New frontiers for anti-biofilm drug development

Meldrum's acid derivates are MepA efflux pump inhibitors: In vitro and in silico essays

Efflux pumps are proteins capable of expelling antibiotics from bacterial cells, have emerged as a major mechanism of bacterial resistance. In the ongoing pursuit to overcome and reduce bacterial resistance, novel substances are being explored as potential efflux pump inhibitors. Meldrum's acid, a synthetic molecule widely studied for its role in synthesizing bioactive compounds, holds promise in this regard. Therefore, the objective of this study is to evaluate the antibacterial activity of three derivatives of Meldrum's acid and assess their ability to inhibit efflux mechanisms, employing both in silico and in vitro approaches. The antibacterial activity of the derivatives was assessed using a broth microdilution testing method. Surprisingly, the derivatives did not exhibit direct antibacterial activity on their own. However, they displayed a significant effect in enhancing the efficacy of antibiotics, suggesting a potential role in potentiating their effects. Furthermore, fluorescence emission assays using ethidium bromide indicated that the derivatives could potentially block efflux pumps, as they exhibited fluorescence levels comparable to the positive control. To further investigate their inhibitory capacity, molecular docking studies were conducted in silico, revealing binding interactions similar to ciprofloxacin and carbonyl cyanide 3-chlorophenylhydrazone, known efflux pump inhibitors. These findings highlight the potential of Meldrum's acid derivatives as effective inhibitors of efflux pumps. By targeting these mechanisms, the derivatives offer a promising avenue to enhance the effectiveness of antibiotics and combat bacterial resistance. This study underscores the importance of exploring novel strategies in the fight against bacterial resistance and provides valuable insights into the potential of Meldrum's acid derivatives as efflux pump inhibitors. Further research and exploration in this field are warranted to fully exploit their therapeutic potential.

Synthesis, antibiofilm activity and molecular docking of N-acylhomoserine lactones containing cinammic moieties

We prepared a series of cinnamoyl-containing furanones by an affordable and short synthesis. The nineteen compounds hold a variety of substituents including electron-donating, electron-withdrawing, bulky and meta-substituted phenyls, as well as heterocyclic rings. Compounds showed antibiofilm activity in S. aureus, K. pneumoniae and, more pronounced, against P. aeruginosa. The disruption of quorum sensing (QS) was tested using the violacein test and molecular docking predicted the antagonism of LasR as a plausible mechanism of action. The trimethoxylated and diene derivatives showed the best antibiofilm and anti-QS properties, thus becoming candidates for further modifications.

Clostridioides difficile Biofilm

Clostridioides difficile infection (CDI), previously Clostridium difficile infection, is a symptomatic infection of the large intestine caused by the spore-forming anaerobic, gram-positive bacterium Clostridioides difficile. CDI is an important healthcare-associated disease worldwide, characterized by high levels of recurrence, morbidity, and mortality. CDI is observed at a higher rate in immunocompromised patients after antimicrobial therapy, with antibiotics disrupting the commensal microbiota and promoting C. difficile colonization of the gastrointestinal tract.A rise in clinical isolates resistant to multiple antibiotics and the reduced susceptibility to the most commonly used antibiotic molecules have made the treatment of CDI more complicated, allowing the persistence of C. difficile in the intestinal environment.Gut colonization and biofilm formation have been suggested to contribute to the pathogenesis and persistence of C. difficile. In fact, biofilm growth is considered as a serious threat because of the related antimicrobial tolerance that makes antibiotic therapy often ineffective. This is the reason why the involvement of C. difficile biofilm in the pathogenesis and recurrence of CDI is attracting more and more interest, and the mechanisms underlying biofilm formation of C. difficile as well as the role of biofilm in CDI are increasingly being studied by researchers in the field.Findings on C. difficile biofilm, possible implications in CDI pathogenesis and treatment, efficacy of currently available antibiotics in treating biofilm-forming C. difficile strains, and some antimicrobial alternatives under investigation will be discussed here.

Sprayable chitosan nanogel with nitric oxide to accelerate diabetic wound healing through bacteria inhibition, biofilm eradication and macrophage polarization

Bacterial infection and chronic inflammation are two major risks in diabetic wound healing, which increase patient mortality. In this study, a multifunctional sprayable nanogel (Ag-G@CS) based on chitosan has been developed to synergistically inhibit bacterial infection, eradicate biofilm, and relieve inflammation of diabetic wounds. The nanogel is successfully crafted by encapsulating with a nitric oxide (NO) donor and performing in-situ reduction of silver nanoparticles (Ag). The released NO enhances the antibacterial efficacy of Ag, nearly achieving complete eradication of biofilms in vitro. Upon application on both normal or diabetic chronic wounds, the combination effects of released NO and Ag offer a notable antibacterial effect. Furthermore, after bacteria inhibition and biofilm eradication, the NO released by the nanogel orchestrates a transformation of M1 macrophages into M2 macrophages, significantly reducing tumor necrosis factor α (TNF-α) release and relieving inflammation. Remarkably, the released NO also promotes M2a to M2c macrophages, thereby facilitating tissue remodeling in chronic wounds. More importantly, it upregulates the expression of vascular endothelial growth factor (VEGF), further accelerating the wound healing process. Collectively, the formed sprayable nanogel exhibits excellent inhibition of bacterial infections and biofilms, and promotes chronic wound healing via inflammation resolution, which has excellent potential for clinical use in the future.

Dissolvable alginate hydrogel-based biofilm microreactors for antibiotic susceptibility assays

Biofilms are found in many infections in the forms of surface-adhering aggregates on medical devices, small clumps in tissues, or even in synovial fluid. Although antibiotic resistance genes are studied and monitored in the clinic, the structural and phenotypic changes that take place in biofilms can also lead to significant changes in how bacteria respond to antibiotics. Therefore, it is important to better understand the relationship between biofilm phenotypes and resistance and develop approaches that are compatible with clinical testing. Current methods for studying antimicrobial susceptibility are mostly planktonic or planar biofilm reactors. In this work, we develop a new type of biofilm reactor-three-dimensional (3D) microreactors-to recreate biofilms in a microenvironment that better mimics those in vivo where bacteria tend to form surface-independent biofilms in living tissues. The microreactors are formed on microplates, treated with antibiotics of 1000 times of the corresponding minimal inhibitory concentrations (1000 × MIC), and monitored spectroscopically with a microplate reader in a high-throughput manner. The hydrogels are dissolvable on demand without the need for manual scraping, thus enabling measurements of phenotypic changes. Bacteria inside the biofilm microreactors are found to survive exposure to 1000 × MIC of antibiotics, and subsequent comparison with plating results reveals no antibiotic resistance-associated phenotypes. The presented microreactor offers an attractive platform to study the tolerance and antibiotic resistance of surface-independent biofilms such as those found in tissues.

Synthesis and Staphylococcus aureus biofilm inhibitory activity of indolenine-substituted pyrazole and pyrimido[1,2-b]indazole derivatives

Staphylococcus aureus is a highly adaptable opportunistic pathogen that can form biofilms and generate persister cells, leading to life-threatening infections that are difficult to treat with antibiotics alone. Therefore, there is a need for an effective S. aureus biofilm inhibitor to combat this public health threat. In this study, a small library of indolenine-substituted pyrazoles and pyrimido[1,2-b]indazole derivatives were synthesised, of which the hit compound exhibited promising antibiofilm activities against methicillin-susceptible S. aureus (MSSA ATCC 29213) and methicillin-resistant S. aureus (MRSA ATCC 33591) at concentrations significantly lower than the planktonic growth inhibition. The hit compound could prevent biofilm formation and eradicate mature biofilms of MSSA and MRSA, with a minimum biofilm inhibitory concentration (MBIC50) value as low as 1.56 µg/mL and a minimum biofilm eradication concentration (MBEC50) value as low as 6.25 µg/mL. The minimum inhibitory concentration (MIC) values of the hit compound against MSSA and MRSA were 50 µg/mL and 25 µg/mL, respectively, while the minimum bactericidal concentration (MBC) values against MSSA and MRSA were > 100 µg/mL. Preliminary structure-activity relationship analysis reveals that the fused benzene ring and COOH group of the hit compound are crucial for the antibiofilm activity. Additionally, the compound was not cytotoxic to human alveolar A549 cells, thus highlighting its potential as a suitable candidate for further development as a S. aureus biofilm inhibitor.

Joining Forces against Antibiotic Resistance: The One Health Solution

Antibiotic resistance is a significant global health concern that affects both human and animal populations. The One Health approach acknowledges the interconnectedness of human health, animal health, and the environment. It emphasizes the importance of collaboration and coordination across these sectors to tackle complex health challenges such as antibiotic resistance. In the context of One Health, antibiotic resistance refers to the ability of bacteria to withstand the efficacy of antibiotics, rendering them less effective or completely ineffective in treating infections. The emergence and spread of antibiotic-resistant bacteria pose a threat to human and animal health, as well as to the effectiveness of medical treatments and veterinary interventions. In particular, One Health recognizes that antibiotic use in human medicine, animal agriculture, and the environment are interconnected factors contributing to the development and spread of antibiotic resistance. For example, the misuse and overuse of antibiotics in human healthcare, including inappropriate prescribing and patient non-compliance, can contribute to the selection and spread of resistant bacteria. Similarly, the use of antibiotics in livestock production for growth promotion and disease prevention can contribute to the development of antibiotic resistance in animals and subsequent transmission to humans through the food chain. Addressing antibiotic resistance requires a collaborative One Health approach that involves multiple participants, including healthcare professionals, veterinarians, researchers, and policymakers.

Effects of Flavonoids and Phenols from Moringa oleifera Leaf Extracts on Biofilm Processes in Xanthomonas campestris pv. campestris

Xanthomonas campestris pv. campestris is the causal agent of black rot in crucifers, a plant disease with significant economic impact. Xanthomonadaceae is a large family of Gram-negative bacteria that cause symptoms by blocking water flow in plants by invading the xylem. To accomplish this, the main mechanism the bacteria use to adapt to environmental changes and colonize tissues is biofilm formation. In recent years, growing interest in natural antimicrobial compounds has led to the study of different phytocomplexes derived from plants. In this work, Moringa oleifera was selected, as its leaves are rich in phenols, essential oils, and vitamins that exert antibacterial activity. X. campestris pv. campestris biofilm, one of its major virulence factors, was studied. Biofilm formation and removal were analyzed on abiotic and biotic surfaces with and without M. oleifera leaf extracts. The data from the analysis show that Moringa oleifera leaf extracts and single phenols were able to inhibit biofilm growth on abiotic surfaces, but the activity of the whole phytocomplex was significantly higher compared to that of individual phenols. The effect of Moringa oleifera extracts on cabbage leaves in vivo was also found to be very important, as scanning electron microscopy showed that treatment with the extracts led to clear unblocking of the xylem, implying many advantages for use in black rot control.

Menthol-based deep eutectic systems as antimicrobial and anti-inflammatory agents for wound healing

Effective antimicrobial treatment has been identified as a serious and unmet medical need. Herein, we present a strategy based on deep eutectic systems (DES) to overcome current limitations, answering the need not only to effectively kill bacterial agents but also to avoid their adhesion and proliferation, which is associated with biofilm formation and have a crucial impact on bacterial virulence. To achieve such a goal, natural deep eutectic systems (NADES) based on menthol (Me) and saturated free fatty acids (FFA) were produced, fully physicochemical characterized, and its bioactive properties were described. The antimicrobial potential of menthol-based NADES with FFA, namely, myristic acid (MA), lauric acid (LA), and stearic acid (SA) were investigated towards a broad panel of microorganisms. The obtained data indicates that NADES possess effective antimicrobial properties towards the Gram-positive bacterial and fungal strains tested. Among the tested formulations, Me:LA at a molar ratio of 4:1 molar was used to carry out a biofilm detachment/removal assay due to is superior microbiological properties. This formulation was able to effectively lead to biofilm removal/dispersion of not only methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans, but also Escherichia coli, without the need of any additional physical force or antibiotic. Furthermore, since microbial invasion and biofilm formation is highly undesired in wound healing, namely in chronic wound healing, the wound healing properties of these eutectic formulations was also investigated. The results suggest that these NADES can cope with microbial invasion and biofilm detachment while not compromising normal keratinocyte proliferation and migration verified in wound healing and epidermis repair, while also contributing to the reduction of cell stress and inflammation via the control of ROS production. In conclusion, these results provide the indication that NADES based on Me and FFA holds great interest as antimicrobial agents for preventive and therapeutic applications in various clinical settings, including wound healing.

A Review of Biofilm Formation of Staphylococcus aureus and Its Regulation Mechanism

Bacteria can form biofilms in natural and clinical environments on both biotic and abiotic surfaces. The bacterial aggregates embedded in biofilms are formed by their own produced extracellular matrix. Staphylococcus aureus (S. aureus) is one of the most common pathogens of biofilm infections. The formation of biofilm can protect bacteria from being attacked by the host immune system and antibiotics and thus bacteria can be persistent against external challenges. Therefore, clinical treatments for biofilm infections are currently encountering difficulty. To address this critical challenge, a new and effective treatment method needs to be developed. A comprehensive understanding of bacterial biofilm formation and regulation mechanisms may provide meaningful insights against antibiotic resistance due to bacterial biofilms. In this review, we discuss an overview of S. aureus biofilms including the formation process, structural and functional properties of biofilm matrix, and the mechanism regulating biofilm formation.

Phage derived lytic peptides, a secret weapon against Acinetobacter baumannii-An in silico approach

Acinetobacter baumannii is a bacterial pathogen that is commonly associated with hospital-acquired illnesses. Antimicrobial drug resistance in A. baumannii includes several penicillin classes, first and second-generation cephalosporins, cephamycins, most aminoglycosides, chloramphenicol, and tetracyclines. The recent rise in multidrug-resistant A. baumannii strains has resulted in an increase in pneumoniae associated with ventilators, urinary tract infections associated with the catheter, and bloodstream infections, all of which have increased complications in treatment, cost of treatment, and death. Small compounds known as antimicrobial peptides (AMPs) are known to have damaging effects on pathogenic bacteria. To determine their antimicrobial activity, AMPs are created from proteins acquired from various sources and evaluated in vitro. In the last phase of lytic cycle, bacteriophages release hydrolytic enzymes called endolysins that cleave the host's cell wall. Due to their superior potency and specificity compared to antibiotics, lysins are used as antibacterial agents. In the present study, different types of endolysin from phages of A. baumannii were selected based on an extensive literature survey. From the PhaLP database, the sequences of the selected lysins were retrieved in FASTA format and antimicrobial peptides were found among them. With the help of available bioinformatic tools, the anti-biofilm property, anti-fungal property, cell-penetrating property, and cellular toxicity of the antimicrobial peptides were determined. Out of the fourteen antimicrobial peptides found from the eight selected endolysins of A. baumannii specific phage, eight of them has anti-biofilm property, nine of them has anti-fungal property, five of them has cell-penetrating property and all of them are non-toxic.

Recent Advances in Multifunctional Antimicrobial Peptides as Immunomodulatory and Anticancer Therapy: Chromogranin A-Derived Peptides and Dermaseptins as Endogenous versus Exogenous Actors

Antimicrobial peptides (AMPs) are produced by all living organisms exhibiting antimicrobial activities and representing the first line of innate defense against pathogens. In this context, AMPs are suggested as an alternative to classical antibiotics. However, several researchers reported their involvement in different processes defining them as Multifunctional AMPs (MF-AMPs). Interestingly, these agents act as the endogenous responses of the human organism against several dangerous stimuli. Still, they are identified in other organisms and evaluated for their anticancer therapy. Chromogranin A (CgA) is a glyco-phosphoprotein discovered for the first time in the adrenal medulla but also produced in several cells. CgA can generate different derived AMPs influencing numerous physiological processes. Dermaseptins (DRSs) are a family of α-helical-shaped polycationic peptides isolated from the skin secretions of several leaf frogs from the Phyllomedusidae family. Several DRSs were identified as AMPs and, until now, more than 65 DRSs have been classified. Recently, these exogenous molecules were characterized for their anticancer activity. In this review, we summarize the role of these two classes of MF-AMPs as an example of endogenous molecules for CgA-derived peptides, able to modulate inflammation but also as exogenous molecules for DRSs, exerting anticancer activities.

The antimicrobial peptides secreted by the chromaffin cells of the adrenal medulla link the neuroendocrine and immune systems: From basic to clinical studies

The increasing resistance to antibiotic treatments highlights the need for the development of new antimicrobial agents. Antimicrobial peptides (AMPs) have been studied to be used in clinical settings for the treatment of infections. Endogenous AMPs represent the first line defense of the innate immune system against pathogens; they also positively interfere with infection-associated inflammation. Interestingly, AMPs influence numerous biological processes, such as the regulation of the microbiota, wound healing, the induction of adaptive immunity, the regulation of inflammation, and finally express anti-cancer and cytotoxic properties. Numerous peptides identified in chromaffin secretory granules from the adrenal medulla possess antimicrobial activity: they are released by chromaffin cells during stress situations by exocytosis via the activation of the hypothalamo-pituitary axis. The objective of the present review is to develop complete informations including (i) the biological characteristics of the AMPs produced after the natural processing of chromogranins A and B, proenkephalin-A and free ubiquitin, (ii) the design of innovative materials and (iii) the involvement of these AMPs in human diseases. Some peptides are elective biomarkers for critical care medicine, may play an important role in the protection of infections (alone, or in combination with others or antibiotics), in the prevention of nosocomial infections, in the regulation of intestinal mucosal dynamics and of inflammation. They could play an important role for medical implant functionalization, such as catheters, tracheal tubes or oral surgical devices, in order to prevent infections after implantation and to promote the healing of tissues.

The Correlation Between Biofilm-Forming Ability of Community-Acquired Methicillin-Resistant Staphylococcus aureus Isolated from the Respiratory Tract and Clinical Characteristics in Children

Objective

This study aimed to investigate the biofilm-forming ability, molecular typing, and antimicrobial resistance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains isolated from the respiratory tract of children and their correlation with clinical characteristics.

Methods

All CA-MRSA strains were isolated from hospitalized children, and their presentation, molecular typing, antimicrobial susceptibility, and biofilm formation were investigated. The clinical characteristics were compared between the strong and weak biofilm producer groups.

Results

Fifty-three CA-MRSA strains were isolated from the respiratory samples of 53 children, with nearly half of them being young infants (0-12 months). Approximately, 88.7% (47/53) of the isolates were resistant to four or more antibiotics, mainly β-lactam antibiotics, lincosamides, and macrolides. Twelve sequence types (STs) and 20 subtypes of staphylococcal protein A (spa) typing were identified, with ST59-t437 (39.6%, 21/53) as the predominant subtype. All strains showed the ability to form biofilms. When compared to children with weak biofilm-forming CA-MRSA strains, those with strong biofilm-forming strains had higher proportions of lower respiratory tract infections (LRTI) (88.5% vs 59.3%), obvious cough symptoms (84.6% vs 51.9%), and severe chest imaging manifestations (76.9% vs 37.0%). Furthermore, a strong biofilm-forming ability significantly increased the risk of prolonged cough in children with LRTI (44.4% vs 14.3%), and a positive correlation between the duration of cough and the extent of biofilm formation was observed. Medical history investigation revealed that the strong biofilm-forming group had a much higher percentage of macrolides intake than the weak biofilm-forming group in the last month before admission (61.5% vs 14.8%).

Conclusion

ST59-t437 was the most prevalent clone in CA-MRSA respiratory isolates among the hospitalized children. All CA-MRSA strains formed biofilms. The stronger the biofilm-forming ability, the more serious and prolonged were the respiratory symptoms.

Quantitative analysis of in vitro biofilm formation by clinical isolates of dermatophyte and antibiofilm activity of common antifungal drugs

BACKGROUND

The ability of dermatophytes to develop biofilm, as one of the virulence factors in fungal infections which contribute to antifungal resistance, is an outstanding aspect of dermatophytosis that has been noted recently. Because of the paucity of data about the biofilm formation by dermatophytes and their susceptibility to antifungal drugs, this study evaluated the biofilm formation by clinical isolates of dermatophytes and antibiofilm activity of common antifungals widely used to manage dermatophytosis.

METHODS

The ribosomal DNA internal transcribed spacer (ITS) regions sequencing for species identification of 50 clinical dermatophyte isolates was performed. The ability of isolates to form biofilm and inhibitory activity of itraconazole, terbinafine, and griseofulvin against biofilm formation was assayed by the crystal violet staining method. Optical microscopy and scanning electron microscopy (SEM) were applied for the visualization of the biofilm structures.

RESULTS

Trichophyton (T.) mentagrophytes (n: 14; 28%) and T. rubrum (n: 13;26%) were included in more than half of the dermatophyte isolates. Biofilm formation was observed in 37 out of 50 (74%) isolates that were classified as follows: nonproducers (n: 13; 26%), weak producers (n: 4; 8%), moderate producers (n: 16; 32%), and strong producers (n: 17; 34%) by comparison of the absorbance of biofilms produced by clinical strains with control. The mean IC50 values for terbinafine, griseofulvin, and itraconazole were 2.42, 3.18, and 3.78 μg/ml, respectively.

CONCLUSIONS

The results demonstrated that most of the clinical dermatophyte isolates are capable to form biofilm in vitro with variable strength. Moreover, terbinafine can be suggested as the first-line choice for the treatment of biofilm-formed dermatophytosis.

Antibiofilm properties of Clitoria ternatea flower anthocyanin-rich fraction towards Pseudomonas aeruginosa

In Asia, Clitoria ternatea flowers are commonly used as a traditional medicinal herb and as a food colourant. Their bioactive compounds have anti-inflammatory, anti-microbial and anti-biofilm activities. Pseudomonas aeruginosa is one of the major pathogens that cause biofilm-associated infections resulting in an increase in antimicrobial resistance. Hence, the aim of this study was to investigate if the anti-biofilm properties of the anthocyanin-rich fraction of C. ternatea flowers were effective against P. aeruginosa . The effect of the anthocyanin-rich fraction of C. ternatea flowers on P. aeruginosa biofilms formed on a polystyrene surface was determined using the crystal violet assay and scanning electron microscopy (SEM). The anthocyanin-rich fraction reduced biofilm formation by four P. aeruginosa strains with a minimum biofilm inhibitory concentration value ranging between 0.625 and 5.0 mg ml−1. We further show that the biofilm-inhibiting activity of C. ternatea flowers is not due to the flavonols but is instead attributed to the anthocyanins, which had significant biofilm inhibitory activity (64.0±1.1 %) at 24 h in a time–response study. The anthocyanin-rich fraction also significantly reduced bacterial attachment on the polystyrene by 1.1 log c.f.u. cm−2 surface based on SEM analysis. Hence, anthocyanins from C. ternatea flowers have potential as an agent to decrease the risk of biofilm-associated infections.

Polymicrobial Biofilm Dynamics of Multidrug-Resistant Candida albicans and Ampicillin-Resistant Escherichia coli and Antimicrobial Inhibition by Aqueous Garlic Extract

The polymicrobial biofilm of C. albicans with E. coli exhibits a dynamic interspecies interaction and is refractory to conventional antimicrobials. In this study, a high biofilm-forming multidrug-resistant strain of C. albicans overcomes inhibition by E. coli in a 24 h coculture. However, following treatment with whole Aqueous Garlic Extract (AGE), these individual biofilms of multidrug-resistant C. albicans M-207 and Ampicillin-resistant Escherichia coli ATCC 39936 and their polymicrobial biofilm were prevented, as evidenced by biochemical and structural characterization. This study advances the antimicrobial potential of AGE to inhibit drug-resistant C. albicans and bacterial-associated polymicrobial biofilms, suggesting the potential for effective combinatorial and synergistic antimicrobial designs with minimal side effects.

Phytolectin conjugated positively charged fatty acid amide impairs virulence factors and inhibits cross-kingdom biofilm formation of Candida albicans and uropathogenic Escherichia coli

AIM

Polymicrobial biofilm encasing cross-kingdom microorganisms are apparent in medicine, which imposes serious resistance to conventional antimicrobial treatment. The objective of the study was to explore Butea monosperma seed lectin (BMSL) conjugated antimicrobial lipid, 2-((N-(2-hydroxyethyl)palmitamido)methyl)-1-methylpyridin-1-ium iodide (cN16E) to inhibit mixed-species biofilm of uropathogenic Escherichia coli-Candida albicans.

METHODS AND RESULTS

Antimicrobial activity and antibiofilm of cN16E and cN16E-BMSL conjugate (BcN16E) were analyzed against single- and mixed microbial cultures. The minimum inhibitory concentration (MIC) indicates that the MIC of cN16E-BMSL conjugate (BcN16E) against cohabiting UPEC-C. albicans was eightfold lower than the cN16E. BcN16E affects membrane integrity to elicit antimicrobial activity. BcN16E inhibits the dual-species biofilm even with 16 times lower MIC of cN16E. BcN16E impairs the biofilm-associated virulence factors which include extracellular polysaccharides, cell surface hydrophobicity, swimming, swarming motilities, hyphal filamentous morphology, curli formation, and hemolysin activity. As a proof of concept, we demonstrated BcN16E ability to inhibit dual-species biofilm formation on a urinary catheter.

CONCLUSION

The study revealed that the BcN16E is better than cN16E in impairing biofilm-associated virulence factors and exerting antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings emphasize that phytolectin has the potential to enhance the anti-virulence strategies of antimicrobials against cross-kingdom biofilm-related infections.

Formation of Biofilm by Tetragenococcus halophilus Benefited Stress Tolerance and Anti-biofilm Activity Against S. aureus and S. Typhimurium

Tetragenococcus halophilus, a halophilic lactic acid bacterium (LAB), plays an important role in the production of high-salt fermented foods. Generally, formation of biofilm benefits the fitness of cells when faced with competitive and increasingly hostile fermented environments. In this work, the biofilm-forming capacity of T. halophilus was investigated. The results showed that the optimal conditions for biofilm formation by T. halophilus were at 3–9% salt content, 0–6% ethanol content, pH 7.0, 30°C, and on the surface of stainless steel. Confocal laser scanning microscopy (CLSM) analysis presented a dense and flat biofilm with a thickness of about 24 μm, and higher amounts of live cells were located near the surface of biofilm and more dead cells located at the bottom. Proteins, polysaccharides, extracellular-DNA (eDNA), and humic-like substances were all proved to take part in biofilm formation. Higher basic surface charge, greater hydrophilicity, and lower intracellular lactate dehydrogenase (LDH) activities were detected in T. halophilus grown in biofilms. Atomic force microscopy (AFM) imaging revealed that biofilm cultures of T. halophilus had stronger surface adhesion forces than planktonic cells. Cells in biofilm exhibited higher cell viability under acid stress, ethanol stress, heat stress, and oxidative stress. In addition, T. halophilus biofilms exhibited aggregation activity and anti-biofilm activity against Staphylococcus aureus and Salmonella Typhimurium. Results presented in the study may contribute to enhancing stress tolerance of T. halophilus and utilize their antagonistic activities against foodborne pathogens during the production of fermented foods.

Green, novel, and one-step synthesis of silver oxide nanoparticles: antimicrobial activity, synergism with antibiotics, and cytotoxic studies

Silver oxide nanoparticles (Ag2ONPs) were synthesized by a one-step, green, and novel method. Ag2ONPs were characterized independently as well as in mixtures with common antibiotics. The antibacterial activity of Ag2ONPs...

The Glucocorticoid PYED-1 Disrupts Mature Biofilms of Candida spp. and Inhibits Hyphal Development in Candida albicans

Invasive Candida infections have become a global public health problem due to the increase of Candida species resistant against antifungal therapeutics. The glucocorticoid PYED-1 (pregnadiene-11-hydroxy-16α,17α-epoxy-3,20-dione-1) has antimicrobial activity against various bacterial taxa. Consequently, it might be considered for the treatment of Candida infections. The antifungal activity of PYED-1 was evaluated against several fungal strains that were representative of the five species that causes the majority of Candida infections-namely, Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei. PYED-1 exhibited a weak antifungal activity and a fungistatic effect on all five Candida species. On the other hand, PYED-1 exhibited a good anti-biofilm activity, and was able to eradicate the preformed biofilms of all Candida species analyzed. Moreover, PYED-1 inhibited germ tube and hyphae formation of C. albicans and reduced adhesion of C. albicans to abiotic surfaces by up to 30%.

Challenges and solutions in polymer drug delivery for bacterial biofilm treatment: A tissue-by-tissue account

To tackle the emerging antibiotic resistance crisis, novel antimicrobial approaches are urgently needed. Bacterial communities (biofilms) are a particular concern in this context. Biofilms are responsible for most human infections and are inherently less susceptible to antibiotic treatments. Biofilms have been linked with several challenging chronic diseases, including implant-associated osteomyelitis and chronic wounds. The specific local environments present in the infected tissues further contribute to the rise in antibiotic resistance by limiting the efficacy of systemic antibiotic therapies and reducing drug concentrations at the infection site, which can lead to reoccurring infections. To overcome the shortcomings of systemic drug delivery, encapsulation within polymeric carriers has been shown to enhance antimicrobial efficacy, permeation and retention at the infection site. In this Review, we present an overview of current strategies for antimicrobial encapsulation within polymeric carriers, comparing challenges and solutions on a tissue-by-tissue basis. We compare challenges and proposed drug delivery solutions from the perspective of the local environments for biofilms found in oral, wound, gastric, urinary tract, bone, pulmonary, vaginal, ocular and middle/inner ear tissues. We will also discuss future challenges and barriers to clinical translation for these therapeutics. The following Review demonstrates there is a significant imbalance between the research focus being placed on different tissue types, with some targets (oral and wound biofims) being extensively more studied than others (vaginal and otitis media biofilms and endocarditis). Furthermore, the importance of the local tissue environment when selecting target therapies is demonstrated, with some materials being optimal choices for certain sites of bacterial infection, while having limited applicability in others.

Probing Antimicrobial Halloysite/Biopolymer Composites with Electron Microscopy: Advantages and Limitations

Halloysite is a tubular clay nanomaterial of the kaolin group with a characteristic feature of oppositely charged outer and inner surfaces, allowing its selective spatial modification. The natural origin and specific properties of halloysite make it a potent material for inclusion in biopolymer composites with polysaccharides, nucleic acids and proteins. The applications of halloysite/biopolymer composites range from drug delivery and tissue engineering to food packaging and the creation of stable enzyme-based catalysts. Another important application field for the halloysite complexes with biopolymers is surface coatings resistant to formation of microbial biofilms (elaborated communities of various microorganisms attached to biotic or abiotic surfaces and embedded in an extracellular polymeric matrix). Within biofilms, the microorganisms are protected from the action of antibiotics, engendering the problem of hard-to-treat recurrent infectious diseases. The clay/biopolymer composites can be characterized by a number of methods, including dynamic light scattering, thermo gravimetric analysis, Fourier-transform infrared spectroscopy as well as a range of microscopic techniques. However, most of the above methods provide general information about a bulk sample. In contrast, the combination of electron microscopy with energy-dispersive X-ray spectroscopy allows assessment of the appearance and composition of biopolymeric coatings on individual nanotubes or the distribution of the nanotubes in biopolymeric matrices. In this review, recent contributions of electron microscopy to the studies of halloysite/biopolymer composites are reviewed along with the challenges and perspectives in the field.

Efficacy of Indolicidin, Cecropin A (1-7)-Melittin (CAMA) and Their Combination Against Biofilm-Forming Multidrug-Resistant Enteroaggregative Escherichia coli

The present study examined the anti-biofilm efficacy of two short-chain antimicrobial peptides (AMPs), namely, indolicidin and cecropin A (1-7)-melittin (CAMA) against biofilm-forming multidrug-resistant enteroaggregative Escherichia coli (MDR-EAEC) isolates. The typical EAEC isolates re-validated by PCR and confirmed using HEp-2 cell adherence assay was subjected to antibiotic susceptibility testing to confirm its MDR status. The biofilm-forming ability of MDR-EAEC isolates was assessed by Congo red binding, microtitre plate assays and hydrophobicity index; broth microdilution technique was employed to determine minimum inhibitory concentrations (MICs) and minimum biofilm eradication concentrations (MBECs). The obtained MIC and MBEC values for both AMPs were evaluated alone and in combination against MDR-EAEC biofilms using crystal violet (CV) staining and confocal microscopy-based live/dead cell quantification methods. All the three MDR-EAEC strains revealed weak to strong biofilm-forming ability and were found to be electron-donating and weakly electron-accepting (hydrophobicity index). Also, highly significant (P < 0.001) time-dependent hydrodynamic growth of the three MDR-EAEC strains was observed at 48 h of incubation in Dulbecco's modified Eagle's medium (DMEM) containing 0.45% D-glucose. AMPs and their combination were able to inhibit the initial biofilm formation at 24 h and 48 h as evidenced by CV staining and confocal quantification. Further, the application of AMPs (individually and combination) against the preformed MDR-EAEC biofilms resulted in highly significant eradication (P < 0.001) at 24 h post treatment. However, significant differences were not observed between AMP treatments (individually or in combination). The AMPs seem to be an effective candidates for further investigations such as safety, stability and appropriate biofilm-forming MDR-EAEC animal models.

Down-regulation of biofilm-associated genes in mecA-positive methicillin-resistant S. aureus treated with M. communis extract and its antibacterial activity

Considering the prevalence of resistance to antibiotics, the discovery of effective agents against resistant pathogens is of extreme urgency. Herein, 26 mecA-positive methicillin-resistant S. aureus (MRSA) isolated from clinical samples were identified, and their resistance to 11 antibiotics was investigated. Next, the antibacterial and anti-biofilm activity of the ethanolic extract of M. communis on these strains was evaluated. Furthermore, the effect of this extract on the expression of biofilm-associated genes, icaA, icaD, bap, sarA, and agr, was studied. According to the results, all isolated strains were multidrug-resistant and showed resistance to oxacillin and tetracycline. Also, 96.15 and 88.46 % of them were resistant to gentamicin and erythromycin. However, the extract could effectively combat the strains. The minimum inhibitory concentration (MIC) against different strains ranged from 1.56 to 25 mg/ml and the minimum bactericidal concentration (MBC) was between 3.125 and 50 mg/ml. Even though most MRSA (67 %) strongly produced biofilm, the sub-MIC concentration of the extract destroyed the pre-formed biofilm and affected the bacterial cells inside the biofilm. It could also inhibit biofilm development by significantly decreasing the expression of icaA, icaD, sarA and bap genes involved in biofilm formation and development. In conclusion, the extract inhibits biofilm formation, ruins pre-formed biofilm, and kills cells living inside the biofilm. Furthermore, it down-regulates the expression of necessary genes and nips the biofilm formation in the bud.

Simultaneous Delivery of Multiple Antimicrobial Agents by Biphasic Scaffolds for Effective Treatment of Wound Biofilms

Biofilms pose a major challenge to control wound-associated infections. Due to biofilm impenetrability, traditional antimicrobial agents are often ineffective in combating biofilms. Herein, a biphasic scaffold is reported as an antimicrobial delivery system by integrating nanofiber mats with dissolvable microneedle arrays for the effective treatment of bacterial biofilms. Different combinations of antimicrobial agents, including AgNO3 , Ga(NO3 )3 , and vancomycin, are incorporated into nanofiber mats by coaxial electrospinning, which enables sustained delivery of these drugs. The antimicrobial agents-incorporated dissolvable microneedle arrays allow direct penetration of drugs into biofilms. By optimizing the administration strategies, drug combinations, and microneedle densities, biphasic scaffolds are able to eradicate both methicillin-resistant Staphylococcus aureus (MRSA) and MRSA/Pseudomonas aeruginosa blend biofilms in an ex vivo human skin wound infection model without necessitating surgical debridement. Taken together, the combinatorial system comprises of nanofiber mats and microneedle arrays can provide an efficacious delivery of multiple antimicrobial agents for the treatment of bacterial biofilms in wounds.

Surfactants of microbial origin as antibiofilm agents

The microbial world provides new energy sources and many various 'green' chemicals. One type of chemicals produced by microorganisms is the biosurfactant group. Biosurfactants are universal molecules, exhibiting surface properties often accompanied by desired biological activity. Biosurfactants are considered to be environmentally 'friendly' due to their low toxicity and biodegradable nature. These compounds have unique features and therefore they can find potential applications in many different industries, ranging from biotechnology to environmental remediation technologies. Antibacterial and antifungal activities make them relevant for applications as inhibitory agents against microbial biofilm. This review covers the current knowledge and the recent advances in the field of biosurfactants as antibiofilm agents.

Biological Evaluation of Selected 1,2,3-triazole Derivatives as Antibacterial and Antibiofilm Agents

BACKGROUND

Resistance to antimicrobial agents is a major public health problem, being Staphylococcus aureus prevalent in infections in hospital and community environments and, admittedly, related to biofilm formation in biotic and abiotic surfaces. Biofilms form a complex and structured community of microorganisms surrounded by an extracellular matrix adhering to each other and to a surface that gives them even more protection from and resistance against the action of antimicrobial agents, as well as against host defenses.

METHODS

Aiming to control and solve these problems, our study sought to evaluate the action of 1,2,3- triazoles against a Staphylococcus aureus isolate in planktonic and in the biofilm form, evaluating the activity of this triazole through Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) tests. We have also performed cytotoxic evaluation and Scanning Electron Microscopy (SEM) of the biofilms under the treatment of the compound. The 1,2,3-triazole DAN 49 showed bacteriostatic and bactericidal activity (MIC and MBC 128 μg/mL). In addition, its presence interfered with the biofilm formation stage (1/2 MIC, p <0.000001) and demonstrated an effect on young preformed biofilm (2 MICs, p <0.05).

RESULTS

Scanning Electron Microscopy images showed a reduction in the cell population and the appearance of deformations on the surface of some bacteria in the biofilm under treatment with the compound.

CONCLUSION

Therefore, it was possible to conclude the promising anti-biofilm potential of 1,2,3-triazole, demonstrating the importance of the synthesis of new compounds with biological activity.

The Role of Biofilm in Central Venous Catheter Related Bloodstream Infections: Evidence-based Nursing and Review of the Literature

BACKGROUND

Biofilm is a fundamental component in the pathogenesis of infections related to the use of the central venous catheter (CVC,) which can represent an important health issue in everyday practice of nursing and medical staff.

OBJECTIVE

The objective of the following review is to analyze the components of biofilm and their role in catheter-related infection determinism in an evidencebased nursing perspective in such a way as to give health professionals useful suggestions in the prevention and management of these complications.

METHODS

The following databases were consulted for the bibliographic search: Medline, Scopus, Science Direct. Biofilm can be the cause of CVC extraction and can lead to serious haematogenic infectious complications that can increase the morbidity and mortality of affected patients.

RESULTS

Updated pathophysiologic knowledge of biofilm formation and appropriate diagnostic methodology are pivotal in understanding and detecting CVC-related infections. Lock therapy appears to be a useful, preventive, and therapeutic aid in the management of CVCrelated infections. New therapies attempting to stop bacterial adhesion on the materials used could represent new frontiers for the prevention of CVC-related infections.

CONCLUSION

The correct evidence-based nursing methods, based on the use of guidelines, provides the opportunity to minimize the risks of infection through the implementation of a series of preventive measures both during the CVC positioning phase and in the subsequent phase, for example, during device management which is performed by medical and nursing staff.

A patent review of antibiofilm fungal drugs (2002-present)

Fungal biofilms, such as Candida albicans biofilms, are capable of surviving in hostile environments owing to their remarkable ability to adhere to surfaces and their tolerance to chemical interventions. Currently, therapeutic treatment options are few, making these biofilm-based infections problematic particularly due to their great tolerance to conventional antimicrobial drugs, thus causing serious health and economic problems. Therefore, the development of new drugs and antibiofilm specific therapies for the prevention and treatment of antifungal to eradicate biofilms are needed. This study was aimed at carrying out a patent review analysis to identify the innovation trends, and to explore the latest antifungal drugs and the specific therapeutic strategies available for the treatment of fungal biofilms. The present patent review was carried out using the Espacenet database, using the key words "biofilm and antifungal," from 2002 to December 2019. Through this review, it was possible to identify that most of the patent contents refer to new synthetic drugs derived from natural products and associations thereof with existing antifungal drugs. Methods and biomaterials for the treatment and prevention of fungal biofilms, mainly for C. albicans biofilms, which is the most isolated and studied fungal species, were also disclosed. The lack of scientific and technical information on the biofilm eradication subject is remarkable and further confirmed by the small number of patents identified in this survey.

Clarithromycin Exerts an Antibiofilm Effect against Salmonella enterica Serovar Typhimurium rdar Biofilm Formation and Transforms the Physiology towards an Apparent Oxygen-Depleted Energy and Carbon Metabolism

Upon biofilm formation, production of extracellular matrix components and alteration in physiology and metabolism allows bacteria to build up multicellular communities which can facilitate nutrient acquisition during unfavorable conditions and provide protection toward various forms of environmental stresses to individual cells. Thus, bacterial cells within biofilms become tolerant against antimicrobials and the immune system. In the present study, we evaluated the antibiofilm activity of the macrolides clarithromycin and azithromycin. Clarithromycin showed antibiofilm activity against rdar (red, dry, and rough) biofilm formation of the gastrointestinal pathogen Salmonella enterica serovar Typhimurium ATCC 14028 (Nal^r) at a 1.56 μM subinhibitory concentration in standing culture and dissolved cell aggregates at 15 μM in a microaerophilic environment, suggesting that the oxygen level affects the activity of the drug. Treatment with clarithromycin significantly decreased transcription and production of the rdar biofilm activator CsgD, with biofilm genes such as csgB and adrA to be concomitantly downregulated. Although fliA and other flagellar regulon genes were upregulated, apparent motility was downregulated. RNA sequencing showed a holistic cell response upon clarithromycin exposure, whereby not only genes involved in the biofilm-related regulatory pathways but also genes that likely contribute to intrinsic antimicrobial resistance, and the heat shock stress response were differentially regulated. Most significantly, clarithromycin exposure shifted the cells toward an apparent oxygen- and energy-depleted status, whereby the metabolism that channels into oxidative phosphorylation was downregulated, and energy gain by degradation of propane 1,2-diol, ethanolamine and l-arginine catabolism, potentially also to prevent cytosolic acidification, was upregulated. This analysis will allow the subsequent identification of novel intrinsic antimicrobial resistance determinants.

Antimicrobial Peptides: Classification, Design, Application and Research Progress in Multiple Fields

Antimicrobial peptides (AMPs) are a class of small peptides that widely exist in nature and they are an important part of the innate immune system of different organisms. AMPs have a wide range of inhibitory effects against bacteria, fungi, parasites and viruses. The emergence of antibiotic-resistant microorganisms and the increasing of concerns about the use of antibiotics resulted in the development of AMPs, which have a good application prospect in medicine, food, animal husbandry, agriculture and aquaculture. This review introduces the progress of research on AMPs comprehensively and systematically, including their classification, mechanism of action, design methods, environmental factors affecting their activity, application status, prospects in various fields and problems to be solved. The research progress on antivirus peptides, especially anti-coronavirus (COVID-19) peptides, has been introduced given the COVID-19 pandemic worldwide in 2020.

Chitosan coated catheters alleviates mixed species biofilms of Staphylococcus epidermidis and Candida albicans

Microorganisms which adhere to the surfaces of indwelling medical implants develop into a sessile microbial community to form monomicrobial or polymicrobial biofilms. Staphylococcus epidermidis and Candida albicans are the most common pathogens co-isolated from device mediated infections. Hence development of catheters coated with anti-fouling substances is of great interest. In this current study, chitosan, extracted from the shells of marine crab Portunus sanguinolentus was coated over the surface of the urinary catheters and checked for its efficacy to inhibit the adherence of both mono and mixed species biofilms. The Extracted Chitosan (EC) coated catheters showed profound activity in reducing the preformed biofilms and the other virulence factors of the pathogens like slime production in S. epidermidis and yeast to hyphal swtich in C. albicans. Furthermore, qPCR analysis showed that EC could downregulate the virulence genes in both the pathogens when grown as monospecies and mixed species biofilms.

Diversity of Bacteria and Bacterial Products as Antibiofilm and Antiquorum Sensing Drugs Against Pathogenic Bacteria

The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.

Characterization, antibiofilm and biocompatibility properties of chitosan hydrogels loaded with silver nanoparticles and ampicillin: an alternative protection to central venous catheters

The purpose of this study was to generate novel chitosan hydrogels (CHs) loaded with silver nanoparticles (AgNPs) and ampicillin (AMP) to prevent early formation of biofilms. AgNPs and CHs were characterized by UV-Vis, DLS, TEM, rheology, FT-IR, Raman, and SEM. The antibiofilm effect of the formulations was investigated against four multidrug-resistant and extensively drug-resistant pathogens using a colony biofilm, a high cell density and gradients model. Also, their hemostatic properties and cytotoxic effect were evaluated. Rheology results showed that CHs with AgNPs and AMP are typical non-Newtonian pseudoplastic fluids. The CH with 25 ppm of AgNPs and 50 ppm AMP inhibited the formation of biofilms of Acinetobacter baumannii, Enterococcus faecium and Staphylococcus epidermidis, while a ten-fold increase of the antimicrobial's concentration was needed to inhibit the biofilm of the β-lactamase positive Enterobacter cloacae. Further, CH with 250 ppm of AgNPs and 500 ppm AMP showed anticoagulant effect, and it was shown that all formulations were biocompatible. Besides to previous reports that described the bioadhesion properties of chitosan, these results suggest that AgNPs and AMP CHs loaded could be used as prophylactic treatment in patients with central venous catheter (CVC), inhibiting the formation of biofilms in their early stages, in addition to their anticoagulant effect and biocompatibility, those properties could keep the functionality of CVC helping to prevent complications such as sepsis and thrombosis.

Streptomyces sp SM01 isolated from Indian soil produces a novel antibiotic picolinamycin effective against multi drug resistant bacterial strains

A Kashmir Himalayan (India) soil isolate, Streptomyces sp. SM01 was subjected to small scale fermentation for the production of novel antimicrobials, picolinamycin (SM1). The production has been optimized which found to be maximum while incubated in AIA medium (pH 7) for 7 days at 30 °C. Seven days grew crude cell-free culture media (50 µL) showed a larger zone of inhibition against Staphylococcus aureus compared to streptomycin (5 µg) and ampicillin (5 µg). Extraction, purification, and chemical analysis of the antimicrobial component has been proved to be a new class of antibiotic with 1013 dalton molecular weight. We have named this new antibiotic as picolinamycin for consisting picolinamide moiety in the center of the molecule and produced by a Streptomyces sp. In general, the antimicrobial potency of this newly characterized antibiotic found to be higher against Gram-positive organisms than the tested Gram-negative organisms. The MIC of this antimicrobial compound was found to be 0.01 µg/ml for tested Gram-positive organisms and 0.02 to 5.12 µg/ml for Gram-negative organisms. Furthermore, it showed strong growth impairments of several multidrug resistance (MDR) strains, including methicillin-resistant strains of Staphylococci and Enterococci with the MIC value of 0.04 to 5.12 µg/ml and MDR (but methicillin-sensitive) strains of S. aureus with the MIC value of 0.084 µg/ml. It also showed anti-mycobacterial potential in higher concentrations (MIC is 10.24 µg/ml). Picolinamycin however did not show toxicity against tested A549 human cell line indicating that the spectrum of its activity limited within bacteria only.

Sulfonamide-based diffusible signal factor analogs interfere with quorum sensing in Stenotrophomonas maltophilia and Burkholderia cepacia

Aim: Stenotrophomonas maltophilia (Sm) and Burkholderia cepacia complex (BCC) are Gram-negative bacterial pathogens, which are typically multidrug resistant and excellent biofilm producers. These phenotypes are controlled by quorum sensing (QS) systems from the diffusible signal factor (DSF) family. We aim to interfere with this QS system as an alternative approach in combatting such difficult-to-treat infections. Materials & methods: A library of sulfonamide-based DSF bioisosteres was synthesized and tested against the major phenotypes regulated by QS. Results & conclusion: Several analogs display significant antibiofilm activity while the majority increase the action of the last-resort antibiotic colistin against Sm and BCC. Most compounds inhibit DSF synthesis in the Sm K279a strain. Our results support the strategy of interfering with QS communications to combat multidrug resistance.

Effect of Adiantum philippense Extract on Biofilm Formation, Adhesion With Its Antibacterial Activities Against Foodborne Pathogens, and Characterization of Bioactive Metabolites: An in vitro-in silico Approach

Adiantum philippense (A. philippense), an ethnomedicinally important fern, has become an interesting herb in the search for novel bioactive metabolites, which can also be used as therapeutic agents. Primarily, in this study, A. philippense crude extract was screened for its phytochemical constituents, antagonistic potential, and effect on bacterial adhesion and biofilm formation against common food pathogens. Phytochemical profiling of A. philippense was carried out by using High Resolution-Liquid Chromatography and Mass Spectroscopy (HR-LCMS) followed by antibacterial activity via agar cup/well diffusion, broth microdilution susceptibility methods, and growth curve analysis. Antibiofilm potency and efficacy were assessed on the development, formation, and texture of biofilms through light microscopy, fluorescent microscopy, scanning electron microscopy, and the assessment of exopolysaccharide production. Correspondingly, a checkerboard test was performed to evaluate the combinatorial effect of A. philippense and chloramphenicol. Lastly, molecular docking studies of identified phytochemicals with adhesin proteins of tested food pathogens, which helps the bacteria in surface attachment and leads to biofilm formation, were assessed. A. philippense crude extract was found to be active against all tested food pathogens, displaying the rapid time-dependent kinetics of bacterial killing. A. philippense crude extract also impedes the biofilm matrix by reducing the total content of exopolysaccharide, and, likewise, the microscopic images revealed a great extent of disruption in the architecture of biofilms. A synergy was observed between A. philippense crude extract and chloramphenicol for E. coli, S. aureus, and P. aeruginosa, whereas an additive effect was observed for S. flexneri. Various bioactive phytochemicals were categorized from A. philippense crude extract using HR-LCMS. The molecular docking of these identified phytochemicals was interrelated with the active site residues of adhesin proteins, IcsA, Sortase A, OprD, EspA, and FimH from S. flexneri, S. aureus, P. aeruginosa, and E. coli, respectively. Thus, our findings represent the bioactivity and potency of A. philippense crude extract against food pathogens not only in their planktonic forms but also against/in biofilms for the first time. We have also correlated these findings with the possible mechanism of biofilm inhibition via targeting adhesin proteins, which could be explored further to design new bioactive compounds against biofilm producing foodborne bacterial pathogens.

Correlation between biofilm formation and carbapenem resistance among clinical isolates of Klebsiella pneumoniae

Background

Klebsiella pneumoniae is a Gram-negative enteric bacterium that causes nosocomial infections; this bacterium has survived from harsh condition using biofilm formation in hospital equipment and cause severe infection. In the other hand, the emergence and extension of carbapenem resistance burden among K. pneumonia producing biofilm is the current concern of public health services. There are controversial findings about this subject. The aim of this study was to evaluate the correlation between biofilm formation and resistance to carbapenem among clinical isolates of K. pneumoniae.

Methods

A total of 160 K. pneumoniae isolates were collected from various infections of hospitalized patients. The Carba NP test and molecular methods were used for detection of carbapenem resistance isolates of K. pneumonia. Subsequently, the ability for biofilm production was performed from all isolates. Finally, Correlation of biofilm formation among carbapenem resistant isolates was calculated using χ2 and Fisher's exact tests.

Results

Among K. pneumoniae isolates 42.5% have carbapenemase activity by Carba NP test, while carbapenemase genes were detected in 35.6% of isolates in amplification assay. Moreover, there are 52.5% (n= 84) of all isolates were formed a strong biofilm, while 38.1% (n= 61) and 9.3% (n= 15) of isolates were middle and weak biofilm producer, respectively. Among carbapenem resistant cases (n= 68), there are 77.9% (n= 53) and 22% (n= 15) of isolates were reported as strong and middle biofilm producer, respectively. We see a significant correlation was seen between biofilm formation ability and carbapenem resistant isolates (p-value < 0.00001).

Conclusion

The increase of carbapenem resistance burden in biofilm producing isolates of K. pneumoniae is considered as serious alert and the basic measures to combat this phenomenon is imperative.

Free radical-releasing systems for targeting biofilms

The recent rise in antibiotic drug resistance and biofilm formation by microorganisms has driven scientists from different fields to develop newer strategies to target microorganisms responsible for infectious diseases. There is a growing interest in free radicals as therapeutic agents for antimicrobial applications. However, limitations such as short half-life has hindered their usage. Currently, several research groups are exploring various biomaterials that can prolong the half-life, increase storage duration and control the release of the therapeutic ranges of free radicals required for different applications, including biofilm eradication. This review paper initially provides a background to, and theoretical knowledge on, free radicals; and then proceeds to review studies that have employed various free radical-incorporated drug delivery systems as an approach to target biofilm formation and eradication. Some of the free radical releasing systems highlighted include polymers, nanoparticles and hydrogels, with a focus on biofilm eradication, where they impact significantly. The various challenges associated with their application are also discussed. Further, the review identifies future research and strategies that can potentiate the application of free radical-incorporated drug delivery systems for inhibiting biofilm formation and eradicating formed biofilms.

Allium ursinum and Allium oschaninii against Klebsiella pneumoniae and Candida albicans Mono- and Polymicrobic Biofilms in In Vitro Static and Dynamic Models

The present study assesses the in vitro antibiofilm potential activity of extracts of wild Allium ursinum and Allium oschaninii. The active ingredients of the extracts were obtained with a technique named Naviglio (rapid solid-liquid dynamic extraction, RSLDE) which is based on an innovative and green solid-liquid extraction methodology. The extracts were tested against models of mono- and polymicrobial biofilm structures of clinically antibiotic-resistant pathogens, Klebsiella pneumoniae ATCC 10031 and Candida albicans ATCC 90028. Biofilms were studied using a static and a dynamic model (microtiter plates and a CDC reactor) on three different surfaces reproducing what happens on implantable medical devices. Antimicrobic activities were determined through minimum inhibitory concentration (MIC), while antibiofilm activity was assessed by minimum biofilm eradication concentration (MBEC) using a crystal violet (CV) biofilm assay and colony forming unit (CFU) counts. Results showed that both Allium extracts eradicated biofilms of the tested microorganisms well; biofilms on Teflon were more susceptible to extracts than those on polypropylene and polycarbonate, suggesting that when grown on a complex substrate, biofilms may be more tolerant to antibiotics. Our data provide significant advances on antibiotic susceptibility testing of biofilms grown on biologically relevant materials for future in vitro and in vivo applications.

Antibacterial Efficacy of Two Commercially Available Bacteriophage Formulations, Staphylococcal Bacteriophage and PYO Bacteriophage, Against Methicillin-Resistant Staphylococcus aureus: Prevention and Eradication of Biofilm Formation and Control of a Systemic Infection of Galleria mellonella Larvae

Sessile bacteria growing on surfaces are more resistant to standard antibiotics than their planktonic counterpart. Due to their antimicrobial properties, bacteriophages have re-emerged as a promising approach to treat bacterial biofilm-associated infections. Here, we evaluated the ability of two commercially available phage formulations, Staphylococcal bacteriophage (containing the monophage Sb-1) and PYO bacteriophage (a polyphage), in preventing and eradicating an in vitro biofilm of methicillin-resistant Staphylococcus aureus (MRSA) by isothermal microcalorimetry and high-resolution confocal laser scanning microscopy (CLSM). Moreover, to assess the potential in vivo efficacy of both phage preparations, a Galleria mellonella model of MRSA systemic infection was used. Microcalorimetry measurement showed that 10⁷ PFU/ml (the highest tested titer) of both phage formulations were able to inhibit planktonic growth in a concentration-dependent manner. However, MRSA biofilm was eradicated only by co-incubation of 5–7 days with the highest phage titers, respectively. In the experiments of biofilm prevention, isothermal microcalorimetry revealed that the heat production was completely abolished in the presence of sub-inhibitory titers (10⁴ PFU/ml) of phages. These data were also confirmed by confocal laser scanning microscopy. Both phage formulations increased the survival of G. mellonella larvae preventing or treating MRSA infection compared to untreated control. In conclusion, tested phage formulations are promising for preventing device colonization and killing biofilm bacteria attached on a surface. Novel strategies for direct coating and release of phages from material should be investigated.

Combination of Rhamnolipid and Chitosan in Nanoparticles Boosts Their Antimicrobial Efficacy

Nanomaterials have emerged as antimicrobial agents due to their unique physical and chemical properties. The development of nanoparticles (NPs) composed of natural biopolymers and biosurfactants have sparked interest, as they can be obtained without the use of complex chemical synthesis and toxic materials. In this study, we develop antimicrobial nanoparticles combining the biopolymer chitosan with the biosurfactant rhamnolipid. Addition of rhamnolipid reduced the size and polydispersity index of chitosan nanoparticles showing a more positive surface charge with improved stability, suggesting that chitosan-free amino groups are predominantly present on the surface of nanoparticles. Antimicrobial activity of chitosan/rhamnolipid nanoparticles (C/RL-NPs) against Staphylococcus strains surpassed that of either single rhamnolipid or chitosan, both in planktonic bacteria and biofilms. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of C/RL-NPs were determined considering the concentration of each individual molecule in NPs. MIC values of 14/19 μg mL^-1 and MBC of 29/37 μg mL^-1 were observed for S. aureus DSM 1104 and MIC and MBC of 29/37 and 58/75 μg mL^-1 were observed against S. aureus ATCC 29213, respectively. For S. epidermidis, MIC and MBC of 7/9 and 14/19 μg mL^-1 were noticed. Chitosan and chitosan nanoparticles eliminate the bacteria present in the upper parts of biofilms, while C/RL-NPs were more effective, eradicating most sessile bacteria and reducing the number of viable cells below the detection limit, when NPs concentration of 58/75 μg mL^-1 was applied for both S. aureus DSM 1104 and S. epidermidis biofilms. The improved antibacterial efficacy of C/RL-NPs was linked to the increased local delivery of chitosan and rhamnolipid at the cell surface and, consequently, to their targets in Gram-positive bacteria. The combination of chitosan and rhamnolipid offers a promising strategy to the design of novel nanoparticles with low cytotoxicity, which can be exploited in pharmaceutical and food industries.

Candida spp./Bacteria Mixed Biofilms

The ability to form biofilms is a common feature of microorganisms, such as bacteria or fungi. These consortiums can colonize a variety of surfaces, such as host tissues, dentures, and catheters, resulting in infections highly resistant to drugs, when compared with their planktonic counterparts. This refractory effect is particularly critical in polymicrobial biofilms involving both fungi and bacteria. This review emphasizes Candida spp.-bacteria biofilms, the epidemiology of this community, the challenges in the eradication of such biofilms, and the most relevant treatments.

Bioactive Peptides Against Fungal Biofilms

Infections caused by invasive fungal biofilms have been widely associated with high morbidity and mortality rates, mainly due to the advent of antibiotic resistance. Moreover, fungal biofilms impose an additional challenge, leading to multidrug resistance. This fact, along with the contamination of medical devices and the limited number of effective antifungal agents available on the market, demonstrates the importance of finding novel drug candidates targeting pathogenic fungal cells and biofilms. In this context, an alternative strategy is the use of antifungal peptides (AFPs) against fungal biofilms. AFPs are considered a group of bioactive molecules with broad-spectrum activities and multiple mechanisms of action that have been widely used as template molecules for drug design strategies aiming at greater specificity and biological efficacy. Among the AFP classes most studied in the context of fungal biofilms, defensins, cathelicidins and histatins have been described. AFPs can also act by preventing the formation of fungal biofilms and eradicating preformed biofilms through mechanisms associated with cell wall perturbation, inhibition of planktonic fungal cells’ adhesion onto surfaces, gene regulation and generation of reactive oxygen species (ROS). Thus, considering the critical scenario imposed by fungal biofilms and associated infections and the application of AFPs as a possible treatment, this review will focus on the most effective AFPs described to date, with a core focus on antibiofilm peptides, as well as their efficacy in vivo, application on surfaces and proposed mechanisms of action.