In the present study, attention was given to Enterococcus faecalis and Klebsiella pneumoniae commonly causing healthcare-associated infections highly recalcitrant to antimicrobial therapy, also for their ability to form biofilms. These pathogens are often associated with a high risk of urinary tract infections due to biofilm-related complications in indwelling devices, commonly used in urological surgery. Currently, research is focusing on the development of new therapeutic strategies aimed at targeting bacterial virulence factors, such as biofilm, to reduce the increasing development of multidrug-resistant pathogens. In the present research, the activity of two antibiofilm proteins deriving from Antarctic marine bacteria, PsyOmp38 and Cold-Azurin, was evaluated on a collection of clinical E. faecalis and K. pneumoniae strains. In particular, the antibiofilm capabilities of PsyOmp38 and Cold-Azurin were tested against clinical bacterial strains characterized by different antimicrobial resistant profiles during distinctive phasis of biofilm development: initial attachment to the surface, pre-adhesion period and mature biofilm. This study provides interesting insights into the mechanism of action of the two proteins at different stages of the biofilm. Both proteins are able to impair, with different capabilities, biofilm formation of almost all bacterial tested strains. While Cold-Azurin disrupts mature biofilm only in a limited number of bacterial strains, PsyOmp38 shows disrupting activity against all Klebsiella strains and almost all E. faecalis strains. These findings suggest that Antarctic-derived proteins, particularly PsyOmp38, may represent promising candidates for the development of novel antibiofilm strategies against multidrug-resistant ESKAPE pathogens.

The development of antimicrobial resistance is a very complex mechanism, sometimes due to phenotypic variations of the microbial community rather than to the appearance of genetic mutations. A phenotypic variant is certainly the ability of bacteria to form biofilms, in which they are incorporated into a matrix of self-produced extracellular polymeric substances. Biofilm formation is a physiological condition that provides bacteria with protection from the action of the immune system and antimicrobial agents. In the present study, attention was given to Enterococcus spp and Klebsiella pneumoniae , belonging to ESKAPE pathogens, commonly causing healthcare-associated infections, also for their ability to form biofilms. K. pneumoniae and Enterococcus spp are often together associated with a high risk of urinary tract infections due to biofilm-related complications in indwelling devices, commonly used in urological surgery. Currently, research is focusing on the development of new therapeutic strategies aimed at targeting bacterial virulence factors, such as biofilm, to reduce the increasing development of multidrug-resistant pathogens. In this context, microorganisms capable of thriving in extreme environments are of particular interest. In extreme environments, Antarctic marine bacteria have developed survival strategies aimed at reducing the presence of competing microorganisms. In the present research, the activity of Psy Omp38 and Cold-Azurin was evaluated on a collection of clinical Enterococcus spp. and K. pneumoniae strains. Both proteins are able to impair, with different capabilities, biofilm formation of almost all bacterial tested strains.

About 71% of healthcare-associated infections are due to antibiotic-resistant bacteria, such as carbapenem-resistant A. baumannii, classified by World Health Organization into a critical priority group of pathogens. The antimicrobial resistance profile of A. baumannii relies on its ability to produce several virulence factors, including biofilm formation. Its ability to adhere and persist on surfaces as biofilm has contributed to its pathogenicity and drug resistance. In this study, the ability of an antimicrobial peptide (a chionodracine-derived peptide named KHS-Cnd) to inhibit or reduce biofilm formation was investigated as an example of a potential strategy to counteract infections caused by biofilm-forming pathogens. To this aim, the antimicrobial profiles were first analyzed in selected A. baumannii strains, two reference and six clinical strains, all biofilm-forming with different capability, regardless of whether they are drug resistant or sensitive. Successively, we investigated the bactericidal activity of the peptide that showed MIC values ranging from 5 to 10 µM and a significative antibiofilm activity on all tested strains at sub-inhibitory concentrations. In fact, KHS-Cnd can hinder biofilm A. baumannii strains formation with an inhibition percentage ranging between 65% and 10%. Also a statistically significant reduction of mature biofilm ranging from 20% to 50% was observed in four out of eight tested A. baumannii strains. KHS-Cnd impacts various stages of biofilm formation, including the inhibition of surface-associated and twitching motilities depending on the different strain. In particular, our results showed that only two strains possessed surface-associated motility that was strongly impaired by KHS-Cnd treatment; three clinical strains, instead, showed twitching motility, whose inhibition for two of them was evident after 24 h of incubation with peptide. Moreover, the invasion of pulmonary cells by A. baumannii was significantly impaired with a reduction of about 32% after treatment with 1.25 µM KHS-Cnd. Finally, when the peptide was used together with ceftazidime/avibactam against resistant A. baumannii strains, it was able to reduce the minimal inhibitory concentration of antibiotics needed to inhibit the microorganism growth.

Acinetobacter baumannii is a multidrug-resistant (MDR) pathogen associated with nosocomial infections, sporadically detected in cystic fibrosis (CF) patients. Treatment of A. baumannii may be hindered by polysaccharide capsule production of some isolates and extended resistance to most antibiotics. In these fearsome cases, colistin (COL) and cefiderocol (FDC) are considered last resort antibiotics. Unfortunately, resistance to these molecules is increasing. Indeed, we observed a hypermucoid (HM) A. baumannii strain producing OXA-23, isolated from a CF patient, rapidly evolving concomitant resistance to COL and FDC. At her first visit to our hospital, the 24-year-old female with a delayed CF diagnosis and advanced lung disease presented with one HM and one low mucoid (LM) A. baumannii phenotypes. Due to Pseudomonas aeruginosa infection, she received inhaled tobramycin and COL treatment. Five months later, two HM strains were isolated, with different susceptibility profiles to COL and FDC, one being completely resistant. Whole genome sequencing revealed that all four isolates, the initial HM and LM strains and the two subsequent HM strains, belonged to Sequence Type 2 and carried OXA-23 gene. Genetic distance revealed evolution from the same strain. HM strains carried mutations in genes involved in polysaccharide production while the resistant strain also harboured mutations conferring COL and FDC resistance. Biofilm production and motility of the four strains were evaluated to establish possible links between multiresistance, mucoidity and virulence. Phenotypic characterisation showed that HM strains lost some virulence traits during chronicisation and resistance development but likely persisted by exploiting the biofilm-mediated protection, maintaining both virulent and resistant subpopulations. We speculate that COL treatment forced A. baumannii resistance occurrence in a bacterial population already heteroresistant to FDC, resulting in a pan-resistant strain in this CF patient. Considering that lung transplantation still represents a life-saving option for CF patient with advanced lung disease, this study highlights the critical need for careful administration of last-resort molecules in patients that may face immunosuppression. Indeed, given the possibility of simultaneous emergence of resistance and the limited treatment options available to patients infected with MDR A. baumannii, last-resort antibiotics should be spared to avoid selection of pan-resistant microorganisms.

The ability of Acinetobacter baumannii to form biofilm is correlated with its antimicrobial resistance. The identification of antimicrobial drugs acting on biofilm is crucial to develop effective therapies. Previously, we determined that a chionodracine‐derived peptide, KHS‐Cnd, was able to impair A. baumannii biofilm formation. Here, to investigate the physiological changes underlying this activity, extracellular metabolite profiles of four A. baumannii strains were analyzed by NMR during biofilm formation in the presence of KHS‐Cnd. Metabolites involved in biofilm energy metabolism were found extracellularly after KHS‐Cnd treatment. Significantly altered pathways were associated with glyoxylate/dicarboxylate and branched‐chain/aromatic amino acid metabolism. Overall, differences in extracellular metabolites reflect modifications of biofilm metabolism due to peptide treatment, thus highlighting its therapeutic potential against A. baumannii biofilm‐sustained infections.

Bacteria can colonize and develop biofilm on a large variety of biotic and abiotic materials, it is accountable for nosocomial infections and chronic illness and consequently, it is a serious economic and public health problem. Staphylococcus epidermidis, thanks to its ability to form biofilm and colonize biomaterials, represents the most frequent causative agent involved in bio-film-associated infections of medical devices. Due to the biofilm presence, S. epidermidis infections are extremely difficult to treat and the research of new molecules able to interfere with its biofilm formation has a remarkable interest. In the present work, the attention was focused on Pseudomonas sp. TAE6080, an Antarctic marine bacterium able to produce and secrete an effective antibiofilm compound. The molecule responsible for this activity was purified by an activity-guided approach and it resulted to be a periplasmic protein, named Cold-Azurin. The Cold-Azurin was recombinantly produced in E. coli and purified. The recombinant protein was able to impair S. epidermidis attachment to the polystyrene surface and effectively prevent biofilm formation.

Biofilm is accountable for nosocomial infections and chronic illness, making it a serious economic and public health problem. Staphylococcus epidermidis, thanks to its ability to form biofilm and colonize biomaterials, represents the most frequent causative agent involved in biofilm-associated infections of medical devices. Therefore, the research of new molecules able to interfere with S. epidermidis biofilm formation has a remarkable interest. In the present work, the attention was focused on Pseudomonas sp. TAE6080, an Antarctic marine bacterium able to produce and secrete an effective antibiofilm compound. The molecule responsible for this activity was purified by an activity-guided approach and identified by LC-MS/MS. Results indicated the active protein was a periplasmic protein similar to the Pseudomonas aeruginosa PAO1 azurin, named cold-azurin. The cold-azurin was recombinantly produced in E. coli and purified. The recombinant protein was able to impair S. epidermidis attachment to the polystyrene surface and effectively prevent biofilm formation.

The airways of cystic fibrosis (CF) patients are colonized by many pathogens and the most common is Pseudomonas aeruginosa, an environmental pathogen that is able to infect immunocompromised patients thanks to its ability to develop resistance to conventional antibiotics. Over 12% of all patients colonized by P. aeruginosa harbour multi-drug resistant species. During airway infection in CF, P. aeruginosa adopts various mechanisms to survive in a hostile ecological niche characterized by low oxygen concentration, nutrient limitation and high osmotic pressure. To this end, P. aeruginosa uses a variety of virulence factors including pigment production, biofilm formation, motility and the secretion of toxins and proteases. This study represents the first report that systematically analyzes the differences in virulence features, in normoxia and anoxia, of clinical P. aeruginosa isolated from CF patients, characterized by multi- or pan-drug antibiotic resistance compared to antibiotic sensitive strains. The virulence features, such as biofilm formation, protease secretion and motility, are highly diversified in anaerobiosis, which reflects the condition of chronic CF infection. These findings may contribute to the understanding of the real-world lifestyle of pathogens isolated during disease progression in each particular patient and to assist in the design of therapeutic protocols for personalized medicine.

The ESKAPE pathogens, including bacteria such as Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, pose a global health threat due to their ability to resist antimicrobial drugs and evade the immune system. These pathogens are responsible for hospital-acquired infections, especially in intensive care units, and contribute to the growing problem of multi-drug resistance. In this study, researchers focused on exploring the potential of Antarctic marine bacteria as a source of anti-biofilm molecules to combat ESKAPE pathogens. Four Antarctic bacterial strains were selected, and their cell-free supernatants were tested against 60 clinical ESKAPE isolates. The results showed that the supernatants did not exhibit antimicrobial activity but effectively prevented biofilm formation and dispersed mature biofilms. This research highlights the promising potential of Antarctic bacteria in producing compounds that can counteract biofilms formed by clinically significant bacterial species. These findings contribute to the development of new strategies for preventing and controlling infections caused by ESKAPE pathogens.

Urinary tract infections (UTI), which are among the most frequent cases of infectious diseases, mainly affect women. The most common treatment approach involves the use of antibiotics, although this solution is not always the most suitable, mainly because of the resistance that bacterial strains develop. Proanthocyanidins are a class of polyphenols, abundantly contained in cranberry extracts, which have shown beneficial effects in the treatment of urinary tract infections, due to their anti-adhesive properties toward bacteria, with respect to the membranes of the cells of the urothelium and intestine, thus reducing their virulence. In this work, we demonstrate via microscopy and scattering measurements how a mixture of cranberry and chondroitin sulfate can form a crosslinked structure with barrier properties. By using a design of experiment (DOE), we optimized the mass ratio to obtain a precipitate between cranberry extract and chondroitin sulfate in the presence of N-acetylcysteine and hyaluronic acid. By using transepithelial electrical resistance (TEER) chambers, we confirmed the barrier properties of the best mixture obtained with the DOE. Lastly, the antibiofilm action was investigated against five strains of Escherichia coli with different antibiotic sensitivity. The precipitate displayed a variable inhibitory effect in biofilm formation with major effects in UTI with an antibiotic resistance profile.

The aim of the study was to investigate how essential oil production and associated chemical composition and related biological activity could be influenced by different cultivation treatments and distillation methods. Foeniculum vulgare Mill. (fennel), Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) were cultivated in absence of any fertilizer (control) and in presence of three different fertilizers: a chemical one with augmented mineral phosphorus and potassium, a second added with hydrolyzed organic substance and mineral phosphorus and potassium (organic-mineral) and a third one treated with a high content of organic nitrogen of protein origin (organic). The plants were subjected to steam distillation using two modalities, recycled and continuous, to obtain 32 essential oil samples. Chemical composition analysis was performed using gas chromatography-mass spectrometry; in vitro antimicrobial activity was evaluated using a broth microdilution method. In general, the recycled distillation method appeared to have a slightly higher yield than the continuous method. The "mineral" and "organic-mineral" treatments resulted in a higher yield compared to the "organic" or "control" treatments, and this was particularly evident in the recycled method. The "control" plants had a lower yield of essential oils. Anethole (13.9-59.5%) and estragole (13.4-52.2%) were the main constituents of the fennel oils; p-cymene and its derivatives carvacrol and thymol were the main constituents of the oregano and thyme samples. The antimicrobial activity of the thyme oils on Staphylococcus aureus ranged from 0.31 to 0.16% (v/v); a lower effect of the oregano samples and no activity of the fennel samples were observed. The essential oils failed to inhibit the growth of Pseudomonas aeruginosa strains.

Several microscopic methodologies have been used in biofilm studies, each one giving its contribution to deepening the knowledge of biofilm structure. This chapter illustrates two electron microscopy techniques, scanning electron microscopy (SEM) and variable-pressure SEM (VP-SEM). SEM needs sample dehydration and metal coating, with its operating conditions of high vacuum and high voltage. Variable-pressure SEM works at low vacuum and low voltage, so samples can be imagined in their natural hydrated state. Each one of these two techniques has its advantages and disadvantages; for this reason, a new protocol for sample observation in high-voltage and high-vacuum operating conditions, named OsO4-RR-TA-IL, was developed. The best, perfect protocol to observe biofilms does not exist but is possible to choose the most suitable one, depending on what kind of study has to be carried on. The choice of the most appropriate protocol has to be done carefully, based on the specific aim of the study. If the characterization of new biofilm types has to be performed, OsO4-RR-TA-IL has to be preferred. It allows observation of the most detailed ultrastructural features of the biofilm, due to the properties of every single reagent used. This customized protocol for biofilm uses osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA), and ionic liquid (IL), and it is unrivaled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preservation. If instead, the research has to examine the drug effects on a biofilm, or if a low amount of sample is available and magnification up to 8000 × is sufficient, VP-SEM has to be preferred. It is fast and has a few-step protocol that ensures very minimal sample loss giving images at sufficiently good resolution.

Pseudomonas aeruginosa is an opportunistic pathogen causing several chronic infections resistant to currently available antibiotics. Its pathogenicity is related to the production of different virulence factors such as biofilm and protease secretion. Pseudomonas communities can persist in biofilms that protect bacterial cells from antibiotics. Hence, there is a need for innovative approaches that are able to counteract these virulence factors, which play a pivotal role, especially in chronic infections. In this context, antimicrobial peptides are emerging drugs showing a broad spectrum of antibacterial activity. Here, we tested the anti-virulence activity of a chionodracine-derived peptide (KHS-Cnd) on five P. aeruginosa clinical isolates from cystic fibrosis patients. We demonstrated that KHS-Cnd impaired biofilm development and caused biofilm disaggregation without affecting bacterial viability in nearly all of the tested strains. Ultrastructural morphological analysis showed that the effect of KHS-Cnd on biofilm could be related to a different compactness of the matrix. KHS-Cnd was also able to reduce adhesion to pulmonary cell lines and to impair the invasion of host cells by P. aeruginosa. A cytotoxic effect of KHS-Cnd was observed only at the highest tested concentration. This study highlights the potential of KHS-Cnd as an anti-biofilm and anti-virulence molecule against P. aeruginosa clinical strains.

Cystic fibrosis (CF) is the most common rare disease caused by a mutation of the CF transmembrane conductance regulator gene encoding a channel protein of the apical membrane of epithelial cells leading to alteration of Na+ and K+ transport, hence inducing accumulation of dense and sticky mucus and promoting recurrent airway infections. The most detected bacterium in CF patients is Pseudomonas aeruginosa (PA) which causes chronic colonization, requiring stringent antibiotic therapies that, in turn induces multi-drug resistance. Despite eradication attempts at the first infection, the bacterium is able to utilize several adaptation mechanisms to survive in hostile environments such as the CF lung. Its adaptive machinery includes modulation of surface molecules such as efflux pumps, flagellum, pili and other virulence factors. In the present study we compared surface protein expression of PA multi- and pan-drug resistant strains to wild-type antibiotic-sensitive strains, isolated from the airways of CF patients with chronic colonization and recent infection, respectively. After shaving with trypsin, microbial peptides were analyzed by tandem-mass spectrometry on a high-resolution platform that allowed the identification of 174 differentially modulated proteins localized in the region from extracellular space to cytoplasmic membrane. Biofilm assay was performed to characterize all 26 PA strains in term of biofilm production. Among the differentially expressed proteins, 17 were associated to the virulome (e.g., Tse2, Tse5, Tsi1, PilF, FliY, B-type flagellin, FliM, PyoS5), six to the resistome (e.g., OprJ, LptD) and five to the biofilm reservoir (e.g., AlgF, PlsD). The biofilm assay characterized chronic antibiotic-resistant isolates as weaker biofilm producers than wild-type strains. Our results suggest the loss of PA early virulence factors (e.g., pili and flagella) and later expression of virulence traits (e.g., secretion systems proteins) as an indicator of PA adaptation and persistence in the CF lung environment. To our knowledge, this is the first study that, applying a shaving proteomic approach, describes adaptation processes of a large collection of PA clinical strains isolated from CF patients in early and chronic infection phases.

Pseudomonas aeruginosa is frequently involved in cystic fibrosis (CF) airway infections. Biofilm, motility, production of toxins and the invasion of host cells are different factors that increase P. aeruginosa's virulence. The sessile phenotype offers protection to bacterial cells and resistance to antimicrobials and host immune attacks. Motility also contributes to bacterial colonization of surfaces and, consequently, to biofilm formation. Furthermore, the ability to adhere is the prelude for the internalization into lung cells, a common immune evasion mechanism used by most intracellular bacteria, such as P. aeruginosa. In previous studies we evaluated the activity of metalloprotease serratiopeptidase (SPEP) in impairing virulence-related properties in Gram-positive bacteria. This work aimed to investigate SPEP's effects on different physiological aspects related to the virulence of P. aeruginosa isolated from CF patients, such as biofilm production, pyoverdine and pyocyanin production and invasion in alveolar epithelial cells. Obtained results showed that SPEP was able to impair the attachment to inert surfaces as well as adhesion/invasion of eukaryotic cells. Conversely, SPEP's effect on pyocyanin and pyoverdine production was strongly strain-dependent, with an increase and/or a decrease of their production. Moreover, SPEP seemed to increase swarming motility and staphylolytic protease production. Our results suggest that a large number of clinical strains should be studied in-depth before drawing definitive conclusions. Why different strains sometimes react in opposing ways to a specific treatment is of great interest and will be the object of future studies. Therefore, SPEP affects P. aeruginosa's physiology by differently acting on several bacterial factors related to its virulence.

Several imaging methodologies have been used in biofilm studies, contributing to deepening the knowledge on their structure. This review illustrates the most widely used microscopy techniques in biofilm investigations, focusing on traditional and innovative scanning electron microscopy techniques such as scanning electron microscopy (SEM), variable pressure SEM (VP-SEM), environmental SEM (ESEM), and the more recent ambiental SEM (ASEM), ending with the cutting edge Cryo-SEM and focused ion beam SEM (FIB SEM), highlighting the pros and cons of several methods with particular emphasis on conventional SEM and VP-SEM. As each technique has its own advantages and disadvantages, the choice of the most appropriate method must be done carefully, based on the specific aim of the study. The evaluation of the drug effects on biofilm requires imaging methods that show the most detailed ultrastructural features of the biofilm. In this kind of research, the use of scanning electron microscopy with customized protocols such as osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA) staining, and ionic liquid (IL) treatment is unrivalled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preservation. The combined use of innovative SEM protocols and 3-D image analysis software will allow for quantitative data from SEM images to be extracted; in this way, data from images of samples that have undergone different antibiofilm treatments can be compared.

Pseudomonas aeruginosa is an opportunistic pathogen often involved in airway infections of cystic fibrosis (CF) patients. Its pathogenicity is related to several virulence factors, such as biofilm formation, motility and production of toxins and proteases. The expression of these virulence factors is controlled by quorum sensing (QS). Thus, QS inhibition is considered a novel strategy for the development of antipathogenic compounds acting on specific bacterial virulence programs without affecting bacterial vitality. In this context, cold-adapted marine bacteria living in polar regions represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire. In this paper, we investigated the biological activity of a supernatant derived from a novel Antarctic bacterium (SN_TAE2020) against specific virulence factors produced by P. aeruginosa strains isolated from FC patients. Our results clearly show a reduction in pyocyanin and protease production in the presence of SN_TAE2020. Finally, SN_TAE2020 was also able to strongly affect swarming and swimming motility for almost all tested strains. Furthermore, the effect of SN_TAE2020 was investigated on biofilm growth and texture, captured by SEM analysis. In consideration of the novel results obtained on clinical strains, polar bacteria might represent potential candidates for the discovery of new compounds limiting P. aeruginosa virulence in CF patients.

Pseudomonas aeruginosa is an opportunistic pathogen responsible for nosocomial infections, and is often involved in airway infections of cystic fibrosis (CF) patients. P. aeruginosa virulence is related to its ability to form biofilm, trigger different types of motilities, and produce toxins (for example, bacterial pigments). In this scenario, essential oils (EOs) have gained notoriety for their role in phenotype modulation, including virulence modulation. Among different EOs previously analyzed, herein we investigated the activity of Coridothymus capitatus EO (CCEO) against specific virulence factors produced by P. aeruginosa isolated from CF patients. CCEO showed inhibition of new biofilm formation and reduction in mature biofilm in about half of the tested strains. On selected strains, SEM analysis provided interesting information regarding CCEO action in a pre-adhesion assay. CCEO treatment showed a dramatic modification of the extracellular matrix (ECM) structure. Our results clearly showed a drastic reduction in pyocyanin production (between 84% and 100%) for all tested strains in the presence of CCEO. Finally, CCEO was also able to strongly affect P. aeruginosa swarming and swimming motility for almost all tested strains. In consideration of the novel results obtained on clinical strains isolated from CF patients, CCEO may be a potential candidate to limit P. aeruginosa virulence.

The opportunistic pathogen Pseudomonas aeruginosa is often involved in airway infections of cystic fibrosis (CF) patients. It persists in the hostile CF lung environment, inducing chronic infections due to the production of several virulence factors. In this regard, the ability to form a biofilm plays a pivotal role in CF airway colonization by P. aeruginosa. Bacterial virulence mitigation and bacterial cell adhesion hampering and/or biofilm reduced formation could represent a major target for the development of new therapeutic treatments for infection control. Essential oils (EOs) are being considered as a potential alternative in clinical settings for the prevention, treatment, and control of infections sustained by microbial biofilms. EOs are complex mixtures of different classes of organic compounds, usually used for the treatment of upper respiratory tract infections in traditional medicine. Recently, a wide series of EOs were investigated for their ability to modulate biofilm production by different pathogens comprising S. aureus, S. epidermidis, and P. aeruginosa strains. Machine learning (ML) algorithms were applied to develop classification models in order to suggest a possible antibiofilm action for each chemical component of the studied EOs. In the present study, we assessed the biofilm growth modulation exerted by 61 commercial EOs on a selected number of P. aeruginosa strains isolated from CF patients. Furthermore, ML has been used to shed light on the EO chemical components likely responsible for the positive or negative modulation of bacterial biofilm formation.