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As a notorious food-borne pathogen, Staphylococcus aureus can readily cause diseases in humans via contaminated food. Biofilm formation on various surfaces can increase the capacity of viable S. aureus cells for self-protection due to the stubborn structure of the biofilm matrix. Increased disease risk and economic losses caused by biofilm contamination in the food industry necessitate the urgent development of effective strategies for the inhibition and removal of S. aureus biofilms. Natural products have been extensively used as important sources of "eco-friendly" antibiofilm agents to avoid the side effects of conventional strategies on human health and the environment. This review discusses biofilm formation of S. aureus in food industries and focuses on providing an overview of potential promising target-oriented natural products and their mechanisms of S. aureus biofilm inhibition or removal. Hoping to provide valuable information of attractive research targets or potential undeveloped targets to screen potent natural anti-biofilm agents in food industries. [ABSTRACT FROM AUTHOR]

In the present study, antibacterial activity of four kinds of phloroglucinol derivatives extracted from Dryopteris fragrans (L.) Schott against S. aureus, S. epidermidis and P. acnes has been tested. Aspidin BB exerted the strongest antibacterial activity with minimal inhibition concentration (MIC) values ranging from 7.81 to 15.63 μg/mL. The time-kill assay indicated that aspidin BB could kill P. acnes completely at 2 MIC (MBC) within 4 h. By using AFM, we demonstrated extensive cell surface alterations of aspidin BB-treated P. acnes. SDS-PAGE of supernatant proteins and lipid peroxidation results showed that aspidin BB dose-dependently affected membrane permeability of P. acnes. DNA damage and protein degradation of P. acnes were also verified. SDS-PAGE of precipitated proteins revealed possible targets of aspidin BB, i.e., heat shock proteins (26 kDa) and lipase (33 kDa) which could all cause inflammation. Aspidin BB also seriously increased the inhibition rate of lipase activity from 10.20 to 65.20 % to possibly inhibit the inflammation. In conclusions, the effective constituents of D. fragrans (L.) Schott to treat acne might be phloroglucinol derivatives including aspidin BB, aspidin PB, aspidinol and dryofragin. Among this, aspidin BB inhibited the growth of P. acnes by disrupting their membrane, DNA and proteins and finally leaded to the cell death. The obtained data highlighted the potential of using aspidin BB as an alternative treatment for acne vulgaris. [ABSTRACT FROM AUTHOR]

Biofilm-forming Staphylococcus aureus can easily accumulate on various food contact surfaces which induce cross-contamination and are difficult to eliminate in the food industry. This study aimed to evaluate the anti-biofilm effects of natural product biochanin A against S. aureus. Results showed that biochanin A effectively eradicated established S. aureus biofilms on different food-contact materials. Fluorescence microscopic analyses suggested that biochanin A disintegrated the established biofilms by dissociate extracellular polymeric substance (EPS) in matrix. In addition, biochanin A at the sub-MIC concentration also effectively inhibited the biofilm formation by regulating the expression of biofilm-related genes (icaA, srtA, eno) and suppressing the release of EPS in biofilm matrix. Molecular docking also demonstrated that biochanin A conducted strong interactions with biofilm-related proteins (Ica A, Sortase A, and Enolase). These findings demonstrated that biochanin A has the potential to be developed as a potent agent against S. aureus biofilm in food industries. Key points: • Anti-biofilm effect of biochanin A against S. aureus was revealed for the first time. • Biofilm of S. aureus on various food-contact surfaces were efficiently eradicated. • Biochanin A prevented S. aureus biofilm formation via reducing EPS production. [ABSTRACT FROM AUTHOR]

The foodborne pathogen Staphylococcus aureus continues to challenge the food industry due to the pathogenicity and tolerance of the bacterium. As a common storage condition for frozen food during transportation, distribution, and storage, freezing does not seem to be entirely safe due to the cold tolerance of S. aureus. In addition, our study indicated that the biofilm formation ability of S. aureus was significantly increased in response to freezing stress. To explore the molecular mechanism regulating the response to freezing stress, the proteomics signature of S. aureus after freezing stress based on tandem mass tag (TMT) labeling and liquid chromatography tandem mass spectrometry (LC–MS/MS) was analyzed. Gene Ontology and pathway analysis revealed that ribosome function, metabolism, RNA repair, and stress response proteins were differentially regulated (P < 0.05). Furthermore, transpeptidase sortase A, biofilm operon icaADBC HTH-type negative transcriptional regulator IcaR, and HTH-type transcriptional regulator MgrA were involved in the modulation of increased biofilm formation in response to freezing stress (P < 0.05). Moreover, significant lysine acetylation and malonylation signals in the S. aureus response to freezing stress were observed. Collectively, the current work provides additional insight for comprehending the molecular mechanism of S. aureus in response to freezing stress and presents potential targets for developing strategies to control S. aureus. Key points: • TMT proteomic analysis was first used on S. aureus in response to freezing stress. • Ribosome-, metabolism-, and biofilm-related proteins change after freezing stress. • Increased biofilm formation in S. aureus responded to freezing stress. [ABSTRACT FROM AUTHOR]

The incidence of frequent foodborne disease outbreaks due to Staphylococcus aureus contamination necessitates the urgent searching for effective methods to monitor S. aureus. This research aims to construct model with a dynamic survival curve and some static growth curves to predict the behavior of S. aureus in raw pork. Lack of research about S. aureus kinetics in pork under fluctuating temperature conditions across freezing and thawing necessitates this study. One‐step analysis was used to determine the model parameters, which was more efficient than conventional model analysis with two steps. The results of kinetic analysis showed that Tmin (minimum growth temperature) was 6.85°C, which is close to the estimated values in previous reports. Subsequently, validation results indicated the integrated model can accurately predict the behavior of S. aureus regardless of isothermal or nonisothermal conditions with the root‐mean‐square errors (RMSE < 0.44 log CFU/g, 73.9% of the errors of prediction falls within ±0.5 log CFU/g), accuracy factors Af and bias factors Bf were both close to 1. This work may offer an effective method for the assessment of microbial security related to S. aureus in pork. [ABSTRACT FROM AUTHOR]

Abstract Staphylococcus aureus (S. aureus) is known as a food-borne pathogenic bacteria that is difficult to deal with, especially in a biofilm. An appropriate and effective agent against S. aureus is urgently needed, especially due to the high pathogenicity of S. aureus within biofilms. This paper aims to synthesize Ag 3 PW 12 O 40 nanoparticles (AgWPA-NPs) and investigate their antimicrobial activity and mechanism against S. aureus. N-phenyl-1-naphthylamine (NPN) uptake and membrane potential assays showed that AgWPA-NPs damaged the structure of the cell membrane. Furthermore, the results of crystal violet staining and fluorescence microscopy indicated that AgWPA-NPs were remarkably efficient at suppressing the formation of S. aureus biofilms. Furthermore, real-time PCR analysis showed that the expression of the biofilm-related genes, icaA , sarA and cidA , was downregulated. Taken together, these results suggest that AgWPA-NPs have the potential to be an anti- S. aureus biofilm agent. Highlights • AgWPA-NPs damaged the structure of S. aureus cell membrane. • AgWPA-NPs inhibited growth of S. aureus in biofilm and eliminated S. aureus biofilm. • AgWPA-NPs inhibited the biofilm-related genes and expression of SEA and SEB. [ABSTRACT FROM AUTHOR]

Abstract Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that causes a wide range of diseases, including food poisoning. Tea tree oil (TTO), an essential oil distilled from Melaleuca alternifolia , is well-known for its antibacterial activities. TTO effectively inhibited all 19 tested strains of S. aureus biofilm and planktonic cells. Phenotype analyses of S. aureus biofilm cells exposed to TTO were performed by biofilm adhesion assays, eDNA detection and PIA release. RNA sequencing (RNA-seq) was used in our study to elucidate the mechanism of TTO as a potential antibacterial agent to evaluate differentially expressed genes (DEGs) and the functional network in S. aureus ATCC 29213 biofilms. TTO significantly changed (greater than a 2- or less than a 2-fold change) the expression of 304 genes in S. aureus contained in biofilms. The levels of genes related to the glycine, serine and threonine metabolism pathway, purine metabolism pathway, pyrimidine metabolism pathway and amino acid biosynthesis pathway were dramatically changed in the biofilm exposed to TTO. Furthermore, the expression changes identified by RNA-seq analysis were verified by real-time RT-PCR. To the best of our knowledge, this research is the first study to report the phenotype and expression profiles of S. aureus in biofilms exposed to TTO. Highlights • The inhibitory effect of TTO on S. aureus biofilms was determined. • 304 genes were differentially expressed treated with TTO versus the control biofilm. • GO enrichment and KEGG pathway analysis were provided by RNA-seq. [ABSTRACT FROM AUTHOR]

Food-borne diseases caused by pathogens, such as Staphylococcus aureus and Listeria monocytogenes, have long attracted attention globally from researchers, food industries, and food safety authorities. Nisin (NS) is the only bacteriocin used worldwide as a generally recognised as safe (GRAS) food preservative, while citric acid (CA) has an unrestricted use in foods since it has GRAS status. In this study, synergistic interactions of NS combined with CA against S. aureus and L. monocytogenes were studied by the chequerboard microdilution method, with fractional inhibitory concentration index values ranging from 0.25 to 0.375 and 0.19 to 0.375, respectively. The positive interactions were verified by time-kill studies in pasteurised milk and disk diffusion assays. The mechanism of the synergistic antibacterial of NS and CA is proposed following SEM analysis and the determination of release of cell constituents. These results suggest that the cell walls and membrane are the probable main targets of this antimicrobial combination. These findings indicated that the combination of NS and CA not only could be used as a new promising naturally sourced food preservative, but may also reduce the problem of bacterial resistance. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus ( S. aureus ) infections resistant to a variety of drugs have been increasingly documented in recent years. Drug resistance has appeared largely due to extensive use of antibiotics. Nisin has been widely used in food industry to prevent bacterial growth. However, nisin resistance has been found in several foodborne pathogenic bacteria. p -Anisaldehyde (AS), an extract from Pimpinella anisum seeds, is a very common digestive herb of north India. In this study, synergistic interactions of nisin combined with AS against S. aureus were observed. The synergy was confirmed by checkerboard microdilution method, with the fractional inhibitory concentration index values ranging from 0.25 to 0.375. The positive interactions were verified by the challenge tests in pasteurized milk and agar diffusion assays. In addition, when treatment with nisin or AS alone or in combination, an obvious loss of 260 nm absorbing materials was observed. And flow cytometry assay showed that nisin or AS alone or in combination caused bacterial membrane permeabilization. The LIVE/DEAD Bac Light experiment, scanning electron microscope and transmission electron microscopy observation further confirmed that the compounds could kill bacteria via disrupting membranes. All results above verified that the combination of nisin and AS which showed antibacterial activity by a membrane damage mechanism could not only reduce drug resistance but also be used as a new promising naturally sourced food preservative. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus ( S . aureus ) is the leading cause of a broad range of human infections and associated with food poisoning worldwide. Nisin can be considered as a natural preservative and is widely used by the food industry. However, resistance of nisin has been reported in several species of bacteria. Identification of antibacterial agents that are synergistic with nisin is a method of minimising resistance to nisin. Cinnamaldehyde (CA), a well-studied essential oil isolated from cinnamon bark, has been reported to exhibit a broad spectrum of antimicrobial activity across a wide range of microorganisms. Previous studies have demonstrated that CA could be used in the food industry due to its active antibacterial activity and its safety. In this study, the synergistic antibacterial activity in vitro of nisin and CA against 13 food-borne isolates of S. aureus and S. aureus ATCC 29213 were evaluated by a checkerboard assay. The FICI values of nisin combined with CA ranged from 0.1875 to 0.375, which demonstrated a synergistic effect. The positive interactions were verified using the challenge tests in pasteurized milk and agar diffusion assays. The LIVE/DEAD BacLight experiment and scanning electron microscope (SEM) assay were also performed to distinguish the intact and damaged both of cell walls and membranes with the compounds, the combination group displayed stronger damage both of cell wall and cell membrane than when nisin or CA was used alone. These findings indicated that the combination of nisin and CA could not only be used as a promising naturally sourced food preservative but also to reduce the problem of bacterial resistance. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (S. aureus) can attach to food, host tissues and the surfaces of medical implants and form a biofilm, which makes it difficult to eliminate. The purpose of this study was to evaluate the effect of honokiol on biofilm-grown S. aureus. In this report, honokiol showed effective antibacterial activity against S. aureus in biofilms. S. aureus isolates are capable of producing distinct types of biofilms mediated by polysaccharide intercellular adhesion (PIA) or extracellular DNA (eDNA). The biofilms' susceptibility to honokiol was evaluated using confocal laser scanning microscopy (CLSM) analysis. The transcript levels of the biofilm-related genes, the expression of PIA, and the amount of eDNA of biofilm-grown S. aureus exposed to honokiol were also investigated. The results of this study show that honokiol can detach existing biofilms, kill bacteria in biofilms, and simultaneously inhibit the transcript levels of sarA, cidA and icaA, eDNA release, and the expression of PIA. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus ( S. aureus ), a major food-borne pathogen, causes disease in mammalian hosts by producing a wide variety of exoproteins, such as α-hemolysin and staphylococcal enterotoxins. Tea tree oil (TTO), an essential oil, has broad-spectrum antimicrobial activity. The objectives of this study were to evaluate the inhibitory effects of TTO on S. aureus growth and on α-hemolysin, enterotoxins A and B production. In this study, the effect of TTO on S. aureus growth in laboratory medium and pasteurized milk was determined by time-kill assays. Treatment with half of minimal inhibitory concentration (MIC) of TTO demonstrated very little or no reduction in numbers of viable ATCC 29213 cells; however, 1 × MIC of TTO reduced the viable cell count more noticeably, and 2 × MIC of TTO demonstrated an even greater reduction in the viable cell count, both in TSB and milk. The influence of TTO on enterotoxins was determined by real-time reverse transcriptase-PCR (real-time RT-PCR), a hemolysis assay, Western blot and a tumor necrosis factor alpha (TNF-α) assay. The real-time RT-PCR results revealed that the transcription of genes encoding α-hemolysin, staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) were down regulated after S. aureus was exposed to TTO (0.0625 mg/mL-0.5 mg/mL). The hemolytic assay showed that S. aureus hemolytic activity was inhibited by subinhibitory concentrations of TTO (0.0625 mg/mL-0.5 mg/mL). The Western blot assay identified that the production of the three virulence factors was inhibited by TTO (0.0625 mg/mL-0.5 mg/mL). Moreover, the enzyme linked immunosorbent assay (ELISA) demonstrated that TNF-α production was suppressed by TTO treatment in RAW264.7 cells stimulated by S. aureus supernatant containing staphylococcal enterotoxins (SEs). [ABSTRACT FROM AUTHOR]

The bacterium Staphylococcus aureus is most often recognized as a common cause of food poisoning. S. aureus colonization in humans can cause serious infections, toxinoses and life-threatening diseases. Nisin is a bacteriocin that has been extensively used as a natural preservative in the food industry, but the overall transcriptional response of S. aureus to nisin has not been well characterized. We used whole-genome DNA microarrays of S. aureus to determine the global transcription profile triggered by nisin treatment in S. aureus . In response to nisin treatment, a total of 601 genes were differentially regulated; transcription of 327 genes was up-regulated, and transcription of 274 genes was down-regulated. Various transporter genes showed elevated transcription, including genes involved in capsule polysaccharide (CP) synthesis, cell-wall synthesis, nucleic-acid and nucleotide metabolism as well as genes encoding urease, transport/binding proteins, and lipoproteins. To our knowledge, this transcriptome analysis provides the first insights into the transcriptional response of S. aureus to nisin challenge and enables exploration of the mechanisms of nisin antimicrobial activity toward S. aureus . The findings suggest that nisin regulates multiple desirable targets which could be further explored in the development of new food preservatives to avoid the contamination of S. aureus in food processing and storage. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus ( S. aureus) causes a wide variety of infections, which are of major concern worldwide. S. aureus produces multiple virulence factors, resulting in food infection and poisoning. These virulence factors include hyaluronidases, proteases, coagulases, lipases, deoxyribonucleases and enterotoxins. Among the extracellular proteins produced by S. aureus that contribute to pathogenicity, the exotoxins α-hemolysin, staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) are thought to be of major significance. Totarol, a plant extract, has been revealed to inhibit the proliferation of several pathogens effectively. However, there are no reports on the effects of totarol on the production of α-hemolysin, SEA or SEB secreted by S. aureus. The aim of this study was to evaluate the effects of totarol on these three exotoxins. Hemolysis assay, western blotting and real-time reverse transcriptase-PCR assay were performed to identify the influence of graded subinhibitory concentrations of totarol on the production of α-hemolysin and the two major enterotoxins, SEA and SEB, by S. aureus in a dose-dependent manner. Moreover, an enzyme linked immunosorbent assay showed that the TNF-α production of RAW264.7 cells stimulated by S. aureus supernatants was inhibited by subinhibitory concentrations of totarol. Form the data, we propose that totarol could potentially be used as a promising natural compound in the food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is one of the most important pathogens in humans and animals. The formation of biofilm by S. aureus is considered an important mechanism of antimicrobial resistance. Therefore, finding effective drugs against the biofilm produced by S. aureus has been a high priority. Licochalcone A (LAA), a natural plant product, was reported to have antibacterial activities and showed good activity against all 21 tested strains of S. aureus biofilm and planktonic cells. To detect the possible molecular mechanism of LAA against S. aureus biofilm or planktonic cells, Affymetrix GeneChips were used to determine the global comparative transcription of S. aureus biofilm and planktonic cells triggered by treatment with sub-bactericidal and sub-inhibitory concentrations of LAA, respectively. LAA significantly altered (greater than a 2- or less than −2-fold change) the expression of 693 genes in planktonic cells and 817 genes in biofilm. The levels of genes encoding autolysis-associated proteins, cell wall proteins, pathogenic factors, protein synthesis genes, and enzymes involved in capsule synthesis were significantly altered in LAA-treated S. aureus. Furthermore, some differences observed in the microarray analysis were verified by real-time RT-PCR. To our knowledge, this is the first observation of phenotype and expression profiles of S. aureus biofilm and planktonic cells in response to LAA treatment. [ABSTRACT FROM AUTHOR]

Nisin has been widely used as a natural preservative in foods including dairy products, but the emergence of the nisin-resistant strains could compromise its use to control food-borne pathogens. It has been reported that coenzyme Q (CoQ) is a powerful antioxidant, but a small number of studies have described the antibacterial activity of CoQ. One of the most abundant forms of CoQ is CoQ10. CoQ0 is chosen for this study, which is the water-soluble homolog of CoQ10. In the present study, the in vitro interaction of nisin and CoQ0 against 15 food-borne isolates of Staphylococcus aureus was assessed using a checkerboard microdilution method. Synergism was observed in strains tested, the FICI values ranging from 0.25 to 0.375. No antagonistic interaction between nisin and CoQ0 occurred. The positive interactions were verified confirmed using the time-killing test and agar diffusion assay. Our discovery of efficacy of combining nisin with CoQ0 might pave the way for a novel solution for spoilage problem in food industry and provide an alternative approach to overcome antimicrobial drug resistance. [ABSTRACT FROM AUTHOR]

Abstract: Staphylococcus aureus (S. aureus) is one of the most important pathogens in humans and animals, multiply resistant strains are increasingly widespread, new agents are needed for the treatment of S. aureus. Rhein (RH), a natural plant product, has been reported to have potential antimicrobial activity against S. aureus, but the response mechanisms of S. aureus to RH are still poorly understood. RH showed good in vitro antibacterial activity against all 21 tested S. aureus strains in this experiment. We performed commercial Affymetrix GeneChips™ to determine the overall transcriptional response of S. aureus ATCC25923 triggered by the treatment of subinhibitory concentrations of RH at one time point 45min. A total of 88 genes were identified to be differentially regulated by RH. Of these, 28 transporter genes were differentially regulated by RH; RH stress elevated the transcription of genes (srtB and isdABCDEFGI) encoding iron-regulated surface determinants system and genes (nrdIEF and nrdDG) involved in ribonucleotide reductase systems; but RH repressed genes (pflAB, nirBDR, narGH, ldh1, COL-SA0660, COL-SA2363 and COL-SA2386) responsible for anaerobic respiration and fermentation. To our knowledge, this genome-wide transcriptomics approach revealed first insights into the response of S. aureus to RH challenge. [Copyright &y& Elsevier]