The future of biofilm research - Report on the '2019 Biofilm Bash'

A laboratory perspective on Mycobacterium abscessus biofilm culture, characterization and drug activity testing

Mycobacterium abscessus is an emerging opportunistic pathogen causing severe pulmonary infections in patients with underlying lung disease and cystic fibrosis in particular. The rising prevalence of M. abscessus infections poses an alarming threat, as the success rates of available treatment options are limited. Central to this challenge is the absence of preclinical in vitro models that accurately mimic in vivo conditions and that can reliably predict treatment outcomes in patients. M. abscessus is notorious for its association with biofilm formation within the lung. Bacteria in biofilms are more recalcitrant to antibiotic treatment compared to planktonic bacteria, which likely contributes to the lack of correlation between preclinical drug activity testing (typically performed on planktonic bacteria) and treatment outcome. In recent years, there has been a growing interest in M. abscessus biofilm research. However, the absence of standardized methods for biofilm culture, biofilm characterization and drug activity testing has led to a wide spectrum of, sometimes inconsistent, findings across various studies. Factors such as strain selection, culture medium, and incubation time hugely impact biofilm development, phenotypical characteristics and antibiotic susceptibility. Additionally, a broad range of techniques are used to study M. abscessus biofilms, including quantification of colony-forming units, crystal violet staining and fluorescence microscopy. Yet, limitations of these techniques and the selected readouts for analysis affect study outcomes. Currently, research on the activity of conventional antibiotics, such as clarithromycin and amikacin, against M. abscessus biofilms yield ambiguous results, underscoring the substantial impact of experimental conditions on drug activity assessment. Beyond traditional drug activity testing, the exploration of novel anti-biofilm compounds and the improvement of in vitro biofilm models are ongoing. In this review, we outline the laboratory models, experimental variables and techniques that are used to study M. abscessus biofilms. We elaborate on the current insights of M. abscessus biofilm characteristics and describe the present understanding of the activity of traditional antibiotics, as well as potential novel compounds, against M. abscessus biofilms. Ultimately, this work contributes to the advancement of fundamental knowledge and practical applications of accurate preclinical M. abscessus models, thereby facilitating progress towards improved therapies for M. abscessus infections.

Emerging Issues and Initial Insights into Bacterial Biofilms: From Orthopedic Infection to Metabolomics

Bacterial biofilms, enigmatic communities of microorganisms enclosed in an extracellular matrix, still represent an open challenge in many clinical contexts, including orthopedics, where biofilm-associated bone and joint infections remain the main cause of implant failure. This study explores the scenario of biofilm infections, with a focus on those related to orthopedic implants, highlighting recently emerged substantial aspects of the pathogenesis and their potential repercussions on the clinic, as well as the progress and gaps that still exist in the diagnostics and management of these infections. The classic mechanisms through which biofilms form and the more recently proposed new ones are depicted. The ways in which bacteria hide, become impenetrable to antibiotics, and evade the immune defenses, creating reservoirs of bacteria difficult to detect and reach, are delineated, such as bacterial dormancy within biofilms, entry into host cells, and penetration into bone canaliculi. New findings on biofilm formation with host components are presented. The article also delves into the emerging and critical concept of immunometabolism, a key function of immune cells that biofilm interferes with. The growing potential of biofilm metabolomics in the diagnosis and therapy of biofilm infections is highlighted, referring to the latest research.

A comprehensive review of genomics, transcriptomics, proteomics, and metabolomic insights into the differentiation of Pseudomonas aeruginosa from the planktonic to biofilm state: A multi-omics approach

Biofilm formation by Pseudomonas aeruginosa is primarily responsible for chronic wound and lung infections in humans. These infections are persistent owing to the biofilm's high tolerance to antimicrobials and constantly changing environmental factors. Understanding the mechanism governing biofilm formation can help to develop therapeutics explicitly directed against the molecular markers responsible for this process. After numerous years of research, many genes responsible for both in vitro and in vivo biofilm development remain unidentified. However, there is no "all in one" complete in vivo or in vitro biofilm model. Recent findings imply that the shift from planktonic bacteria to biofilms is a complicated and interrelated differentiation process. Research on the applications of omics technologies in P. aeruginosa biofilm development is ongoing, and these approaches hold great promise for expanding our knowledge of the mechanisms of biofilm formation. This review discusses the different factors that affect biofilm formation and compares P. aeruginosa biofilm formation using the omics approaches targeting essential biological macromolecules, such as DNA, RNA, Protein, and metabolome. Furthermore, we have outlined the application of currently available omics tools, such as genomics, proteomics, metabolomics, transcriptomics, and integrated multi-omics methodologies, to understand the differential gene expression (biofilm vs. planktonic bacteria) of P. aeruginosa biofilms.

Unravelling host-pathogen interactions by biofilm infected human wound models

Approximately 80 % of persistent wound infections are affected by the presence of bacterial biofilms, resulting in a severe clinical challenge associated with prolonged healing periods, increased morbidity, and high healthcare costs. Unfortunately, in vitro models for wound infection research almost exclusively focus on early infection stages with planktonic bacteria. In this study, we present a new approach to emulate biofilm-infected human wounds by three-dimensional human in vitro systems. For this purpose, a matured biofilm consisting of the clinical key wound pathogen Pseudomonas aeruginosa was pre-cultivated on electrospun scaffolds allowing for non-destructive transfer of the matured biofilm to human in vitro wound models. We infected tissue-engineered human in vitro skin models as well as ex vivo human skin explants with the biofilm and analyzed structural tissue characteristics, biofilm growth behavior, and biofilm-tissue interactions. The structural development of biofilms in close proximity to the tissue, resulting in high bacterial burden and in vivo-like morphology, confirmed a manifest wound infection on all tested wound models, validating their applicability for general investigations of biofilm growth and structure. The extent of bacterial colonization of the wound bed, as well as the subsequent changes in molecular composition of skin tissue, were inherently linked to the characteristics of the underlying wound models including their viability and origin. Notably, the immune response observed in viable ex vivo and in vitro models was consistent with previous in vivo reports. While ex vivo models offered greater complexity and closer similarity to the in vivo conditions, in vitro models consistently demonstrated higher reproducibility. As a consequence, when focusing on direct biofilm-skin interactions, the viability of the wound models as well as their advantages and limitations should be aligned to the particular research question of future studies. Altogether, the novel model allows for a systematic investigation of host-pathogen interactions of bacterial biofilms and human wound tissue, also paving the way for development and predictive testing of novel therapeutics to combat biofilm-infected wounds.

Biofilm aggregates and the host airway-microbial interface

Biofilms are multicellular microbial aggregates that can be associated with host mucosal epithelia in the airway, gut, and genitourinary tract. The host environment plays a critical role in the establishment of these microbial communities in both health and disease. These host mucosal microenvironments however are distinct histologically, functionally, and regarding nutrient availability. This review discusses the specific mucosal epithelial microenvironments lining the airway, focusing on: i) biofilms in the human respiratory tract and the unique airway microenvironments that make it exquisitely suited to defend against infection, and ii) how airway pathophysiology and dysfunctional barrier/clearance mechanisms due to genetic mutations, damage, and inflammation contribute to biofilm infections. The host cellular responses to infection that contribute to resolution or exacerbation, and insights about evaluating and therapeutically targeting airway-associated biofilm infections are briefly discussed. Since so many studies have focused on Pseudomonas aeruginosa in the context of cystic fibrosis (CF) or on Haemophilus influenzae in the context of upper and lower respiratory diseases, these bacteria are used as examples. However, there are notable differences in diseased airway microenvironments and the unique pathophysiology specific to the bacterial pathogens themselves.

Characterization and potential oral probiotic properties of Lactobacillus plantarum FT 12 and Lactobacillus brevis FT 6 isolated from Malaysian fermented food

OBJECTIVE

This study aims to characterise the lactic acid bacteria (LAB) isolated from local Malaysian fermented foods with oral probiotics properties.

DESIGN

The LAB strains isolated from Malaysian fermented foods, Lactobacillus brevis FT 6 and Lactobacillus plantarum FT 12, were assessed for their antimicrobial properties against Porphyromonas gingivalis ATCC 33277 via disc diffusion assay. Anti-biofilm properties were determined by treating the overnight P. gingivalis ATCC 33277 biofilm with different concentrations of LAB cell-free supernatant (LAB CFS). Quantification of biofilm was carried out by measuring the optical density of stained biofilm. The ability of L. brevis FT 6 and L. plantarum FT 12 to tolerate salivary amylase was also investigated. Acid production with different sugars was carried out by pH measurement and screening for potential antimicrobial organic acid by disc diffusion assay of neutralised probiotics CFS samples. In this study, L. rhamnosus ATCC 7469, a commercial strain was used to compare the efficacy of the isolated strain with the commercial strain.

RESULTS

Lactobacillus brevis FT 6 and L. plantarum FT 12 possess antimicrobial activity against P. gingivalis with inhibition diameters of more than 10 mm, and the results were comparable with L. rhamnosus ATCC 7469. The MIC and MBC assay results for all tested strains were recorded to be 25 µl/µl concentration. All LAB CFS reduced biofilm formation proportionally to the CFS concentration and tolerated salivary amylase with more than 50% viability. Overnight cultures of all lactic acid bacteria strains showed a pH reduction and neutralised CFS of all lactic acid bacteria strains did not show any inhibition towards P. gingivalis.

CONCLUSIONS

These results indicate that the isolated probiotics have the potential as probiotics to be used as a supportive oral health treatment, especially against a periodontal pathogen, P. gingivalis.

Microrheology of Pseudomonas aeruginosa biofilms grown in wound beds

A new technique was used to measure the viscoelasticity of in vivo Pseudomonas aeruginosa biofilms. This was done through ex vivo microrheology measurements of in vivo biofilms excised from mouse wound beds. To our knowledge, this is the first time that the mechanics of in vivo biofilms have been measured. In vivo results are then compared to typical in vitro measurements. Biofilms grown in vivo are more relatively elastic than those grown in a wound-like medium in vitro but exhibited similar compliance. Using various genetically mutated P. aeruginosa strains, it is observed that the contributions of the exopolysaccharides Pel, Psl, and alginate to biofilm viscoelasticity were different for the biofilms grown in vitro and in vivo. In vitro experiments with collagen containing medium suggest this likely arises from the incorporation of host material, most notably collagen, into the matrix of the biofilm when it is grown in vivo. Taken together with earlier studies that examined the in vitro effects of collagen on mechanical properties, we conclude that collagen may, in some cases, be the dominant contributor to biofilm viscoelasticity in vivo.

Micro-Technologies for Assessing Microbial Dynamics in Controlled Environments

With recent advances in microfabrication technologies, the miniaturization of traditional culturing techniques has provided ideal methods for interrogating microbial communities in a confined and finely controlled environment. Micro-technologies offer high-throughput screening and analysis, reduced experimental time and resources, and have low footprint. More importantly, they provide access to culturing microbes in situ in their natural environments and similarly, offer optical access to real-time dynamics under a microscope. Utilizing micro-technologies for the discovery, isolation and cultivation of "unculturable" species will propel many fields forward; drug discovery, point-of-care diagnostics, and fundamental studies in microbial community behaviors rely on the exploration of novel metabolic pathways. However, micro-technologies are still largely proof-of-concept, and scalability and commercialization of micro-technologies will require increased accessibility to expensive equipment and resources, as well as simpler designs for usability. Here, we discuss three different miniaturized culturing practices; including microarrays, micromachined devices, and microfluidics; advancements to the field, and perceived challenges.

Microbial Biofilms: Structural Plasticity and Emerging Properties

Microbial biofilms are found everywhere and can be either beneficial or detrimental, as they are involved in crucial ecological processes and in severe chronic infections. The functional properties of biofilms are closely related to their three-dimensional (3D) structure, and the ability of microorganisms to collectively and dynamically shape the community spatial organization in response to stresses in such biological edifices. A large number of works have shown a relationship between the modulation of the spatial organization and ecological interactions in biofilms in response to environmental fluctuations, as well as their emerging properties essential for nutrient cycling and bioremediation processes in natural environments. On the contrary, numerous studies have emphasized the role of structural rearrangements and matrix production in the increased tolerance of bacteria in biofilms toward antimicrobials. In these last few years, the development of innovative approaches, relying on recent technological advances in imaging, computing capacity, and other analytical tools, has led to the production of original data that have improved our understanding of this close relationship. However, it has also highlighted the need to delve deeper into the study of cell behavior in such complex communities during 3D structure development and maturation- from a single-cell to a multicellular scale- to better control or harness positive and negative impacts of biofilms. For this Special Issue, the interplay between biofilm emerging properties and their 3D spatial organization considering different models, from single bacteria to complex environmental communities, and various environments, from natural ecosystems to industrial and medical settings are addressed.

Biofilm and Equine Limb Wounds

Simple Summary

Delayed wound healing commonly occurs in limb wounds of horses. These equine limb wounds share many similarities with chronic wounds in humans and one of them seems to be the presence of biofilm, even though equine wound biofilm research is just emerging. Biofilms are aggregates of bacteria, and within these aggregates, the bacteria are protected from both antimicrobial substances and the immune response of the host. Biofilm infections in wounds often delay healing and are impossible to detect with routine diagnostics. However, if suspected, aggressive treatment is needed and includes physically removing biofilm and unhealthy tissue from the wound during debridement and immediately applying antimicrobial compounds to kill any biofilm or bacteria not removed during debridement.

Abstract

In chronic wounds in humans, biofilm formation and wound chronicity are linked, as biofilms contribute to chronic inflammation and delayed healing. Biofilms are aggregates of bacteria, and living as biofilms is the default mode of bacterial life; within these aggregates, the bacteria are protected from both antimicrobial substances and the immune response of the host. In horses, delayed healing is more commonly seen in limb wounds than body wounds. Chronic inflammation and hypoxia are the main characteristics of delayed wound healing in equine limbs, and biofilms might also contribute to this healing pattern in horses. However, biofilm formation in equine wounds has been studied to a very limited degree. Biofilms have been detected in equine traumatic wounds, and recent experimental models have shown that biofilms protract the healing of equine limb wounds. Detection of biofilms within wounds necessitates advanced techniques that are not available in routine diagnostic yet. However, infections with biofilm should be suspected in equine limb wounds not healing as expected, as they are in human wounds. Treatment should be based on repeated debridement and application of topical antimicrobial therapy.

Comparison of Two Cutibacterium acnes Biofilm Models

The study of biofilms in vitro is complex and often limited by technical problems due to simplified models. Here, we compared C. acnes biofilm formation, from species involved in bone and prosthesis infection, in a static model with a dynamic model. Using similar parameters, the percentage of live bacteria within the biofilm was higher in dynamic than in static approach. In both models, bacterial internalization in osteoblast-like cells, playing the role of stress factor, affected this proportion but in opposite ways: increase of live bacteria proportion in the static model (×2.04 ± 0.53) and of dead bacteria proportion (×3.5 ± 1.03) in the dynamic model. This work highlights the huge importance in the selection of a relevant biofilm model in accordance with the environmental or clinical context to effectively improve the understanding of biofilms and the development of better antibiofilm strategies.

Staphylococcus aureus Strain-Dependent Biofilm Formation in Bone-Like Environment

Staphylococcus aureus species is an important threat for hospital healthcare because of frequent colonization of indwelling medical devices such as bone and joint prostheses through biofilm formations, leading to therapeutic failure. Furthermore, bacteria within biofilm are less sensitive to the host immune system responses and to potential antibiotic treatments. We suggested that the periprosthetic bone environment is stressful for bacteria, influencing biofilm development. To provide insights into S. aureus biofilm properties of three strains [including one methicillin-resistant S. aureus (MRSA)] under this specific environment, we assessed several parameters related to bone conditions and expected to affect biofilm characteristics. We reported that the three strains harbored different behaviors in response to the lack of oxygen, casamino acids and glucose starvation, and high concentration of magnesium. Each strain presented different biofilm biomass and live adherent cells proportion, or matrix production and composition. However, the three strains shared common responses in a bone-like environment: a similar production of extracellular DNA and engagement of the SOS response. This study is a step toward a better understanding of periprosthetic joint infections and highlights targets, which could be common among S. aureus strains and for future antibiofilm strategies.

Critical parameters in cultivation of experimental biofilms using the example of Pseudomonas fluorescens

Formation and treatment of biofilms present a great challenge for health care and industry. About 80% of human infections are associated with biofilms including biomaterial centered infections, like infections of prosthetic heart valves, central venous catheters, or urinary catheters. Additionally, biofilms can cause food and drinking water contamination. Biofilm research focusses on application of experimental biofilm models to study initial adherence processes, to optimize physico-chemical properties of medical materials for reducing interactions between materials and bacteria, and to investigate biofilm treatment under controlled conditions. Exploring new antimicrobial strategies plays a key role in a variety of scientific disciplines, like medical material research, anti-infectious research, plant engineering, or wastewater treatment. Although a variety of biofilm models exist, there is a lack of standardization for experimental protocols, and designing experimental setups remains a challenge. In this study, a number of experimental parameters critical for material research have been tested that influence formation and stability of an experimental biofilm using the non-pathogenic model strain of Pseudomonas fluorescens. These parameters include experimental time frame, nutrient supply, inoculum concentration, static and dynamic cultivation conditions, material properties, and sample treatment during staining for visualization of the biofilm. It was shown, that all tested parameters critically influence the experimental biofilm formation process. The results obtained in this study shall support material researchers in designing experimental biofilm setups.

Effect of collagen and EPS components on the viscoelasticity of Pseudomonas aeruginosa biofilms

Pseudomonas aeruginosa is an opportunistic pathogen that causes thousands of deaths every year in part due to its ability to form biofilms composed of bacteria embedded in a matrix of self-secreted extracellular polysaccharides (EPS), e-DNA, and proteins. In chronic wounds, biofilms are exposed to the host extracellular matrix, of which collagen is a major component. How bacterial EPS interacts with host collagen and whether this interaction affects biofilm viscoelasticity is not well understood. Since physical disruption of biofilms is often used in their removal, knowledge of collagen's effects on biofilm viscoelasticity may enable new treatment strategies that are better tuned to biofilms growing in host environments. In this work, biofilms are grown in the presence of different concentrations of collagen that mimic in vivo conditions. In order to explore collagen's interaction with EPS, nine strains of P. aeruginosa with different patterns of EPS production were used to grow biofilms. Particle tracking microrheology was used to characterize the mechanical development of biofilms over two days. Collagen is found to decrease biofilm compliance and increase relative elasticity regardless of the EPS present in the system. However, this effect is minimized when biofilms overproduce EPS. Collagen appears to become a de facto component of the EPS, through binding to bacteria or physical entanglement.

Pulmonary biofilm-based chronic infections and inhaled treatment strategies

Certain pulmonary diseases, such as cystic fibrosis (CF), non-CF bronchiectasis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia, are usually accompanied by respiratory tract infections due to the physiological alteration of the lung immunological defenses. Recurrent infections may lead to chronic infection through the formation of biofilms. Chronic biofilm-based infections are challenging to treat using antimicrobial agents. Therefore, effective ways to eradicate biofilms and thus relieve respiratory tract infection require the development of efficacious agents for biofilm destruction, the design of delivery carriers with biofilm-targeting and/or penetrating abilities for these agents, and the direct delivery of them into the lung. This review provides an in-depth description of biofilm-based infections caused by pulmonary diseases and focuses on current existing agents that are administered by inhalation into the lung to treat biofilm, which include i) inhalable antimicrobial agents and their combinations, ii) non-antimicrobial adjuvants such as matrix-targeting enzymes, mannitol, glutathione, cyclosporin A, and iii) liposomal formulations of anti-biofilm agents. Finally, novel agents that have shown promise against pulmonary biofilms as well as traditional and new devices for pulmonary delivery of anti-biofilm agents into the lung are also discussed.

Legionella and Biofilms-Integrated Surveillance to Bridge Science and Real-Field Demands

Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy.

Mimicking biofilm formation and development: Recent progress in in vitro and in vivo biofilm models

Biofilm formation in living organisms is associated to tissue and implant infections, and it has also been linked to the contribution of antibiotic resistance. Thus, understanding biofilm development and being able to mimic such processes is vital for the successful development of antibiofilm treatments and therapies. Several decades of research have contributed to building the foundation for developing in vitro and in vivo biofilm models. However, no such thing as an "all fit" in vitro or in vivo biofilm models is currently available. In this review, in addition to presenting an updated overview of biofilm formation, we critically revise recent approaches for the improvement of in vitro and in vivo biofilm models.

Microtiter plate assays to assess antibiofilm activity against bacteria

Bacterial biofilms demonstrate high broad-spectrum adaptive antibiotic resistance and cause two thirds of all infections, but there is a lack of approved antibiofilm agents. Unlike the standard minimal inhibitory concentration assay to assess antibacterial activity against planktonic cells, there is no standardized method to evaluate biofilm inhibition and/or eradication capacity of novel antibiofilm compounds. The protocol described here outlines simple and reproducible methods for assessing the biofilm inhibition and eradication capacities of novel antibiofilm agents against adherent bacterial biofilms grown in 96-well microtiter plates. It employs two inexpensive dyes: crystal violet to stain adhered biofilm biomass and 2,3,5-triphenyl tetrazolium chloride to quantify metabolism of the biofilm cells. The procedure is accessible to any laboratory with a plate reader, requires minimal technical expertise or training and takes 4 or 5 d to complete. Recommendations for how biofilm inhibition and eradication results should be interpreted and presented are also described.

Analysis of the Phospholipid Profile of the Collection Strain PAO1 and Clinical Isolates of Pseudomonas aeruginosa in Relation to Their Attachment Capacity

Bacteria form multicellular and resistant structures named biofilms. Biofilm formation starts with the attachment phase, and the molecular actors involved in this phase, except adhesins, are poorly characterized. There is growing evidence that phospholipids are more than simple structural bricks. They are involved in bacterial adaptive physiology, but little is known about their role in biofilm formation. Here, we report a mass spectrometry analysis of the phospholipid (PL) profile of several strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients. The aim of our study was to evaluate a possible link between the PL profile of a strain and its attachment phenotype. Our results showed that PL profile is strongly strain-dependent. The PL profile of P. aeruginosa PAO1, a collection strain, was different from those of 10 clinical isolates characterized either by a very low or a very high attachment capacity. We observed also that the clinical strain’s PL profiles varied even more importantly between isolates. By comparing groups of strains having similar attachment capacities, we identified one PL, PE 18:1-18:1, as a potential molecular actor involved in attachment, the first step in biofilm formation. This PL represents a possible target in the fight against biofilms.

Antibiofilm peptides: overcoming biofilm-related treatment failure

Health leaders and scientists worldwide consider antibiotic resistance among the world's most dangerous pathogens as one of the biggest threats to global health. Antibiotic resistance has largely been attributed to genetic changes, but the role and recalcitrance of biofilms, largely due to growth state dependent adaptive resistance, is becoming increasingly appreciated. Biofilms are mono- and multi-species microbial communities embedded in an extracellular, protective matrix. In this growth state, bacteria are transcriptionally primed to survive extracellular stresses. Adaptations, affecting metabolism, regulation, surface charge, immune recognition and clearance, allow bacteria to thrive in the human body and withstand antibiotics and the host immune system. Biofilms resist clearance by multiple antibiotics and have a major role in chronic infections, causing more than 65% of all infections. No specific antibiofilm agents have been developed. Thus, there is a pressing need for alternatives to traditional antibiotics that directly inhibit and/or eradicate biofilms. Host defence peptides (HDPs) are small cationic peptides that are part of the innate immune system to both directly kill microbes but also function to modulate the immune response. Specific HDPs and their derivatives demonstrate broad-spectrum activity against biofilms. In vivo biofilm assays show efficacy in abscess, respiratory, in-dwelling device, contact lens and skin infection models. Further progress has been made through the study of ex vivo organoid and air-liquid interface models to better understand human infections and treatment while relieving the burden and complex nature of animal models. These avenues pave the way for a better understanding and treatment of the underlying cause of chronic infections that challenge the healthcare system.

Databases for the study of biofilms: current status and potential applications

Biofilms play an important role in health, being associated with >80% of all microbial infections in the body and in the development of antibiotic resistance. Research in this field has continuously produced large volumes of data. Being able to handle all this information will be paramount for progress in this field. However, this places a heavy burden on the development of strategies to gather, organize and make this information available in a way that can be readily and effectively used by those requiring it. Lately, efforts towards this goal have been reported, particularly with the development of Quorumpeps, BiofOmics, BaAMPs, QSPpred, dPABBs, aBiofilm and the Biofilms Structural Database. This work reviews these databases and highlights their applicability and potential, while stressing some of the challenges for the coming years in database development and usage brought about by the use of big data and machine learning.

Biofilm dispersion: The key to biofilm eradication or opening Pandora's box?

Biofilms are extremely difficult to eradicate due to their decreased antibiotic susceptibility. Inducing biofilm dispersion could be a potential strategy to help combat biofilm-related infections. Mechanisms of biofilm dispersion can basically be divided into two groups, i.e. active and passive dispersion. Active dispersion depends on a decrease in the intracellular c-di-GMP levels, leading to the production of enzymes that degrade the biofilm matrix and promote dispersion. In contrast, passive dispersion relies on triggers that directly release cells from the biofilm. In the present review, several active and passive dispersion strategies are discussed. In addition, the disadvantages and possible consequences of using dispersion as a treatment approach for biofilm-related infections are also reviewed.

Clusters of Lactobacillus Strains from Vegetal Origins Are Associated with Beneficial Functions: Experimental Data and Statistical Interpretations

Nine strains of Lactiplantibacillus plantarum and one strain of Lacticaseibacillus paracasei that were recently isolated from prickly pears, fresh figs and blackberries, which are traditionally and largely consumed fruits in Kabylia (north of Algeria), were studied here for their antagonism and antioxidant properties as well as for production of exopolysaccharides. With respect to their inhibitory properties, these strains were tested against three food representative pathogens including Escherichia coli ATCC 8739, Staphylococcus aureus 2S6 and Listeria monocytogenes 162. The antagonism of these pathogens was attributable to lactic acid production, present in the cell free supernatant, at concentrations ranging from 9 to 16.74 g/L. The anti-adhesive properties observed on polystyrene or eukaryotic Caco-2 cells were exerted in a strain dependent-manner. Indeed, the scores obtained ranged from 27% to 75% for S. aureus 2S6, 54% to 95% for L. monocytogenes 162, and 50% to 97% for E. coli ATCC 8739. The co-aggregation of these Lactobacillus strains with the aforementioned target bacteria appeared to be exerted in a strain-dependent manner, with noticeably the upmost rate for Lb. paracasei FB1 on S. aureus 2S6. Interestingly, these novel Lactobacillus strains were able to produce a large amount (315.55 to 483.22 mg/L) of exopolysaccharides, and showed a significant scavenging activity on the 2,2-di-phényl-2-picrylhydrazyle (DPPH) synthetic free radical with rates of 51% to 56%. Of note, the highest antioxidant activity was observed for Lb. paracasei FB1 using the culture supernatants, intact cells or the intracellular extract. The statistical analysis of these data using the principal component analysis (ACP) enabled us to establish three distinct clusters with potential applications as bioprotective and/or probiotic agents, following further evaluation.