Bacterial biofilm and associated infections

Pathogens in FRI - Do bugs matter? - An analysis of FRI studies to assess your enemy

Fracture-related infection (FRI) is a devasting complication for both patients and their treating Orthopaedic surgeon that can lead to loss of limb function or even amputation. The unique and unpredictable features of FRI make its diagnosis and treatment a significant challenge. It has substantial morbidity and financial implications for patients, their families and healthcare providers. In this article, we perform an in-depth and comprehensive review of FRI through recent and seminal literature to highlight evolving definitions, diagnostic and treatment approaches, focusing on common pathogens such as Staphylococcus aureus, polymicrobial infections and multi-drug-resistant organisms (MDRO). Furthermore, multiple resistance mechanisms and adaptations for microbial survival are discussed, as well as modern evidence-based medical and surgical advancements in treatment strategies in combating FRI.

Gram-negative bacteria recognition and photodynamic elimination by Zn-DPA based sensitizers

The abuse and overuse of antibiotics let drug-resistant bacteria emerges. Antibacterial photodynamic therapy (APDT) has shown outstanding merits to eliminate the drug-resistant bacteria via cytotoxic reactive oxygen species produced by irradiating photosensitizer. However, most of photosensitizers are not effective for Gram-negative bacteria elimination. Herein conjugates of NBS, a photosensitizer, linked with one (NBS-DPA-Zn) or two (NBS-2DPA-Zn) equivalents of zinc-dipicolylamine (Zn-DPA) have been designed to achieve the functional recognition of different bacteria. Due to the cationic character of NBS and metal transfer channel effect of Zn-DPA, NBS-DPA-Zn exhibited the first regent to distinguish P. aeruginosa from other Gram-negative bacteria. Whereas NBS-2DPA-Zn showed broad-spectrum antibacterial effect because the two arm of double Zn-DPA enhanced interactions with anionic membranes of bacteria, led the bacteria aggregation and thus provided the efficacy of APDT to bacteria and corresponding biofilm. In combination with a hydrogel of Pluronic, NBS-2DPA-Zn@gel shows promising clinical application in mixed bacterial diabetic mouse model infection. This might propose a new method that can realize functional identification and elimination of bacteria through intelligent regulation of Zn-DPA, and shows excellent potential for antibacterial application.

Nanomaterial in controlling biofilms and virulence of microbial pathogens

The escalating threat of antimicrobial resistance (AMR) poses a grave concern to global public health, exacerbated by the alarming shortage of effective antibiotics in the pipeline. Biofilms, intricate populations of bacteria encased in self-produced matrices, pose a significant challenge to treatment, as they enhance resistance to antibiotics and contribute to the persistence of organisms. Amid these challenges, nanotechnology emerges as a promising domain in the fight against biofilms. Nanomaterials, with their unique properties at the nanoscale, offer innovative antibacterial modalities not present in traditional defensive mechanisms. This comprehensive review focuses on the potential of nanotechnology in combating biofilms, focusing on green-synthesized nanoparticles and their associated anti-biofilm potential. The review encompasses various aspects of nanoparticle-mediated biofilm inhibition, including mechanisms of action. The diverse mechanisms of action of green-synthesized nanoparticles offer valuable insights into their potential applications in addressing AMR and improving treatment outcomes, highlighting novel strategies in the ongoing battle against infectious diseases.

Acinetobacter baumannii biofilm was inhibited by tryptanthrin through disrupting its different stages and genes expression

Biofilm formation plays a significant role in antibiotic resistance, necessitating the search for alternative therapies against biofilm-associated infections. This study demonstrates that 20 μg/mL tryptanthrin can hinder biofilm formation above 50% in various A. baumannii strains. Tryptanthrin impacts various stages of biofilm formation, including the inhibition of surface motility and eDNA release in A. baumannii, as well as an increase in its sensitivity to H202. RT-qPCR analysis reveals that tryptanthrin significantly decreases the expression of the following genes: abaI (19.07%), abaR (33.47%), bfmR (43.41%), csuA/B (64.16%), csuE (50.20%), ompA (67.93%), and katE (72.53%), which are related to biofilm formation and quorum sensing. Furthermore, tryptanthrin is relatively safe and can reduce the virulence of A. baumannii in a Galleria mellonella infection model. Overall, our study demonstrates the potential of tryptanthrin in controlling biofilm formation and virulence of A. baumannii by disrupting different stages of biofilm formation and intercellular signaling communication.

The antibacterial and inhibition effect of chitosan grafted gentisate acid derivatives against Pseudomonas fluorescens: Attacking multiple targets on structure, metabolism system, antioxidant system, and biofilm

This work aimed to investigate the antibacterial ability and potential mechanism of chitosan grafted gentisate acid derivatives (CS-g-GA) against Pseudomonas fluorescens. The results showed that CS-g-GA had a significant suppressive impact on the growth of Pseudomonas fluorescens, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 0.64 mg/mL and 1.28 mg/mL, respectively. Results of scanning electron microscopy (SEM) and alkaline phosphatase (AKPase) confirmed that CS-g-GA destroyed the cell structure thereby causing the leakage of intracellular components. In addition, 1 × MIC of CS-g-GA could significantly inhibit the formation of biofilms, and 74.78 % mature biofilm and 86.21 % extracellular polysaccharide of Pseudomonas fluorescens were eradicated by CS-g-GA at 2 × MIC. The results on the respiratory energy metabolism system and antioxidant system demonstrated that CS-g-GA caused respiratory disturbance and energy limitation by influencing the key enzyme activities. It could also bind to DNA and affect genetic metabolism. From this, it could be seen that CS-g-GA had the potential to control foodborne contamination of Pseudomonas fluorescens by attacking multiple targets.

Probiotic potential of Streptomyces levis strain HFM-2 isolated from human gut and its antibiofilm properties against pathogenic bacteria

BACKGROUND

Antimicrobial resistance (AMR) is a serious worldwide public health concern that needs immediate action. Probiotics could be a promising alternative for fighting antibiotic resistance, displaying beneficial effects to the host by combating diseases, improving growth, and stimulating the host immune responses against infection. This study was conducted to evaluate the probiotic, antibacterial, and antibiofilm potential of Streptomyces levis strain HFM-2 isolated from the healthy human gut.

RESULTS

In vitro antibacterial activity in the cell-free supernatant of S. levis strain HFM-2 was evaluated against different pathogens viz. K. pneumoniae sub sp. pneumoniae, S. aureus, B. subtilis, VRE, S. typhi, S. epidermidis, MRSA, V. cholerae, M. smegmatis, E. coli, P. aeruginosa and E. aerogenes. Further, the ethyl acetate extract from S. levis strain HFM-2 showed strong biofilm inhibition against S. typhi, K. pneumoniae sub sp. pneumoniae, P. aeruginosa and E. coli. Fluorescence microscopy was used to detect biofilm inhibition properties. MIC and MBC values of EtOAc extract were determined at 500 and 1000 µg/mL, respectively. Further, strain HFM-2 showed high tolerance in gastric juice, pancreatin, bile, and at low pH. It exhibited efficient adhesion properties, displaying auto-aggregation (97.0%), hydrophobicity (95.71%, 88.96%, and 81.15% for ethyl acetate, chloroform and xylene, respectively), and showed 89.75%, 86.53%, 83.06% and 76.13% co-aggregation with S. typhi, MRSA, S. pyogenes and E. coli, respectively after 60 min of incubation. The S. levis strain HFM-2 was susceptible to different antibiotics such as tetracycline, streptomycin, kanamycin, ciprofloxacin, erythromycin, linezolid, meropenem, amikacin, gentamycin, clindamycin, moxifloxacin and vancomycin, but resistant to ampicillin and penicillin G.

CONCLUSION

The study shows that S. levis strain HFM-2 has significant probiotic properties such as good viability in bile, gastric juice, pancreatin environment, and at low pH; proficient adhesion properties, and antibiotic susceptibility. Further, the EtOAc extract of Streptomyces levis strain HFM-2 has a potent antibiofilm and antibacterial activity against antibacterial-resistant clinical pathogens.

Revealing roles of S-layer protein (SlpA) in Clostridioides difficile pathogenicity by generating the first slpA gene deletion mutant

Clostridioides difficile infection (CDI) with high morbidity and high mortality is an urgent threat to public health, and C. difficile pathogenesis studies are eagerly required for CDI therapy. The major surface layer protein, SlpA, was supposed to play a key role in C. difficile pathogenesis; however, a lack of isogenic slpA mutants has greatly hampered analysis of SlpA functions. In this study, the whole slpA gene was successfully deleted for the first time via CRISPR-Cas9 system. Deletion of slpA in C. difficile resulted in smaller, smother-edged colonies, shorter bacterial cell size, and aggregation in suspension. For life cycle, the mutant demonstrated lower growth (changes of optical density at 600 nm, OD600) but higher cell density (colony-forming unit, CFU), decreased toxins production, and inhibited sporulation. Moreover, the mutant was more impaired in motility, more sensitive to vancomycin and Triton X-100-induced autolysis, releasing more lactate dehydrogenase. In addition, SlpA deficiency led to robust biofilm formation but weak adhesion to human host cells.IMPORTANCEClostridioides difficile infection (CDI) has been the most common hospital-acquired infection, with a high rate of antibiotic resistance and recurrence incidences, become a debilitating public health threat. It is urgently needed to study C. difficile pathogenesis for developing efficient strategies as CDI therapy. SlpA was indicated to play a key role in C. difficile pathogenesis. However, analysis of SlpA functions was hampered due to lack of isogenic slpA mutants. Surprisingly, the first slpA deletion C. difficile strain was generated in this study via CRISPR-Cas9, further negating the previous thought about slpA being essential. Results in this study will provide direct proof for roles of SlpA in C. difficile pathogenesis, which will facilitate future investigations for new targets as vaccines, new therapeutic agents, and intervention strategies in combating CDI.

Molecular mechanisms of DNase inhibition of early biofilm formation Pseudomonas aeruginosa or Staphylococcus aureus: A transcriptome analysis

In vitro studies show that DNase can inhibit Pseudomonas aeruginosa and Staphylococcus aureus biofilm formation. However, the underlying molecular mechanisms remain poorly understood. This study used an RNA-sequencing transcriptomic approach to investigate the mechanism by which DNase I inhibits early P. aeruginosa and S. aureus biofilm formation on a transcriptional level, respectively. A total of 1171 differentially expressed genes (DEGs) in P. aeruginosa and 1016 DEGs in S. aureus enriched in a variety of biological processes and pathways were identified, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the DEGs were primarily involved in P. aeruginosa two-component system, biofilm formation, and flagellar assembly and in S. aureus biosynthesis of secondary metabolites, microbial metabolism in diverse environments, and biosynthesis of amino acids, respectively. The transcriptional data were validated using quantitative real-time polymerase chain reaction (RT-qPCR), and the expression profiles of 22 major genes remained consistent. These findings suggested that DNase I may inhibit early biofilm formation by downregulating the expression of P. aeruginosa genes associated with flagellar assembly and the type VI secretion system, and by downregulating S. aureus capsular polysaccharide and amino acids metabolism gene expression, respectively. This study offers insights into the mechanisms of DNase treatment-based inhibition of early P. aeruginosa and S. aureus biofilm formation.

Oxidative stress responses in biofilms

Oxidizing agents are low-molecular-weight molecules that oxidize other substances by accepting electrons from them. They include reactive oxygen species (ROS), such as superoxide anions (O2-), hydrogen peroxide (H2O2), and hydroxyl radicals (HO-), and reactive chlorine species (RCS) including sodium hypochlorite (NaOCl) and its active ingredient hypochlorous acid (HOCl), and chloramines. Bacteria encounter oxidizing agents in many different environments and from diverse sources. Among them, they can be produced endogenously by aerobic respiration or exogenously by the use of disinfectants and cleaning agents, as well as by the mammalian immune system. Furthermore, human activities like industrial effluent pollution, agricultural runoff, and environmental activities like volcanic eruptions and photosynthesis are also sources of oxidants. Despite their antimicrobial effects, bacteria have developed many mechanisms to resist the damage caused by these toxic molecules. Previous research has demonstrated that growing as a biofilm particularly enhances bacterial survival against oxidizing agents. This review aims to summarize the current knowledge on the resistance mechanisms employed by bacterial biofilms against ROS and RCS, focussing on the most important mechanisms, including the formation of biofilms in response to oxidative stressors, the biofilm matrix as a protective barrier, the importance of detoxifying enzymes, and increased protection within multi-species biofilm communities. Understanding the complexity of bacterial responses against oxidative stress will provide valuable insights for potential therapeutic interventions and biofilm control strategies in diverse bacterial species.

Biofilm Formation by Hospital-Acquired Resistant Bacteria Isolated from Respiratory Samples

BACKGROUND

Hospital-acquired resistant infections (HARI) are infections, which develop 48 h or more after admission to a healthcare facility. HARI pose a considerably acute challenge, due to limited treatment options. These infections are associated bacterial biofilms, which act as a physical barrier to diverse external stresses, such as desiccation, antimicrobials and biocides. We assessed the influence of multiple factors on biofilm production by HARI -associated bacteria.

METHODS

Bacteria were isolated from samples of patients with respiratory HARI who were hospitalized during 2020-2022 in north Israel. Following antibiotic susceptibility testing by disc diffusion or broth microdilution, biofilm formation capacities of resistant bacteria (methicillin-resistant staphylococcus aureus, extended spectrum beta-lactamase-producing Escherichia coli and Klebsiela pneumonia, and multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii) was assessed using the crystalline violet staining method. Data regarding season, time to infection, bacterial species, patient age and gender, year, and medical department were collected from the patient medical records.

RESULTS

Among the 226 study isolates, K. pneumonia was the most prevalent (35.4%) bacteria, followed by P. aeruginosa (23.5%), and methicillin-resistant staphylococcus aureus (MRSA) (21.7%). A significantly higher rate of HARI was documented in 2022 compared to 2020-2021. The majority of isolates (63.3%) were strong biofilm producers, with K. pneumonia (50.3%) being most dominant, followed by P. aeruginosa (29.4%). Biofilm production strength was significantly affected by seasonality and hospitalization length, with strong biofilm production in autumn and in cases where hospitalization length exceeded 30 days.

CONCLUSION

Biofilm production by HARI bacteria is influenced by bacterial species, season and hospitalization length.

Space biofilms - An overview of the morphology of Pseudomonas aeruginosa biofilms grown on silicone and cellulose membranes on board the international space station

Microorganisms' natural ability to live as organized multicellular communities - also known as biofilms - provides them with unique survival advantages. For instance, bacterial biofilms are protected against environmental stresses thanks to their extracellular matrix, which could contribute to persistent infections after treatment with antibiotics. Bacterial biofilms are also capable of strongly attaching to surfaces, where their metabolic by-products could lead to surface material degradation. Furthermore, microgravity can alter biofilm behavior in unexpected ways, making the presence of biofilms in space a risk for both astronauts and spaceflight hardware. Despite the efforts to eliminate microorganism contamination from spacecraft surfaces, it is impossible to prevent human-associated bacteria from eventually establishing biofilm surface colonization. Nevertheless, by understanding the changes that bacterial biofilms undergo in microgravity, it is possible to identify key differences and pathways that could be targeted to significantly reduce biofilm formation. The bacterial component of Space Biofilms project, performed on the International Space Station in early 2020, contributes to such understanding by characterizing the morphology and gene expression of bacterial biofilms formed in microgravity with respect to ground controls. Pseudomonas aeruginosa was used as model organism due to its relevance in biofilm studies and its ability to cause urinary tract infections as an opportunistic pathogen. Biofilm formation was characterized at one, two, and three days of incubation (37 °C) over six different materials. Materials reported in this manuscript include catheter grade silicone, selected due to its medical relevance in hospital acquired infections, catheter grade silicone with ultrashort pulsed direct laser interference patterning, included to test microtopographies as a potential biofilm control strategy, and cellulose membrane to replicate the column and canopy structure previously reported from a microgravity study. We here present an overview of the biofilm morphology, including 3D images of the biofilms to represent the distinctive morphology observed in each material tested, and some of the key differences in biofilm thickness, mass, and surface area coverage. We also present the impact of the surface microtopography in biofilm formation across materials, incubation time, and gravitational conditions. The Space Biofilms project (bacterial side) is supported by the National Aeronautics and Space Administration under Grant No. 80NSSC17K0036 and 80NSSC21K1950.

A Review of Chlorhexidine Oral Care in Patients Receiving Mechanical Ventilation

BACKGROUND

Chlorhexidine gluconate has been considered the criterion standard of oral care for patients receiving mechanical ventilation because of its ability to reduce the incidence of ventilator-associated events. Optimal concentrations and frequencies remain unclear, as do adverse events related to mortality in various intensive care unit populations.

OBJECTIVE

To examine the current evidence for the efficacy of chlorhexidine gluconate in reducing the incidence of ventilator-associated events, mortality, intensive care unit length of stay, and duration of mechanical ventilation in patients receiving ventilator support.

METHODS

In this integrative review, CINAHL (Cumulative Index to Nursing and Allied Health Literature), MEDLINE, and Health Source: Nursing/Academic Edition were searched using terms related to mechanical ventilation and chlorhexidine gluconate oral care with dates ranging from 2012 to 2023.

RESULTS

Seventeen articles were included in this review: 8 systematic reviews, 8 randomized clinical trials (3 of which were not included in any systematic review), and 1 quasi-experimental study. Chlorhexidine gluconate oral care was associated with a reduced incidence of ventilator-associated events, but efficacy depended on concentration and frequency of administration. With stratification by intensive care unit population type, a nonsignificant trend toward increased mortality was found among non-cardiac surgical patients who received this care.

CONCLUSION

The evidence regarding the efficacy of chlorhexidine gluconate oral care in reducing ventilator-associated events in specific intensive care unit populations is contradictory. Recently published guidelines recommend de-implementation of chlorhexidine gluconate oral care in all patients receiving mechanical ventilation. Such care may be beneficial only in the cardiac surgical population.

Dimeric peptoids as antibacterial agents

Building upon our previous study on peptoid-based antibacterials which showed good activity against Gram-positive bacteria only, herein we report the synthesis of 34 dimeric peptoid compounds and the investigation of their activity against Gram-positive and Gram-negative pathogens. The newly designed peptoids feature a di-hydrophobic moiety incorporating phenyl, bromo-phenyl, and naphthyl groups, combined with variable lengths of cationic units such as amino and guanidine groups. The study also underscores the pivotal interplay between hydrophobicity and cationicity in optimizing efficacy against specific bacteria. The bromophenyl dimeric guanidinium peptoid compound 10j showed excellent activity against S. aureus 38 and E. coli K12 with MIC of 0.8 μg mL-1 and 6.2 μg mL-1, respectively. Further investigation into the mechanism of action revealed that the antibacterial effect might be attributed to the disruption of bacterial cell membranes, as suggested by tethered bilayer lipid membranes (tBLMs) and cytoplasmic membrane permeability studies. Notably, these promising antibacterial agents exhibited negligible toxicity against mammalian red blood cells. Additionally, the study explored the potential of 12 active compounds to disrupt established biofilms of S. aureus 38. The most effective biofilm disruptors were ethyl and octyl-naphthyl guanidinium peptoids (10c and 10 k). These compounds 10c and 10 k disrupted the established biofilms of S. aureus 38 with 51 % at 4x MIC (MIC = 17.6 μg mL-1 and 11.2 μg mL-1) and 56 %-58 % at 8x MIC (MIC = 35.2 μg mL-1 and 22.4 μg mL-1) respectively. Overall, this research contributes insights into the design principles of cationic dimeric peptoids and their antibacterial activity, with implications for the development of new antibacterial compounds.

The limitless endophytes: their role as antifungal agents against top priority pathogens

Multi resistant fungi are on the rise, and our arsenal compounds are limited to few choices in the market such as polyenes, pyrimidine analogs, azoles, allylamines, and echinocandins. Although each of these drugs featured a unique mechanism, antifungal resistant strains did emerge and continued to arise against them worldwide. Moreover, the genetic variation between fungi and their host humans is small, which leads to significant challenges in new antifungal drug discovery. Endophytes are still an underexplored source of bioactive secondary metabolites. Many studies were conducted to isolate and screen endophytic pure compounds with efficacy against resistant yeasts and fungi; especially, Candida albicans, C. auris, Cryptococcus neoformans and Aspergillus fumigatus, which encouraged writing this review to critically analyze the chemical nature, potency, and fungal source of the isolated endophytic compounds as well as their novelty features and SAR when possible. Herein, we report a comprehensive list of around 320 assayed antifungal compounds against Candida albicans, C. auris, Cryptococcus neoformans and Aspergillus fumigatus in the period 1980-2024, the majority of which were isolated from fungi of orders Eurotiales and Hypocreales associated with terrestrial plants, probably due to the ease of laboratory cultivation of these strains. 46% of the reviewed compounds were active against C. albicans, 23% against C. neoformans, 29% against A. fumigatus and only 2% against C. auris. Coculturing was proved to be an effective technique to induce cryptic metabolites absent in other axenic cultures or host extract cultures, with Irperide as the most promising compounds MIC value 1 μg/mL. C. auris was susceptible to only persephacin and rubiginosin C. The latter showed potent inhibition against this recalcitrant strain in a non-fungicide way, which unveils the potential of fungal biofilm inhibition. Further development of culturing techniques and activation of silent metabolic pathways would be favorable to inspire the search for novel bioactive antifungals.

The interplay of Pseudomonas aeruginosa and Staphylococcus aureus in dual-species biofilms impacts development, antibiotic resistance and virulence of biofilms in in vitro wound infection models

Due to high tolerance to antibiotics and pronounced virulence, bacterial biofilms are considered a key factor and major clinical challenge in persistent wound infections. They are typically composed of multiple species, whose interactions determine the biofilm's structural development, functional properties and thus the progression of wound infections. However, most attempts to study bacterial biofilms in vitro solely rely on mono-species populations, since cultivating multi-species biofilms, especially for prolonged periods of time, poses significant challenges. To address this, the present study examined the influence of bacterial composition on structural biofilm development, morphology and spatial organization, as well as antibiotic tolerance and virulence on human skin cells in the context of persistent wound infections. By creating a wound-mimetic microenvironment, the successful cultivation of dual-species biofilms of two of the most prevalent wound pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, was realized over a period of 72 h. Combining quantitative analysis with electron microscopy and label-free imaging enabled a comprehensive evaluation of the dynamics of biofilm formation and matrix secretion, revealing a twofold increased maturation of dual-species biofilms. Antibiotic tolerance was comparable for both mono-species cultures, however, dual-species communities showed a 50% increase in tolerance, mediated by a significantly reduced penetration of the applied antibiotic into the biofilm matrix. Further synergistic effects were observed, where dual-species biofilms exacerbated wound healing beyond the effects observed from either Pseudomonas or Staphylococcus. Consequently, predicting biofilm development, antimicrobial tolerance and virulence for multi-species biofilms based solely on the results from mono-species biofilms is unreliable. This study underscores the substantial impact of a multi-species composition on biofilm functional properties and emphasizes the need to tailor future studies reflecting the bacterial composition of the respective in vivo situation, leading to a more comprehensive understanding of microbial communities in the context of basic microbiology and the development of effective treatments.

Biofilm-derived membrane vesicles exhibit potent immunomodulatory activity in Pseudomonas aeruginosa PAO1

Pathogenic bacteria form biofilms on epithelial cells, and most bacterial biofilms show increased production of membrane vesicles (MVs), also known as outer membrane vesicles in Gram-negative bacteria. Numerous studies have investigated the MVs released under planktonic conditions; however, the impact of MVs released from biofilms on immune responses remains unclear. This study aimed to investigate the characteristics and immunomodulatory activity of MVs obtained from both planktonic and biofilm cultures of Pseudomonas aeruginosa PAO1. The innate immune responses of macrophages to planktonic-derived MVs (p-MVs) and biofilm-derived MVs (b-MVs) were investigated by measuring the mRNA expression of proinflammatory cytokines. Our results showed that b-MVs induced a higher expression of inflammatory cytokines, including Il1b, Il6, and Il12p40, than p-MVs. The mRNA expression levels of Toll-like receptor 4 (Tlr4) differed between the two types of MVs, but not Tlr2. Polymyxin B significantly neutralized b-MV-mediated cytokine induction, suggesting that lipopolysaccharide of native b-MVs is the origin of the immune response. In addition, heat-treated or homogenized b-MVs induced the mRNA expression of cytokines, including Tnfa, Il1b, Il6, and Il12p40. Heat treatment of MVs led to increased expression of Tlr2 but not Tlr4, suggesting that TLR2 ligands play a role in detecting the pathogen-associated molecular patterns in lysed MVs. Taken together, our data indicate that potent immunomodulatory MVs are produced in P. aeruginosa biofilms and that this behavior could be a strategy for the bacteria to infect host cells. Furthermore, our findings would contribute to developing novel vaccines using MVs.

A novel multiplex fluorescent-labeling method for the visualization of mixed-species biofilms in vitro

In nature, bacteria usually exist as mixed-species biofilms, where they engage in a range of synergistic and antagonistic interactions that increase their resistance to environmental challenges. Biofilms are a major cause of persistent infections, and dispersal from initial foci can cause new infections at distal sites thus warranting further investigation. Studies of development and spatial interactions in mixed-species biofilms can be challenging due to difficulties in identifying the different bacterial species in situ. Here, we apply CellTrace dyes to studies of biofilm bacteria and present a novel application for multiplex labeling, allowing identification of different bacteria in mixed-species, in vitro biofilm models. Oral bacteria labeled with CellTrace dyes (far red, yellow, violet, and CFSE [green]) were used to create single- and mixed-species biofilms, which were analyzed with confocal spinning disk microscopy (CSDM). Biofilm supernatants were studied with flow cytometry (FC). Both Gram-positive and Gram-negative bacteria were well labeled and CSDM revealed biofilms with clear morphology and stable staining for up to 4 days. Analysis of CellTrace labeled cells in supernatants using FC showed differences in the biofilm dispersal between bacterial species. Multiplexing with different colored dyes allowed visualization of spatial relationships between bacteria in mixed-species biofilms and relative coverage by the different species was revealed through segmentation of the CSDM images. This novel application, thus, offers a powerful tool for studying structure and composition of mixed-species biofilms in vitro.IMPORTANCEAlthough most chronic infections are caused by mixed-species biofilms, much of our knowledge still comes from planktonic cultures of single bacterial species. Studies of formation and development of mixed-species biofilms are, therefore, required. This work describes a method applicable to labeling of bacteria for in vitro studies of biofilm structure and dispersal. Critically, labeled bacteria can be multiplexed for identification of different species in mixed-species biofilms using confocal spinning disk microscopy, facilitating investigation of biofilm development and spatial interactions under different environmental conditions. The study is an important step in increasing the tools available for such complex and challenging studies.

Sepsis risk in diabetic patients with urinary tract infection

BACKGROUND

Urinary tract infections (UTI) is a prevalent condition in those with diabetes, and in severe cases, it may escalate to sepsis. Therefore, it is important to analyze the risk variables associated with sepsis in diabetes individuals with UTI.

METHODS

This research was a retrospective cross-sectional analysis. From January 2011 to June 2022, a group of individuals with diabetes were identified as having UTI at a tertiary hospital situated in Southeastern China. Patient data, including information on urine culture, was collected retrospectively from a clinical record database. The participants were categorized into the sepsis and non-sepsis groups. The risk variables were derived using both uni-and multiple- variable regression analysis.

RESULTS

The research included 1919 patients, of whom 1106 cases (57.63%) had positive urine cultures. In total, 445 blood culture samples were tested, identifying 186 positive cases (41.80%). The prevalence of bacteria in urine and blood samples was highest for Escherichia coli and Klebsiella pneumoniae, respectively. Moreover, 268 individuals (13.97%) exhibited sepsis. The regression analysis indicated a positive correlation between sepsis and albumin (ALB)<34.35 g/L, C-reactive protein (CRP)>55.84 mg/L and white blood cell count (WBC) >8.485 X 109/L in diabetic cases with UTIs. By integrating the three aforementioned parameters, the area under the receiver operating characteristic curve was 0.809.

CONCLUSIONS

The early detection of sepsis in diabetic individuals with UTI may be achieved using a comprehensive analysis of CRP, WBC, and ALB test findings.

Current Knowledge and Perspectives of Phage Therapy for Combating Refractory Wound Infections

Wound infection is one of the most important factors affecting wound healing, so its effective control is critical to promote the process of wound healing. However, with the increasing prevalence of multi-drug-resistant (MDR) bacterial strains, the prevention and treatment of wound infections are now more challenging, imposing heavy medical and financial burdens on patients. Furthermore, the diminishing effectiveness of conventional antimicrobials and the declining research on new antibiotics necessitate the urgent exploration of alternative treatments for wound infections. Recently, phage therapy has been revitalized as a promising strategy to address the challenges posed by bacterial infections in the era of antibiotic resistance. The use of phage therapy in treating infectious diseases has demonstrated positive results. This review provides an overview of the mechanisms, characteristics, and delivery methods of phage therapy for combating pathogenic bacteria. Then, we focus on the clinical application of various phage therapies in managing refractory wound infections, such as diabetic foot infections, as well as traumatic, surgical, and burn wound infections. Additionally, an analysis of the potential obstacles and challenges of phage therapy in clinical practice is presented, along with corresponding strategies for addressing these issues. This review serves to enhance our understanding of phage therapy and provides innovative avenues for addressing refractory infections in wound healing.

Dual-function antimicrobial-antibiofilm peptide hybrid to tackle biofilm-forming Staphylococcus epidermidis

BACKGROUND

Due to their resistance and difficulty in treatment, biofilm-associated infections are problematic among hospitalized patients globally and account for 60% of all bacterial infections in humans. Antibiofilm peptides have recently emerged as an alternative treatment since they can be effectively designed and exert a different mode of biofilm inhibition and eradication.

METHODS

A novel antibiofilm peptide, BiF, was designed from the conserved sequence of 18 α-helical antibiofilm peptides by template-assisted technique and its activity was improved by hybridization with a lipid binding motif (KILRR). Novel antibiofilm peptide derivatives were modified by substituting hydrophobic amino acids at positions 5 or 7, and both, with positively charged lysines (L5K, L7K). These peptide derivatives were tested for antibiofilm and antimicrobial activities against biofilm-forming Staphylococcus epidermidis and multiple other microbes using crystal violet and broth microdilution assays, respectively. To assess their impact on mammalian cells, the toxicity of peptides was determined through hemolysis and cytotoxicity assays. The stability of candidate peptide, BiF2_5K7K, was assessed in human serum and its secondary structure in bacterial membrane-like environments was analyzed using circular dichroism. The action of BiF2_5K7K on planktonic S. epidermidis and its effect on biofilm cell viability were assessed via viable counting assays. Its biofilm inhibition mechanism was investigated through confocal laser scanning microscopy and transcription analysis. Additionally, its ability to eradicate mature biofilms was examined using colony counting. Finally, a preliminary evaluation involved coating a catheter with BiF2_5K7K to assess its preventive efficacy against S. epidermidis biofilm formation on the catheter and its surrounding area.

RESULTS

BiF2_5K7K, the modified antibiofilm peptide, exhibited dose-dependent antibiofilm activity against S. epidermidis. It inhibited biofilm formation at subinhibitory concentrations by altering S. epidermidis extracellular polysaccharide production and quorum-sensing gene expression. Additionally, it exhibited broad-spectrum antimicrobial activity and no significant hemolysis or toxicity against mammalian cell lines was observed. Its activity is retained when exposed to human serum. In bacterial membrane-like environments, this peptide formed an α-helix amphipathic structure. Within 4 h, a reduction in the number of S. epidermidis colonies was observed, demonstrating the fast action of this peptide. As a preliminary test, a BiF2_5K7K-coated catheter was able to prevent the development of S. epidermidis biofilm both on the catheter surface and in its surrounding area.

CONCLUSIONS

Due to the safety and effectiveness of BiF2_5K7K, we suggest that this peptide be further developed to combat biofilm infections, particularly those of biofilm-forming S. epidermidis.

Surfactants' Interplay with Biofilm Development in Staphylococcus and Candida

The capacity of micro-organisms to form biofilms is a pervasive trait in the microbial realm. For pathogens, biofilm formation serves as a virulence factor facilitating successful host colonization. Simultaneously, infections stemming from biofilm-forming micro-organisms pose significant treatment challenges due to their heightened resistance to antimicrobial agents. Hence, the quest for active compounds capable of impeding microbial biofilm development stands as a pivotal pursuit in biomedical research. This study presents findings concerning the impact of three surfactants, namely, polysorbate 20 (T20), polysorbate 80 (T80), and sodium dodecyl sulfate (SDS), on the initial stage of biofilm development in both Staphylococcus aureus and Candida dubliniensis. In contrast to previous investigations, we conducted a comparative assessment of the biofilm development capacity of these two taxonomically distant groups, predicated on their shared ability to reduce TTC. The common metabolic trait shared by S. aureus and C. dubliniensis in reducing TTC to formazan facilitated a simultaneous evaluation of biofilm development under the influence of surfactants across both groups. Our results revealed that surfactants could impede the development of biofilms in both species by disrupting the initial cell attachment step. The observed effect was contingent upon the concentration and type of compound, with a higher inhibition observed in culture media supplemented with SDS. At maximum concentrations (5%), T20 and T80 significantly curtailed the formation and viability of S. aureus and C. dubliniensis biofilms. Specifically, T20 inhibited biofilm development by 75.36% in S. aureus and 71.18% in C. dubliniensis, while T80 exhibited a slightly lower inhibitory effect, with values ranging between 66.68% (C. dubliniensis) and 65.54% (S. aureus) compared to the controls. Incorporating these two non-toxic surfactants into pharmaceutical formulations could potentially enhance the inhibitory efficacy of selected antimicrobial agents, particularly in external topical applications.

The Influence of Streptococcus mutans Biofilm Formation in a Polymicrobial Environment (Streptococcus gordonii & Porphyromonas gingivalis)

OBJECTIVES

 Biofilms play a vital role in the occurrence or worsening of an infectious disease. Streptococcus mutans is a bacterium with the ability to form biofilms that plays a key role in the development of infectious diseases such as dental caries. The formation of biofilms in S. mutans is mediated by quorum sensing. Inhibiting quorum sensing can be considered as one of the approaches to prevent caries. This study aims to investigate the ability of Streptococcus gordonii and Porphyromonas gingivalis bacteria to inhibit the formation of S. mutans biofilm.

MATERIALS AND METHODS

 This research was conducted to analyze bacterial biofilm formation and metabolism. The bacteria used are S. mutans (serotype C), S. gordonii (ATCC 5165), and P. gingivalis (ATCC 33277). Biofilm formation was analyzed using the crystal violet assay. Bacterial metabolism was analyzed using the methylthiazol tetrazolium (MTT) assay.

RESULTS

 The results of the crystal violet assay indicate a decrease in biofilm formation in S. mutans when in the presence of S. gordonii and S. mutans in the presence of P. gingivalis. The results of the MTT assay show no significant change in the bacterial metabolism of S. mutans in the presence of S. gordonii and S. mutans in the presence of P. gingivalis. However, S. mutans with the presence of S. gordonii and P. gingivalis show an increase in biofilm formation and bacterial metabolism.

CONCLUSION

 S. gordonii and P. gingivalis are each capable of inhibiting the formation of S. mutans biofilm in a polymicrobial environment.

Prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections

Osteomyelitis is a devastating disease caused by microbial infection in deep bone tissue. Its high recurrence rate and impaired restoration of bone deficiencies are major challenges in treatment. Microbes have evolved numerous mechanisms to effectively evade host intrinsic and adaptive immune attacks to persistently localize in the host, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants (SCVs). Moreover, microbial-mediated dysregulation of the bone immune microenvironment impedes the bone regeneration process, leading to impaired bone defect repair. Despite advances in surgical strategies and drug applications for the treatment of bone infections within the last decade, challenges remain in clinical management. The development and application of tissue engineering materials have provided new strategies for the treatment of bone infections, but a comprehensive review of their research progress is lacking. This review discusses the critical pathogenic mechanisms of microbes in the skeletal system and their immunomodulatory effects on bone regeneration, and highlights the prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections. It will inform the development and translation of antimicrobial and bone repair tissue engineering materials for the management of bone infections.

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

The association of bacterial biofilm and middle ear mucosa in patients with mucosal chronic suppurative otitis media

OBJECTIVES

To evaluate the bacterial biofilm's role in mucosal chronic suppurative otitis media (CSOM) utilizing scanning electron microscopy (SEM).

METHODS

This study involved 123 participating patients with active and inactive mucosal CSOM who are undergoing tympanomastoid surgery. SEM was used to examine middle ear mucosa biopsies for the development of biofilms. Middle ear discharge or mucosal swabs from patients were cultured to detect any bacterial growth. The biofilm formation was correlated to the culture results.

RESULTS

The biofilm was present in 69.9 % of patients (59% of them were with active mucosal CSOM) and absent in 30.1% of the patients (70% of them were with inactive mucosal CSOM), being more statistically significant in active mucosal CSOM (p-value = 0.003). A correlation that was statistically significant was found between active mucosal CSOM and higher grades (3 and 4) of biofilms (p-value <0.05). The mucosal CSOM type and the results of the culture had a relationship that was statistically significant (p-value <0.001). 60% of patients had positive culture (70% of them were with active mucosal CSOM). There was a statistically significant relation between Pseudomonas aeruginosa bacterial growth and active mucosal CSOM (p-value = 0.004) as well as higher grades of biofilms in mucosal CSOM.

CONCLUSION

Mucosal CSOM, especially the active type, is a biofilm-related disease. There is a significant relation between the state of mucosal CSOM (active or inactive) and culture results with predominance of Pseudomonas aeruginosa bacterial growth in active mucosal CSOM and in higher grades of biofilms in mucosal CSOM.

The role of shear rates on amyloid formation from biofilm peptide phenol-soluble modulins

Biofilms, microbial communities enclosed in the self-produced extracellular matrix, have a significant impact on human health, environment, and industry. The pathogen Staphylococcus aureus (S. aureus) is recognized as one of the most frequent causes of biofilm-related infections. Phenol-soluble modulins (PSMs) serve as a crucial component, fortifying S. aureus biofilm matrix through self-assembly into amyloid fibrils, which enhances S. aureus colonization and resistance to antibiotics. However, the role of shear rate, one of the critical physiological factors within blood vessels, on the formation of PSM amyloids remains poorly understood. In this work, using a combination of thioflavin T fluorescence kinetic studies, circular dichroism spectrometry, and electron microscopy, we demonstrated that shear rates ranging from 150 to 300 s-1 accelerate fibrillation of PSMα1, α3, and α4 into amyloids, resulting in elongated amyloid structures. Furthermore, PSMα1, α3, and α4 predominantly self-assembled into amyloid fibers with a cross-α structure under shear conditions, deviating from the typical β-sheet configuration of PSM amyloids. These findings imply the role of shear rates within the bloodstream on enhancing PSM self-assembly that is associated with S. aureus biofilm formation.

Anti-Biofilm Activity of Oleacein and Oleocanthal from Extra-Virgin Olive Oil toward Pseudomonas aeruginosa

New antimicrobial molecules effective against Pseudomonas aeruginosa, known as an antibiotic-resistant "high-priority pathogen", are urgently required because of its ability to develop biofilms related to healthcare-acquired infections. In this study, for the first time, the anti-biofilm and anti-virulence activities of a polyphenolic extract of extra-virgin olive oil as well as purified oleocanthal and oleacein, toward P. aeruginosa clinical isolates were investigated. The main result of our study was the anti-virulence activity of the mixture of oleacein and oleocanthal toward multidrug-resistant and intermediately resistant strains of P. aeruginosa isolated from patients with ventilator-associated pneumonia or surgical site infection. Specifically, the mixture of oleacein (2.5 mM)/oleocanthal (2.5 mM) significantly inhibited biofilm formation, alginate and pyocyanin production, and motility in both P. aeruginosa strains (p < 0.05); scanning electron microscopy analysis further evidenced its ability to inhibit bacterial cell adhesion as well as the production of the extracellular matrix. In conclusion, our results suggest the potential application of the oleacein/oleocanthal mixture in the management of healthcare-associated P. aeruginosa infections, particularly in the era of increasing antimicrobial resistance.

Human-Derived collagen hydrogel as an antibiotic vehicle for topical treatment of bacterial biofilms

The complexity of chronic wounds creates difficulty in effective treatments, leading to prolonged care and significant morbidity. Additionally, these wounds are incredibly prone to bacterial biofilm development, further complicating treatment. The current standard treatment of colonized superficial wounds, debridement with intermittent systemic antibiotics, can lead to systemic side-effects and often fails to directly target the bacterial biofilm. Furthermore, standard of care dressings do not directly provide adequate antimicrobial properties. This study aims to assess the capacity of human-derived collagen hydrogel to provide sustained antibiotic release to disrupt bacterial biofilms and decrease bacterial load while maintaining host cell viability and scaffold integrity. Human collagen harvested from flexor tendons underwent processing to yield a gellable liquid, and subsequently was combined with varying concentrations of gentamicin (50-500 mg/L) or clindamycin (10-100 mg/L). The elution kinetics of antibiotics from the hydrogel were analyzed using liquid chromatography-mass spectrometry. The gel was used to topically treat Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium perfringens in established Kirby-Bauer and Crystal Violet models to assess the efficacy of bacterial inhibition. 2D mammalian cell monolayers were topically treated, and cell death was quantified to assess cytotoxicity. Bacteria-enhanced in vitro scratch assays were treated with antibiotic-embedded hydrogel and imaged over time to assess cell death and mobility. Collagen hydrogel embedded with antibiotics (cHG+abx) demonstrated sustained antibiotic release for up to 48 hours with successful inhibition of both MRSA and C. perfringens biofilms, while remaining bioactive up to 72 hours. Administration of cHG+abx with antibiotic concentrations up to 100X minimum inhibitory concentration was found to be non-toxic and facilitated mammalian cell migration in an in vitro scratch model. Collagen hydrogel is a promising pharmaceutical delivery vehicle that allows for safe, precise bacterial targeting for effective bacterial inhibition in a pro-regenerative scaffold.

The mechanism of biofilm detachment in porous medium under flow field

Biofilms are communities formed by bacteria adhering to surfaces, widely present in porous medium, and their growth can lead to clogging. Our experiment finds that under certain flow conditions, biofilms detach in pores and form a dynamically changing flow path. We define detachment that occurs far from the boundary of the flow path (with a distance greater than 200 μm) as internal detachment and detachment that occurs at the boundary of the flow path as external detachment. To understand the mechanism of biofilm detachment, we study the detachment behaviors of the Bacillus subtilis biofilm in a porous medium in a microfluidic device, where Bacillus subtilis strain is triple fluorescent labeled, which can represent three main phenotypes during the biofilm formation: motile cells, matrix-producing cells, and spores. We find that slow small-scale internal detachment occurs in regions with very few motile cells and matrix-producing cells, and bacterial movement in these areas is disordered. The increase in the number of matrix-producing cells induces clogging, and after clogging, the rapid detachment of the bulk internal biofilm occurs due to the increased pressure difference at the inlet and outlet. When both internal and external detachments occur simultaneously, the number of matrix-producing cells in the internal detachment area is 2.5 times that in the external detachment area. The results indicate that biofilm detachment occurs in areas with fewer matrix-producing cells, as matrix-producing cells can help resist detachment by secreting extracellular polymeric substances (EPSs).

Persisting cancer cells are different from bacterial persisters

The persistence of drug-sensitive tumors poses a significant challenge in cancer treatment. The concept of bacterial persisters, which are a subpopulation of bacteria that survive lethal antibiotic doses, is frequently used to compare to residual disease in cancer. Here, we explore drug tolerance of cancer cells and bacteria. We highlight the fact that bacteria, in contrast to cancer cells, have been selected for survival at the population level and may therefore possess contingency mechanisms that cancer cells lack. The precise mechanisms of drug-tolerant cancer cells and bacterial persisters are still being investigated. Undoubtedly, by understanding common features as well as differences, we, in the cancer field, can learn from microbiology to find strategies to eradicate persisting cancer cells.

Proteus mirabilis biofilm expansion microscopy yields over 4-fold magnification for super-resolution of biofilm structure and subcellular DNA organization

Bacterial biofilms form when bacteria attach to surfaces and generate an extracellular matrix that embeds and stabilizes a growing community. Detailed visualization and quantitative analysis of biofilm architecture by optical microscopy are limited by the law of diffraction. Expansion Microscopy (ExM) is a novel Super-Resolution technique where specimens are physically enlarged by a factor of ∼4, prior to observation by conventional fluorescence microscopy. ExM requires homogenization of rigid constituents of biological components by enzymatic digestion. We developed an ExM approach capable of expanding 48-h old Proteus mirabilis biofilms 4.3-fold (termed PmbExM), close to the theoretic maximum expansion factor without gross shape distortions. Our protocol, based on lytic and glycoside-hydrolase enzymatic treatments, degrades rigid components in bacteria and extracellular matrix. Our results prove PmbExM to be a versatile and easy-to-use Super-Resolution approach for enabling studies of P. mirabilis biofilm architecture, assembly, and even intracellular features, such as DNA organization.

Characterization of biofilm formation and multi-drug resistance among Pseudomonas aeruginosa isolated from hospital wastewater in Dhaka, Bangladesh

Hospital wastewater has been identified as a hotspot for the emergence and transmission of multidrug-resistant (MDR) pathogens that present a serious threat to public health. Therefore, we investigated the current status of antibiotic resistance as well as the phenotypic and genotypic basis of biofilm formation in Pseudomonas aeruginosa from hospital wastewater in Dhaka, Bangladesh. The disc diffusion method and the crystal violet assay were performed to characterize antimicrobial resistance and biofilm formation, respectively. Biofilm and integron-associated genes were amplified by the polymerase chain reaction. Isolates exhibited varying degrees of resistance to different antibiotics, in which >80% of isolates showed sensitivity to meropenem, amikacin, and gentamicin. The results indicated that 93.82% of isolates were MDR and 71 out of 76 MDR isolates showed biofilm formation activities. We observed the high prevalence of biofilm-related genes, in which algD+pelF+pslD+ (82.7%) was found to be the prevalent biofilm genotypic pattern. Sixteen isolates (19.75%) possessed class 1 integron (int1) genes. However, statistical analysis revealed no significant association between biofilm formation and multidrug resistance (χ2 = 0.35, P = 0.55). Taken together, hospital wastewater in Dhaka city may act as a reservoir for MDR and biofilm-forming P. aeruginosa, and therefore, the adequate treatment of wastewater is recommended to reduce the occurrence of outbreaks.

A review of recent advances in the use of complex metal nanostructures for biomedical applications from diagnosis to treatment

Complex metal nanostructures represent an exceptional category of materials characterized by distinct morphologies and physicochemical properties. Nanostructures with shape anisotropies, such as nanorods, nanostars, nanocages, and nanoprisms, are particularly appealing due to their tunable surface plasmon resonances, controllable surface chemistries, and effective targeting capabilities. These complex nanostructures can absorb light in the near-infrared, enabling noteworthy applications in nanomedicine, molecular imaging, and biology. The engineering of targeting abilities through surface modifications involving ligands, antibodies, peptides, and other agents potentiates their effects. Recent years have witnessed the development of innovative structures with diverse compositions, expanding their applications in biomedicine. These applications encompass targeted imaging, surface-enhanced Raman spectroscopy, near-infrared II imaging, catalytic therapy, photothermal therapy, and cancer treatment. This review seeks to provide the nanomedicine community with a thorough and informative overview of the evolving landscape of complex metal nanoparticle research, with a specific emphasis on their roles in imaging, cancer therapy, infectious diseases, and biofilm treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Diagnostic Nanodevices.

Current treatment strategies for targeting virulence factors and biofilm formation in Acinetobacter baumannii

A higher prevalence of Acinetobacter baumannii infections and mortality rate has been reported recently in hospital-acquired infections (HAI). The biofilm-forming capability of A. baumannii makes it an extremely dangerous pathogen, especially in device-associated hospital-acquired infections (DA-HAI), thereby it resists the penetration of antibiotics. Further, the transmission of the SARS-CoV-2 virus was exacerbated in DA-HAI during the epidemic. This review specifically examines the complex interconnections between several components and genes that play a role in the biofilm formation and the development of infections. The current review provides insights into innovative treatments and therapeutic approaches to combat A. baumannii biofilm-related infections, thereby ultimately improving patient outcomes and reducing the burden of HAI.

Prevalence of Infections and Antimicrobial Resistance of ESKAPE Group Bacteria Isolated from Patients Admitted to the Intensive Care Unit of a County Emergency Hospital in Romania

The ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella Pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) is a group of bacteria very difficult to treat due to their high ability to acquire resistance to antibiotics and are the main cause of nosocomial infections worldwide, posing a threat to global public health. Nosocomial infections with MDR bacteria are found mainly in Intensive Care Units, due to the multitude of maneuvers and invasive medical devices used, the prolonged antibiotic treatments, the serious general condition of these critical patients, and the prolonged duration of hospitalization.

MATERIALS AND METHODS

During a period of one year, from January 2023 to December 2023, this cross-sectional study was conducted on patients diagnosed with sepsis admitted to the Intensive Care Unit of the Sibiu County Emergency Clinical Hospital. Samples taken were tracheal aspirate, catheter tip, pharyngeal exudate, wound secretion, urine culture, blood culture, and peritoneal fluid.

RESULTS

The most common bacteria isolated from patients admitted to our Intensive Care Unit was Klebsiella pneumoniae, followed by Acinetobacter baumanii and Pseudomonas aeruginosa. Gram-positive cocci (Enterococcus faecium and Staphilococcus aureus) were rarely isolated. Most of the bacteria isolated were MDR bacteria.

CONCLUSIONS

The rise of antibiotic and antimicrobial resistance among strains in the nosocomial environment and especially in Intensive Care Units raises serious concerns about limited treatment options.

Nature-Inspired Micro/Nano-Structured Antibacterial Surfaces

The problem of bacterial resistance has become more and more common with improvements in health care. Worryingly, the misuse of antibiotics leads to an increase in bacterial multidrug resistance and the development of new antibiotics has virtually stalled. These challenges have prompted the need to combat bacterial infections with the use of radically different approaches. Taking lessons from the exciting properties of micro-/nano-natural-patterned surfaces, which can destroy cellular integrity, the construction of artificial surfaces to mimic natural functions provides new opportunities for the innovation and development of biomedicine. Due to the diversity of natural surfaces, functional surfaces inspired by natural surfaces have a wide range of applications in healthcare. Nature-inspired surface structures have emerged as an effective and durable strategy to prevent bacterial infection, opening a new way to alleviate the problem of bacterial drug resistance. The present situation of bactericidal and antifouling surfaces with natural and biomimetic micro-/nano-structures is briefly reviewed. In addition, these innovative nature-inspired methods are used to manufacture a variety of artificial surfaces to achieve extraordinary antibacterial properties. In particular, the physical antibacterial effect of nature-inspired surfaces and the functional mechanisms of chemical groups, small molecules, and ions are discussed, as well as the wide current and future applications of artificial biomimetic micro-/nano-surfaces. Current challenges and future development directions are also discussed at the end. In the future, controlling the use of micro-/nano-structures and their subsequent functions will lead to biomimetic surfaces offering great potential applications in biomedicine.

Multitasking functions of bacterial extracellular DNA in biofilms

Bacterial biofilms are intricate ecosystems of microbial communities that adhere to various surfaces and are enveloped by an extracellular matrix composed of polymeric substances. Within the context of bacterial biofilms, extracellular DNA (eDNA) originates from cell lysis or is actively secreted, where it exerts a significant influence on the formation, stability, and resistance of biofilms to environmental stressors. The exploration of eDNA within bacterial biofilms holds paramount importance in research, with far-reaching implications for both human health and the environment. An enhanced understanding of the functions of eDNA in biofilm formation and antibiotic resistance could inspire the development of strategies to combat biofilm-related infections and improve the management of antibiotic resistance. This comprehensive review encapsulates the latest discoveries concerning eDNA, encompassing its origins, functions within bacterial biofilms, and significance in bacterial pathogenesis.

Emerging Approaches for Mitigating Biofilm-Formation-Associated Infections in Farm, Wild, and Companion Animals

The importance of addressing the problem of biofilms in farm, wild, and companion animals lies in their pervasive impact on animal health and welfare. Biofilms, as resilient communities of microorganisms, pose a persistent challenge in causing infections and complicating treatment strategies. Recognizing and understanding the importance of mitigating biofilm formation is critical to ensuring the welfare of animals in a variety of settings, from farms to the wild and companion animals. Effectively addressing this issue not only improves the overall health of individual animals, but also contributes to the broader goals of sustainable agriculture, wildlife conservation, and responsible pet ownership. This review examines the current understanding of biofilm formation in animal diseases and elucidates the complex processes involved. Recognizing the limitations of traditional antibiotic treatments, mechanisms of resistance associated with biofilms are explored. The focus is on alternative therapeutic strategies to control biofilm, with illuminating case studies providing valuable context and practical insights. In conclusion, the review highlights the importance of exploring emerging approaches to mitigate biofilm formation in animals. It consolidates existing knowledge, highlights gaps in understanding, and encourages further research to address this critical facet of animal health. The comprehensive perspective provided by this review serves as a foundation for future investigations and interventions to improve the management of biofilm-associated infections in diverse animal populations.

Phytochemical screening of Podocarpus lambertii Klotzch ex Endl. leaf extracts and potential antimicrobial, antioxidant and antibiofilm activity

Species of the genus Podocarpus L'Hér. ex Pers.present biological activities, such as analgesic, antioxidant, antifungal, acting in the fight against anemia, depurative and fortifying. Podocarpus lambertii Klotzch ex Endl. is a Brazilian native species popularly known as maritime pine and lacks information about its phytochemical profile and possible biological activities. The study was conducted to determine the phytochemical composition of soluble plant extracts of acetone (EA), ethyl acetate (EAE) and hexane (HE) from leaves of P. lambertii; evaluate the antimicrobial potential by the broth microdilution technique; antioxidant potential by the DPPH method, as well as to evaluate the biofilm inhibition capacity by the crystal violet assay and reduction of the yellow tetrazolium salt (MTT). Phytochemical screening detected the presence of flavonoids, triterpenoids, steroids, tannins, alkaloids and saponins. All extracts showed antimicrobial activity on the microorganisms tested, and the EA showed the best results. High free radical scavenging potential was observed only in EAE (96.35%). The antibiofilm potential was observed in the EAE extract. The results contribute to the knowledge of the species and indicate the potential of P. lambertii extracts as a source of plant bioactives for the development of new alternative strategies to control resistant microorganisms.

Rapid eradication of vancomycin and methicillin-resistant Staphylococcus aureus by MDP1 antimicrobial peptide coated on photocrosslinkable chitosan hydrogel: in vitro antibacterial and in silico molecular docking studies

Introduction

Antibiotic resistance and weak bioavailability of antibiotics in the skin due to systemic administration leads to failure in eradication of vancomycin- and methicillin-resistant Staphylococcus aureus (VRSA and MRSA)-associated wound infections and subsequent septicemia and even death. Accordingly, this study aimed at designing a photocrosslinkable methacrylated chitosan (MECs) hydrogel coated by melittin-derived peptide 1 (MDP1) that integrated the antibacterial activity with the promising skin regenerative capacity of the hydrogel to eradicate bacteria by burst release strategy.

Methods

The MECs was coated with MDP1 (MECs-MDP1), characterized, and the hydrogel-peptide interaction was evaluated by molecular docking. Antibacterial activities of MECs-MDP1 were evaluated against VRSA and MRSA bacteria and compared to MECs-vancomycin (MECs-vanco). Antibiofilm activity of MECs-MDP1 was studied by our novel 'in situ biofilm inhibition zone (IBIZ)' assay, and SEM. Biocompatibility with human dermal fibroblast cells (HDFs) was also evaluated.

Results and Discussion

Molecular docking showed hydrogen bonds as the most interactions between MDP1 and MECs at a reasonable affinity. MECs-MDP1 eradicated the bacteria rapidly by burst release strategy whereas MECs-vanco failed to eradicate them at the same time intervals. Antibiofilm activity of MECs-MDP1 were also proved successfully. As a novel report, molecular docking analysis has demonstrated that MDP1 covers the structure of MECs and also binds to lysozyme with a reasonable affinity, which may explain the inhibition of lysozyme. MECs-MDP1 was also biocompatible with human dermal fibroblast skin cells, which indicates its safe future application. The antibacterial properties of a photocrosslinkable methacrylated chitosan-based hydrogel coated with MDP1 antimicrobial peptide were successfully proved against the most challenging antibiotic-resistant bacteria causing nosocomial wound infections; VRSA and MRSA. Molecular docking analysis revealed that MDP1 interacts with MECs mainly through hydrogen bonds with reasonable binding affinity. MECs-MDP1 hydrogels eradicated the planktonic state of bacteria by burst release of MDP1 in just a few hours whereas MECs-vanco failed to eradicate them. inhibition zone assay showed the anti-biofilm activity of the MECs-MDP1 hydrogel too. These findings emphasize that MECs-MDP1 hydrogel would be suggested as a biocompatible wound-dressing candidate with considerable and rapid antibacterial activities to prevent/eradicate VRSA/MRSA bacterial wound infections.

Antibiotic lock solutions as adjunct therapy for catheter-related blood stream infections in pediatric hemodialysis patients

The predominant use of intravenous catheters as primary access type in the pediatric hemodialysis population is associated with an increased risk of catheter related blood stream infections. While strict adherence to catheter placement and long-term care guidelines have helped to decrease the incidence of these infections, blood stream infections remain an infection burden in pediatric patients with long term hemodialysis catheters. The formation of biofilms on the surfaces of these catheters has been shown to be a source of microbes causing blood stream infections. One of the strategies for preventing bacterial colonization, inhibiting microbial multiplication, and suppressing the seeding of these microbes from biofilms upon maturation, has been the use of antibiotic-based lock solutions in-between dialysis treatments. Although clinical guidelines for the use of antibiotic lock solutions are yet to be developed, available evidence suggests a beneficial role of antibiotic lock solutions in the management of catheter related blood stream infections. Additionally, a clear understanding of how biofilms are formed and their role in the pathogenesis of catheter related bloodstream infection will facilitate the development of solutions that can prevent biofilm formation and inhibit their multiplication, maturation and seeding into the bloodstream.

Antibacterial Activity of Various Morphologies of Films Based on Guanidine Derivatives of Pillar[5]arene: Influence of the Nature of One Substitute on Self-assembly

The progress of the pillar[5]arene chemistry allowed us to set out a new concept on application of the supramolecular assemblies to create antimicrobial films with variable surface morphologies and biological activities. Antibacterial films were derived from the substituted pillar[5]arenes containing nine pharmacophoric guanidine fragments and one thioalkyl substituent. Changing the only thioalkyl fragment in the macrocycle structure made it possible to control the biological activity of the resulting antibacterial coating. Pretreatment of the surface with aqueous solution of the amphiphilic pillar[5]arenes reduced the biofilm thickness by 56 ± 10% of Gram-positive Staphylococcus aureus in the case of the pillar[5]arene containing a thiooctyl fragment and by 52 ± 7% for the biofilm of Gram-negative Klebsiella pneumoniae in the case of pillar[5]arene containing a thiooctadecyl fragment. Meanwhile, the cytotoxicity of the synthesized macrocycles was examined at a concentration of 50 μg/mL, which was significantly lower than that of bis-guanidine-based antimicrobial preparations.

The Anti-Microbial Peptide Citrocin Controls Pseudomonas aeruginosa Biofilms by Breaking Down Extracellular Polysaccharide

Citrocin is an anti-microbial peptide that holds great potential in animal feed. This study evaluates the anti-microbial and anti-biofilm properties of Citrocin and explores the mechanism of action of Citrocin on the biofilm of P. aeruginosa. The results showed that Citrocin had a significant inhibitory effect on the growth of P. aeruginosa with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 0.3 mg/mL. All five concentrations (1/4MIC, 1/2MIC, MIC, 2MIC, and 4MIC) of Citrocin inhibited P. aeruginosa biofilm formation. Citrocin at the MIC, 2MIC and 4MIC removed 42.7%, 76.0% and 83.2% of mature biofilms, respectively, and suppressed the swarming motility, biofilm metabolic activity and extracellular polysaccharide production of P. aeruginosa. Metabolomics analysis indicated that 0.3 mg/mL of Citrocin up- regulated 26 and down-regulated 83 metabolites, mainly comprising amino acids, fatty acids, organic acids and sugars. Glucose and amino acid metabolic pathways, including starch and sucrose metabolism as well as arginine and proline metabolism, were highly enriched by Citrocin. In summary, our research reveals the anti-biofilm mechanism of Citrocin at the metabolic level, which provides theoretical support for the development of novel anti-biofilm strategies for combatting P. aeruginosa.

Biofilm and bacterial membrane vesicles: recent advances

INTRODUCTION

Bacterial Membrane Vesicles (MVs) play important roles in cell-to-cell communication and transport of several molecules. Such structures are essential components of Extracellular Polymeric Substances (EPS) biofilm matrix of many bacterial species displaying a structural function and a role in virulence and pathogenesis.

AREAS COVERED

In this review were included original articles from the last ten years by searching the keywords 'biofilm' and 'vesicles' on PUBMED and Scopus databases. The articles available in literature mainly describe a positive correlation between bacterial MVs and biofilms formation. The research on Espacenet and Google Patent databases underlines the available patents related to the application of both biofilm MVs and planktonic MVs in inhibiting biofilm formation.

EXPERT OPINION

This review covers and analyzes recent advances in the study of the relationship between bacterial vesicles and biofilm. The huge number of papers discussing the role of MVs confirms the interest aimed at developing new applications in the medical field. The study of the MVs composition and biogenesis may contribute to the identification of components which could be (i) the target for the development of new drugs inhibiting the biofilm establishment; (ii) candidates for the development of vaccines; (iii) biomarkers for the diagnosis of bacterial infections.

Repurposing cinacalcet suppresses multidrug-resistant Staphylococcus aureus by disruption of cell membrane and inhibits biofilm by targeting IcaR

BACKGROUND

MDR Staphylococcus aureus infections, along with the severity of biofilm-associated infections, continue to threaten human health to a great extent. It necessitates the urgent development of novel antimicrobial and antibiofilm agents.

OBJECTIVES

To reveal the mechanism and target of cinacalcet as an antibacterial and antimicrobial agent for S. aureus.

METHODS

Screening of non-antibiotic drugs for antibacterial and antibiofilm properties was conducted using a small-molecule drug library. In vivo efficacy was assessed through animal models, and the antibacterial mechanism was studied using quantitative proteomics, biochemical assays, LiP-SMap, BLI detection and gene knockout techniques.

RESULTS

Cinacalcet, an FDA-approved drug, demonstrated antibacterial and antibiofilm activity against S. aureus, with less observed development of bacterial resistance. Importantly, cinacalcet significantly improved survival in a pneumonia model and bacterial clearance in a biofilm infection model. Moreover, the antibacterial mechanism of cinacalcet mainly involves the destruction of membrane-targeted structures, alteration of energy metabolism, and production of reactive oxygen species (ROS). Cinacalcet was found to target IcaR, inhibiting biofilm formation through the negative regulation of IcaADBC.

CONCLUSIONS

The findings suggest that cinacalcet has potential for repurposing as a therapeutic agent for MDR S. aureus infections and associated biofilms, warranting further investigation.

Synergistic bactericidal effects of phage-enhanced antibiotic therapy against MRSA biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) causes biofilm-related medical device infections. Phage-antibiotic combinations offer potential therapy due to proven in vitro antibiofilm efficacy. We evaluated phage-antibiotic synergy against biofilms using modified checkerboard and 24-h time-kill assays. Humanized-simulated daptomycin (DAP) (10, 8, and 6 mg/kg q24h) and ceftaroline (CPT) (600 mg q12h) were combined with Intesti13, Sb-1, and Romulus phages (tMOI 1, q12h). Assays were conducted in 168-h biofilm reactor models against DAP non-susceptible (DNS) vancomycin intermediate S. aureus (VISA) MRSA D712 and DAP-susceptible MRSA 8014. Synergistic activity and bactericidal activity were defined as ≥2log10 CFU/mL reduction from antibiotic-only regimens and ≥3log10 CFU/mL decrease from baseline at 24 h. Differences were analyzed by one-way analysis of variance with Tukey's post hoc test (P ≤ 0.05 is considered significant). Surviving bacteria were examined for antibiotic minimum biofilm inhibitory concentration (MBIC) changes and phage susceptibility. In 168-h biofilm models, humanized DAP 10 mg/kg + CPT, combined with a 2-phage cocktail (Intesti13 + Sb-1) against D712, and a 3-phage cocktail (Intesti13 + Sb-1 + Romulus) against 8014, demonstrated synergistic bactericidal activity. At 168 h, bacteria were minimally detectable [2log10 CFU/cm2 (-Δ4.23 and -Δ4.42 log10 CFU/cm2; both P < 0.001)]. Antibiotic MBIC remained unchanged compared to baseline across various time points. None of the tested bacteria at 168 h exhibited complete phage resistance. This study reveals bactericidal efficacy of DAP + CPT with 2-phage and 3-phage cocktails against DNS VISA and MRSA isolates (D712 and 8014) in biofilm models, maintaining susceptibility. Further research is needed for diverse strains and durations, aligning with infection care.

IMPORTANCE

The prevalence of biofilm-associated medical device infections caused by methicillin-resistant Staphylococcus aureus (MRSA) presents a pressing medical challenge. The latest research demonstrates the potential of phage-antibiotic combinations (PACs) as a promising solution, notably in vitro antibiofilm efficacy. By adopting modified checkerboard and 24-h time-kill assays, the study investigated the synergistic action of phages combined with humanized-simulated doses of daptomycin (DAP) and ceftaroline (CPT). The results were promising: a combination of DAP, CPT, and either a 2-phage or 3-phage cocktail effectively exhibited bactericidal activity against both DAP non-susceptible vancomycin intermediate S. aureus MRSA and DAP-susceptible MRSA strains within 168-h biofilm models. Moreover, post-treatment evaluations revealed no discernible rise in antibiotic resistance or complete phage resistance. This pioneering work suggests the potential of PACs in addressing MRSA biofilm infections, setting the stage for further expansive research tailored to diverse bacterial strains and treatment durations.

Z-Form Extracellular DNA in Pediatric CRS May Provide a Mechanism for Recalcitrance to Treatment

OBJECTIVES

We examined sinus mucosal samples recovered from pediatric chronic rhinosinusitis (CRS) patients for the presence of Z-form extracellular DNA (eDNA) due to its recently elucidated role in pathogenesis of disease. Further, we immunolabeled these specimens for the presence of both members of the bacterial DNA-binding DNABII protein family, integration host factor (IHF) and histone-like protein (HU), due to their known role in converting common B-DNA to the rare Z-form.

METHODS

Sinus mucosa samples recovered from 20 patients during functional endoscopic sinus surgery (FESS) were immunolabelled for B- and Z-DNA, as well as for both bacterial DNABII proteins.

RESULTS

Nineteen of 20 samples (95%) included areas rich in eDNA, with the majority in the Z-form. Areas positive for B-DNA were restricted to the most distal regions of the mucosal specimen. Labeling for both DNABII proteins was observed on B- and Z-DNA, which aligned with the role of these proteins in the B-to-Z DNA conversion.

CONCLUSIONS

Abundant Z-form eDNA in culture-positive pediatric CRS samples suggested that bacterial DNABII proteins were responsible for the conversion of eukaryotic B-DNA that had been released into the luminal space by PMNs during NETosis, to the Z-form. The presence of both DNABII proteins on B-DNA and Z-DNA supported the known role of these bacterial proteins in the B-to-Z DNA conversion. Given that Z-form DNA both stabilizes the bacterial biofilm and inactivates PMN NET-mediated killing of trapped bacteria, we hypothesize that this conversion may be contributing to the chronicity and recalcitrance of CRS to treatment.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1564-1571, 2024.

Preliminary identification and semi-quantitative characterization of a multi-faceted high-stability alginate lyase from marine microbe Seonamhaeicola algicola with anti-biofilm effect on Pseudomonas aeruginosa

Alginate lyases with unique characteristics for degrading alginate into size-defined oligosaccharide fractions, were considered as the potential agents for disrupting Pseudomonas aeruginosa biofilms. In our study, a novel endolytic PL-7 alginate lyase, named AlyG2, was cloned and expressed through Escherichia coli. This enzyme exhibited excellent properties: it maintained more than 85% activity at low temperatures of 4 °C and high temperatures of 70 °C. After 1 h of incubation at 4 °C, it still retained over 95% activity, demonstrating the ability to withstand low temperature. The acid-base and salt tolerance properties shown it preserves more than 50% activity in the pH range of 5.0 to 11.0 and in a high salt environment at 3000 mM NacCl, indicating its high stability in several aspects. More importantly, AlyG2 in our research was revealed to be effective at removing mature biofilms and inhibiting biofilm formation produced by Pseudomonas aeruginosa, and the inhibition and disruption rates were 47.25 ± 4.52% and 26.5 ± 6.72%, respectively. Additionally, the enzyme AlyG2 promoted biofilm disruption in combination with antibiotics, particularly manifesting the synergistic effect with erythromycin (FIC=0.5). In all, these results offered that AlyG2 with unique characteristics may be an effective technique for the clearance or disruption of biofilm produced by P. aeruginosa.

New Alpiniamide-Type Polyketide with Antibiofilm Activities from the Marine-Derived Streptomyces sp. ZS-A65

Two new alpiniamide-type polyketides, alpiniamides H-I (1-2), in addition to four recognized compounds, were discovered in Streptomyces sp. ZSA65 derived from the marine sediments. The planar structure and absolute configuration of alpiniamides H-I were elucidated using a combination of 1D, 2D NMR, HRESIMS data analysis, Mosher's method and ECD calculations. The antibiofilm and antibacterial activities against P. aeruginosa were evaluated using the microdilution method. Notably, Compound 2 exhibited strong antibiofilm property.

Optimization of periodic treatment strategies for bacterial biofilms using an agent-based in silico approach

Biofilms are responsible for most chronic infections and are highly resistant to antibiotic treatments. Previous studies have demonstrated that periodic dosing of antibiotics can help sensitize persistent subpopulations and reduce the overall dosage required for treatment. Because the dynamics and mechanisms of biofilm growth and the formation of persister cells are diverse and are affected by environmental conditions, it remains a challenge to design optimal periodic dosing regimens. Here, we develop a computational agent-based model to streamline this process and determine key parameters for effective treatment. We used our model to test a broad range of persistence switching dynamics and found that if periodic antibiotic dosing was tuned to biofilm dynamics, the dose required for effective treatment could be reduced by nearly 77%. The biofilm architecture and its response to antibiotics were found to depend on the dynamics of persister cells. Despite some differences in the response of biofilm governed by different persister switching rates, we found that a general optimized periodic treatment was still effective in significantly reducing the required antibiotic dose. As persistence becomes better quantified and understood, our model has the potential to act as a foundation for more effective strategies to target bacterial infections.