Anti-biofilm potential of Lavandula preparations against Campylobacter jejuni

Essential Oils for Biofilm Control: Mechanisms, Synergies, and Translational Challenges in the Era of Antimicrobial Resistance

Biofilms, structured microbial consortia embedded in self-produced extracellular matrices, pose significant challenges across the medical, industrial, and environmental sectors due to their resistance to antimicrobial therapies and ability to evade the immune system. Their resilience is driven by multifaceted mechanisms, including matrix-mediated drug sequestration, metabolic dormancy, and quorum sensing (QS)-regulated virulence, which collectively sustain persistent infections and contribute to the amplification of antimicrobial resistance (AMR). This review critically examines the potential of plant-derived essential oils (EOs) as innovative agents for biofilm control. EOs exhibit broad-spectrum antibiofilm activity through multi-target mechanisms, including disrupting initial microbial adhesion, degrading extracellular polymeric substances (EPSs), suppressing QS pathways, and compromising membrane integrity. Their ability to act synergistically with conventional antimicrobials at sub-inhibitory concentrations enhances therapeutic efficacy while reducing the selection pressure for resistance. Despite their potential, EO applications face technical challenges, such as compositional variability due to botanical sources, formulation stability issues, and difficulties in standardization for large-scale production. Clinical translation is further complicated by biofilm stage- and strain-dependent efficacy, insufficient in vivo validation of therapeutic outcomes, and potential cytotoxicity at higher doses. These limitations underscore the need for optimized delivery systems, such as nanoencapsulation, to enhance bioavailability and mitigate adverse effects. Future strategies should include combinatorial approaches with antibiotics or EPS-degrading enzymes, advanced formulation technologies, and standardized protocols to bridge laboratory findings to clinical practice. By addressing these challenges, EOs hold transformative potential to mitigate biofilm-associated AMR, offering sustainable, multi-target alternatives for infection management and biofilm prevention in diverse contexts.

Campylobacter jejuni Biofilm Assessment by NanoLuc Luciferase Assay

Campylobacter jejuni, a widespread pathogen found in birds and mammals, poses a significant risk for zoonosis worldwide despite its susceptibility to environmental and food-processing stressors. One of its main survival mechanisms is the formation of biofilms that can withstand various food-processing stressors, which is why efficient methods for assessing biofilms are crucial. Existing methods, including the classical culture-based plate counting method, biomass-staining methods (e.g., crystal violet and safranin), DNA-staining methods, those that use metabolic substrates to detect live bacteria (e.g., tetrazolium salts and resazurin), immunofluorescence with flow cytometry or fluorescence microscopy, and PCR-based methods for quantification of bacterial DNA, are diverse but often lack specificity, sensitivity, and suitability. In response to these limitations, we propose an innovative approach using NanoLuc as a reporter protein. The established protocol involves growing biofilms in microtiter plates, washing unattached cells, adding Nano-Glo luciferase substrate, and measuring bioluminescence. The bacterial concentrations in the biofilms are calculated by linear regression based on the calibration curve generated with known cell concentrations. The NanoLuc protein offers a number of advantages, such as its small size, temperature stability, and highly efficient bioluminescence, enabling rapid, non-invasive, and comprehensive assessment of biofilms together with quantification of a wide range of cell states. Although this method is limited to laboratory use due to the involvement of genetically modified organisms, it provides valuable insights into C. jejuni biofilm dynamics that could indirectly help in the development of improved food safety measures. Key features • Quantification of C. jejuni using NanoLuc luciferase. • The assay is linear in the range of 1.9 × 107 to 1.5 × 108 CFU/mL. • Following biofilm growth, less than 1 h is required for detection. • The assay requires genetically modified bacterial strains.

Holistic monitoring of Campylobacter jejuni biofilms with NanoLuc bioluminescence

Campylobacter jejuni, a major cause of foodborne zoonotic infections worldwide, shows a paradoxical ability to survive despite its susceptibility to environmental and food-processing stressors. This resilience is likely due to the bacterium entering a viable but non-culturable state, often within biofilms, or even initiating biofilm formation as a survival strategy. This study presents an innovative application of NanoLuc bioluminescence to accurately monitor the development of C. jejuni biofilms on various substrates, such as polystyrene plates, mucin-coated surfaces, and chicken juice matrices. Introduction of NanoLuc luciferase in a pathogenic C. jejuni strain enables rapid non-invasive holistic observation, capturing a spectrum of cell states that may comprise live, damaged, and viable but non-culturable populations. Our comparative analysis with established biofilm quantification methods highlights the specificity, sensitivity, and simplicity of the NanoLuc assay. The assay is efficient and offers precise cell quantification and thus represents an important complementary or alternative method to conventional biofilm monitoring methods. The findings of this study highlight the need for a versatile approach and suggest combining the NanoLuc assay with other methods to gain comprehensive insight into biofilm dynamics. KEY POINTS: • Innovative NanoLuc bioluminescence assay for sophisticated biofilm quantification. • Holistic monitoring of C. jejuni biofilm by capturing live, damaged and VBNC cells. • Potential for improving understanding of biofilm development and structure.

Campylobacter control strategies at postharvest level

Campylobacter is highly associated with poultry and frequently causes foodborne illness worldwide. Thus, effective control measures are necessary to reduce or prevent human infections. In this review, Campylobacter control methods applicable at postharvest level for poultry meat during production, storage, and preparation are discussed. Drying and temperature are discussed as general strategies. Traditional strategies such as steaming, freezing, sanitizing, organic acid treatment, and ultraviolet light treatment are also discussed. Recent advances in nanotechnology using antibacterial nanoparticles and natural antimicrobial agents from plants and food byproducts are also discussed. Although advances have been made and there are various methods for preventing Campylobacter contamination, it is still challenging to prevent Campylobacter contamination in raw poultry meats with current methods. In addition, some studies have shown that large strain-to-strain variation in susceptibility to these methods exists. Therefore, more effective methods or approaches need to be developed to substantially reduce human infections caused by Campylobacter.

Exploring the Antibacterial Potential of Lamiaceae Plant Extracts: Inhibition of Bacterial Growth, Adhesion, Invasion, and Biofilm Formation and Degradation in Pseudomonas aeruginosa PAO1

In response to the global rise in antibiotic resistance and the prevalence of bacterial biofilm-related infections, the antibacterial efficacy of methanolic, ethanolic, and aqueous extracts of 18 Lamiaceae plants from Serbia was evaluated. The total coumarins and triterpenes were detected spectrophotometrically, while a microdilution assay measured their effects on bacterial growth. Additionally, the impact of these extracts was assessed on Pseudomonas aeruginosa PAO1 adhesion and invasion in human fibroblasts and biofilm formation and degradation. The alcoholic extracts had the highest phytochemical content, with Teucrium montanum and Lavandula angustifolia being the richest in coumarins and triterpenes, respectively. Gram-positive bacteria, particularly Bacillus subtilis, were more susceptible to the extracts. Hyssopus officinalis ethanolic and Sideritis scardica methanolic extracts inhibited bacterial growth the most efficiently. Although the extracts did not inhibit bacterial adhesion, most ethanolic extracts significantly reduced bacterial invasion. Origanum vulgare and H. officinalis ethanolic extracts significantly inhibited biofilm formation, while Teucrium chamaedrys extract was the most active in biofilm degradation. This study significantly contributes to the literature by examining the antibacterial activity of Lamiaceae extracts, addressing major literature gaps, and underscoring their antibacterial potential, particularly Satureja montana and O. vulgare ethanolic extracts, linking their efficacy to coumarins and triterpenes.

Biofilm inhibition/eradication: exploring strategies and confronting challenges in combatting biofilm

Biofilms are complex communities of microorganisms enclosed in a self-produced extracellular matrix, posing a significant threat to different sectors, including healthcare and industry. This review provides an overview of the challenges faced due to biofilm formation and different novel strategies that can combat biofilm formation. Bacteria inside the biofilm exhibit increased resistance against different antimicrobial agents, including conventional antibiotics, which can lead to severe problems in livestock and animals, including humans. In addition, biofilm formation also imposes heavy economic pressure on industries. Hence it becomes necessary to explore newer alternatives to eradicate biofilms effectively without applying selection pressure on the bacteria. Excessive usage of antibiotics may also lead to an increase in the number of resistant strains as bacteria employ an advanced antimicrobial resistance mechanism. This review provides insight into multifaceted technologies like quorum sensing inhibition, enzymes, antimicrobial peptides, bacteriophage, phytocompounds, and nanotechnology to neutralize biofilms without developing antimicrobial resistance (AMR). Furthermore, it will pave the way for developing newer therapeutic agents to deal with biofilms more efficiently.

Inhibitory potential of natural plant extracts against Escherichia coli strain isolated from diarrheic camel calves

BACKGROUND

Camel calf's diarrhea is considered the chief economic loss in the camelid population. There is currently no vaccine licensed to prevent colibacillosis in camel calves. The new era of bacterial antibiotic resistance explains the treatment failure and the high mortality and morbidity associated with the disease. Current protective treatments have thus far limited efficacy and need to be replaced. Due to their antimicrobial properties and safety, natural products are recently finding a capital role in infection management.

AIMS

The current study explores Escherichia coli F17 susceptibility as a clinical strain isolated from diarrheic camel calves to a wide panel of natural products.

METHODS

Agar diffusion method, integrity of cell membrane, hydrophobicity of bacterial surface, biofilm assays, and motility were used to evaluate the antibacterial activity of Coffea, Retama raetam, Moringa oleifera, Juniperus phoenicea, Uritica dioica, Camellia sinensis, Lavandula angustifolia, and Cuminum cyminum extracts against isolated bacteria.

RESULTS

Interestingly, all eight tested extracts have the damaging ability of E. coli F17's cell membrane and cause the nucleic acid release after 12 hours. Escherichia coli F17 strain has the surface of hydrophobicity which changed after contact with extracts of the plant. Moreover, the motility of the studied bacteria changed after exposure to all plant extracts.

CONCLUSION

This study demonstrated that all extracts, exempt U. dioica, can remove up to 50% biofilm of E. coli biomass as compared with the control. Natural extracts can be used as potential antimicrobial agents to mitigate diarrhea in camel calves.

Antibiofilm Effect of Lavandula multifida Essential Oil: A New Approach for Chronic Infections

Fungal infections are associated with high morbidity and mortality rates, being highly prevalent in patients with underlying health complications such as chronic lung disease, HIV, cancer, and diabetes mellitus. To mitigate these infections, the development of effective antifungals is imperative, with plants standing out as promising sources of bioactive compounds. In the present study, we focus on the antibiofilm potential of Lavandula multifida essential oil (EO) against dermatophyte strains and Candida albicans. The EO was characterized using GC and GC-MS, and its antifungal effect was assessed on both biofilm formation and disruption. Biofilm mass, extracellular matrix, and viability were quantified using crystal violet, safranin, and XTT assays, respectively, and morphological alterations were confirmed using optical and scanning electron microscopy. L. multifida EO showed very high amounts of carvacrol and was very effective in inhibiting and disrupting fungal biofilms. The EO significantly decreased biofilm mass and viability in all tested fungi. In addition, a reduction in dermatophytes' extracellular matrix was observed, particularly during biofilm formation. Morphological alterations were evident in mature biofilms, with a clear decrease in hypha diameter. These promising results support the use of L. multifida EO in the development of effective plant-based antifungal products.

Effects of linalyl acetate on oxidative stress, inflammation and endothelial dysfunction: can linalyl acetate prevent mild cognitive impairment?

Mild cognitive impairment (MCI) is a major public health challenge with an increasing prevalence. Although the mechanisms underlying the development of MCI remain unclear, MCI has been reported to be associated with oxidative stress, inflammatory responses, and endothelial dysfunction, suggesting that agents that reduce these factors may be key to preventing MCI. Currently, no agents have been approved for the treatment of MCI, with the efficacy of commonly prescribed cholinesterase inhibitors remaining unclear. Relatively safe natural products that can prevent the development of MCI are of great interest. Linalyl acetate (LA), the major component of clary sage and lavender essential oils, has been shown to have a variety of pharmacological effects, including anti-hypertensive, anti-diabetic, neuroprotective, anti-inflammatory, and antioxidant properties, which may have the potential for the prevention of MCI. The present review briefly summarizes the pathogenesis of MCI related to oxidative stress, inflammatory responses, and endothelial dysfunction as well as the benefits of LA against these MCI-associated factors. The PubMed and Google Scholar databases were used to search the relevant literature. Further clinical research may lead to the development of new strategies for preventing MCI, particularly in high-risk populations with oxidative stress, inflammatory responses, and endothelial dysfunction (e.g., patients with hypertension and/or diabetes mellitus).

The action of phytochemicals in biofilm control

Covering: 2009 to 2021Antimicrobial resistance is now rising to dangerously high levels in all parts of the world, threatening the treatment of an ever-increasing range of infectious diseases. This has becoming a serious public health problem, especially due to the emergence of multidrug-resistance among clinically important bacterial species and their ability to form biofilms. In addition, current anti-infective therapies have low efficacy in the treatment of biofilm-related infections, leading to recurrence, chronicity, and increased morbidity and mortality. Therefore, it is necessary to search for innovative strategies/antibacterial agents capable of overcoming the limitations of conventional antibiotics. Natural compounds, in particular those obtained from plants, have been exhibiting promising properties in this field. Plant secondary metabolites (phytochemicals) can act as antibiofilm agents through different mechanisms of action from the available antibiotics (inhibition of quorum-sensing, motility, adhesion, and reactive oxygen species production, among others). The combination of different phytochemicals and antibiotics have revealed synergistic or additive effects in biofilm control. This review aims to bring together the most relevant reports on the antibiofilm properties of phytochemicals, as well as insights into their structure and mechanistic action against bacterial pathogens, spanning December 2008 to December 2021.

The Role of luxS in Campylobacter jejuni Beyond Intercellular Signaling

The full role of the luxS gene in the biological processes, such as essential amino acid synthesis, nitrogen and pyruvate metabolism, and flagellar assembly, of Campylobacter jejuni has not been clearly described to date. Therefore, in this study, we used a comprehensive approach at the cellular and molecular levels, including transcriptomics and proteomics, to investigate the key role of the luxS gene and compared C. jejuni 11168ΔluxS (luxS mutant) and C. jejuni NCTC 11168 (wild type) strains. Transcriptomic analysis of the luxS mutant grown under optimal conditions revealed upregulation of luxS mutant metabolic pathways when normalized to wild type, including oxidative phosphorylation, carbon metabolism, citrate cycle, biosynthesis of secondary metabolites, and biosynthesis of various essential amino acids. Interestingly, induction of these metabolic pathways was also confirmed by proteomic analysis, indicating their important role in energy production and the growth of C. jejuni. In addition, genes important for the stress response of C. jejuni, including nutrient starvation and oxidative stress, were upregulated. This was also evident in the better survival of the luxS mutant under starvation conditions than the wild type. At the molecular level, we confirmed that metabolic pathways were upregulated under optimal conditions in the luxS mutant, including those important for the biosynthesis of several essential amino acids. This also modulated the utilization of various carbon and nitrogen sources, as determined by Biolog phenotype microarray analysis. In summary, transcriptomic and proteomic analysis revealed key biological differences in tricarboxylic acid (TCA) cycle, pyruvate, nitrogen, and thiamine metabolism as well as lipopolysaccharide biosynthesis in the luxS mutant. IMPORTANCE Campylobacter jejuni is the world's leading foodborne bacterial pathogen of gastrointestinal disease in humans. C. jejuni is a fastidious but widespread organism and the most frequently reported zoonotic pathogen in the European Union since 2005. This led us to believe that C. jejuni, which is highly sensitive to stress factors (starvation and oxygen concentration) and has a low growth rate, benefits significantly from the luxS gene. The role of this gene in the life cycle of C. jejuni is well known, and the expression of luxS regulates many phenotypes, including motility, biofilm formation, host colonization, virulence, autoagglutination, cellular adherence and invasion, oxidative stress, and chemotaxis. Surprisingly, this study confirmed for the first time that the deletion of the luxS gene strongly affects the central metabolic pathway of C. jejuni, which improves its survival, showing its role beyond the intercellular signaling system.

Chemical Composition and Biological Activity of Essential Oil and Extract from the Seeds of Tropaeolum majus L. var. altum

Research background

Plant Tropaeolum majus L. (garden nasturtium) belongs to the family Tropaeolaceae and contains benzyl glucosinolate. The breakdown product of benzyl glucosinolate, benzyl isothiocyanate (BITC), exhibits various biological activities such as antiproliferative, antibacterial and antiinflammatory. In order to optimize the content of biologically active volatile compounds in plant extract and essential oil, the use of appropriate extraction technique has a crucial role.

Experimental approach

The current study investigates the effect of two modern extraction methods, microwave-assisted distillation (MAD) and microwave hydrodiffusion and gravity (MHG), on the chemical composition of volatile components present in the essential oil and extract of garden nasturtium (T. majus L. var. altum) seeds. Investigation of the biological activity of samples (essential oil, extract and pure compounds) was focused on the antiproliferative effect against different cancer cell lines: cervical cancer cell line (HeLa), human colon cancer cell line (HCT116) and human osteosarcoma cell line (U2OS), and the antibacterial activity which was evaluated against the growth and adhesion of Staphylococcus aureus and Escherichia coli to polystyrene surface.

Results and conclusions

Essential oil and extract of garden nasturtium (T. majus) seeds were isolated by two extraction techniques: MAD and MHG. BITC and benzyl cyanide (BCN) present in the extract were identified by gas chromatography-mass spectrometry. Essential oil of T. majus showed higher antiproliferative activity (IC50<5 µg/mL) than T. majus extract (IC50<27 µg/mL) against three cancer cell lines: HeLa, HCT116 and U2OS. BITC showed much higher inhibitory effect on all tested cells than BCN. The essential oil and extract of T. majus showed strong antimicrobial activity against S. aureus and E. coli.

Novelty and scientific contribution

This work represents the first comparative report on the antiproliferative activity of the essential oil and extract of T. majus seeds, BITC and BCN against HeLa, HCT116 and U2OS cells as well as their antimicrobial activity against S. aureus and E. coli. This study demonstrates that the essential oil of T. majus seeds exhibits stronger antiproliferative and antimicrobial activity than the plant extract.

Campylobacter jejuni Biofilm Control with Lavandin Essential Oils and By-Products

The food industry is constantly struggling with one of the most prevalent biofilm-forming and food-borne pathogenic bacteria, Campylobacter jejuni. Different approaches are used to control biofilms in the food production chain, but none is fully effective. In this study, we aim to produce and determine the chemical profile of essential oils (EOs), ethanolic extracts of flowers prior to distillation (EFs), and ethanolic extracts of post-distillation waste material (EWMs) from Lavandula × intermedia 'Bila', 'Budrovka' St Nicholas and 'Budrovka', which were further used to reduce C. jejuni intercellular signaling, adhesion, and biofilm formation, as well as to test their antioxidant activity. Glycosides of hydroxycinnamic acids were the major constituents of both types of lavandin ethanolic extract, while linalool, linalyl acetate, 1,8-cineol, and camphor were the major compounds found in lavandin EOs. Tested EOs showed the best antibacterial activity with a minimal inhibitory concentration of 0.25 mg/mL. Lavandin EFs proved more effective in reducing C. jejuni intercellular signaling and adhesion compared to lavandin EOs and EWMs, while lavandin EOs showed a slightly better effect against biofilm formation. Interestingly, the best antioxidant activity was determined for lavandin EWMs. A positive and moderate correlation was found between the reduction of C. jejuni intercellular signaling and adhesion, as well as between adhesion and biofilm formation. These findings mean novel bacterial targets are of interest for biofilm control with alternative natural agents throughout the whole food production chain.

The elimination effects of lavender essential oil on Listeria monocytogenes biofilms developed at different temperatures and the induction of VBNC state

Listeria monocytogenes is a typical foodborne pathogen that causes hard-to-treat bacterial infections, mainly due to its ability to form biofilm and enter into a viable but non-culturable state (VBNC). In this study, we investigated the removal effects of four antimicrobial agents on L. monocytogenes biofilms formed at 32 ℃ and 10 ℃, analyzed the resistances of the mature biofilms to antimicrobial agents, and explored the VBNC state of cells in mature biofilms induced by lavender essential oil (LEO). The results showed that the growth of L. monocytogenes was completely inhibited when 1.6% (v/v) of the LEO was added. Meanwhile, the results of the crystal violet staining and XTT reduction method indicated that different concentrations of LEO significantly reduced L. monocytogenes biofilms biomass and metabolic activities, followed by sodium hypochlorite, lactic acid, and hydrogen peroxide. Moreover, the confocal laser scanning microscopy (CLSM) images confirmed that the treated biofilms became thinner, the structure was sparse, and the appearance was blurry. More interestingly, L. monocytogenes biofilms developed at 10 ℃ were less susceptible to the sanitizers than that formed at 32 ℃. In addition, LEO presented a more significant dispersing effect on the biofilm cells, and 1/2 MIC to 4 MIC of LEO could induce fewer VBNC state cells in biofilm and plankton compared with sodium hypochlorite. This study indicated that the LEO could be considered as an ideal antibiofilm agent for controlling L. monocytogenes. But we should pay attention to the resistance of the biofilms developed at low temperatures.

Campylobacter Biofilms: Potential of Natural Compounds to Disrupt Campylobacter jejuni Transmission

Microbial biofilms occur naturally in many environmental niches and can be a significant reservoir of infectious microbes in zoonotically transmitted diseases such as that caused by Campylobacter jejuni, the leading cause of acute human bacterial gastroenteritis world-wide. The greatest challenge in reducing the disease caused by this organism is reducing transmission of C. jejuni to humans from poultry via the food chain. Biofilms enhance the stress tolerance and antimicrobial resistance of the microorganisms they harbor and are considered to play a crucial role for Campylobacter spp. survival and transmission to humans. Unconventional approaches to control biofilms and to improve the efficacy of currently used antibiotics are urgently needed. This review summarizes the use plant- and microorganism-derived antimicrobial and antibiofilm compounds such as essential oils, antimicrobial peptides (AMPs), polyphenolic extracts, algae extracts, probiotic-derived factors, d-amino acids (DAs) and glycolipid biosurfactants with potential to control biofilms formed by Campylobacter, and the suggested mechanisms of their action. Further investigation and use of such natural compounds could improve preventative and remedial strategies aimed to limit the transmission of campylobacters and other human pathogens via the food chain.