Recent Strategies to Combat Biofilms Using Antimicrobial Agents and Therapeutic Approaches

Exploring naphthoquinone and anthraquinone derivatives as antibiotic adjuvants against Staphylococcus aureus biofilms: Synergistic effects of menadione

Given the ability of Staphylococcus aureus to form biofilms and produce persister cells, making infections difficult to treat with antibiotics alone, there is a pressing need for an effective antibiotic adjuvant to address this public health threat. In this study, a series of quinone derivatives were evaluated for their antimicrobial and antibiofilm activities against methicillin-susceptible and methicillin-resistant S. aureus reference strains. Following analyses using broth microdilution, growth curve analysis, checkerboard assay, time-kill experiments, and confocal laser scanning microscopy, menadione was identified as a hit compound. Menadione exhibited a notable antibacterial profile (minimum inhibitory concentration, MIC = 4-16 μg/ml; minimum bactericidal concentration, MBC = 256 μg/ml) against planktonic S. aureus and its biofilms (minimum biofilm inhibitory concentration, MBIC50 = 0.0625-0.25 μg/ml). When combined with oxacillin, erythromycin, and vancomycin, menadione exhibited a synergistic or additive effect against planktonic cells and biofilms of two S. aureus reference strains and six clinical isolates, highlighting its potential as a suitable adjuvant for further development against S. aureus biofilm-associated infections.

Antimicrobial Peptides and Their Biomedical Applications: A Review

The emergence of drug resistance genes and the detrimental health effects caused by the overuse of antibiotics are increasingly prominent problems. There is an urgent need for effective strategies to antibiotics or antimicrobial resistance in the fields of biomedicine and therapeutics. The pathogen-killing ability of antimicrobial peptides (AMPs) is linked to their structure and physicochemical properties, including their conformation, electrical charges, hydrophilicity, and hydrophobicity. AMPs are a form of innate immune protection found in all life forms. A key aspect of the application of AMPs involves their potential to combat emerging antibiotic resistance; certain AMPs are effective against resistant microbial strains and can be modified through peptide engineering. This review summarizes the various strategies used to tackle antibiotic resistance, with a particular focus on the role of AMPs as effective antibiotic agents that enhance the host's immunological functions. Most of the recent studies on the properties and impregnation methods of AMPs, along with their biomedical applications, are discussed. This review provides researchers with insights into the latest advancements in AMP research, highlighting compelling evidence for the effectiveness of AMPs as antimicrobial agents.

Characterization and Anti-Biofilm Activity of Lytic Enterococcus Phage vB_Efs8_KEN04 against Clinical Isolates of Multidrug-Resistant Enterococcus faecalis in Kenya

Enterococcus faecalis (E. faecalis) is a growing cause of nosocomial and antibiotic-resistant infections. Treating drug-resistant E. faecalis requires novel approaches. The use of bacteriophages (phages) against multidrug-resistant (MDR) bacteria has recently garnered global attention. Biofilms play a vital role in E. faecalis pathogenesis as they enhance antibiotic resistance. Phages eliminate biofilms by producing lytic enzymes, including depolymerases. In this study, Enterococcus phage vB_Efs8_KEN04, isolated from a sewage treatment plant in Nairobi, Kenya, was tested against clinical strains of MDR E. faecalis. This phage had a broad host range against 100% (26/26) of MDR E. faecalis clinical isolates and cross-species activity against Enterococcus faecium. It was able to withstand acidic and alkaline conditions, from pH 3 to 11, as well as temperatures between -80 °C and 37 °C. It could inhibit and disrupt the biofilms of MDR E. faecalis. Its linear double-stranded DNA genome of 142,402 bp contains 238 coding sequences with a G + C content and coding gene density of 36.01% and 91.46%, respectively. Genomic analyses showed that phage vB_Efs8_KEN04 belongs to the genus Kochikohdavirus in the family Herelleviridae. It lacked antimicrobial resistance, virulence, and lysogeny genes, and its stability, broad host range, and cross-species lysis indicate strong potential for the treatment of Enterococcus infections.

Synergistic combination of baicalein and rifampicin against Staphylococcus aureus biofilms

Staphylococcus aureus, a Gram-positive bacterium, is a predominant pathogen associated with various infections. The rapid emergence of antibiotic resistance has intensified the challenge of managing fracture-related infections in severe osteoporotic patients. Rifampicin, a potent antimicrobial agent employed against fracture and implant-related infections, necessitates combination therapies due to its susceptibility to antibiotic resistance. In this study, we explored the potential of baicalein, a bioactive flavonoid from Oroxylum indicum and Scutellaria baicalensis, in combination with rifampicin against S. aureus biofilms invitro. The minimum inhibitory concentration of baicalein and rifampicin were determined as 500 μg/mL and 12.5 ng/mL respectively. The synergistic activity of baicalein and rifampicin was determined by the fractional inhibitory concentration index (FICI) using checkerboard assay. The results showed the FICI of baicalein and rifampicin was lesser than 0.5, demonstrating synergistic effect. Furthermore, the efficacy of baicalein and rifampicin, both individually and in combination, was evaluated for biofilm inhibition and eradication. Scanning electron microscopy and confocal laser microscopy also confirmed that the synergistic combinations effectively removed most of the biofilms and partially killed pre-formed biofilms. In conclusion, the findings demonstrate that baicalein is as effective as rifampicin in inhibiting and eradicating S. aureus biofilms. Their combination exhibits synergistic effect, enhancing their bactericidal effect in completely eradicating S. aureus biofilms. The findings of this research underscore the research potential of combining baicalein and rifampicin as a novel therapeutic strategy against S. aureus biofilms, offering a promising direction for future research in the treatment of fracture-related S. aureus infections.

Mechanobiology of bacterial biofilms: Implications for orthopedic infection

Postoperative bacterial infections are prevalent complications in both human and veterinary orthopedic surgery, particularly when a biofilm develops. These infections often result in delayed healing, early revision, permanent functional loss, and, in severe cases, amputation. The diagnosis and treatment pose significant challenges, and bacterial biofilm further amplifies the therapeutic difficulty as it confers protection against the host immune system and against antibiotics which are usually administered as a first-line therapeutic option. However, the inappropriate use of antibiotics has led to the emergence of numerous multidrug-resistant organisms, which largely compromise the already imperfect treatment efficiency. In this context, the study of bacterial biofilm formation allows to better target antibiotic use and to evaluate alternative therapeutic strategies. Exploration of the roles played by mechanical factors on biofilm development is of particular interest, especially because cartilage and bone tissues are reactive environments that are subjected to mechanical load. This review delves into the current landscape of biofilm mechanobiology, exploring the role of mechanical factors on biofilm development through a multiscale prism starting from bacterial microscopic scale to reach biofilm mesoscopic size and finally the macroscopic scale of the fracture site or bone-implant interface.

HAMLET, a human milk protein-lipid complex, modulates amoxicillin induced changes in an ex vivo biofilm model of the oral microbiome

Challenges from infections caused by biofilms and antimicrobial resistance highlight the need for novel antimicrobials that work in conjunction with antibiotics and minimize resistance risk. In this study we investigated the composite effect of HAMLET (human alpha-lactalbumin made lethal to tumor cells), a human milk protein-lipid complex and amoxicillin on microbial ecology using an ex vivo oral biofilm model with pooled saliva samples. HAMLET was chosen due to its multi-targeted antimicrobial mechanism, together with its synergistic effect with antibiotics on single species pathogens, and low risk of resistance development. The combination of HAMLET and low concentrations of amoxicillin significantly reduced biofilm viability, while each of them alone had little or no impact. Using a whole metagenomics approach, we found that the combination promoted a remarkable shift in overall microbial composition compared to the untreated samples. A large proportion of the bacterial species in the combined treatment were Lactobacillus crispatus, a species with probiotic effects, whereas it was only detected in a minor fraction in untreated samples. Although resistome analysis indicated no major shifts in alpha-diversity, the results showed the presence of TEM beta-lactamase genes in low proportions in all treated samples but absence in untreated samples. Our study illustrates HAMLET's capability to alter the effects of amoxicillin on the oral microbiome and potentially favor the growth of selected probiotic bacteria when in combination. The findings extend previous knowledge on the combined effects of HAMLET and antibiotics against target pathogens to include potential modulatory effects on polymicrobial biofilms of human origin.

Bacterial vaginosis and biofilms: Therapeutic challenges and innovations - A narrative review

Bacterial vaginosis (BV), characterised by an imbalance in vaginal microbiota, frequently leading to recurrent episodes, has garnered recent research attention due to the significance of biofilms in its pathogenesis. BV biofilms contribute to recurrence by providing a shelter for harmful bacteria, rendering them resistant to conventional treatment. Objectives of this review include characterising BV biofilms, evaluating the limitations of current antibiotic therapy, highlighting emerging solutions and emphasising multifaceted approaches. The review presents data from clinical studies and trials on biofilm-focused treatments which might reduce BV recurrence, with the ultimate goal of improving the quality of life of women with BV and reducing its burden on their reproductive health.

A novel Enterococcus faecalis bacteriophage Ef212: biological and genomic features

This study aimed to isolate and characterize biological and genomic features of a phage infecting Enterococcus faecalis. The phage was isolated from environmental water and temperature and pH stability, one-step growth curve, and multiplicity of infection (MOI) were determined. Whole genome sequencing (WGS) and structural and functional annotations were performed. Its antibiofilm activity was also evaluated. The optimal MOI was 0.01, the latency period was 5 min, and the burst size was 202 plaque forming unit (PFU). High phage survival rates were observed at between pH 4-10 and temperatures between 4-50 °C. WGS and Transmission electron microscopy (TEM) showed that it was an Efquatrovirus representing siphovirus morphotype respectively. It was named as Enterococcus phage Ef212 and has a linear 40,690 bp double-stranded DNA with 45.3% G + C content (GenBank accession number: OR052631). BACPHLIP tool demonstrated that Enterococcus phage Ef212 is a lytic phage (88%). A total of 80 open reading frames (ORFs) were found and there were no antibiotic resistance genes, pathogenicity, virulence genes, or tRNAs in the phage genome. It was diverged from the most similar phages (identity, 88.35%; coverage, 89%) by phylogenetic analysis. Phage Ef212 shared a large part of its genome (60/80) with several other phages, yet some unique parts were found in their genomes. Host range analysis showed that phage Ef212 showed lytic activity against vancomycin-resistant and vancomycin-susceptible E. faecalis clinical isolates. This novel phage Ef212 showed the ability to inhibit and reduce the biofilm formation by around 42% and 38%, respectively. The biological and genomic features indicate that having an effective antibacterial activity, phage Ef212 seemed a promising therapeutic and biocontrol agent.

Revolutionizing healthcare: Harnessing nano biotechnology with zinc oxide nanoparticles to combat biofilm and bacterial infections-A short review

A crucial pathogenic mechanism in many bacterial diseases is the ability to create biofilms. Biofilms are suspected to play a role in over 80 % of microbial illnesses in humans. In light of the critical requirement for efficient management of bacterial infections, researchers have explored alternative techniques for treating bacterial disorders. One of the most promising ways to address this issue is through the development of long-lasting coatings with antibacterial properties. In recent years, antibacterial treatments based on metallic nanoparticles (NPs) have emerged as an effective strategy in the fight over bacterial drug resistance. Zinc oxide nanoparticles (ZnO-NPs) are the basis of a new composite coating material. This article begins with a brief overview of the mechanisms that underlie bacterial resistance to antimicrobial drugs. A detailed examination of the properties of metallic nanoparticles (NPs) and their potential use as antibacterial drugs for curing drug-sensitive and resistant bacteria follows. Furthermore, we assess metal nanoparticles (NPs) as powerful agents to fight against antibiotic-resistant bacteria and the growth of biofilm, and we look into their potential toxicological effects for the development of future medicines.

Molecular insights into flavone-mediated quorum sensing interference: A novel strategy against Serratiamarcescens biofilm-induced antibiotic resistance"

Antibiotic resistance poses a significant challenge in modern medicine, urging the exploration of innovative approaches to combat bacterial infections. Biofilms, complex bacterial communities encased in a protective matrix, contribute to resistance by impeding antibiotic efficacy and promoting genetic exchange. Understanding biofilm dynamics is crucial for developing effective antimicrobial therapies against antibiotic resistance. This study explores the potential of flavone to combat biofilm-induced antibiotic resistance by employing in-vitro biochemical, cell biology, and Insilico (MD simulation), approaches. Flavone exhibited potent antibacterial effects with a low minimum inhibitory concentration by inducing intracellular reactive oxygen species. Flavones further inhibited the formation of biofilms by 50-60 % and disrupted the pre-formed biofilms by reducing the extracellular polysaccharide substance protective layer formed on the biofilm by 80 %. Quorum sensing (QS) plays a crucial role in bacterial pathogenicity and flavone significantly attenuated the production of QS-induced virulence factors like urease, protease, lipase, hemolysin and prodigiosin pigment in a dose-dependent manner. Further Insilico molecular docking studies along with molecular dynamic simulations run for 100 ns proved the stable binding affinity of flavone with QS-specific proteins which are crucial for biofilm formation. This study demonstrates the therapeutic potential of flavone to target QS-signaling pathway to combat S.marcescens biofilms.

Plant-Derived Compounds: A Promising Tool for Dental Caries Prevention

There is a growing shift from the use of conventional pharmaceutical oral care products to the use of herbal extracts and traditional remedies in dental caries prevention. This is attributed to the potential environmental and health implications of contemporary oral products. This comprehensive review aims at the analysis of plant-derived compounds as preventive modalities in dental caries research. It focuses on data collected from 2019 until recently, trying to emphasize current trends in this topic. The research findings suggest that several plant-derived compounds, either aqueous or ethanolic, exhibit notable antibacterial effects against Streptococcus mutans and other bacteria related to dental caries, with some extracts demonstrating an efficacy comparable to that of chlorhexidine. Furthermore, in vivo studies using plant-derived compounds incorporated in food derivatives, such as lollipops, have shown promising results by significantly reducing Streptococcus mutans in high-risk caries children. In vitro studies on plant-derived compounds have revealed bactericidal and bacteriostatic activity against S. mutans, suggesting their potential use as dental caries preventive agents. Medicinal plants, plant-derived phytochemicals, essential oils, and other food compounds have exhibited promising antimicrobial activity against oral pathogens, either by their anti-adhesion activity, the inhibition of extracellular microbial enzymes, or their direct action on microbial species and acid production. However, further research is needed to assess their antimicrobial activity and to evaluate the cytotoxicity and safety profiles of these plant-derived compounds before their widespread clinical use can be recommended.

Synergistic activity of gold nanoparticles with amphotericin B on persister cells of Candida tropicalis biofilms

AIM

The antifungal activity was studied on sessile and persister cells (PCs) of Candida tropicalis biofilms of gold nanoparticles (AuNPs) stabilized with cetyltrimethylammonium bromide (CTAB-AuNPs) and those conjugated with cysteine, in combination with Amphotericin B (AmB).

MATERIALS/METHODS

The PC model was used and synergistic activity was tested by the checkerboard assay. Biofilms were studied by crystal violet and scanning electron microscopy.

RESULTS/CONCLUSIONS

After the combination of both AuNPs and AmB the biofilm biomass was reduced, with significant differences in architecture being observed with a reduced biofilm matrix. In addition, the CTAB-AuNPs-AmB combination significantly reduced PCs. Understanding how these AuNPs aid in the fight against biofilms and the development of new approaches to eradicate PCs has relevance for chronic infection treatment.

The Biofilm Inhibition Properties of Glucosamine Gold Nanoparticles in Combination with Meropenem against Pseudomonas aeruginosa on the Endotracheal Tube: A Model of Biofilm-Related Ventilator-Associated Pneumonia

Biofilm-related infections play a significant role in the development and persistence of ventilator-associated pneumonia. Pseudomonas aeruginosa (P. aeruginosa) frequently causes biofilm-related infections associated with ventilator tubing. Glucosamine gold nanoparticles (AuNPs) may exhibit antibiofilm properties; however, more studies, including combinatorial therapy with antibiotics, are needed to explore their potential applications in clinical settings. This study aims to investigate the biofilm inhibition properties of glucosamine AuNPs in combination with meropenem against P. aeruginosa ATCC 9027 on the endotracheal tube. A biofilm inhibition assay of glucosamine AuNPs at 0.02 mg/mL, both singly and in combination with meropenem at 1 mg/mL, was carried out against P. aeruginosa ATCC 9027 on an endotracheal tube using the tissue culture plate method. Scanning electron microscopy was performed for visualization. Glucosamine AuNPs at 0.02 mg/mL combined with meropenem at 1 mg/mL showed greater biofilm inhibition (72%) on the endotracheal tube than glucosamine nanoparticles at 0.02 mg/mL alone (26%) (p = 0.001). The scanning electron microscopic visualization revealed that the untreated P. aeruginosa biofilm was denser than the glucosamine nanoparticles-treated biofilm, whether combined with meropenem or using glucosamine nanoparticles alone. The combination of glucosamine AuNPs and meropenem may have the synergistic effect of inhibiting biofilm production of P. aeruginosa on the endotracheal tubes of patients with mechanical ventilation. Conducting additional experiments to explore the impact of combining glucosamine-coated gold nanoparticles (AuNPs) with meropenem on the inhibition of biofilm production by clinical P. aeruginosa isolates would be beneficial.

Efficacy of disinfectant and bacteriophage mixture against planktonic and biofilm state of Listeria monocytogenes to control in the food industry

Fresh produce and animal-based products contaminated with Listeria monocytogenes have been the main cause of listeriosis outbreaks for many years. The present investigation explored the potential of combination treatment of disinfectants with a bacteriophage cocktail to control L. monocytogenes contamination in the food industry. A mixture of 1 minimal inhibitory concentration (MIC) of disinfectants (sodium hypochlorite [NaOCl], hydrogen peroxide [H2O2], and lactic acid [LA]) and multiplicity of infection (MOI) 100 of phage cocktail was applied to both planktonic cells in vitro and already-formed biofilm cells on food contact materials (FCMs; polyethylene, polypropylene, and stainless steel) and foods (celery and chicken meat). All the combinations significantly lowered the population, biofilm-forming ability, and the expression of flaA, motB, hlyA, prfA, actA, and sigB genes of L. monocytogenes. Additionally, in the antibiofilm test, approximately 4 log CFU/cm2 was eradicated by 6 h treatment on FCMs, and 3 log CFU/g was eradicated within 3 days on celery. However, <2 log CFU/g was eradicated in chicken meat, and regrowth of L. monocytogenes was observed on foods after 5 days. The biofilm eradication efficacy of the combination treatment was proven through visualization using scanning electron microscopy (SEM) and confocal microscopy. In the SEM images, the unusual behavior of L. monocytogenes invading from the surface to the inside was observed after treating celery with NaOCl+P or H2O2 + P. These results suggested that combination of disinfectants (NaOCl, H2O2, and LA) with Listeria-specific phage cocktail can be employed in the food industry as a novel antimicrobial and antibiofilm approach, and further research of L. monocytogenes behavior after disinfection is needed.

Activity of biogenic silver nanoparticles in planktonic and biofilm-associated Corynebacterium pseudotuberculosis

Corynebacterium pseudotuberculosis is a gram-positive bacterium and is the etiologic agent of caseous lymphadenitis (CL) in small ruminants. This disease is characterized by the development of encapsulated granulomas in visceral and superficial lymph nodes, and its clinical treatment is refractory to antibiotic therapy. An important virulence factor of the Corynebacterium genus is the ability to produce biofilm; however, little is known about the characteristics of the biofilm produced by C. pseudotuberculosis and its resistance to antimicrobials. Silver nanoparticles (AgNPs) are considered as promising antimicrobial agents, and are known to have several advantages, such as a broad-spectrum activity, low resistance induction potential, and antibiofilm activity. Therefore, we evaluate herein the activity of AgNPs in C. pseudotuberculosis, through the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antibiofilm activity, and visualization of AgNP-treated and AgNP-untreated biofilm through scanning electron microscopy. The AgNPs were able to completely inhibit bacterial growth and inactivate C. pseudotuberculosis at concentrations ranging from 0.08 to 0.312 mg/mL. The AgNPs reduced the formation of biofilm in reference strains and clinical isolates of C. pseudotuberculosis, with interference values greater than 80% at a concentration of 4 mg/mL, controlling the change between the planktonic and biofilm-associated forms, and preventing fixation and colonization. Scanning electron microscopy images showed a significant disruptive activity of AgNP on the consolidated biofilms. The results of this study demonstrate the potential of AgNPs as an effective therapeutic agent against CL.

Using chronobiology-based second-generation artificial intelligence digital system for overcoming antimicrobial drug resistance in chronic infections

Antimicrobial resistance results from the widespread use of antimicrobial agents and is a significant obstacle to the effectiveness of these agents. Numerous methods are used to overcome this problem with moderate success. Besides efforts of antimicrobial stewards, several artificial intelligence (AI)-based technologies are being explored for preventing resistance development. These first-generation systems mainly focus on improving patients' adherence. Chronobiology is inherent in all biological systems. Host response to infections and pathogens activity are assumed to be affected by the circadian clock. This paper describes the problem of antimicrobial resistance and reviews some of the current AI technologies. We present the establishment of a second-generation AI chronobiology-based approach to help in preventing further resistance and possibly overcome existing resistance. An algorithm-controlled regimen that improves the long-term effectiveness of antimicrobial agents is being developed based on the implementation of variability in dosing and drug administration times. The method provides a means for ensuring a sustainable response and improved outcomes. Ongoing clinical trials determine the effectiveness of this second-generation system in chronic infections. Data from these studies are expected to shed light on a new aspect of resistance mechanisms and suggest methods for overcoming them.IMPORTANCE SECTIONThe paper presents the establishment of a second-generation AI chronobiology-based approach to help in preventing further resistance and possibly overcome existing resistance.Key messagesAntimicrobial resistance results from the widespread use of antimicrobial agents and is a significant obstacle to the effectiveness of these agents.We present the establishment of a second-generation AI chronobiology-based approach to help in preventing further resistance and possibly overcome existing resistance.

Antimicrobial and Cytotoxic Activities of Water-Soluble Isoxazole-Linked 1,3,4-Oxadiazole with Delocalized Charge: In Vitro and In Vivo Results

The distinct structure of cationic organic compounds plays a pivotal role in enhancing their water solubility, which in turn influences their bioavailability. A representative of these compounds, which contains a delocalized charge, is 5-amino-2-(5-amino-3-methyl-1,2-oxazol-4-yl)-3-methyl-2,3-dihydro-1,3,4-oxadiazol-2-ylium bromide (ED). The high-water solubility of ED obviates the need for potentially harmful solvents during in vitro testing. The antibacterial and antifungal activities of the ED compound were assessed in vitro using the microtiter plate method and a biocellulose-based biofilm model. Additionally, its cytotoxic effects on wound bed fibroblasts and keratinocytes were examined. The antistaphylococcal activity of ED was also evaluated using an in vivo larvae model of Galleria mellonella. Results indicated that ED was more effective against Gram-positive bacteria than Gram-negative ones, exhibiting bactericidal properties. Furthermore, ED demonstrated greater efficacy against biofilms formed by Gram-positive bacteria. At bactericidal concentrations, ED was non-cytotoxic to fibroblasts and keratinocytes. In in vivo tests, ED was non-toxic to the larvae. When co-injected with a high load of S. aureus, it reduced the average larval mortality by approximately 40%. These findings suggest that ED holds promise for further evaluation as a potential treatment for biofilm-based wound infections, especially those caused by Gram-positive pathogens like S. aureus.

Natural nanogels crosslinked with S-benzyl-L-cysteine exhibit potent antibacterial activity

Biofilm-forming bacteria E. coli and P. aeruginosa have both exhibited resistance against multiple antibiotics in clinical settings. To find a solution, researchers have turned to antibacterial structurally modified from natural materials that are harmless to the human body. Among these is DNA, a natural polymer composed of deoxyribose that when treated with HCl exposes its aldehyde groups and produces DNA-HCl. Here, we crosslinked these aldehyde groups with the primary amines in S-benzyl-L-cysteine (SBLC) using a Schiff reaction to obtain DNA-HCl-SBLC. We additionally treated alginate acid (AA) with EDAC, obtaining AA-EDAC, and substituting it with SBLC to produce AA-SBLC. We incorporated the above reactions with an emulsification process to produce nanogels (NGs) that were verified to be spherical and possessing benzene rings successfully grafted onto DNA-HCl and AA-EDAC. These natural NGs were proven to be negatively charged through zeta potential analysis and presented low cytotoxicity toward normal cells in cell organoid viability assays. These SBLC-modified polymers provided better inhibition of bacterial growth than those without modification. Moreover, after incubation with SBLC-modified NGs, bacteria expressed intracellular recA or pvdA in a dose-dependent manner, which was consistent with SEM data from damaged bacteria. Out of four tested NGs, DNA-HCl-SBLC NGs suppressed P. aeruginosa-induced sepsis most effectively and extended the lifespan of C. elegans. This study provides an alternative clinical solution to antibiotics-resistant biofilm strains.

Bithionol Restores Sensitivity of Multidrug-Resistant Gram-Negative Bacteria to Colistin with Antimicrobial and Anti-biofilm Effects

Being among the few last-resort antibiotics, colistin (COL) has been used to treat severe infectious diseases, such as those caused by multidrug-resistant Gram-negative bacteria (MDR GNB). However, the appearance of colistin-resistant (COL-R) GNB has been frequently reported. Therefore, novel antimicrobial strategies need to be urgently sought to address this resistance challenge. In the present study, antimicrobial drug screening conducted revealed that bithionol (BT), approved by the Food and Drug Administration and used as an anthelminthic drug for paragonimiasis, exhibited a synergistic antibacterial effect with COL. Clinically isolated COL-R GNB were used as candidates to evaluate the synergistic antibacterial activity. The results revealed that BT could significantly reverse the sensitivity of COL-R GNB to COL. Furthermore, the combined application of BT and COL can reduce bacterial biofilm formation and have a scavenging effect on the mature biofilm in vitro. The damage caused to the bacterial cell membrane integrity by the BT/COL combination was observed under a fluorescence microscope. The fluorescence intensity of reactive oxygen species also increased in the experimental group. The BT/COL combination also exhibited a synergistic antibacterial effect in vivo. Importantly, BT was confirmed to be safe at the highest concentrations that exerted synergistic effects on all tested strains. In conclusion, our findings demonstrated that BT exerted synergistic antimicrobial and anti-biofilm effects when combined with COL against MDR organisms, especially COL-R GNB, in vitro and in vivo. The findings thus provide a reference for the clinical response to the serious challenge of MDR GNB and the exploitation of the potential antibacterial activities of existing clinical non-antibacterial drugs.

Titanium complexes affect Bacillus subtilis biofilm formation

Biofilms are surface or interface-associated communities of bacterial cells, embedded in a self-secreted extracellular matrix (ECM). Cells in biofilms are 100-1000 times more resistant to antibiotic treatment relative to planktonic cells due to various reasons, including the ECM acting as a diffusion barrier to antibiotic molecules, the presence of persister cells that divide slowly and are less susceptible to cell-wall targeting drugs, and the activation of efflux pumps in response to antibiotic stress. In this study we tested the effect of two titanium(iv) complexes that have been previously reported as potent and non-toxic anticancer chemotherapeutic agents on Bacillus subtilis cells in culture and in biofilm forming conditions. The Ti(iv) complexes tested, a hexacoordinate diaminobis(phenolato)-bis(alkoxo) complex (phenolaTi) and a bis(isopropoxo) complex of a diaminobis(phenolato) "salan"-type ligand (salanTi), did not affect the growth rate of cells in shaken cultures, however they did affect biofilm formation. Surprisingly, while phenolaTi inhibited biofilm formation, the presence of salanTi induced the formation of more mechanically robust biofilms. Optical microscopy images of biofilm samples in the absence and presence of Ti(iv) complexes suggest that Ti(iv) complexes affect cell-cell and/or cell-matrix adhesion, and that these are interfered with phenolaTi and enhanced by salanTi. Our results highlight the possible effect of Ti(iv) complexes on bacterial biofilms, which is gaining interest in light of the emerging relations between bacteria and cancerous tumors.

Compassionate Use of Bacteriophages for Failed Persistent Infections During the First 5 Years of the Israeli Phage Therapy Center

The use of bacteriophages (phages) is reemerging as a potential treatment option for antibiotic-resistant or nonresolving bacterial infections. Phages are bacteria-specific viruses that may serve as a personalized therapeutic option with minimal collateral damage to the patient or the microbiome. In 2018 we established the Israeli Phage Therapy Center (IPTC) as a shared initiative of the Hadassah Medical Center and the Hebrew University of Jerusalem, aiming to conduct all of the steps required for phage-based solutions, from phage isolation and characterization to treatments, for nonresolving bacterial infections. So far, a total of 159 requests for phage therapy arrived to the IPTC; 145 of them were from Israel and the rest from other countries. This number of registered requests is growing annually. Multidrug-resistant bacteria accounted for 38% of all phage requests. Respiratory and bone infections were the most prevalent among clinical indications and accounted for 51% of the requests. To date, 20 phage therapy courses were given to 18 patients by the IPTC. In 77.7% (n = 14) of the cases, a favorable clinical outcome of infection remission or recovery was seen. Clearly, establishing an Israeli phage center has led to an increased demand for compassionate use of phages with favorable outcomes for many previously failed infections. As clinical trials are still lacking, publishing patient data from cohort studies is pertinent to establish clinical indications, protocols, and success and failure rates. Last, workflow processes and bottlenecks should be shared to enable faster availability and authorization of phages for clinical use.

Bioengineering Approaches to Fight against Orthopedic Biomaterials Related-Infections

One of the most serious complications following the implantation of orthopedic biomaterials is the development of infection. Orthopedic implant-related infections do not only entail clinical problems and patient suffering, but also cause a burden on healthcare care systems. Additionally, the ageing of the world population, in particular in developed countries, has led to an increase in the population above 60 years. This is a significantly vulnerable population segment insofar as biomaterials use is concerned. Implanted materials are highly susceptible to bacterial and fungal colonization and the consequent infection. These microorganisms are often opportunistic, taking advantage of the weakening of the body defenses at the implant surface–tissue interface to attach to tissues or implant surfaces, instigating biofilm formation and subsequent development of infection. The establishment of biofilm leads to tissue destruction, systemic dissemination of the pathogen, and dysfunction of the implant/bone joint, leading to implant failure. Moreover, the contaminated implant can be a reservoir for infection of the surrounding tissue where microorganisms are protected. Therefore, the biofilm increases the pathogenesis of infection since that structure offers protection against host defenses and antimicrobial therapies. Additionally, the rapid emergence of bacterial strains resistant to antibiotics prompted the development of new alternative approaches to prevent and control implant-related infections. Several concepts and approaches have been developed to obtain biomaterials endowed with anti-infective properties. In this review, several anti-infective strategies based on biomaterial engineering are described and discussed in terms of design and fabrication, mechanisms of action, benefits, and drawbacks for preventing and treating orthopaedic biomaterials-related infections.

Fungicidal and antibiofilm activities of gold nanoparticles on Candida tropicalis

Aim: To investigate the antifungal activity of two different functionalized gold nanoparticles (AuNP), those stabilized with cetyltrimethylammonium bromide and those conjugated with cysteine, and their effects on the architecture of Candida tropicalis biofilms. Materials & methods: Biofilms were studied by crystal violet binding assay and scanning electron microscopy. We investigated the effects of AuNPs on reactive oxygen species, reactive nitrogen intermediates and enzymatic and nonenzymatic antioxidant defenses. Results/Conclusion: The fungicidal activity and cellular stress of both AuNPs affected biofilm growth through accumulation of reactive oxygen species and reactive nitrogen intermediates. However, cetyltrimethylammonium bromide-stabilized AuNPs revealed a higher redox imbalance. We correlated, for the first time, AuNP effects with the redox imbalance and alterations in the architecture of C. tropicalis biofilms.

Treatment of Pseudomonas aeruginosa infectious biofilms: Challenges and strategies

Pseudomonas aeruginosa, a Gram-negative bacterium, is one of the major pathogens implicated in human opportunistic infection and a common cause of clinically persistent infections such as cystic fibrosis, urinary tract infections, and burn infections. The main reason for the persistence of P. aeruginosa infections is due to the ability of P. aeruginosa to secrete extracellular polymeric substances such as exopolysaccharides, matrix proteins, and extracellular DNA during invasion. These substances adhere to and wrap around bacterial cells to form a biofilm. Biofilm formation leads to multiple antibiotic resistance in P. aeruginosa, posing a significant challenge to conventional single antibiotic therapeutic approaches. It has therefore become particularly important to develop anti-biofilm drugs. In recent years, a number of new alternative drugs have been developed to treat P. aeruginosa infectious biofilms, including antimicrobial peptides, quorum-sensing inhibitors, bacteriophage therapy, and antimicrobial photodynamic therapy. This article briefly introduces the process and regulation of P. aeruginosa biofilm formation and reviews several developed anti-biofilm treatment technologies to provide new directions for the treatment of P. aeruginosa biofilm infection.