The Screening and Evaluation of Fucus serratus and Fucus vesiculosus Extracts against Current Strains of MRSA Isolated from a Clinical Hospital Setting

Biochemical profiling and antioxidant activity analysis of commercially relevant seaweeds from northwest Europe

BACKGROUND

The drive towards ensuring the sustainability of bioresources has been linked with better valorising primary materials and developing biorefinery pipelines. Seaweeds constitute valuable coastal resources with applications in the bioenergy, biofertiliser, nutrition, pharmaceutical and cosmetic sectors. Owing to the various sought-after metabolites they possess, several seaweed species are commercially exploited throughout Western Europe, including Ireland. Here, four commercially relevant brown (Fucus serratus and Fucus vesiculosus) and red (Chondrus crispus and Mastocarpus stellatus) seaweed species were sampled during a spring tide in July 2021 on moderately exposed shores across three coastal regions in the west of Ireland.

RESULTS

Significant regional differences were identified when specimens were analysed for carbohydrates (max. 80.3 μg glucose eq mg-1 DW), proteins (max. 431.3 μg BSA eq. mg-1 DW), lipids (max. 158.6 mg g-1 DW), pigment signature and antioxidant potential. Protein content for F. serratus recorded a twofold difference between northern and southern specimens. The antioxidant potential of F. vesiculosus and M. stellatus returned greater activity compared to F. serratus and C. crispus, respectively. Multivariate analysis showed a clear latitudinal pattern across the three western coastal regions (north, west and south) for both F. vesiculosus and F. serratus.

CONCLUSION

F. vesiculosus thalli from the northwest were richer in pigment content while the F. serratus thalli from the northwest were richer in antioxidants. Such biogeographic patterns in the biochemical make-up of seaweeds need consideration for the development of regional integrated aquaculture systems and the optimisation of the biomass content for targeted downstream applications. © 2024 Society of Chemical Industry.

Natural antibiotics against antimicrobial resistance: sources and bioinspired delivery systems

The current burden associated to multidrug resistance, and the emerging superbugs, result in a decreased and even loss of antibiotic efficacy, which poses significant challenges in the treatment of infectious diseases. This situation has created a high demand for the discovery of novel antibiotics that are both effective and safe. However, while antibiotics play a crucial role in preventing and treating diseases, they are also associated with adverse effects. The emergence of multidrug-resistant and the extensive appearance of drug-resistant microorganisms, has become one of the major hurdles in healthcare. Addressing this problem will require the development of at least 20 new antibiotics by 2060. However, the process of designing new antibiotics is time-consuming. To overcome the spread of drug-resistant microbes and infections, constant evaluation of innovative methods and new molecules is essential. Research is actively exploring alternative strategies, such as combination therapies, new drug delivery systems, and the repurposing of existing drugs. In addition, advancements in genomic and proteomic technologies are aiding in the identification of potential new drug targets and the discovery of new antibiotic compounds. In this review, we explore new sources of natural antibiotics from plants, algae other sources, and propose innovative bioinspired delivery systems for their use as an approach to promoting responsible antibiotic use and mitigate the spread of drug-resistant microbes and infections.

Bioactivity of Fucoidan-Rich Extracts from Fucus vesiculosus against Rotavirus and Foodborne Pathogens

Marine algae are sources of bioactive components with defensive properties of great value against microbial infections. This study investigated the bioactivity of extracts from brown algae Fucus vesiculosus against rotavirus, the worldwide leading cause of acute gastroenteritis in infants and young children. Moreover, one of the extracts was tested against four foodborne bacteria: Campylobacter jejuni, Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes, and the non-pathogenic: E. coli K12. In vitro tests using MA104 cells revealed that both whole algae extracts and crude fucoidan precipitates neutralized rotavirus in a dose-responsive manner. The maximum neutralization activity was observed when the rotavirus was incubated with 100 μg mL-1 of the hydrochloric acid-obtained crude fucoidan (91.8%), although crude fucoidan extracted using citric acid also demonstrated high values (89.5%) at the same concentration. Furthermore, molecular weight fractionation of extracts decreased their antirotaviral activity and high molecular weight fractions exhibited higher activity compared to those of lower molecular weight. A seaweed extract with high antirotaviral activity was also found to inhibit the growth of C. jejuni, S. Typhimurium, and L. monocytogenes at a concentration of 0.2 mg mL-1. Overall, this study expands the current knowledge regarding the antimicrobial mechanisms of action of extracts from F. vesiculosus.

Evaluation of the antimicrobial function of Ginkgo biloba exocarp extract against clinical bacteria and its effect on Staphylococcus haemolyticus by disrupting biofilms

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Ginkgo biloba L. (Ginkgo nuts) has been used for a long time as a critical Chinese medicine material to treat cough and asthma, as well as a disinfectant. Similar records were written in the Compendium of Materia Medica (Ben Cao Gang Mu, pinyin in Chinese) and Sheng Nong's herbal classic (Shen Nong Ben Cao Jing, pinyin in Chinese). Recent research has shown that Ginkgo biloba exocarp extract (GBEE) has the functions of unblocking blood vessels and improving brain function, as well as antitumour activity and antibacterial activity. GBEE was shown to inhibit methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation as a traditional Chinese herb in our previous report in this journal. AIM OF THE STUD: yThe antibiotic resistance of clinical bacteria has recently become increasingly serious. Thus, this study aimed to investigate the Ginkgo biloba exocarp extract (GBEE) antibacterial lineage, as well as its effect and mechanism on S. haemolyticus biofilms. This study will provide a new perspective on clinical multidrug resistant (MDR) treatment with ethnopharmacology herbs.

METHODS

The microbroth dilution assay was carried out to measure the antibacterial effect of GBEE on 13 types of clinical bacteria. Bacterial growth curves with or without GBEE treatment were drawn at different time points. The potential targets of GBEE against S. haemolyticus were screened by transcriptome sequencing. The effects of GBEE on bacterial biofilm formation and mature biofilm disruption were determined by crystal violet staining and scanning electron microscopy. The metabolic activity of bacteria inside the biofilm was assessed by colony-forming unit (CFU) counting and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2HY-tetrazolium bromide (MTT) assay. Quantitative polymerase chain reaction (qPCR) was used to measure the gene expression profile of GBEE on S. haemolyticus biofilm-related factors.

RESULTS

The results showed that GBEE has bacteriostatic effects on 3 g-positive (G⁺) and 2 g-negative (G^-) bacteria among 13 species of clinical bacteria. The antibacterial effect of GBEE supernatant liquid was stronger than the antibacterial effect of GBEE supernviaould-like liquid. GBEE supernatant liquid inhibited the growth of S. epidermidis, S. haemolyticus, and E. faecium at shallow concentrations with minimum inhibitory concentrations (MICs) of 2 μg/ml, 4 μg/ml and 8 μg/ml, respectively. Genes involved in quorum sensing, two-component systems, folate biosynthesis, and ATP-binding cassette (ABC) transporters were differentially expressed in GBEE-treated groups compared with controls. Crystal violet, scanning electron microscopy (SEM) and MTT assays showed that GBEE suppressed S. haemolyticus biofilm formation in a dose-dependent manner. Moreover, GBEE supernatant liquid downregulated cidA, cidB and atl, which are involved in cell lysis and extracellular DNA (eDNA) release, as well as downregulated the cbp, ebp and fbp participation in encoding cell-surface binding proteins.

CONCLUSIONS

GBEE has an excellent antibacterial effect on gram-positive bacteria and also inhibits the growth of gram-negative bacteria, such as A. baumannii (carbapenem-resistant Acinetobacter baumannii) CRABA and S. maltophilia. GBEE inhibits the biofilm formation of S. haemolyticus by altering the regulation and biofilm material-related genes, including the release of eDNA and cell-surface binding proteins.

Marine algae as efficacious bioresources housing antimicrobial compounds for preserving foods - A review

Certain synthetic chemicals used in global food industries eliminate pathogenic food microbes and prevent spoilage. Nevertheless, their toxicity precludes human consumption. This phenomenon has made scientific fraternity to look for alternative antimicrobial compounds from natural resources. In recent times, marine algae have been illustrated to be potent and rich sources of antimicrobial agents as chemical replacements for applications in food. Identifying novel antimicrobial agents from natural resources have become a worldwide research with immense significance. Marine algae are now considered as one of the most inexhaustible and unexposed sources of antimicrobial agents due to their abundance in seawaters and renewability. This review elaborated on marine algal antimicrobial agents against foodborne pathogens, mode of action and cumulated the prospective use of algal compounds in active food packaging as a natural food preservative. Due to poor solubility, unpleasant odor and ineffectiveness of plant derived antimicrobial agents against Gram-negative bacteria, researchers opted for marine algae, an ideal candidate to be used as natural food preservatives. This article elaborates and summarizes the efficient bioactive molecules in marine algae and their possible application in food preservation to extend shelf life of foods without causing any toxicity. In conclusion, marine algae have potential antimicrobial property against food pathogens and have more advantages than other natural sources of antimicrobial agents.

Ginkgo biloba exocarp extracts inhibit S. aureus and MRSA by disrupting biofilms and affecting gene expression

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. fruit, also known as Bai Guo, Ya Jiao Zi (in pinyin Chinese), and ginkgo nut (in English), has been used for many years as an important material in Chinese traditional medicine to treat coughs and asthma and as a disinfectant, as described in the Compendium of Materia Medica (Ben Cao Gang Mu, pinyin in Chinese), an old herbal book. Ginkgo nuts are used to treat phlegm-associated asthma, astringent gasp, frequent urination, gonorrhoea and turgidity; consumed raw to reduce phlegm and treat hangovers; and used as a disinfectant and insecticide. A similar record was also found in Sheng Nong's herbal classic (Shen Nong Ben Cao Jing, pinyin in Chinese). Recent research has shown that Ginkgo biloba L. exocarp extract (GBEE) can unblock blood vessels and improve brain function and exhibits antitumour and antibacterial activities.

AIM OF STUDY

To investigate the inhibitory effect of Ginkgo biloba L. exocarp extract (GBEE) on methicillin-resistant S. aureus (MRSA) biofilms and assess its associated molecular mechanism.

MATERIALS AND METHODS

The antibacterial effects of GBEE on S. aureus and MRSA were determined using the broth microdilution method. The growth curves of bacteria treated with or without GBEE were generated by measuring the CFU (colony forming unit) of cultures at different time points. The effects of GBEE on bacterial biofilm formation and mature biofilm disruption were determined by crystal violet staining. Quantitative polymerase chain reaction (qPCR) was used to measure the effects of GBEE on the gene expression profiles of MRSA biofilm-related factors at 6, 8, 12, 16 and 24 h.

RESULTS

The minimum inhibitory concentration (MIC) of GBEE on S. aureus and MRSA was 4 μg/mL, and the minimum bactericidal concentration (MBC) was 8 μg/ml. Moreover, GBEE (4-12 μg/mL) inhibited S. aureus and MRSA biofilm formation in a dose-dependent manner. Interestingly, GBEE also destroyed mature biofilms of S. aureus and MRSA at 12 μg/ml. The expression of the MRSA biofilm-associated factor icaA and sarA were downregulated after 6 h of treatment with GBEE, while sigB was downregulated after 12 h. MeanwhileMeanwhile, icaR was upregulated at 12 h. In addition, GBEE also downregulated the virulence gene hld and inhibited the synthesis of staphyloxanthin.

CONCLUSIONS

GBEE has excellent antibacterial effects against S. aureus and MRSA and inhibits their biofilm-forming ability by altering related gene expression.

Antibacterial Use of Macroalgae Compounds against Foodborne Pathogens

The search for food resources is a constant in human history. Nowadays, the search for natural and safe food supplies is of foremost importance. Accordingly, there is a renewed interest in eco-friendly and natural products for substitution of synthetic additives. In addition, microbial contamination of food products during their obtaining and distribution processes is still a sanitary issue, and an important target for the food industry is to avoid food contamination and its related foodborne illnesses. These diseases are fundamentally caused by certain microorganisms listed in this review and classified according to their Gram negative or positive character. Algae have proven to possess high nutritional value and a wide variety of biological properties due to their content in active compounds. Among these capabilities, macroalgae are recognized for having antimicrobial properties. Thus, the present paper revises the actual knowledge of microbial contaminants in the food industry and proposes antimicrobial algal compounds against those pathogenic bacteria responsible for food contamination as valuable molecules for its growth inhibition. The capacity of algae extracts to inhibit some major food pathogen growth was assessed. Moreover, the main applications of these compounds in the food industry were discussed while considering their favorable effects in terms of food safety and quality control.

Macroalgae as a Source of Valuable Antimicrobial Compounds: Extraction and Applications

In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Macroalgae play a special role in the pursuit of new active molecules as they have been traditionally consumed and are known for their chemical and nutritional composition and their biological properties, including antimicrobial activity. Among the bioactive molecules of algae, proteins and peptides, polysaccharides, polyphenols, polyunsaturated fatty acids and pigments can be highlighted. However, for the complete obtaining and incorporation of these molecules, it is essential to achieve easy, profitable and sustainable recovery of these compounds. For this purpose, novel liquid-liquid and solid-liquid extraction techniques have been studied, such as supercritical, ultrasound, microwave, enzymatic, high pressure, accelerated solvent and intensity pulsed electric fields extraction techniques. Moreover, different applications have been proposed for these compounds, such as preservatives in the food or cosmetic industries, as antibiotics in the pharmaceutical industry, as antibiofilm, antifouling, coating in active packaging, prebiotics or in nanoparticles. This review presents the main antimicrobial potential of macroalgae, their specific bioactive compounds and novel green extraction technologies to efficiently extract them, with emphasis on the antibacterial and antifungal data and their applications.