials, in general, improve the dispersibility, stability, and availability of bioactive substances, and this study discusses the controlled release of nanoencapsulated biopreservative agents.

Efficacy and Synergistic Potential of Cinnamon (Cinnamomum zeylanicum) and Clove (Syzygium aromaticum L. Merr. & Perry) Essential Oils to Control Food-Borne Pathogens in Fresh-Cut Fruits.

The presence of microbial pathogens in ready-to-eat produce represents a serious health problem. The antibacterial activity of cinnamon (Cinnamomum zeylanicum) and clove (Syzygium aromaticum L. Merr. & Perry) essential oils (EOs) was determined toward food-borne pathogens by agar disk diffusion and minimum inhibitory concentration (MIC) assays. The growth kinetics of all strains, both in a buffer suspension assay and "on food" in artificially contaminated samples, were also investigated. The two EOs demonstrated a good antibacterial effect both alone and in combination (EO/EO). The use of EO/EO led to a synergistic antibacterial effect, also confirmed by the growth kinetics studies, where the EOs were active after 10 h of incubation (p < 0.0001) at significantly lower concentrations than those when alone. In the "on food" studies performed on artificially contaminated fruit samples stored at 4 °C for 8 days, the greatest killing activity was observed at the end of the trial (8 days) with a reduction of up to 7 log CFU/g compared to the control. These results confirm the good antibacterial activity of the EOs, which were more effective when used in combination. Data from the "on food" studies suggest cinnamon and clove essential oils, traditionally used in the food industry, as a possible natural alternative to chemical additives.

Validating the protective role of orange and tangerine peel extracts foramending food safety against microorganisms' contamination using molecular docking.

Latest studies indicated that agro-food wastes are considered renewable sources of bioactive compounds. This investigation aimed to utilize natural extracts of citrus peels as antimicrobial and anti-aflatoxigenic agents for food safety. The bioactivity of two citrus peels was assessed by total phenolic, flavonoids, and antioxidant activity. Nanoemulsions were manufactured using high-speed homogenization. The mean particle size of the nanoemulsions ranged from 29.41 to 66.41 nm with a polydispersity index of 0.11-0.16. The zeta potential values ranged from -14.27 to -26.74 mV, indicating stability between 81.44% and 99.26%. The orange peel extract showed the highest contents of total phenolic and flavonoids compared to the other extracts and nanoemulsions (39.54 mg GAE/g and 79.54 mg CE/100 g, respectively), which agreed with its potential antioxidant activity performed by DPPH free radical-scavenging and ABTS assays. Chlorogenic, caffeic, ferulic, and catechin were the dominant phenolic acids in the extracts and nanoemulsions, while quercitrin, rutin, and hesperidin were the most abundant flavonoids. Limonene was the major volatile component in both oils; however, it was reduced dramatically from 92.52% to 76.62% in orange peel oil and from 91.79 to 79.12% in tangerine peel oil. Consistent with the differences in phenolics, flavonoids, and volatiles between orange and tangerine peel extracts, the antibacterial properties of orange extracts had more potential than tangerine ones. Gram-positive bacteria were more affected by all the examined extracts than Gram-negative ones. The antifungal activity of orange extract and nanoemulsion on seven fungal strains from Aspergillus spp had more potential than tangerine extracts. Additionally, using a simulated media, the orange peel extract and its nanoemulsion had a more anti-aflatoxigenic influence. Molecular docking confirmed the high inhibitory action of flavonoids, especially hesperidin, on the polyketide synthase (-9.3 kcal/mol) and cytochrome P450 monooxygenase (-10.1 kcal/mol) key enzymes of the aflatoxin biosynthetic mechanism.

UHPLC-MS/MS and GC-MS Metabolic Profiling of a Medicinal Flourensia Fiebrigii Chemotype.

The comparative metabolic profiling and their biological properties of eight extracts obtained from diverse parts (leaves, flowers, roots) of the medicinal plant Flourensia fiebrigii S.F. Blake, a chemotype growing in highland areas (2750 m a.s.l.) of northwest Argentina, were investigated. The extracts were analysed by GC-MS and UHPLC-MS/MS. GC-MS analysis revealed the presence of encecalin (relative content: 24.86 %) in ethereal flower extract (EF) and this benzopyran (5.93 %) together sitosterol (11.35 %) in the bioactive ethereal leaf exudate (ELE). By UHPLC-MS/MS the main compounds identified in both samples were: limocitrin, (22.31 %), (2Z)-4,6-dihydroxy-2-[(4-hydroxy-3,5-dimethoxyphenyl)methylidene]-1-benzofuran-3-one (21.31 %), isobavachin (14.47 %), naringenin (13.50 %), and sternbin, (12.49 %). Phytocomplexes derived from aerial parts exhibited significant activity against biofilm production of Pseudomonas aeruginosa and Staphylococcus aureus, reaching inhibitions of 74.7-99.9 % with ELE (50 µg/mL). Notably, the extracts did not affect nutraceutical and environmental bacteria, suggesting a selective activity. ELE also showed the highest reactive species scavenging ability. This study provides valuable insights into the potential applications of this chemotype.

Serovar-level identification of bacterial foodborne pathogens from full-length 16S rRNA gene sequencing.

The resolution of variation within species is critical for interpreting and acting on many microbial measurements. In the key foodborne pathogens Salmonella and Escherichia coli, the primary subspecies classification scheme used is serotyping: differentiating variants within these species by surface antigen profiles. Serotype prediction from whole-genome sequencing (WGS) of isolates is now seen as comparable or preferable to traditional laboratory methods where WGS is available. However, laboratory and WGS methods depend on an isolation step that is time-consuming and incompletely represents the sample when multiple strains are present. Community sequencing approaches that skip the isolation step are, therefore, of interest for pathogen surveillance. Here, we evaluated the viability of amplicon sequencing of the full-length 16S rRNA gene for serotyping Salmonella enterica and E. coli. We developed a novel algorithm for serotype prediction, implemented as an R package (Seroplacer), which takes as input full-length 16S rRNA gene sequences and outputs serovar predictions after phylogenetic placement into a reference phylogeny. We achieved over 89% accuracy in predicting Salmonella serotypes on in silico test data and identified key pathogenic serovars of Salmonella and E. coli in isolate and environmental test samples. Although serotype prediction from 16S rRNA gene sequences is not as accurate as serotype prediction from WGS of isolates, the potential to identify dangerous serovars directly from amplicon sequencing of environmental samples is intriguing for pathogen surveillance. The capabilities developed here are also broadly relevant to other applications where intraspecies variation and direct sequencing from environmental samples could be valuable.IMPORTANCEIn order to prevent and stop outbreaks of foodborne pathogens, it is important that we can detect when pathogenic bacteria are present in a food or food-associated site and identify connections between specific pathogenic bacteria present in different samples. In this work, we develop a new computational technology that allows the important foodborne pathogens Escherichia coli and Salmonella enterica to be serotyped (a subspecies level classification) from sequencing of a single-marker gene, and the 16S rRNA gene often used to surveil bacterial communities. Our results suggest current limitations to serotyping from 16S rRNA gene sequencing alone but set the stage for further progress that we consider likely given the rapid advance in the long-read sequencing technologies and genomic databases our work leverages. If this research direction succeeds, it could enable better detection of foodborne pathogens before they reach the public and speed the resolution of foodborne pathogen outbreaks.

Bacterial adhesion inhibition by microalgal EPSs from Cylindrotheca closterium and Tetraselmis suecica biofilms.

In the food industry, successful bacterial pathogen colonization and persistence begin with their adhesion to a surface, followed by the spatial development of mature biofilm of public health concerns. Compromising bacterial settlement with natural inhibitors is a promising alternative to conventional anti-fouling treatments typically based on chemical biocides that contribute to the growing burden of antimicrobial resistance. In this study, three extracellular polymeric substance (EPS) fractions extracted from microalgae biofilms of Cylindrotheca closterium (fraction C) and Tetraselmis suecica (fraction Ta rich in insoluble scale structure and fraction Tb rich in soluble EPS) were screened for their anti-adhesive properties, against eight human food-borne pathogens belonging to Escherichia coli, Staphylococcus aureus, Salmonella enterica subsp. enterica, and Listeria monocytogenes species. The results showed that the fraction Ta was the most effective inducing statistically significant reduction for three strains of E. coli, S. aureus, and L. monocytogenes. Overall, EPSs coating on polystyrene surfaces of the different fractions increased the hydrophilic character of the support. Differences in bacterial adhesion on the different coated surfaces could be explained by several dissimilarities in the structural and physicochemical EPS compositions, according to HPLC and ATR-FTIR analysis. Interestingly, while fractions Ta and Tb were extracted from the same microalgal culture, distinct adhesion patterns were observed, highlighting the importance of the extraction process. Overall, the findings showed that EPS extracted from microalgal photosynthetic biofilms can exhibit anti-adhesive effects against food-borne pathogens and could help develop sustainable and non-toxic anti-adhesive surfaces for the food industry. KEY POINTS: •EPSs from a biofilm-based culture of C. closterium/T. suecica were characterized. •Microalgal EPS extracted from T. suecica biofilms showed bacterial anti-adhesive effects. •The anti-adhesive effect is strain-specific and affects both Gram - and Gram + bacteria.

Genetic diversity of Toxoplasma gondii in goats and sheep from the Northeast Region of Brazil destined for human consumption.

This study aimed to genotype isolates of Toxoplasma gondii obtained from samples of brain, diaphragm and heart of goats and sheep intended for human consumption in the State of Paraíba, Brazil. Tissue samples from 14 animals, goats (n = 5) and lambs (n = 9), were sourced from public slaughterhouses in seven cities and bio-assayed in mice. The brains of the mice were utilized for DNA extraction. Genotyping was carried out by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) using 10 markers (SAG1, SAG2, SAG3, BTUB, c22-8, PK1, GRA6, L358, c-29-2 and Apico). A total of 10 isolates were fully genotyped (i.e. at all loci), three from goats and seven from sheep, revealing five distinct genotypes: #13 (n = 4); #48 (n = 3); #57 (n = 1); #273 (n = 1); and one new genotype that had not been previously described. Genotype #13 is frequently found in the Northeast of Brazil and represents a clonal lineage circulating in this region and was the most prevalent genotype identified (n = 4). Moreover, in the present study genotypes #13, #48, #57, and #273 were documented for the first time in sheep from Brazil, and the novel genotype was isolated from a goat. Our findings align with previous studies on T. gondii from Brazil, where new genotypes are continuously being identified, highlighting a high level of genetic diversity of T. gondii isolates in the country.

Draft genome sequences of Campylobacter species isolated from the cecal contents of broiler chickens.

Here, we report the draft genomes of 10 Campylobacter strains isolated from the cecal contents of market-age broiler chickens naturally colonized with Campylobacter. Through a comprehensive analysis of these draft genomes, we have unveiled their core genetic elements and several antimicrobial resistance genes.

Insights into virulence: structure classification of the Vibrio parahaemolyticus RIMD mobilome.

IMPORTANCE: The pandemic Vpar strain RIMD causes seafood-borne illness worldwide. Previous comparative genomic studies have revealed pathogenicity islands in RIMD that contribute to the success of the strain in infection. However, not all virulence determinants have been identified, and many of the proteins encoded in known pathogenicity islands are of unknown function. Based on the EOCD database, we used evolution-based classification of structure models for the RIMD proteome to improve our functional understanding of virulence determinants acquired by the pandemic strain. We further identify and classify previously unknown mobile protein domains as well as fast evolving residue positions in structure models that contribute to virulence and adaptation with respect to a pre-pandemic strain. Our work highlights key contributions of phage in mediating seafood born illness, suggesting this strain balances its avoidance of phage predators with its successful colonization of human hosts.

Green synthesis of zinc oxide nanoparticles using novel bacterium strain (Bacillus subtilis NH1-8) and their in vitro antibacterial and antibiofilm activities against Salmonellatyphimurium.

Zinc oxide nanoparticles (ZnO NPs) are used in a range of applications, including food packaging, preservation, and storage. In the current investigation, extracellular green synthesis of ZnO NPs through an simple, eco-friendly, and rapid approach using a novel bacterial strain (Bacillus subtilis NH1-8) was studied. To assess the morphological, optical, and structural properties of ZnO NPs, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and X-ray diffraction (XRD) techniques were carried out. In addition, disk diffusion, minimum bactericidal concentration (MBC), and minimum inhibitory concentration (MIC) methods were performed to determine the antibacterial activity of ZnO NPs. The average size of biosynthesized ZnO NPs was 39 nm, exhibiting semi-spherical, which was confirmed by TEM analyses. The UV-vis spectroscopy exhibited the absorption peak at 200-800nm. The ZnO NPs have shown effective antimicrobial and antibiofilm activities against S. typhimurium. Thus, biosynthesized ZnO NPs could be exploited as a breakthrough technology in the surface coating of food containers and cans to minimize contamination by S. typhimurium.

Application of quasimetagenomics methods to define microbial diversity and subtype Listeria monocytogenes in dairy and seafood production facilities.

IMPORTANCE: In developed countries, the human diet is predominated by food commodities, which have been manufactured, processed, and stored in a food production facility. Little is known about the application of metagenomic sequencing approaches for detecting foodborne pathogens, such as L. monocytogenes, and characterizing microbial diversity in food production ecosystems. In this work, we investigated the utility of 16S rRNA amplicon and quasimetagenomic sequencing for the taxonomic and phylogenetic classification of Listeria culture enrichments of environmental swabs collected from dairy and seafood production facilities. We demonstrated that single-nucleotide polymorphism (SNP) analyses of L. monocytogenes metagenome-assembled genomes (MAGs) from quasimetagenomic data sets can achieve similar resolution as culture isolate whole-genome sequencing. To further understand the impact of genome coverage on MAG SNP cluster resolution, an in silico downsampling approach was employed to reduce the percentage of target pathogen sequence reads, providing an initial estimate of required MAG coverage for subtyping resolution of L. monocytogenes.