Staphylococcus aureus as a Foodborne Pathogen

Real-time Detection of Foodborne Pathogens and Biofilm in the Food Processing Environment with Bactiscan, A Macro-scale Fluorescence Device

Food safety relies on rapid detection methods and rigorous sampling of the food processing environment and is challenged by recurrent biofilm contamination and by sublethally injured bacteria that can evade detection. Bactiscan is investigated as an alternative detection approach, a macro-scale and reagentless device that detects microbial contamination through activating the green fluorescence of glycoproteins in the bacterial cell wall. The detection capability of Bactiscan was tested on foodborne pathogens Escherichia coli, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus. Detection by Bactiscan was assessed using 3 independent observers viewing bacterial samples dried on stainless steel, using 3 biological repeats and 5 technical repeats. Detection by Bactiscan was possible to 1.20 * 106 colony forming units (CFU), compared to 1.36 * 104 CFU by ATP swab testing, where Bactiscan detection limits were defined by the concentration at which 50% of the samples were observed under illumination of the device. Heat-killed and chlorine-stressed E. coli and S. enterica caused a 2-log reduction in detection by ATP swab tests (p ≤ 0.05), while detection by Bactiscan was unaffected (p ≥ 0.05). Pathogen biofilms were detectable via Bactiscan with >80% accuracy at 4 days of growth; E. coli and L. monocytogenes biofilms were visible at 2 days of growth. In situ contamination studies determined that Bactiscan can detect microbial contamination on chicken, salmon, and yoghurt samples with stronger fluorescence than a competitor's UV torch. The presence of one of the pathogens on the food samples was confirmed by metagenome sequencing, determining that S. aureus was present in 7 samples out of 9 with a relative abundance of >0.5%. These data demonstrate that Bactiscan can effectively detect bacteria present in the food processing environment and can complement existing technologies to improve food industry cleaning practices and infection prevention.

Occurrence & characterization of Staphylococcus aureus from ready-to-eat (RTE), and cooked food in Singapore: A retrospective analysis

Staphylococcus aureus is one of the major foodborne pathogens that poses significant public health risk, particularly in ready-to-eat (RTE) food prepared under inadequate hygiene conditions. Staphylococcal food poisoning (SFP) is increasingly prevalent worldwide, yet it is not reportable in Singapore, leaving a knowledge gap regarding the clinical incidence and virulence of local strains. This study examined the genetic diversity, antimicrobial resistance (AMR), and virulence determinants of S. aureus in RTE, and cooked food using both conventional testing and whole-genome sequencing (WGS) tools. We retrospectively analyzed 12178 RTE, and cooked food samples collected in Singapore from 2020 to 2023, detecting S. aureus in 0.19 % (23/12178) of samples. Genotype t4171_ST1155 was most common (4/23), followed by t91_ST2990 (3/23). Immunoassays detected the production of classical staphylococcal enterotoxin (SE) A, B, and C types in 43.5 % (10/23) of the isolates. Additionally, genomic analysis identified three more isolates that contained only non-classical SE genes, which were not detectable through immunoassays. AMR occurrence was highest for tetracycline (21.7 %, 5/23), followed by erythromycin (8.7 %, 2/23), clindamycin, gentamicin, and sulfamethoxazole-trimethoprim (4.3 %, 1/23 each). A minority (30.4 %, 7/23) of isolates possessed the complete icaADBC operon, which is associated with the well-studied matrix component involved in biofilm formation. Our findings indicate a low occurrence of S. aureus in RTE, and cooked foods in Singapore, with a minority carrying AMR and biofilm formation features, though about half are enterotoxigenic. This investigation plays a crucial role in comprehending the food safety landscape in Singapore, enabling the development of effective risk mitigation strategies aimed at improving community food safety.

Discovery and Optimisation of Novel Bombinin-Derived Peptides from Bombina variegata against Staphylococcus aureus

Amphibian skin-secreted antimicrobial peptides (AMPs) have garnered significant attention for their excellent biological activity and low propensity for drug resistance over the past 40 years. Bombinins and bombinin H, two classes of AMPs isolated from the skin secretions of Bombina species, demonstrate strong antimicrobial activity against broad-spectrum microorganisms. In this study, two novel peptides, bombinin-like peptide 7S and bombinin-H2L, were identified from the toad, Bombina variegata. While both peptides exhibited broad-spectrum antimicrobial activity, they also showed relatively high cytotoxicity. To explore the structure-activity relationship and enhance therapeutic potential, bombinin-H2L, which displayed stronger average antimicrobial activity, was used as a template. With the aid of bioinformatics analysis, a series of bombinin-H2L analogues were designed by increasing the net positive charges and/or adjusting the amphiphilicity of the parent peptide. Among these analogues, [Arg8, 15]BH2L and [Lys7, 8]BH2L demonstrated high therapeutic efficacy and specificity toward clinically isolated, drug-resistant Staphylococcus aureus strains in both in vitro and ex vivo tests. Their notable biosafety profiles, sensitivity to diverse environments, and ability to disrupt biofilms highlight their potential for further development. Additionally, studies on the mechanism of [Arg8, 15]BH2L and [Lys7, 8]BH2L revealed a membrane-targeted antimicrobial mechanism, with its antibacterial function exerted by disrupting the integrity of bacterial membranes. These findings provide valuable insights into structural modifications of bombinin H peptides for enhanced activity, and [Arg8, 15]BH2L and [Lys7, 8]BH2L have the potential as promising candidates for novel antibacterial agents in treated bacterial skin infections.

Prevalence, virulence factors, and antibiotic resistance of Staphylococcus aureus in seafood products

INTRODUCTION

Seafood contamination by bacteria is a pervasive issue, contributing to foodborne illnesses. This study investigates the prevalence, virulence factors, and antibiotic resistance in Staphylococcus aureus (S. aureus) isolated from various seafood products.

METHODS

A total of 460 samples, including fresh, smoked, salted, and dried fish, as well as oysters, crab, lobster, and shrimp, were collected in Shahrekord, Iran. S. aureus isolation followed ISO standards, with confirmation via PCR for 16S rRNA and nuc genes. Antibiotic susceptibility was determined via Kirby-Bauer disc diffusion, while PCR detected enterotoxin and antibiotic resistance genes.

FINDINGS

S. aureus was prevalent in all seafood types, with 27.83% positivity. Methicillin-resistant S. aureus (MRSA) was found in most samples, except oysters and crabs. Virulence genes were common, with Sea, Seb, Sed, Sec, and See being the most prevalent. High resistance to penicillin G and ampicillin (70%- 100%) was observed. Resistance varied for other antibiotics, with linezolid showing 100% susceptibility. The mecA gene was present in over 50% of isolates, with blaZ being the most detected resistance gene.

CONCLUSION

The study underscores the need for Good Hygiene Practices (GHP) in seafood processing to mitigate S. aureus transmission. While specific comparisons between sample types were limited, the findings emphasize the prevalence of virulence factors and antibiotic resistance in seafood-associated S. aureus, highlighting the importance of vigilant food safety measures.

Insight into the Phenolic Composition of Cabernet Sauvignon Grapevine Berries During Fermentation-Towards the Application of Winery By-Products for Antibacterial Purposes

BACKGROUND

Wine production generates significant amounts of grape marc, which can serve as a potential source of bioactive compounds, including polyphenols.

OBJECTIVES

In this study, we aimed to investigate the polyphenol content of skin and seeds separated from grape marc, and test their extracts against two significant bacteria, Listeria monocytogenes (LM) and Staphylococcus aureus (SA).

METHODS

A comprehensive analysis of the phenolic composition in the skin, seeds, and juice/wine derived from Cabernet Sauvignon grape berries was conducted over an 18-day fermentation period. High-performance liquid chromatography was performed to identify and quantify the main flavan-3-ols, flavonols, anthocyanins, and stilbenes. In addition, the total phenolic content (TPC) was determined by the Folin-Ciocalteu method.

RESULTS

The TPC of both seeds and skins significantly decreased over time. In parallel, the TPC in the wine gradually increased, indicating a release of phenolic compounds into the wine. We found that the TPC in seeds was consistently higher than in the skin at all examined time points. The main flavonoids in seeds were flavan-3-ols (catechin and epicatechin), while anthocyanins (delphinidin-, cyanidin-, petunidin-, peonidin-, and malvidin-3-O-glucoside) were the predominant ones in skins. Crude seed and skin extracts enriched in phenolics were prepared, of which only the crude seed extract was proven effective against LM and SA. Following the time-kill assay, our findings revealed that the minimal bactericidal concentration of the crude seed extract against LM was 5.02 mg/mL after 12 h incubation, demonstrating the eradication of the living bacterial cell number by ~6 log. A 24 h exposure time was required for complete inactivation of SA, but a lower concentration was sufficient (2.54 mg/mL).

CONCLUSIONS

Grape waste remains a valuable source of polyphenols, with grape seeds, in particular, exhibiting significant antimicrobial activity against certain foodborne pathogens.

Phytochemical Screening, Antibacterial Activity, and Toxicity of Calathea lutea Leaf Extracts

In Colombia, there is a long tradition of using bijao (Calathea lutea) leaves to package or wrap various foods. However, scientific studies on C. lutea are limited, and research to evaluate its toxicity and/or antibacterial activity has not yet been conducted. The objective of this research, therefore, was to evaluate the content of phytochemical compounds, levels of toxicity, and antibacterial activity of the extracts, fractions, and essential oil derived from C. lutea leaves. The plant material was subjected to extraction by maceration, Soxhlet extraction, and steam distillation, and fractions of hexane, dichloromethane, ethyl acetate, and a residual ethanol-water fraction were obtained. Preliminary phytochemical screening was performed using standard procedures with staining reagents. Estimation of the toxicity was carried out using the Caenorhabditis elegans biological model. Antibacterial activity was determined by broth microdilution against Staphylococcus aureus and Escherichia coli. The results showed that the characteristic metabolites were flavonoids, triterpenes, and tannins. At the concentrations tested, the extracts, fractions, and essential oil showed minimal toxicity levels. In terms of antibacterial activity, E. coli showed no susceptibility; meanwhile, the dichloromethane fraction had high antibacterial activity against S. aureus, with a growth inhibition rate of 81.2%. The results suggested that the of dichloromethane fraction of C. lutea has antibacterial activity against S. aureus, suggesting its potential as a possible candidate as a natural antibacterial agent in the food industry. This alternative could offer a safer and more sustainable solution compared to the conventional synthetic preservatives.

Invited review: Quantifying multiple burdens of dairy cattle production diseases and reproductive inefficiency-Current knowledge and proposed metrics

The economic burden of diseases and reproductive inefficiency in dairy cattle is evident and has been quantified. Dairy diseases and reproductive inefficiency are however associated with other issues as well, including animal welfare, environmental pressure, and public health risks. Quantifying these other issues is becoming important to help farmers make decisions. Quantification of the noneconomic burdens of diseases and reproductive inefficiency is rare and lacks an overview of approaches and metrics. The first aim of this paper is to provide trends for associating diseases and reproductive inefficiency with economic and noneconomic burdens of disease. The second aim is to provide a review of approaches and metrics used to quantify the noneconomic burdens of disease and reproductive inefficiency. For the economic burden of diseases and reproductive performance, only an overview of the approaches used to quantify the burden is provided. The final aim is to propose approaches and metrics for future quantification of noneconomic burdens caused by individual diseases. A literature search was conducted in Web of Science to identify scientific articles on mastitis, lameness, metabolic disorders, and reproductive inefficiency in dairy cows. The search was restricted to articles published between January 1, 2010 and December 31, 2022 and resulted in 7,565 articles. The total number of articles that mentioned the economic, animal welfare, public health, and environmental burden was 1,253, 428, 291, and 77, respectively. An increase in the percentage of articles mentioning the economic, animal welfare, and public health burden was observed between 2010 and 2022. Despite the 2,049 articles that mentioned one of the burdens, the results showed that approximately 10% of the articles quantified one or more of these burdens. The economic burden of diseases and reproductive inefficiency has been quantified in 154 articles and very few articles quantified the noneconomic burdens (9 articles for environment, 29 articles for public health, and 2 articles for animal welfare). Eleven articles were identified that quantified multiple burdens, and in all these studies the economic burden was combined with a noneconomic burden through a modeling approach (mainly simulation). We propose to link the noneconomic burdens to biological simulation models, and thus develop bioburden simulation models. Well-established approaches and metrics can be used to quantify economic, environmental, and public health burdens. For the economic impact, costs per cow per year can be assessed. A life cycle assessment can be performed for environmental impact and the public health impact can be assessed by a defined daily dose for antimicrobial use and disability-adjusted life years for zoonotic diseases. Regarding animal welfare, approaches and metrics to quantify the welfare impact of a diseased animal are not well established. For animal welfare, we propose a welfare-adjusted life years approach. The mentioned approaches and metrics are a proposal, and it is up to the scientific community to use them or, based on empirics and research experience, propose changes so that we will end up with robust approaches and metrics that enable us to compare research results and provide more evidence for animal health decision makers.

Relevant foodborne bacteria associated to pork production chain

Foodborne diseases affect millions of people globally, resulting in a huge number of hospitalizations and deaths. In this context, laboratory-based research is crucial to identify the major pathogens as well as the relevance of each one for distinct food production chains. Pork meat is very popular, being the most consumed meat in many countries and its inspection at the slaughterhouse is the main component of surveillance to protect consumers. Healthy pigs may carry pathogenic and antibiotic resistant bacteria that can be subsequently transferred to humans through the consumption of contaminated meat. Further, the food processing environment can harbor pathogenic persistent bacteria, representing a risk of cross-contamination to pork meat, demanding strict slaughtering procedures. Among these foodborne bacteria, Salmonella, Yersinia enterocolitica, Escherichia coli, Campylobacter spp., Listeria monocytogenes and Staphylococcus aureus are the most relevant in the pork production chain. Molecular subtyping has been fundamental for pathogen detection and also to track transmission, and nowadays it is a key component of the efforts to prevent and control foodborne diseases. In this chapter, characteristics of these major foodborne bacteria associated to pork meat will be addressed, including their occurrence and importance along the pork production chain, worldwide distribution, typing, as well as control and prevention measures from farm to fork.

The effect of 3D printing speed and temperature on transferability of Staphylococcus aureus and Escherichia coli during 3D food printing

The current study aimed to determine if the 3D-printing speed and temperature would impact the transferability of foodborne pathogens from the stainless-steel (SS) food cartridge to the 3D-printed food ink. Staphylococcus aureus and Escherichia coli were inoculated onto the interior surface of the SS food cartridges. Subsequently, a model food ink was extruded with a recommended macronutrient contribution of 55.8, 23.7, and 20.5% of carbohydrates, proteins, and fat, respectively. The impact of 3D-printing temperatures and speeds on transfer rates was analysed using a Two-Way ANOVA. S. aureus was transferred more from the cartridge to the food ink with a population of 3.39, 2.98, and 3.09 log CFU/g compared to 2.03, 2.06, and 2.00 log CFU/g for E. coli at 2000, 3000, and 4000 mm/s printing speed, respectively, at 25 °C. A Kruskal-Wallis Test was employed to investigate the effect of different speeds and temperatures on the transferability of S. aureus and E. coli. Speed was the main factor affecting S. aureus transferability, while temperature (25 and 50 °C) had the greatest impact on E. coli transferability. This research seeks to advance the understanding of 3D-printing parameters in pathogen transferability and help the food industry move towards this technology's quick and safe adoption.

Characterization of bacterial diversity in rhizospheric soils, irrigation water, and lettuce crops in municipalities near the Bogotá river, Colombia

The use of wastewater in agricultural practices poses a potential risk for the spread of foodborne diseases. Therefore, this study aimed to characterize the bacterial biodiversity in rhizospheric soil, irrigation water, and lettuce crops in three municipalities adjacent to the Bogotá River, Colombia. Samples were collected in Mosquera, Funza, and Cota municipalities, including rhizospheric soil, lettuce leaves, and irrigation water. The total DNA extraction was performed to analyze bacterial diversity through high-throughput sequencing of the 16S ribosomal RNA genes, utilizing the Illumina HiSeq 2500 PE 300 sequencing platform. A total of 198 genera from the rhizospheric soil were detected including a higher abundance of zOTUs such as Bacillus, Streptomyces, and clinically relevant genera such as Mycobacterium and Pseudomonas. In lettuce, the detection of 26 genera of endophytic bacteria showed to Proteobacteria and Firmicutes as the predominant phyla, with Staphylococcus and Bacillus as the most abundant genera. Notably, Funza's crops exhibited the highest abundance of endophytes, approximately 50 %, compared to Cota (20 %). Furthermore, the most abundant bacterial genera in the irrigation water were Flavobacterium and Pseudomonas. The most prevalent Enterobacteriaceae were Serratia, Enterobacter, Citrobacter, Klebsiella, Yersinia, Shigella, Escherichia, and Erwinia. The Bacillus genus was highly enriched in both rhizospheric soils and lettuce crops, indicating its significant contribution as the main endophytic bacterium.

Hook-Like DNAzyme-Activated Autocatalytic Biosensor for the Universal Detection of Pathogenic Bacteria

DNAzyme-based assays have found extensive utility in pathogenic bacteria detection but often suffer from limited sensitivity and specificity. The integration of a signal amplification strategy could address this challenge, while the existing combination methods require extensive modification to accommodate various DNAzymes, limiting the wide-spectrum bacteria detection. We introduced a novel hook-like DNAzyme-activated autocatalytic nucleic acid circuit for universal pathogenic bacteria detection. The hook-like connector DNA was employed to seamlessly integrate the recognition element DNAzyme with the isothermal enzyme-free autocatalytic hybridization chain reaction and catalytic hairpin assembly for robust exponential signal amplification. This innovative autocatalytic circuit substantially amplifies the output signals from the DNAzyme recognition module, effectively overcoming DNAzyme's inherent sensitivity constraints in pathogen identification. The biosensor exhibits a strong linear response within a range of 1.5 × 103 to 3.7 × 107 CFU/mL, achieving a detection limit of 1.3 × 103 CFU/mL. Noted that the sensor's adaptability as a universal detection platform is established by simply modifying the hook-like connector module, enabling the detection of various pathogenic bacteria of considerable public health importance reported by the World Health Organization, including Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Salmonella typhimurium. Additionally, the specificity of DNAzyme in bacterial detection is markedly improved due to the signal amplification process of the autocatalytic circuit. This hook-like DNAzyme-activated autocatalytic platform presents a versatile, sensitive, and specific approach for pathogenic bacteria detection, promising to significantly expand the applications of DNAzyme in bacteria detection.

Acute toxicity and anti-enterotoxigenic activity of pigment extracted from Micrococcus roseus

Microbial pigments are considered as one of the main sources of natural types, and the attention to them is increasing in the food and pharmaceutical industries. This study aimed to investigate the effects of pigments extracted from Micrococcus roseus (PEM) on the gene expression of a and b staphylococcal enterotoxins (sea and seb) and their acute toxicity. Real-time PCR was used to study the anti-enterotoxigenic activity of PEM against Staphylococcus aureus at sub-inhibitory concentrations. In addition, the acute toxicity of PEM was evaluated on albino mice through alkaline phosphatase (ALP), aspartate aminotransferas (AST), and alanine aminotransferase (ALT) of liver and its histopathological changes. Based on the results, the expression of sea and seb was decreased in the presence of PEM at sub-inhibitory concentrations. The 2-∆∆CT was measured 0.02 and 0.01 for the expression of sea and seb of S. aureus grown in the MHB containing 16 mg/ml PEM. The results showed that the expression of seb is more sensitive to PEM compared to the expression of sea. After treatment of mice with PEM for two weeks, the condition of mice was normal, and the results of liver enzymatic activities and histopathological changes showed insignificant difference compared to the control sample.

Genomic epidemiology of the primary methicillin-resistant Staphylococcus aureus clones causing invasive infections in Paraguayan children

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major human pathogens. It could carry numerous resistance genes and virulence factors in its genome, some of which are related to the severity of the infection. An observational, descriptive, cross-sectional study was designed to molecularly analyze MRSA isolates that cause invasive infections in Paraguayan children from 2009 to 2013. Ten representative MRSA isolates of the main clonal complex identified were analyzed with short-read paired-end sequencing and assessed for the virulome, resistome, and phylogenetic relationships. All the genetically linked MRSA isolates were recovered from diverse clinical sources, patients, and hospitals at broad gap periods. The pan-genomic analysis of these clones revealed three major and different clonal complexes (CC30, CC5, and CC8), each composed of clones closely related to each other. The CC30 genomes prove to be a successful clone, strongly installed and disseminated throughout our country, and closely related to other CC30 public genomes from the region and the world. The CC5 shows the highest genetic variability, and the CC8 carried the complete arginine catabolic mobile element (ACME), closely related to the USA300-NAE-ACME+, identified as the major cause of CA-MRSA infections in North America. Multiple virulence and resistance genes were identified for the first time in this study, highlighting the complex virulence profiles of MRSA circulating in the country. This study opens a wide range of new possibilities for future projects and trials to improve the existing knowledge on the epidemiology of MRSA circulating in Paraguay.

IMPORTANCE

The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) is a public health problem worldwide. The most frequent MRSA clones identified in Paraguay in previous studies (including community and hospital acquired) were the Pediatric (CC5-ST5-IV), the Cordobes-Chilean (CC5-ST5-I), the SouthWest Pacific (CC30-ST30-IV), and the Brazilian (CC8-ST239-III) clones. In this study, the pan-genomic analysis of the most representative MRSA clones circulating in invasive infection in Paraguayan children over the years 2009-2013, such as the CC30-ST30-IV, CC5-ST5-IV, and CC8-ST8-IV, was carried out to evaluate their genetic diversity, their repertoire of virulence factors, and antimicrobial resistance determinants. This revealed multiple virulence and resistance genes, highlighting the complex virulence profiles of MRSA circulating in Paraguay. Our work is the first genomic study of MRSA in Paraguay and will contribute to the development of genomic surveillance in the region and our understanding of the global epidemiology of this pathogen.

Line image sensor-based colony fingerprinting system for rapid pathogenic bacteria identification

The rapid identification of pathogenic bacteria is crucial across various industries, including food or beverage manufacturing. Bacterial microcolony image-based classification has emerged as a promising approach to expedite identification, automate inspections, and reduce costs. However, conventional imaging methods have significant practical limitations, namely low throughput caused by the limited imaging range and slow imaging speed. To address these challenges, we developed an imaging system based on a line image sensor for rapid and wide-field imaging compared to existing colony imaging methods. This system can image a standard Petri dish (92 mm in diameter) completely within 22 s, successfully acquiring bacterial microcolony images. This process yielded a set of discrimination parameters termed as colony fingerprints, which were employed for machine learning. We demonstrated the performance of our system by identifying Staphylococcus aureus in food products using a machine learning model trained on a colony fingerprint dataset of 15 species from 9 genera, including foodborne pathogens. While conventional mass spectrometry-based methods require 24 h of incubation, our colony fingerprinting approach achieved 96% accuracy in just 10 h of incubation. Line image sensor offer high imaging speeds and scalability, allowing for swift and straightforward microbiological testing, eliminating the need for specialized expertise and overcoming the limitations of conventional methods. This innovation marks a transformative shift in industrial applications.

Effect of Gamma Irradiation on Pathogenic Staphylococcus aureus in Packaged Ready-to-Eat Salads Treated with Biological Extracts

Providing pathogen-free ready-to-eat (RTE) salads is critical for all consumers, especially individuals with weakened immunity. In this study, the efficacy of γ-irradiation on Staphylococcus aureus (S. aureus) in freshly packaged salads (4.24 log CFU/g) treated with essential oil (EO) and myrtle juice during 10 days of storage and their impact on organoleptic properties were investigated. EO was extracted by hydrodistillation and the chemical composition was analyzed by gas chromatography with Flame Ionization Detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS). Myrtle juice was prepared from fresh fruits. The cytotoxic effects of Thymus capitatus (T. capitatus) EO against a normal human umbilical vein endothelial cell (HUVEC) were assessed. GC/FID and GC-MS analysis of the thyme EO revealed the presence of 13 compounds, including carvacrol (79.55%) and p-cymene (7.93%) as major components. The EO was found to be noncytotoxic, with concentrations lower than 0.16 µL/mL. A reduction of more than 3 log CFU/g and a total inactivation of S. aureus were achieved with the combination of gamma irradiation at 0.5 kGy with myrtle juice at 6 µL/mL and EO at 0.08 µL/mL, respectively. The treatment of fresh RTE salads with thyme and myrtle juice was evaluated as acceptable by the sensory panel. The combined effect showed a synergistic potential on the inactivation of S. aureus.

Toxigenic characterization, spoilage potential, and antimicrobial susceptibility of coagulase-positive Staphylococcus species isolated from Minas Frescal cheese

This study aimed to identify coagulase-positive staphylococci (CPS) species from 21 samples of clandestine Minas Frescal cheese, investigate the potential for deterioration in psychrotrophic and mesophilic conditions, verify the toxigenic potential of Staphylococcus aureus, and determine the antimicrobial susceptibility profile of toxigenic S. aureus. Species determination was performed based on the detection of β-hemolysis in 5% ovine blood agar; fermentation of mannitol, maltose, and trehalose sugars; and production of acetoin. After species determination, DNA extraction and analysis was performed for S. aureus colonies for genes encoding staphylococcal toxins (eta, etb, tst, sea, seb, sec, sed, and see) using 2 multiplex PCR assays. Isolates identified as toxigenic S. aureus were tested for antimicrobial susceptibility to tetracycline, erythromycin, clindamycin, gentamicin, ciprofloxacin, sulfazotrim, trimethoprim, streptomycin, cefoxitin, vancomycin and enrofloxacin. Elevated CPS counts were observed with an average of >6 log cfu/g. Of the 355 isolates, 177 (49.86%) were identified as S. aureus. Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus delphini, and Staphylococcus coagulans were identified in 3 (0.84%), 2 (0.56%), 2 (0.56%), and 1 (0.28%) isolates, respectively. Of the total number of S. aureus, 25 (52.08%) were positive for the gene that encodes for toxic shock toxin (TSST-1). Another 16 (33.33%) were positive for the sea gene, and 4 isolates (8.33%) were positive for see and one isolate each was positive for seb (2.08%), sec (2.08%), and etb (2.08%) genes. All isolates demonstrated lipolytic activity under mesophilic and psychrotrophic conditions. S. intermedius and S. hyicus had the most prominent proteolytic potential. Multidrug resistance was observed in most of the potentially toxigenic isolates, with clindamycin having the lowest efficiency (40%), whereas the aminoglycosides (gentamicin and streptomycin) had the highest effectiveness demonstrating inhibition in all evaluated isolates. Methicillin-resistant S. aureus (MRSA) was detected. Minas Frescal cheeses, marketed in the north of Tocantins in the Brazilian Amazon region, do not comply with legal quality standards and pose a public health risk due to the enterotoxigenic potential of multiresistant isolates, in addition to low shelf life of the samples given the high spoilage potential of this microbiota.

Exploring the Antibacterial Potential and Underlying Mechanisms of Prunella vulgaris L. on Methicillin-Resistant Staphylococcus aureus

Prunella vulgaris L. (PV) is a widely distributed plant species, known for its versatile applications in both traditional and contemporary medicine, as well as in functional food development. Despite its broad-spectrum antimicrobial utility, the specific mechanism of antibacterial action remains elusive. To fill this knowledge gap, the present study investigated the antibacterial properties of PV extracts against methicillin-resistant Staphylococcus aureus (MRSA) and assessed their mechanistic impact on bacterial cells and cellular functions. The aqueous extract of PV demonstrated greater anti-MRSA activity compared to the ethanolic and methanolic extracts. UPLC-ESI-MS/MS tentatively identified 28 phytochemical components in the aqueous extract of PV. Exposure to an aqueous extract at ½ MIC and MIC for 5 h resulted in a significant release of intracellular nucleic acid (up to 6-fold) and protein (up to 10-fold) into the extracellular environment. Additionally, this treatment caused a notable decline in the activity of several crucial enzymes, including a 41.51% reduction in alkaline phosphatase (AKP), a 45.71% decrease in adenosine triphosphatase (ATPase), and a 48.99% drop in superoxide dismutase (SOD). Furthermore, there was a decrease of 24.17% at ½ MIC and 27.17% at MIC in tricarboxylic acid (TCA) cycle activity and energy transfer. Collectively, these findings indicate that the anti-MRSA properties of PV may stem from its ability to disrupt membrane and cell wall integrity, interfere with enzymatic activity, and impede bacterial cell metabolism and the transmission of information and energy that is essential for bacterial growth, ultimately resulting in bacterial apoptosis. The diverse range of characteristics exhibited by PV positions it as a promising antimicrobial agent with broad applications for enhancing health and improving food safety and quality.

Novel helix loop-mediated isothermal amplification (HAMP) assay for colorimetric detection of Staphylococcus aureus in milk

Staphylococcus aureus is an important and leading cause of foodborne diseases worldwide. Prompt detection and recall of contaminated foods are crucial to prevent untoward health consequences caused by S. aureus. Helix loop-mediated isothermal amplification (HAMP) is an exciting recent addition to the array of available isothermal-based nucleic acid amplification techniques. This study aimed to develop and evaluate a HAMP assay for detecting S. aureus in milk and milk products. The assay is completed in 75 minutes of isothermal temperature incubation (64 ˚C) and dye-based visual interpretation of results based on colour change. The specificity of the developed assay was ascertained using 27 S. aureus and 17 non S. aureus bacterial strains. The analytical sensitivity of the developed HAMP assay was 9.7 fg/µL of pure S. aureus DNA. The detection limit of the HAMP assay in milk (86 CFU/mL) was 1000x greater than the routinely used endpoint PCR (86 × 103 CFU/mL). The practicality of applying the HAMP assay was also assessed by analysing milk and milk product samples (n = 95) obtained from different dairy farms and retail outlets. The developed test is a more rapid, sensitive, and user-friendly method for the high-throughput screening of S. aureus in food samples and may therefore be suitable for field laboratories. To our knowledge, this is the first study to develop and evaluate the HAMP platform for detecting S. aureus.

Presence and Resistance Profile of Staphylococcus spp. Isolated from Slaughtered Pigs

Background: The objective of this study was to isolate Staphylococcus spp. and to characterize the resistance profile in nasal samples from pigs slaughtered for consumption. Material and Methods: Intranasal swabs were collected from 100 pigs immediately after bleeding in a slaughterhouse located in the largest pork production region in Brazil, these samples were cultured and isolated to identify Staphylococcus spp. in coagulase positive (CoPS) and coagulase negative (CoNS) and molecular identification of Staphylococcus aureus and then subjected to the disk-diffusion test to identify the bacterial resistance profile and search for the mecA gene. Results: Of the 100 samples collected, it was possible to isolate 79 Staphylococcus spp., of these, 72.15% were classified as CoNS and 27.85% of the isolates classified as CoPS. Among the CoPS isolates, 77.27% were identified as S. aureus. Through the disk-diffusion test, it was possible to verify isolates resistant to clindamycin and erythromycin (98.73%), chloramphenicol (93.67%), and doxycycline (89.87%). There was amplification of the mecA gene in 30.38% of Staphylococcus spp. Conclusion: The results of this study highlight the need for the careful use of antibiotics in swine production, in addition to aiming at continuous surveillance in relation to the rate of multiresistant microorganisms within these environments, focused on large industrial centers; such results also indicate the importance of understanding, through future studies, possible pathways to transmission of these microorganisms directly, or indirectly, through meat products derived from these pigs, which can be considered neglected diffusers of variants of Staphylococcus spp. resistant to antibiotics or carriers of important resistance genes related to One Health.

Prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates in frozen flour and rice products in Shanghai, China

Staphylococcus aureus is widely recognized as a highly hazardous pathogen that poses significant threats to food safety and public health. This study aimed to assess the prevalence, antimicrobial resistance, and genetic characteristics of S. aureus isolates recovered from 288 frozen flour and rice product samples in Shanghai, China, between September 2019 and May 2020. A total of 81 S. aureus isolates were obtained, representing 25 sequence types (STs), with ST7 being the most prevalent (17.28%, n = 14). The majority of S. aureus isolates (85.19%, n = 69) carried at least one enterotoxin gene, with the seg gene being the most frequently detected (51.85%, n = 42). Additionally, 12 isolates (14.81%) were identified as methicillin-resistant S. aureus (MRSA) through mecA gene detection. Notably, this study reported the presence of an ST398 MRSA isolate in frozen flour and rice products for the first time. All MRSA isolates displayed multidrug resistance, with the highest resistance observed against cefoxitin (100.00%), followed by penicillin (91.67%) and erythromycin (66.67%). Genomic analysis of the 12 MRSA isolates revealed the presence of twenty distinct acquired antimicrobial resistance genes (ARGs), eight chromosomal point mutations, and twenty-four unique virulence genes. Comparative genome analysis indicated close genetic relationships between these MRSA isolates and previously reported MRSA isolates from clinical infections, highlighting the potential transmission of MRSA through the food chain and its implications for public health. Significantly, the identification of three plasmids harboring ARGs, insertion sequences (ISs), the origin of transfer site (oriT), and the relaxase gene suggested the potential for horizontal transfer of ARGs via conjugative plasmids in S. aureus. In conclusion, this study revealed significant contamination of retail frozen flour and rice products with S. aureus, and provided essential data for ensuring food safety and protecting public health.

Genomic Insights into Methicillin-Resistant Staphylococci and Mammaliicocci from Bulk Tank Milk of Dairy Farms in Serbia

The potential risk to human and animal health provides a rationale for research on methicillin-resistant staphylococci (MRS) and mammaliicocci (MRM) in dairy herds. Here, we aimed to estimate their occurrence in the bulk tank milk (BTM) samples collected in 2019-2021 from 283 bovine dairy farms in the Belgrade district. We used whole-genome sequencing to characterize the obtained isolates and assess their genetic relatedness. A total of 70 MRS/MRM were recovered, most frequently Staphylococcus haemolyticus and Mammaliicoccus sciuri. Five clusters of 2-4 genetically related isolates were identified and epidemiological data indicated transmission through, e.g., farm visits by personnel or milk collection trucks. Most MRSA isolates belonged to the typical livestock-associated lineage ST398-t034. One MRSA isolate (ST152-t355) harbored the PVL-encoding genes. Since MRS/MRM isolates obtained in this study frequently harbored genes conferring multidrug resistance (MDR), this argues for their role as reservoirs for the spread of antimicrobial resistance genes. The pipeline milking system and total bacterial count >100,000 CFU/mL were significantly associated with higher occurrences of MRS/MRM. Our study confirms that BTM can be a zoonotic source of MRS, including MDR strains. This highlights the urgent need for good agricultural practices and the continuous monitoring of MRS/MRM in dairy farms.

Prevalence of Foodborne Bacterial Pathogens and Antibiotic Resistance Genes in Sweets from Local Markets in Iran

BACKGROUND

This study aimed to investigate the prevalences of some important antibiotic-resistance genes (ARGs) and foodborne bacterial pathogens in sweet samples collected from local markets in Iran.

METHODS

Forty sweet samples were collected. Foodborne pathogens and ARGs were detected in the sweet samples by conventional and multiplex PCR assays using species-specific primers.

RESULTS

Staphylococcus aureus, Cronobacter sakazakii, Shigella spp., Campylobacter jejuni, and Campylobacter coli were detected and identified in 47.5%, 20%, 45%, 5%, and 30% of the sweet samples, respectively. We found S. aureus and Shigella spp. were the most prevalent bacterial pathogens. S. aureus was found to be the most frequent pathogenic bacteria profiled in these samples. We also found a significant correlation between the presence of C. coli and Cr. sakazakii. We detected the blaSHV resistance gene in 97.5% of the sweet samples; however, blaTEM was detected in only one sample (2.5%).

CONCLUSIONS

Regarding these results, we suggest preventive strategies such as implementing automation of food processing; monitoring the personal hygiene and health of food handlers, and testing regularly for antibiotic resistance in raw materials and products.

Effect of Time on the Properties of Bio-Nanocomposite Films Based on Chitosan with Bio-Based Plasticizer Reinforced with Nanofiber Cellulose

The deterioration of the performance of polysaccharide-based films over time, particularly their hydrophilicity and mechanical properties, is one of the main problems limiting their applications in the packaging industry. In the present study, we proposed to improve the performance of chitosan-based films through the use of: (1) nanocellulose as an additive to reduce their hydrophilic nature; (2) bio-based plasticizer to improve their mechanical properties; and (3) chestnut extract as an antimicrobial agent. To evaluate their stability over time, the properties of as-formed films (mechanical, hydrophilic, barrier and antibacterial) were studied immediately after preparation and after 7, 14 and 30 days. In addition, the morphological properties of the films were characterized by scanning electron microscopy, their structure by FTIR, their transparency by UV-Vis and their thermal properties by TGA. The films showed a hydrophobic character (contact angle above 100°), barrier properties to oxygen and carbon dioxide and strong antibacterial activity against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Moreover, the use of nanofillers did not deteriorate the elongation at breaks or the thermal properties of the films, but their addition reduced the transparency. In addition, the results showed that the greatest change in film properties occurred within the first 7 days after sample preparation, after which the properties were found to stabilize.

Stress Lowers Staphylococcal Enterotoxin C Production Independently of Agr, SarA, and SigB

Staphylococcal enterotoxin C (SEC) can cause staphylococcal food poisoning, one of the most prevalent foodborne intoxications. It is produced by Staphylococcus aureus during growth in the food matrix. While the surrounding bacteria in food matrices usually repress the growth of S.aureus, the organism possesses a remarkable growth advantage under stressful conditions encountered in many foods. Examples for such food matrices are pastry and bakery products with their high sugar content that lowers water availability. While S. aureus can still grow in these challenging environments, it remains unclear how these conditions affect SEC expression. Here, the influence of 30% glucose on sec mRNA in a qPCR assay and SEC protein expression was investigated for the first time in an ELISA. In addition, regulatory knockout mutants Δagr, ΔsarA, and ΔsigB were generated to investigate regulatory gene elements in glucose stress. In five out of seven strains, glucose stress led to a pronounced decrease in sec mRNA transcription and SEC protein levels were substantially lower under glucose stress. It could be shown that key regulatory elements Δagr, ΔsarA, and ΔsigB in strain SAI48 did not contribute to the pronounced downregulation under glucose stress. Based on these findings, glucose effectively lowers SEC synthesis in the food matrix. However, the mechanism by which it acts on toxin expression and regulatory elements in S. aureus remains unclear. Future studies on other regulatory elements and transcriptomics may shed light on the mechanisms.

Biosynthesis of selenium nanoparticles by lactic acid bacteria and areas of their possible applications

Lactic acid bacteria, being generally recognized as safe, are the preferred choice among other microbial producers of selenium nanoparticles. For successful production of SeNPs, it is necessary to take into account the physiological properties of the bacterium used as a biotransformer of inorganic forms of selenium in Se⁰. The antimicrobial and antioxidant activity of SeNPs allows to use them in the form of pure nanoparticles or biomass of lactic acid bacteria enriched with selenium in preparation of food, in agriculture, aquaculture, medicine, veterinary, and manufacturing of packing materials for food products. To attract attention to the promising new directions of lactic acid bacteria applications and to accelerate their implementation, the examples of the use of SeNPs synthesized by lactic acid bacteria in the mentioned above areas of human activity are described.

Laboratory evaluation of the broad-spectrum antibacterial efficacy of a low-irradiance visible 405-nm light system for surface-simulated decontamination

Purpose

Lighting systems which use visible light blended with antimicrobial 405-nm violet-blue light have recently been developed for safe continuous decontamination of occupied healthcare environments. This paper characterises the optical output and antibacterial efficacy of a low irradiance 405-nm light system designed for environmental decontamination applications, under controlled laboratory conditions.

Methods

In the current study, the irradiance output of a ceiling-mounted 405-nm light source was profiled within a 3×3×2 m (18 m3) test area; with values ranging from 0.001-2.016 mWcm-2. To evaluate antibacterial efficacy of the light source for environmental surface decontamination, irradiance levels within this range (0.021-1 mWcm-2) at various angular (Δ ϴ=0-51.3) and linear (∆s=1.6-2.56 m) displacements from the source were used to generate inactivation kinetics, using the model organism, Staphylococcus aureus. Additionally, twelve bacterial species were surface-seeded and light-exposed at a fixed displacement below the source (1.5 m; 0.5 mWcm-2) to demonstrate broad-spectrum efficacy at heights typical of high touch surfaces within occupied settings.

Results

Results demonstrate that significant (P≤0.05) inactivation was successfully achieved at all irradiance values investigated, with spatial positioning from the source affecting inactivation, with greater times required for inactivation as irradiance decreased. Complete/near-complete (≥93.28%) inactivation of all bacteria was achieved following exposure to 0.5 mWcm-2 within exposure times realistic of those utilised practically for whole-room decontamination (2-16 h).

Conclusion

This study provides fundamental evidence of the efficacy, and energy efficiency, of low irradiance 405-nm light for bacterial inactivation within a controlled laboratory setting, further justifying its benefits for practical infection control applications.

Nanostructured biosensing platforms for the detection of food- and water-borne pathogenic Escherichia coli

Pathogenic bacterial infection is one of the principal causes affecting human health and ecosystems. The accurate identification of bacteria in food and water samples is of significant interests to maintain safety and health for humans. Culture-based tests are practically tedious and may produce false-positive results, while viable but non-culturable microorganisms (NCMs) cannot be retrieved. Thus, it requires fast, reliable, and low-cost detection strategies for on-field analysis and point-of-care (POC) monitoring. The standard detection methods such as nucleic acid analysis (RT-PCR) and enzyme-linked immunosorbent assays (ELISA) are still challenging in POC practice due to their time-consuming (several hours to days) and expensive laboratory operations. The optical (surface plasmon resonance (SPR), fluorescence, and surface-enhanced Raman scattering (SERS)) and electrochemical-based detection of microbes (early stage of infective diseases) have been considered as alternative routes in the emerging world of nanostructured biosensing since they can attain a faster and concurrent screening of several pathogens in real samples. Moreover, optical and electrochemical detection strategies are opening a new route for the ability of detecting pathogens through the integration of cellphones, which is well fitted for POC analysis. This review article covers the current state of sensitive mechanistic approaches for the screening and detection of Escherichia coli O157:H7 (E. coli) pathogens in food and water samples, which can be potentially applied in clinical and environmental monitoring.

"Forbidden Fish": Did King Henry I Die of Lamprey Poisoning?

For centuries, the sudden and mysterious death of King Henry I has been attributed to a large meal of lampreys that accidentally poisoned the unfortunate monarch. In this article, we conclude that lampreys were likely not the cause of the king's illness, nor is it likely that he was deliberately poisoned. Although a wide variety of abdominal pathologies could have been responsible, we suggest that a sporadic central nervous system (CNS) infection of Listeria monocytogenes appears to be the most likely cause of Henry's death, correlating with both his symptoms and rapid decline.

Impact of the revision of European food hygiene legislation and the introduction of convenience-based food on food safety in the German military

The implementation of the European Food Regulation in the German military started in 2003 and was fully implemented in 2006. In addition, in 2003 the German military introduced the concept of using convenience-based foods targeted to improve the safety of food served to the troops. The aim of this study was to evaluate the impact of these changes on food safety and the occurrence of food-borne disease outbreaks in the German military. For this purpose, data from a total of 517 food-borne outbreaks that occurred between 1995 and 2019 in the responsible areas of the German military both within the country and abroad were subjected to a retrospective analysis. As a result, a significant decrease (p = 2.47 × 10^-5) in the number of the food-borne outbreak was observed in the second observation period (2003-2019) compared to the first period (1995-2002). Food groups often found contaminated with pathogens were desserts and prepared dishes (first period), fresh produce, soups, and sauces (second period). Bacillus cereus, Enterobacteriaceae, Salmonella spp., and Staphylococcus aureus were dominant pathogens isolated from suspected foods during disease outbreaks in both periods, however, the absolute number of isolates reduced significantly in the second period. Therefore it can be concluded that the implementation of European food hygiene regulations together with the introduction of convenience-based foods had a significant positive impact on food safety in the German military.

Fluoroplast Doped by Ag2O Nanoparticles as New Repairing Non-Cytotoxic Antibacterial Coating for Meat Industry

Foodborne infections are an important global health problem due to their high prevalence and potential for severe complications. Bacterial contamination of meat during processing at the enterprise can be a source of foodborne infections. Polymeric coatings with antibacterial properties can be applied to prevent bacterial contamination. A composite coating based on fluoroplast and Ag₂O NPs can serve as such a coating. In present study, we, for the first time, created a composite coating based on fluoroplast and Ag₂O NPs. Using laser ablation in water, we obtained spherical Ag₂O NPs with an average size of 45 nm and a ζ-potential of -32 mV. The resulting Ag₂O NPs at concentrations of 0.001-0.1% were transferred into acetone and mixed with a fluoroplast-based varnish. The developed coating made it possible to completely eliminate damage to a Teflon cutting board. The fluoroplast/Ag₂O NP coating was free of defects and inhomogeneities at the nano level. The fluoroplast/Ag₂O NP composite increased the production of ROS (H₂O₂, OH radical), 8-oxogualnine in DNA in vitro, and long-lived active forms of proteins. The effect depended on the mass fraction of the added Ag₂O NPs. The 0.01-0.1% fluoroplast/NP Ag₂O coating exhibited excellent bacteriostatic and bactericidal properties against both Gram-positive and Gram-negative bacteria but did not affect the viability of eukaryotic cells. The developed PTFE/NP Ag₂O 0.01-0.1% coating can be used to protect cutting boards from bacterial contamination in the meat processing industry.

In Vivo Pathogenicity of Methicillin-Susceptible Staphylococcus aureus Strains Carrying Panton-Valentine Leukocidin Gene

Toxin-producing Staphylococcus aureus strains posing a potential risk for public health have long been a topic of scientific research. Effects of Panton-Valentine leukocidin (PVL) on tissue destruction mechanisms and activities of inflammatory cells were presented in animal models of pneumonia and skin infections induced by PVL-producing S. aureus strains. This study aimed to demonstrate the in vivo pathogenicity of PVL-producing S. aureus strains isolated from some foodstuffs, which can be a potential risk to public health. PVL-positive methicillin-susceptible S. aureus (MSSA) strains M1 and YF1B-b isolated from different foodstuffs and a PVL-positive MSSA strain HT480 (positive control) were administered to New Zealand rabbits. Blood samples were harvested three and six hours after the intratracheal inoculation. Lung tissue samples were collected for gross and microscopic exams and immunohistochemical (IHC) demonstration of IL-6, IL8, IL-10, and TNF-α expressions. Serum cytokine levels were also measured by ELISA. The strains isolated from lung tissue samples were confirmed by pulsed-field gel electrophoresis. The development of acute necrotising pneumonia and a significant elevation in IL-6, IL-8, IL-10, and TNF-α expressions demonstrated the significance of foodborne PVL-positive MSSA strains in public health for the first time.

Review of major meat-borne zoonotic bacterial pathogens

The importance of meat-borne pathogens to global disease transmission and food safety is significant for public health. These pathogens, which can cause a variety of diseases, include bacteria, viruses, fungi, and parasites. The consumption of pathogen-contaminated meat or meat products causes a variety of diseases, including gastrointestinal ailments. Humans are susceptible to several diseases caused by zoonotic bacterial pathogens transmitted through meat consumption, most of which damage the digestive system. These illnesses are widespread worldwide, with the majority of the burden borne by developing countries. Various production, processing, transportation, and food preparation stages can expose meat and meat products to bacterial infections and/or toxins. Worldwide, bacterial meat-borne diseases are caused by strains of Escherichia coli, Salmonella, Listeria monocytogenes, Shigella, Campylobacter, Brucella, Mycobacterium bovis, and toxins produced by Staphylococcus aureus, Clostridium species, and Bacillus cereus. Additionally, consuming contaminated meat or meat products with drug-resistant bacteria is a severe public health hazard. Controlling zoonotic bacterial pathogens demands intervention at the interface between humans, animals, and their environments. This review aimed to highlight the significance of meat-borne bacterial zoonotic pathogens while adhering to the One Health approach for creating efficient control measures.

Relationship between Biofilm Formation and Antibiotic Resistance and Adherence Genes in Staphylococcus aureus Strains Isolated from Raw Cow Milk in Shahrekord, Iran

The production of biofilms by S. aureus contributes significantly to treatment failures. The present study aims to establish the relationship between biofilm formation and antibiotic resistance and adhesion genes in Staphylococcus aureus strains isolated from raw cow milk in Shahrekord, Iran. A total of 90 samples of raw cow's milk were collected. Presumptive S. aureus strains were obtained using Baird-Parker plates after enrichment in tryptone soy broth, and final colonies were selected from brain heart infusion. Additional tests such as coagulase were done, and the identification was confirmed by the detection of the aroA gene. Biofilm producing strains were screened using a spectrophotometry method applied to microplates. Crystal violet staining was used to quantify the formation of biofilm. An antibiotic susceptibility test was performed using the Kirby-Bauer disc diffusion method. PCR was used to detect several biofilm and antibiotics resistance related genes. The chi-square test and Fisher's exact test were used to establish a statistically significant relationship between biofilm reaction and antibiotic resistance (p value <0.05). Results show a moderate (38.88%) recovery rate of S. aureus in milk and 65.71% of the isolates were strong biofilm producers. Antibiotic susceptibility tests show an alarming rate of resistance to beta-lactam antibiotics, especially penicillin (100%), ampicillin (91.42%), and oxacillin (71.42%). This finding correlates with antibiotic resistance gene detection, in which the gene blaZ was most found (71.42%), followed by mecA and Aac-D (42.85%). Detection of biofilm-related genes shows that all the genes targeted were found among S. aureus isolates. Statistical tests show a significant correlation between biofilm production and antibiotic resistance in S. aureus. This study revealed that there is a significant correlation between biofilm production and antibiotic resistance in S. aureus isolated from raw milk. These results highlight the need for regular surveillance of the occurrence of S. aureus strains in milk and milk products in Iran.

Whole-Genome Analysis of Staphylococcus aureus Isolates from Ready-to-Eat Food in Russia

This study provides a thorough investigation of a diverse set of antimicrobial resistant (AMR) Staphylococcus aureus isolates collected from a broad range of ready-to-eat (RTE) food in various geographic regions of Russia ranging from Pskov to Kamchatka. Thirty-five isolates were characterized using the whole genome sequencing (WGS) analysis in terms of clonal structure, the presence of resistance and virulence determinants, as well as plasmid replicon sequences and CRISPR/Cas systems. To the best of our knowledge, this is the first WGS-based surveillance of Russian RTE food-associated S. aureus isolates. The isolates belonged to fifteen different multilocus sequence typing (MLST)-based types with a predominant being the ones of clonal complex (CC) 22. The isolates studied can pose a threat to public health since about 40% of the isolates carried at least one enterotoxin gene, and 70% of methicillin-resistant (MRSA) isolates carried a tsst1 gene encoding a toxin that may cause severe acute disease. In addition, plasmid analysis revealed some important characteristics, e.g., Rep5 and Rep20 plasmid replicons were a “signature” of MRSA CC22. By analyzing the isolates belonging to the same/single strain based on cgMLST analysis, we were able to identify the differences in their accessory genomes marking their dynamics and plasticity. This data is very important since S. aureus isolates studied and RTE food, in general, represent an important route of transmission and dissemination of multiple pathogenic determinants. We believe that the results obtained will facilitate performing epidemiological surveillance and developing protection measures against this important pathogen in community settings.

The antimicrobial and bioactive properties of lactobionic acid

Lactobionic acid (LBA) is a bioactive molecule that has generated keen interest in different industries. However, its future application in the food area is one of the most promising. Chemically, it is a polyhydroxy acid formed by the union of two molecules (galactose and gluconic acid) linked by an ether-bond, showing many interesting and unusual properties due to its structure and composition, although it is traditionally known in the food industry for its chelating, moisturizing, gelling, and antioxidant properties. There has been much research into the production of LBA, either by microbial fermentation or biocatalytic approaches such as enzymatic synthesis, but its use in foodstuffs, to produce new functional products and to evaluate its antimicrobial activity against food-borne pathogens, is a relatively new topic that has attracted the interest of the international research community recently. Furthermore, in spite of the potential of LBA, it has been approved only by the US Food and Drug Administration, and for its use as the salt form, but the publication of new comprehensive studies, able to agglutinate all the new food-related LBA research results, could disseminate knowledge about this compound and have an influence on its current regulation status. The aim of the present review is to describe the most recent advances and research on its antimicrobial potential, as well as summarizing the significant aspects that make LBA a promising bioactive compound for the food sector. © 2022 Society of Chemical Industry.

New 1,3,4-oxadiazole compound with effective antibacterial and antibiofilm activity against Staphylococcus aureus

Staphylococcus aureus is one of the main aetiological agents causing food-borne diseases. Some strains produce enterotoxins responsible for food poisoning. In addition, they can form biofilms on several surfaces such as plastics, glass and stainless steel making it difficult to eliminate them. The present study evaluated, for the first time, the antibacterial and antibiofilm activities of the synthetic compound LMM6 against S. aureus. The minimum inhibitory concentration was 0·97, 1·95 and 1·95 μg ml^-1 against S. aureus ATCC 25923, S. aureus 629/94 and S. aureus FRI S-6, respectively. The time-kill curves showed that 96 h treatment with LMM6 reduced approximately 4 log CFU per ml at all tested concentrations. Furthermore, LMM6 reduced S. aureus preformed biofilm by approximately 1 log CFU per cm² . During biofilm formation, a reduction of approximately 4 log CFU per cm² was observed. LMM6 also reduced biofilm biomass during (~60%) and after biofilm formation (~25 to 45%), as shown by the crystal violet assay. Based on these results, we conclude that LMM6 exhibits antibacterial and antibiofilm activity and may be an innovative synthetic molecule for controlling S. aureus.

Virulence and antimicrobial resistance gene profiles of Staphylococcus aureus associated with clinical mastitis in cattle

Staphylococcus aureus (S. aureus) is the most prevalent microorganism associated with mastitis in cattle, which harbours several virulence factors and antibiotic resistance genes. The present study aimed to characterize S. aureus isolated from mastitic milk of the cattle for antibiotic resistance (blaZ and mecA), haemolysins (hla and hlb) and enterotoxins (sea, seb, sec, and sed) genes. A total of 69 staphylococci were isolated and phenotypically characterized for haemolytic properties on 5% sheep blood agar medium. Out of 69 isolates, 55 (79.71%) were identified as S. aureus by polymerase chain reaction assay. Among S. aureus, the majority of the isolates harboured the gene blaZ (92.73%), followed by coa (89.09%), hlb (60%) and hla (49.09%). Gene mecA responsible for methicillin resistance was detected in 23.64% of S. aureus isolates. Enterotoxin genes seb (9.09%), sec (1.82%) and sed (7.27%) responsible for food poisoning were detected at a comparatively lower rate and none of the S. aureus strain was found positive for sea. Additionally, antimicrobial susceptibility study of S. aureus against 18 antimicrobial discs showed maximum resistance to oxytetracycline, penicillin, and fluoroquinolone groups, contrarily, we observed maximum sensitivity to methicillin and cefuroxime antimicrobials. The high occurrence rate of S. aureus harbouring genes for virulence factors and antimicrobial resistance needs appropriate strategies to control the pathogen spread to the human population.

Detection of Enterotoxigenic Potential of Staphylococcus aureus Isolates from Cheese Samples with Two Different Methods

The primary objective of our study was to detect the occurrence of enterotoxigenic Staphylococcus aureus in diverse types of cheese (cow's milk cheese and mixed milk cheese) samples from R.N. Macedonia. Cheese samples were analyzed for enumeration and isolation of the S. aureus strains according to ISO 6888-1. We detected the toxigenic potential of the strains by the use of the Enzyme Link Fluorescent Assay VIDAS system, and we confirmed the presence of the SEs (sea, seb, sec, sed, see) genes by multiplex PCR. The results showed that out of 270 samples of cheese, coagulase-positive staphylococci (CPS) were detected in 27 (10%), and coagulase-negative staphylococci in five samples (1.8%). Biochemically, all 27 CPS samples were confirmed to be Staphylococcus aureus. With VIDAS SET2 test we confirmed that 11 isolates are producers of one of the toxins limited by the test. With the conventional PCR we confirmed genes in only 7 isolates. Most common detected gene was seb n=3 (42.8%), followed by sea n=2 (28.6%), and sec n=2 (28.6%). Additionally, sed and see genes were not detected in any of the S. aureus isolates. Discrepancies between the two test methods for detection of enterotoxigenic potential are not uncommon. The presence of viable Staphylococcus aureus cells that have enterotoxin potency demonstrates the importance of appropriate hygiene practices in the diary process and also the maintenance of the products in order to obtain a safe final product for the consumers.

Novel Bovine Plasma Protein Film Reinforced with Nanofibrillated Cellulose Fiber as Edible Food Packaging Material

Proteins, such as those in blood from slaughterhouses, are a good option for developing edible films. However, films made exclusively from proteins have low strength and high water solubility, which makes them difficult to use in the food industry. The use of cellulosic material, such as nanofibrillated cellulose (NFC), can improve the properties of these films. In the present work, bovine plasma was acidified and treated with ethanol to precipitate its proteins, and these proteins were used to prepare films reinforced with several concentrations of NFC. In addition, control films prepared with untreated bovine plasma and reinforced with NFC were prepared as well. These new edible films were characterized according to their mechanical properties, water vapor permeability, light transmittance, and microstructure. Furthermore, the film with the best properties was selected to be additivated with nisin to test its antimicrobial properties by wrapping meat previously contaminated with Staphylococcus aureus. In this sense, films prepared with the extracted proteins showed better properties than the films prepared with untreated plasma. In addition, the results showed that the reinforcement of the films with a 10% (w/w) of NFC decreased their water solubility and improved their puncture strength and water vapor barrier properties. Finally, the addition of nisin to the films prepared with extracted protein from bovine plasma and NFC gave them antimicrobial properties against S. aureus.

Influence of Tissue Type on the Bacterial Diversity and Community in Pork Bacon

In current study, bacterial diversity and community in different tissues of pork bacon were determined using high-throughput sequencing. In total, six phyla and 111 bacterial genera were identified. Among them, three dominant genera (Staphylococcus, Acinetobacter, and Macrococcus) were shared by all bacon samples. The linear discriminant analysis showed that 24 bacterial taxa significantly differentiated between the tissues. Results of non-metric Multidimensional Scaling and redundancy analysis showed that physicochemical characteristics of the tissue prominently structured the bacterial communities. Network analysis also illustrated that tissue type was an important factor impacting the bacterial interactions in different types of tissue. The results of current study can add valuable insights to the traditional homemade pork bacon.

Metagenomic Analysis of Bacterial Diversity in Traditional Fermented Foods Reveals Food-Specific Dominance of Specific Bacterial Taxa

Traditional fermented foods have been recognized by various communities to be good for health since ancient times. There is a provincial legacy of traditional fermented foods among the ethnic population of North-East India. Fermented bamboo shoots (local name: Tuaither), soybeans (Bekang), and pork fat (Sa-um) are famous in the Mizoram state and represent a primary portion of the daily diet. These foods are prepared using methods based on cultural traditions inherited from previous generations, and prepared using a relatively uncontrolled fermentation process. Analysis of the bacterial diversity in these foods can provide important information regarding the flavor and texture of the final products of fermentation. Unfortunately, studies on the microbial composition and health benefits of such traditional fermented foods have rarely been documented. Therefore, the present study aims to highlight this bacterial diversity, along with the proximate composition of different traditional fermented foods (Tuaither, Bekang and Sa-um) primarily consumed in Mizoram state, India. Samples were collected on three different days of fermentation (3rd, 5th and 7th day), and bacterial diversity analysis was performed using the V3-V4 variable region of 16S rRNA gene with Illumina sequencing. Results revealed differences in the bacterial composition of dominant group members among all of the three food types. Firmicutes (82.72–94.00%), followed by Proteobacteria (4.67–15.01%), were found to dominate to varying degrees in all three of the fermented foods. However, at genus level high variation was observed in bacterial composition among these three different types of fermented foods. Lactobacillus (91.64–77.16%), Staphylococcus (52.00–17.90%), and Clostridium (72.48–55.40%) exhibited the highest relative abundances in the Tuaither, Bekang and Sa-um foods, respectively, in descending order from the 3rd to 7th day of fermentation. A few of the bacterial genera such as Lactobacilli were positively correlated with fermented bamboo shoot samples, and Staphylococcus was positively correlated with protein, carbohydrate and crude fiber content in soybean samples. In general, Tuaither, Bekang and Sa-um exhibited distinct differences in bacterial composition. This variation may be due to differences in the raw materials and/or methods used in the preparation of the different fermented food products. This is the first study to describe the bacterial composition of these traditional fermented foods using high-throughput sequencing techniques, and could help to drive research attention to comprehensive studies on improving understanding of the role of microbial communities in the preparation of traditional foods and their health benefits.

Livestock-Associated Meticillin-Resistant Staphylococcus aureus—Current Situation and Impact From a One Health Perspective

Purpose of Review

In this article, we aim to provide an overview of the occurrence and characteristics of livestock-associated (LA-) meticillin-resistant Staphylococcus aureus (MRSA). We further question the role of LA-MRSA as a potential foodborne pathogen. We investigate recent findings and developments from a One Health perspective also highlighting current strategies and initiatives aiming to improve reporting, control, and prevention of LA-MRSA.

Recent Findings

While the overall number of invasive MRSA infections in humans is decreasing (in most European countries and the USA) or steadily increasing (in the Asia-Pacific region), the role of LA-MRSA as causative agent of invasive disease and as potential foodborne pathogen is still poorly understood. LA-MRSA prevalence in livestock remains high in many geographical regions and the acquisition of new virulence and resistance determinants constitutes a growing threat for human health.

Summary

The true incidence of LA-MRSA infections due to occupational exposure is unknown. Improved MRSA monitoring and tracking procedures are urgently needed. Strain typing is crucial to enable improved understanding of the impact of LA-MRSA on human and animal health.

Effect of Temperature on the Expression of Classical Enterotoxin Genes among Staphylococci Associated with Bovine Mastitis

Staphylococcal food poisoning (SFP), caused by the contamination of staphylococcal enterotoxins, is a common foodborne disease worldwide. The aims of this study were: (1) to investigate classical staphylococcal enterotoxin genes, sea, seb, sec, sed, and see, among Staphylococcus aureus and coagulase-negative staphylococci (CNS) associated with bovine mastitis; (2) to determine the effect of temperature on the expression of classical staphylococcal enterotoxin genes in staphylococci in milk. The detection of classical staphylococcal enterotoxin genes was performed using S. aureus (n = 51) and CNS (n = 47). The expression of classical enterotoxin genes, including sea, seb, sec, and see, was determined during the growth of staphylococci in milk subjected to ultra-high-temperature processing at two different temperatures: 8 °C and room temperature. Classical staphylococcal enterotoxin genes were expressed more frequently in S. aureus (35.30%) than in CNS (12.77%). The sec gene was most frequently detected in S. aureus (29.41%) and CNS (6.38%). Moreover, the expression of sea and sec was significantly higher at room temperature than at 8 °C after 16 h of incubation (p < 0.05). These results emphasize the importance of maintaining the storage temperature of milk below 8 °C to reduce the risk of SFP.

Confocal spectral microscopy, a non-destructive approach to follow contamination and biofilm formation of mCherry Staphylococcus aureus on solid surfaces

Methods to test the safety of wood material for hygienically sensitive places are indirect, destructive and limited to incomplete microbial recovery via swabbing, brushing and elution-based techniques. Therefore, we chose mCherry Staphylococcus aureus as a model bacterium for solid and porous surface contamination. Confocal spectral laser microscope (CSLM) was employed to characterize and use the autofluorescence of Sessile oak (Quercus petraea), Douglas fir (Pseudotsuga menziesii) and poplar (Populus euramericana alba L.) wood discs cut into transversal (RT) and tangential (LT) planes. The red fluorescent area occupied by bacteria was differentiated from that of wood, which represented the bacterial quantification, survival and bio-distribution on surfaces from one hour to one week after inoculation. More bacteria were present near the surface on LT face wood as compared to RT and they persisted throughout the study period. Furthermore, this innovative methodology identified that S. aureus formed a dense biofilm on melamine but not on oak wood in similar inoculation and growth conditions. Conclusively, the endogenous fluorescence of materials and the model bacterium permitted direct quantification of surface contamination by using CSLM and it is a promising tool for hygienic safety evaluation.