ESCMID∗ guideline for the diagnosis and treatment of biofilm infections 2014

Integrated transcriptomics and metabolomics study on the biofilm formation of Haemophilus influenzae by the stimulation of amoxicillin-clavulanate at subinhibitory concentration

Exposure to subinhibitory concentrations of β-lactam antibiotics has been shown to induce the biofilm formation of microorganisms, but the underlying mechanisms remain poorly understood. This study aims to explore the effect of different concentrations of amoxicillin-clavulanate, the most commonly used antibiotic in pediatrics, on the biofilm formation of Haemophilus influenza (H. influenzae) in vitro and to explore the underlying mechanisms. The effect of amoxicillin-clavulanate on the in vitro biofilm formation was assessed by crystal violet assay, colony counts, MTT colorimetric method, scanning electron microscopy, and confocal laser scanning microscopy. Integrated transcriptomics and metabolomics analyses were performed to identify key genes and metabolites. Our findings revealed that 1/2 MIC of amoxicillin-clavulanate significantly enhanced H. influenzae ATCC 49247 biofilm formation in vitro, while simultaneously reducing culturable bacterial counts and metabolic activity of biofilm-embedded bacteria. When exposed to 1/2 MIC of amoxicillin-clavulanate, the biofilm ultrastructure was altered, with an increase in biofilm structure, a decrease in bacteria embedded within the biofilms with abnormal bacterial morphology. Transcriptomics identified 118 differentially expressed genes (DEGs), comprising 62 upregulated and 56 downregulated genes. Metabolomics identified 21 differentially expressed metabolites (DEMs), with 13 upregulated and 8 downregulated. Integrated transcriptomics and metabolomics implicated amino sugar and nucleotide sugar metabolism as a key regulatory pathway. This study has provided novel insights into the relationship between a commonly prescribed pediatric antibiotic and H. influenzae biofilm formation, elucidating the underlying mechanisms, emphasizing the critical importance of judicious antibiotic use and clinical consideration of subinhibitory antibiotic effects, particularly in pediatric populations.

Secreted retropepsin-like enzymes are essential for stress tolerance and biofilm formation in Pseudomonas aeruginosa

Proteases regulate important biological functions. Here, we present the structural and functional characterization of three previously uncharacterized aspartic proteases in Pseudomonas aeruginosa. We show that these proteases have structural hallmarks of retropepsin peptidases and play redundant roles for cell survival under hypoosmotic stress conditions. Consequently, we named them retropepsin-like osmotic stress tolerance peptidases (Rlo). Our research shows that while Rlo proteases are homologous to RimB, an aspartic peptidase involved in rhizosphere colonization and plant infection, they contain N-terminal signal peptides and perform distinct biological functions. Mutants lacking all three secreted Rlo peptidases show defects in antibiotic resistance, biofilm formation, and cell morphology. These defects are rescued by mutations in the inactive transglutaminase transmembrane protein RloB and the cytoplasmic ATP-grasp protein RloC, two previously uncharacterized genes in the same operon as one of the Rlo proteases. These studies identify Rlo proteases and rlo operon products as critical factors in clinically relevant processes, making them appealing targets for therapeutic strategies against Pseudomonas infections.IMPORTANCEBacterial infections have become harder to treat due to the ability of pathogens to adapt to different environments and the rise of antimicrobial resistance. This has led to longer illnesses, increased medical costs, and higher mortality rates. The opportunistic pathogen Pseudomonas aeruginosa is particularly problematic because of its inherent resistance to many antibiotics and its capacity to form biofilms, structures that allow bacteria to withstand hostile conditions. Our study uncovers a new class of retropepsin-like proteases in P. aeruginosa that are required for biofilm formation and bacterial survival under stress conditions, including antibiotic exposure. By identifying critical factors that determine bacterial fitness and adaptability, our research lays the foundation for developing new therapeutic strategies against bacterial infections.

Visualization of Staphylococcus aureus in the bovine mammary gland by fluorescence in situ hybridization

Bovine mastitis poses significant challenges to the dairy industry. Staphylococcus aureus is particularly problematic because of its ability to cause long-lasting infections. The aim of this study was to visualize S. aureus in infected mammary gland tissues via a specific fluorescent oligonucleotide probe and confocal microscopy. Tissue samples were obtained from cows with confirmed positive S. aureus milk cultures. Fluorescent in situ hybridization revealed the existence of large bacterial aggregates, spanning 30-50 μm in size and specifically located within the mammary parenchyma. This is the first direct visualization of S. aureus aggregates within the udder of naturally infected cows.

Cystic fibrosis and the clinical biofilm revolution A survey of the Danish CF Center's contribution

Biofilm infections are chronic infections which are difficult to diagnose. Biofilm infections are tolerant to antibiotics and the defense mechanisms of the host. Patients with the genetic disease cystic fibrosis (CF) produce viscid mucus in the respiratory tract and therefore suffer from chronic biofilm infections in their lungs and paranasal sinuses. The most important microorganism is the mucoid phenotype of Pseudomonas aeruginosa which causes chronic biofilm infections in the lungs of CF patients and untreated patients succumb as children if they contact this biofilm infection. Since CF patients are treated in CF Centers all over the world, it is possible to do longitudinal studies on epidemiology, pathophysiology, diagnosis, prevention and treatment of P. aeruginosa biofilm infection which is not possible if such patients are not followed in specialized centers. This survey describes the research through several decades in the Danish CF Center in Copenhagen which have changed the epidemiology, treatment, prophylaxis and prognosis of CF patients worldwide. Based on these results ESCMID Guidelines for diagnosis and treatment of biofilm infections were published which have influenced biofilm research and treatment in other areas.

A novel MIR imaging approach for precise detection of S. epidermidis biofilms in seconds

The impact of microbial biofilm growth poses a threat to both human health and the performance of industrial systems, manifesting as a global crisis with noteworthy economic implications for modern society. Exploring new methods and alternative approaches for the detection of biofilm signatures are imperative for developing optimized and cost-effective strategies that can help to identify early-stage biofilm formation. Clinical diagnostic technologies are constantly looking for more affordable, practical and faster methods of prevention and detection of chronic infections in periprosthetic joint infections (PJIs), which are often characterized by biofilm formation on implant surfaces. Staphylococcus epidermidis (SE) is especially known for its strong biofilm production and is considered a leading cause of biomaterial-associated infections, including PJIs. Implant-associated infections are severe and difficult to treat, therefore it is crucial to continue identifying bacterial biomarkers that contribute to its structural stability and attachment to implant surfaces. This study presents a pioneering approach for fast spectral detection of biofilm formation with a novel mid-infrared (MIR) scanning system. To highlight the advantages of our MIR system, we performed a comparative analysis with measurements from a commercially available Fourier-transform infrared (FTIR) scanner. We have assessed SE biofilms grown for 3 days comparing the processing times between a commercially available infrared (IR) scanning system (∼8 h/cm2), and our innovative scanning approach with rapid self-built MIR detection, achieving a reduction in scanning time to seconds. K-means clustering analysis identified pronounced differences in distribution of clusters, representing a significant variation between biofilm producing (RP62A) and non-biofilm producing (ATCC 12228) bacterial strains. The distribution serves as a critical tool for identifying biofilm phenotypes, particularly where poly-N-acetylglucosamine (PNAG), a key constituent of extracellular polymeric substances (EPS) in S. epidermidis, represents the dominant mass fraction in the samples analyzed by our infrared (IR) scanning systems. In addition to faster processing times, our novel MIR system demonstrated significantly higher sensitivity compared to FTIR, enabling clear differentiation between the chemical signatures of biofilm and planktonic strains. The corresponding novel approach integrates advanced data analytics with a newly designed rapid MIR prototype, enabling optimized and swift detection of biofilm signatures. These signatures, now recognized as critical targets in diagnosing complex infections, provide an alternative to traditional microbial detection methods in clinical diagnostics.

Microbiological Profiles, Antibiotic Susceptibility Patterns and the Role of Multidrug-Resistant Organisms in Patients Diagnosed with Periprosthetic Joint Infection over 8 Years: Results from a Single-Center Observational Cohort Study from Romania

This study examines temporal patterns in pathogens isolated from prosthetic joint infection (PJI) cases and antimicrobial resistance patterns at a Romanian orthopedic center. We have conducted a retrospective cohort study that included 674 patients undergoing hip or knee replacement revision surgery between January 2016 and December 2023. From these, 102 confirmed PJI cases requiring surgical intervention were selected for analysis. We isolated 27 microorganisms from acute PJI cultures and 82 from chronic PJIs. Staphylococcus epidermidis (33 cases, 30.3%; 95% CI 22.0-40.3) was the predominant pathogen, with coagulase-negative Staphylococci (22 cases, 20.18%; 95% CI 0.9-41.3) and Enterobacteriaceae (13 cases, 11.9%; 95% CI 6.4-18.3) also prevalent. Methicillin resistance was identified in 43.6% of coagulase-negative staphylococci and 45.5% of Staphylococcus aureus isolates. All Gram-positive isolates remained susceptible to vancomycin, linezolid, and tigecycline. Among Gram-negative bacilli, Klebsiella oxytoca and Proteus mirabilis showed resistance to third-generation cephalosporins, with phenotypic profiles suggestive of extended-spectrum β-lactamase (ESBL) production. All Escherichia coli, Enterobacter spp., and Citrobacter freundii strains were fully susceptible to tested agents, while Pseudomonas aeruginosa exhibited reduced susceptibility to ciprofloxacin, aztreonam, and imipenem. Among the isolated strains, 47 were multidrug-resistant (MDR), with Staphylococcus aureus accounting for the highest MDR count, including methicillin resistance. The distribution of microorganism types and MDR strains remained consistent throughout the study period, with no significant association between infection type and MDR strain presence or between infection site and microorganism presence except for a strong association between MDR strains and the type of microorganism (p < 0.05). The microbial profile and resistance patterns in PJIs have remained stable over eight years. Our observations do not suggest that MDR PJIs are more commonly acute cases, contrary to what has been highlighted in previous reports. The ongoing prevalence of MDR strains underscores the importance of targeted antimicrobial treatments based on local susceptibility profiles.

SEMTWIST Quantification of Biofilm Infection in Human Chronic Wound Using Scanning Electron Microscopy and Machine Learning

Objective: To develop scanning electron microscopy-based Trainable Weka (Waikato Environment for Knowledge Analysis) Intelligent Segmentation Technology (SEMTWIST), an open-source software tool, for structural detection and rigorous quantification of wound biofilm aggregates in complex human wound tissue matrix. Approach: SEMTWIST model was standardized to quantify biofilm infection (BFI) abundance in 240 distinct SEM images from 60 human chronic wound-edge biospecimens (four technical replicates of each specimen). Results from SEMTWIST were compared against human expert assessments and the gold standard for molecular BFI detection, that is, peptide nucleic acid fluorescence in situ hybridization (PNA-FISH). Results: Correlation and Bland-Altman plot demonstrated a robust correlation (r = 0.82, p < 0.01), with a mean bias of 1.25, and 95% limit of agreement ranging from -43.40 to 47.11, between SEMTWIST result and the average scores assigned by trained human experts. While interexpert variability highlighted potential bias in manual assessments, SEMTWIST provided consistent results. Bacterial culture detected infection but not biofilm aggregates. Whereas the wheat germ agglutinin staining exhibited nonspecific staining of host tissue components and failed to provide a specific identification of BFI. The molecular identification of biofilm aggregates using PNA-FISH was comparable with SEMTWIST, highlighting the robustness of the developed approach. Innovation: This study introduces a novel approach "SEMTWIST" for in-depth analysis and precise differentiation of biofilm aggregates from host tissue elements, enabling accurate quantification of BFI in chronic wound SEM images. Conclusion: Open-source SEMTWIST offers a reliable and robust framework for standardized quantification of BFI burden in human chronic wound-edge tissues, supporting clinical diagnosis and guiding treatment.

Evaluating the Antibiofilm Effects of Antibiotics on Staphylococcus Species from Pediatric Hematology-Oncology Patients

Biofilms are microbial communities and occur on different medical devices such as catheters. The formation of bacterial biofilms on medical devices leads to indwelling medical device-related infections. Since biofilm bacteria are more resistant to antibiotics than planktonic bacteria, using these antibiotics in indwelling medical device-related infections causes recurrence of infections, treatment failure, and death. Minimum inhibitory concentration (MIC) is an important reference in treating acute infections caused by planktonic bacteria. However, MIC is ineffective in indwelling medical device-related infections caused by biofilm bacteria. The study aims to demonstrate the necessity and development of effective and standard methods such as minimum biofilm prevention concentration, minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration in the case of indwelling medical device-related infection. The study was conducted with 10 isolates of Staphylococcus species from patients who developed infections in the Pediatric Hematology-Oncology Department at Medical Park Bahcelievler Hospital. According to the study results, even if planktonic bacteria are sensitive to antibiotics, they can become resistant to this antibiotic when they are in a biofilm (p < 0.05, Crosstab). Also, inhibiting the growth of planktonic bacteria does not prevent biofilm formation. The study additionally revealed that inhibiting and eradicating biofilm is more difficult than preventing biofilm formation (p < 0.05).

Current State and Advances in Antimicrobial Strategies for Burn Wound Dressings: From Metal-Based Antimicrobials and Natural Bioactive Agents to Future Perspectives

Burn wounds represent a complex clinical challenge, primarily due to their high susceptibility to infections and the frequent formation of the biofilm, which significantly hinder the healing process. Therefore, effective infection prevention and management are critical components of burn wound care. This review provides a comprehensive overview of the current and emerging antimicrobial strategies in burn management, with a particular focus on alternative approaches to conventional antiseptics and antibiotics. This manuscript highlights the role of metals and metal-based agents, including silver, zinc oxide, and copper compounds, alongside plant-derived bioactive substances such as aloe vera, marigold, and turmeric. Additionally, the potential of antimicrobial peptides and probiotics as innovative therapeutic options is explored, emphasizing their antimicrobial, anti-inflammatory, and pro-healing properties. Finally, this review presents an analysis of recent patents in the field of burn wound care, offering insights into current trends and future directions in the development of advanced wound dressings. By addressing both established and novel strategies, this review aims to provide a valuable resource for clinicians, researchers, and innovators seeking to improve outcomes in burn wound management.

Secreted retropepsin-like enzymes are essential for stress tolerance and biofilm formation in Pseudomonas aeruginosa

Proteases regulate important biological functions. Here we present the structural and functional characterization of three previously uncharacterized aspartic proteases in Pseudomonas aeruginosa. We show that these proteases have structural hallmarks of retropepsin peptidases and play redundant roles for cell survival under hypoosmotic stress conditions. Consequently, we named them retropepsin-like osmotic stress tolerance peptidases (Rlo). Our research shows that while Rlo proteases are homologous to RimB, an aspartic peptidase involved in rhizosphere colonization and plant infection, they contain N-terminal signal peptides and perform distinct biological functions. Mutants lacking all three secreted Rlo peptidases show defects in antibiotic resistance, biofilm formation, and cell morphology. These defects are rescued by mutations in the inactive transglutaminase transmembrane protein RloB and the cytoplasmic ATP-grasp protein RloC, two previously uncharacterized genes in the same operon as one of the Rlo proteases. These studies identify Rlo proteases and rlo operon products as critical factors in clinically relevant processes, making them appealing targets for therapeutic strategies against Pseudomonas infections.

Clinical and Lung Microbiome Impact of Chronic Versus Intermittent Pseudomonas aeruginosa Infection in Bronchiectasis

BACKGROUND

In patients with non-cystic fibrosis bronchiectasis (BE) Pseudomonas aeruginosa (PA) has been recently associated with low rather than high number of exacerbations without distinguishing chronic versus intermittent infection. The aim of our study was to determine whether the intermittent or chronic stage of P. aeruginosa (PA) infection is associated with the rate of exacerbations, quality of life and respiratory microbiome biodiversity after a one-year follow-up.

METHODS

We conducted a longitudinal study, with 1-year follow-up, in patients with BE intermittently or chronically infected by PA involving sequential (3-monthly) measurements of microbiological (cultures, PA load, phenotype and biofilms presence) immunological (Serum IgGs against P. aeruginosa were measured by ELISA immunoassay) and clinical variables (Quality-of-Life and the number exacerbations). Additionaly, 16S sequencing was performed on a MiSeq Platform and compared between chronically infected patients with the mucoid PA versus intermittently infected patients with the non-mucoid PA.

RESULTS

We collected 235 sputa and 262 serum samples from 80 BE patients, 61 with chronic and 19 with intermittent PA infection. Chronically compared to intermittently. Presented reduced quality of life but less hospitalized exacerbations after 1-year follow-up. Chronically infected patients presented reduced sputum biodiversity and higher systemic IgGs against P. aeruginosa levels that were associated to decreased number of hospitalized exacerbations.

CONCLUSIONS

The assessment of Chronic versus intermittent P. aeruginosa infection has clinical implications such as quality of life, rate of hospitalized exacerbations and lung microbiome biodiversity. The distinction of these two phenotypes is easy to perform in clinical practice.

TRIAL REGISTRATION

NCT04803695.

Fatty Acid-Containing p(HEMA) Hydrogels; A Promising Coating Platform to Reduce Encrustation on Urinary Catheters

Two significant clinical issues associated with the use of urinary catheters are catheter-associated urinary tract infection and encrustation. This study describes the design of novel hydrogels based on fatty acid-containing p(hydroxyethylmethacrylate, HEMA) and their resistance to both microbial adherence and encrustation. Incorporation of fatty acids increased the contact angle (surface hydrophobicity), decreased the ultimate tensile strength only after storage at pH 9 in artificial urine (AU) but not at lower pH values, decreased the Young's modulus and % elongation at break (both stored in deionised water, AU pH 6 and AU pH 9) and decreased equilibrium swelling (only when stored in deionised water or AU pH 6 but not AU pH 9). Moderate reductions in adherence of Escherichia coli, Proteus mirabilis and Staphylococcus epidermidis to certain fatty acid containing (primarily decanoic acid and myristic acid) hydrogels were observed. No relationship was observed between hydrogel contact angle and resistance to microbial attachment. Most fatty acid-containing hydrogels exhibited significant, concentration-dependent resistance to encrustation, postulated to be due both to a greasy film resultant from the formation of the calcium/magnesium fatty acid salts at the surface and the role of Tween® 80 in facilitating the removal of the fatty acid salts from the surface of the hydrogel. The observed enhanced resistance of the hydrogels to encrustation offers opportunities for the use of such systems as platforms for coatings of urinary catheters.

Stimuli-responsive mesoporous silica nanoplatforms for smart antibacterial therapies: From single to combination strategies

The demand for new antibacterial therapies is urgent and crucial in the clinical setting because of the growing degree of antibiotic resistance and the limits of conventional antibacterial therapies. Stimuli- responsive nanoplatforms, are sensitive to endogenous or exogenous stimulus (pH, temperature, light, and magnetic fields, etc.) which activate cargo release locally and on-demand, hold great potential in developing next generation personalized precision medicine. For instance, pH-sensitive nanoplatforms can selectively release antibacterial agents in the acidic environment of infection sites. To achieve the stimuli-responsive delivery, mesoporous silica nanoplatforms (MSNs) have demonstrated as prospective candidates for efficient cargo loading and controlled release through strategies such as tunable pore engineering, versatile surface modification/coating, and tailored framework composition. Furthermore, aiming for more precise delivery of MSNs, current research interests are increasingly shifting from single-stimuli antibacterial strategy to integrated strategy that combine multiple-stimulus. In this review, we briefly discuss the microenvironment of bacterial infections and provide a comprehensive summary of current stimuli-responsive strategies, and associated materials design principles of stimuli-responsive mesoporous silica-based smart nanoplatforms (SRMSNs). Additionally, integrative antibacterial strategies with synergistic effects, combining chemodynamic, photodynamic, photothermal, sonodynamic and gas therapies, have also been elaborated. Present research advances and limitations of SRMSNs-based antibacterial therapies, such as limited biodegradability and potential cytotoxicity, have been overviewed with future outlooks presented. This review aims to inspire and guide future research in developing novel antibacterial strategies with integrative solutions.

In vitro antibiofilm efficacy of ertapenem, tobramycin, and moxifloxacin against biofilms grown in a glass bead or CDC Biofilm Reactor®

Laboratory grown biofilms are used to simulate bacterial growth in diverse environmental conditions and screen the effectiveness of anti-biofilm therapies. Recently, we developed a glass bead biofilm reactor that utilizes low broth volume to provide high-throughput biofilm growth for testing and translation across the research continuum (e.g., benchtop assays to preclinical models). Bioburden per mm2 surface area of Staphylococcus aureus and Pseudomonas aeruginosa biofilms were comparable on beads and CDC Biofilm Reactor® coupons. In this study, we hypothesized that biofilms grown on beads would be more susceptible to ertapenem, moxifloxacin, and tobramycin than those grown on coupons. Results indicated a significant reduction in S. aureus bioburden on glass beads compared to glass coupons following treatment with ertapenem (p = 0.005) and tobramycin (p = 0.014). P. aeruginosa biofilms had smaller differences in antibiotic response between the two systems. There was a significantly greater reduction in bead P. aeruginosa biofilm than coupon when treated with tobramycin (p = 0.035). This work offered insight into how the bead biofilm reactor could be used as a tool for antibiotic screening and translation across the continuum of in vitro to in vivo systems that support development of antimicrobial technology.

Photoimmunologic Therapy of Stubborn Biofilm via Inhibiting Bacteria Revival and Preventing Reinfection

Stubborn biofilm infections pose serious threats to public health. Clinical practices highly rely on mechanical debridement and antibiotics, which often fail and lead to persistent and recurrent infections. The main culprits are 1) persistent bacteria reviving, colonizing, and rejuvenating biofilms, and 2) secondary pathogen exposure, particularly in individuals with chronic diseases. Addressing how to inhibit persistent bacteria revival and prevent reinfection simultaneously is still a major challenge. Herein, an oligo-ethylene glycol-modified lipophilic cationic photosensitizer (PS), TBTCP-PEG7, is developed. It effectively eradicates Methicillin-Resistant Staphylococcus aureus (MRSA) under light irradiation. Furthermore, TBTCP-PEG7-mediated photodynamic therapy (PDT) not only conquers stubborn biofilm infections by downregulating the two-component system (TCS), quorum sensing (QS), and virulence factors, thereby reducing intercellular communication, inhibiting persistent bacterial regrowth and biofilm remodeling but also prevents reinfection by upregulating heat shock protein-related genes to induce immunogenetic cell death (ICD) and establish immune memory. In vivo, TBTCP-PEG7 efficiently eradicates MRSA biofilm adhered to medical catheters, stimulates angiogenesis, reduces inflammatory factor expression, and accelerates wound healing. Furthermore, ICD promotes short-term immune and long-term immunological memory for coping with secondary infections. This two-pronged strategy not only effectively overcomes stubborn, persistent and recurrent biofilm infection, but also provides theoretical guidance for designing the next generation of antibacterial materials.

Antimicrobial and anti-biofilm effects of dihydroartemisinin-loaded chitosan nanoparticles against methicillin-resistant Staphylococcus aureus

The formation of biofilms enhances bacterial antibiotic resistance, posing significant challenges to clinical treatment. Methicillin-resistant Staphylococcus aureus (MRSA) is a primary pathogen in biofilm-associated infections. Its high antibiotic resistance and incidence rates make it a major clinical challenge, underscoring the urgent need for novel therapeutic strategies. Building on previous research, this study employs nanotechnology to fabricate dihydroartemisinin-chitosan nanoparticles (DHA-CS NPs) and, for the first time, applies them to the treatment of MRSA biofilm infections. The antibacterial and anti-biofilm activities of these compounds were evaluated, and their potential mechanisms of action were preliminarily explored. The results demonstrated that the DHA-CS NPs exhibited a minimum inhibitory concentration (MIC) of15 μg/mLand a minimum bactericidal concentration (MBC) of 30 μg/mL. At 15 μg/mL, the DHA-CS NPs significantly inhibited MRSA biofilm formation (P < 0.001),while at 7.5 μg/mL, they dispersed 67.4 ± 3.77 % of the preformed biofilms (P < 0.001). Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) confirmed the disruption of MRSA biofilms. Mechanistic studies, including phenol-sulfuric acid assays, static biofilm microtiter plate assays, and RT-qPCR, revealed that the DHA-CS NPs inhibited the synthesis of extracellular polymeric substances (EPS), suppressed the release of extracellular DNA (eDNA), and downregulated key biofilm-related genes (icaA, sarA, cidA, and agrA). These findings suggest that DHA-CS NPs hold significant promise for inhibiting and eradicating MRSA biofilms, providing a theoretical basis for the development of novel antibiofilm therapies.

Pressure injuries and biofilms: Microbiome, model systems and therapies

Chronic wounds have emerged as significant clinical problems owing to their increasing incidence and greater recognition of associated morbidity and socio-economic burden. They are defined as wounds that do not progress normally through the stages of healing in a timely and/or orderly manner. Pressure injuries, in particular, represent a serious problem for patients who are elderly or have limited mobility, such as wheelchair users or those who spend most of the day in bed. These injuries often result from prolonged pressure exerted on the skin over the bone. Treatment of pressure injuries is complex and costly. Emerging evidence suggests that the pressure injury microbiome plays a vital role in chronic wound formation and delaying wound healing. Additionally, antibiotics often fail due to the formation of resistant biofilms and the emergence of antimicrobial-resistant bacteria. In this review, we will summarise the current knowledge on: (a) biofilms and microbiomes in pressure injuries; (b) in vitro and in vivo model systems to study pressure injuries, and (c) current therapies and novel treatment approaches. Understanding the complex interactions between microbes and the host immune system in pressure injuries will provide valuable insights to improve patient outcomes.

Clinical management of chronic wound infections: The battle against biofilm

Bacteria constitute the most abundant life form on earth, of which the majority exist in a protective biofilm state. Since the 1980s, we have learned much about the role of biofilm in human chronic infections, with associated global healthcare costs recently estimated at ~$386 billion. Chronic wound infection is a prominent biofilm-induced condition that is characterised by persistent inflammation and associated host tissue destruction, and clinical signs that are distinct from signs of acute wound infection. Biofilm also enables greater tolerance to antimicrobial agents in chronic wound infections compared with acute wound infections. Given the difficulty in eliminating wound biofilm, a multi-targeted strategy (namely biofilm-based wound care) involving debridement and antimicrobial therapies were introduced and have been practiced since the early 2000s. More recently, acknowledgement of the speed at which biofilm can develop and hence quickly interfere with wound healing has highlighted the need for an early anti-biofilm strategy to combat biofilm before it takes control and prevents wound healing. This strategy, referred to as wound hygiene, involves multiple tools in combination (debridement, cleansing, and antimicrobial dressings) to maximise success in biofilm removal and encourage wound healing. This review is intended to highlight the issues and challenges associated with biofilm-induced chronic infections, and specifically address the challenges in chronic wound management, and tools required to combat biofilm and encourage wound healing.

Bacterial infections associated with cutaneous leishmaniasis in Salah Al-Din province, Iraq

Bacterial co-infection with cutaneous leishmaniasis (CL) can effect on the clinical appearance of lesions and delay the healing process. The pattern of bacterial pathogens involved has rarely been investigated in Iraq. The aim of present study was to identify the bacterial agents contaminating CL and their susceptibility to commonly used antibiotics. Four hundred cases of CL were diagnosed in Salah El-Din General Hospital, Iraq. A total of 424 ulcer samples obtained from 400 patients of CL were cultured, and all isolates were diagnosed based on phenotypic characteristics of colonies, bacterial cells and using biochemical tests. No bacterial growth appeared in 124 cases (29.25 %) of the total number of examined ulcer samples, whereas 300 cases (70.75 %) were contaminated. Both Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes) and Gram-negative bacterial species (Escherichi coli, Klebsiella spp., Pseudomonas aeruginosa) were present. The infection with S. aureus represented the highest percentage (26.42 %), while Ps. aeruginosa had the lowest percentage (2.83 %) compared with other bacterial infections. The sensitivity of the isolated bacteria associated with CL was tested against a number of antibiotics (Amoxicillin, Ampicillin, Cefixime, Chloramphenlcol, Doxycycline, Tetracycline). Resistance to Amoxicillin, Ampicillin, and Cefixime was generally high. While, Chloramphenicol showed absolute effectiveness against isolated bacteria. The results of the current study show that bacterial infections should be considered in diagnosing and treating CL lesions, with Chloramphenicol demonstrating the highest efficiency in treating such bacterial infections. The present study also suggests that hygiene, use of suitable disinfectants, controlling of antibiotic administration and prescription in hospitals and pharmacies must be ensured. In addition, regular surveillance in the endemic area will help control bacterial co-infection and hamper the occurrence of drug-resistant pathogens. The lesion care and management of secondary bacterial infection are essential and anti -leishmanial therapy in CL may be more effective when combined with antibiotics. Future molecular studies are needed to identify the species of Leishmania causing CL in Iraq to gain a better understanding of their clinical manifestations (dry or moist ulcers) and their associated bacteria.

Antimicrobial Peptides: A Promising Alternative to Conventional Antimicrobials for Combating Polymicrobial Biofilms

Polymicrobial biofilms adhere to surfaces and enhance pathogen resistance to conventional treatments, significantly contributing to chronic infections in the respiratory tract, oral cavity, chronic wounds, and on medical devices. This review examines antimicrobial peptides (AMPs) as a promising alternative to traditional antibiotics for treating biofilm-associated infections. AMPs, which can be produced as part of the innate immune response or synthesized therapeutically, have broad-spectrum antimicrobial activity, often disrupting microbial cell membranes and causing cell death. Many specifically target negatively charged bacterial membranes, unlike host cell membranes. Research shows AMPs effectively inhibit and disrupt polymicrobial biofilms and can enhance conventional antibiotics' efficacy. Preclinical and clinical research is advancing, with animal studies and clinical trials showing promise against multidrug-resistant bacteria and fungi. Numerous patents indicate increasing interest in AMPs. However, challenges such as peptide stability, potential cytotoxicity, and high production costs must be addressed. Ongoing research focuses on optimizing AMP structures, enhancing stability, and developing cost-effective production methods. In summary, AMPs offer a novel approach to combating biofilm-associated infections, with their unique mechanisms and synergistic potential with existing antibiotics positioning them as promising candidates for future treatments.

Synergistic effects of reduced graphene oxide on the antibacterial activity of calcium hydroxide-based intracanal medicaments containing different vehicles

PURPOSE

This study investigated the synergistic effects of reduced graphene oxide (RGO) on the antibacterial activity of three calcium hydroxide-based intracanal medicaments with different vehicles.

METHODS

Multispecies biofilms were cultured in a bovine root canal model. Intracanal medicaments containing nonaqueous vehicles, including N-methyl-2-pyrrolidone (NMP; CleaniCal), propylene glycol (PG; UltraCal XS), and polyethylene glycol (PEG; Calcipex II), were placed in the model. The synergistic effects of RGO were evaluated by analyzing colony-forming units, extracellular deoxyribonucleic acid (eDNA) levels, and findings from confocal laser-scanning microscopy (CLSM) and scanning electron microscopy. To evaluate the cytotoxicity of each vehicle, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed. To determine whether RGO altered the physicochemical properties of the medicaments, flowability and pH were measured. A P-value of <0.05 was considered to indicate statistical significance.

RESULTS

In the CleaniCal group, bacterial viability, eDNA levels, and extracellular polymeric substrate (EPS) were significantly lower in the presence of RGO. However, only bacterial viability significantly differed in the other groups. PEG resulted in the highest cell viability among the vehicles. Furthermore, there was no significant difference in flowability or pH in relation to the inclusion of RGO.

CONCLUSION

The results suggest that RGO enhances the antibacterial effect of intracanal medicaments containing NMP.

Covalent Grafting of Quaternary Ammonium Salt-Containing Polyurethane onto Silicone Substrates to Enhance Bacterial Contact-Killing Ability

Catheter-associated urinary tract infection (CAUTI) induced by rapid bacterial colonization and biofilm formation on urinary catheters is a key issue that urgently needs to be addressed. To prevent CAUTI, many contact-killing, non-leaching coatings have been developed for the surfaces of silicone catheters. However, due to the chemical inertness of the silicone substrate, most current coatings lack adhesion and are unstable under external forces. Thus, the aim of this study was to develop a surface coating that has both good antibacterial ability and a high affinity toward silicone substrates. To achieve high affinity, a pre-coating layer with abundant surface vinyl groups, named SI-vinyl, was prepared on the silicone substrate by moisture curing using a mixture of α,ω-dihydroxy polydimethylsiloxane and vinyltrimethoxysilane as the painting agent. To endow the surface with contact-killing ability, a series of polyurethanes with different contents of quaternary ammonium salt groups in their main chain and two vinyl end groups were synthesized and covalently grafted onto the surface of SI-vinyl, resulting in corresponding bactericidal coatings with different surface contents of quaternary ammonium salt groups (SI-QAS). Of these bactericidal coatings, SI-QAS-2, with a surface QAS content of 2.1 × 1016 N+ cm-2, was selected as the best coating based on the consideration of stability, compatibility, and antibacterial ability. The SI-QAS-2 coating demonstrated high contact-killing performance, rapidly inactivating 72.8%, 99.9%, and 98.9% of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa within 30 min. Furthermore, even after being exposed to a high concentration of bacteria (106 CFU/mL) for 4 days, the SI-QAS-2 coating still maintained a high bactericidal ratio of over 80%. In summary, we developed a novel contact-killing coating that reduces the risk of bacterial infections caused by catheter implantation, demonstrating that it has high affinity toward silicone substrates, excellent contact-killing efficiency, a facile preparation method, and potential for further application.

Fluoroquinolones and Biofilm: A Narrative Review

Background: Biofilm-associated infections frequently span multiple body sites and represent a significant clinical challenge, often requiring a multidisciplinary approach involving surgery and antimicrobial therapy. These infections are commonly healthcare-associated and frequently related to internal or external medical devices. The formation of biofilms complicates treatment, as they create environments that are difficult for most antimicrobial agents to penetrate. Fluoroquinolones play a critical role in the eradication of biofilm-related infections. Numerous studies have investigated the synergistic potential of combining fluoroquinolones with other chemical agents to augment their efficacy while minimizing potential toxicity. Comparative research suggests that the antibiofilm activity of fluoroquinolones is superior to that of beta-lactams and glycopeptides. However, their activity remains less effective than that of minocycline and fosfomycin. Noteworthy combinations include fluoroquinolones with fosfomycin and aminoglycosides for enhanced activity against Gram-negative organisms and fluoroquinolones with minocycline and rifampin for more effective treatment of Gram-positive infections. Despite the limitations of fluoroquinolones due to the intrinsic characteristics of this antibiotic, they remain fundamental in this setting thanks to their bioavailability and synergisms with other drugs. Methods: A comprehensive literature search was conducted using online databases (PubMed/MEDLINE/Google Scholar) and books written by experts in microbiology and infectious diseases to identify relevant studies on fluoroquinolones and biofilm. Results: This review critically assesses the role of fluoroquinolones in managing biofilm-associated infections in various clinical settings while also exploring the potential benefits of combination therapy with these antibiotics. Conclusions: The literature predominantly consists of in vitro studies, with limited in vivo investigations. Although real world data are scarce, they are in accordance with fluoroquinolones' effectiveness in managing early biofilm-associated infections. Also, future perspectives of newer treatment options to be placed alongside fluoroquinolones are discussed. This review underscores the role of fluoroquinolones in the setting of biofilm-associated infections, providing a comprehensive guide for physicians regarding the best use of this class of antibiotics while highlighting the existing critical issues.

Collateral susceptibility-guided alternation of ceftolozane/tazobactam with imipenem prevents resistance development in XDR Pseudomonas aeruginosa biofilms

Objectives

New combinations of β-lactams and β-lactamase inhibitors, such as ceftolozane/tazobactam could be useful to combat biofilm-driven chronic infections by extensively resistant (XDR) Pseudomonas aeruginosa but resistance development by mutations in the Ω-loop of AmpC has been described. However, these mutations confer collateral susceptibility to carbapenems. Thus we aimed to evaluate the therapeutic efficacy and the prevention of resistance development of regimen alternating ceftolozane/tazobactam and imipenem.

Methods

A carbapenem-resistant XDR P. aeruginosa clinical strain (ST175, 104-B7) and its isogenic imipenem-susceptible ceftolozane/tazobactam-resistant mutant derivative (AmpC T96I, 104-I9) were used. Experiments of single strains and mixed (104-B7 and 104-I9, 1:0.01 ratio) biofilms were performed. 48h biofilms (flow cell system) were treated for 6 days with either ceftolozane/tazobactam, 4/4 mg/L or the alternation of ceftolozane/tazobactam (2 days)-imipenem 4 mg/L (2 days) - ceftolozane/tazobactam (2 days). After treatment, biofilms were collected and plated on Mueller-Hinton agar± ceftolozane/tazobactam 4/4 mg/L. Structural dynamics were monitored using confocal laser scanning microscopy and images were processed with IMARIS software. At least, three independent triplicate experiments per condition were performed. Emerging resistant mutants were characterized through whole genome sequencing (Illumina).

Results

Ceftolozane/tazobactam monotherapy failed to reduce the biofilms of the 104-B7 XDR strain and led to the selection of resistant mutants that showed AmpC Ω-loop mutations (T96I, L244R or aa236Δ7). On the contrary, alternation with imipenem enhanced activity (3 Logs reduction at day 6) and prevented the emergence of ceftolozane/tazobactam-resistant mutants. Likewise, treatment with ceftolozane/tazobactam dramatically amplified the resistant strain 104-I9 in mixed biofilms (>90 % of the population), while the alternation regimen counterselected it.

Conclusions

Collateral susceptibility-guided alternation of ceftolozane/tazobactam with imipenem effectively prevented the selection of resistant mutants and thus could be a potential therapeutic strategy for the treatment of P. aeruginosa XDR chronic infections.

Global challenges and microbial biofilms: Identification of priority questions in biofilm research, innovation and policy

Priority question exercises are increasingly used to frame and set future research, innovation and development agendas. They can provide an important bridge between the discoveries, data and outputs generated by researchers, and the information required by policy makers and funders. Microbial biofilms present huge scientific, societal and economic opportunities and challenges. In order to identify key priorities that will help to advance the field, here we review questions from a pool submitted by the international biofilm research community and from practitioners working across industry, the environment and medicine. To avoid bias we used computational approaches to group questions and manage a voting and selection process. The outcome of the exercise is a set of 78 unique questions, categorized in six themes: (i) Biofilm control, disruption, prevention, management, treatment (13 questions); (ii) Resistance, persistence, tolerance, role of aggregation, immune interaction, relevance to infection (10 questions); (iii) Model systems, standards, regulatory, policy education, interdisciplinary approaches (15 questions); (iv) Polymicrobial, interactions, ecology, microbiome, phage (13 questions); (v) Clinical focus, chronic infection, detection, diagnostics (13 questions); and (vi) Matrix, lipids, capsule, metabolism, development, physiology, ecology, evolution environment, microbiome, community engineering (14 questions). The questions presented are intended to highlight opportunities, stimulate discussion and provide focus for researchers, funders and policy makers, informing future research, innovation and development strategy for biofilms and microbial communities.

Recent progress in antibiofilm strategies in the dairy industry

Biofilm formation allows microorganisms including bacteria to persist on abiotic or biotic surfaces, to resist treatments with biocides (disinfectants and antibiotics) and to evade the immune response in animal hosts much more than they do in the planktonic form. Bacteria able to form biofilm can be troublesome in the dairy industry, both by causing clinical symptoms in livestock and by colonizing milking devices and milk processing equipment, resulting in dairy products of lower quality and sometimes raising serious food safety issues. In fact, most of the bacterial species isolated frequently in the dairy chain have the ability to form biofilm. Common examples include Staphylococcus aureus and other staphylococci that frequently infect mammary glands, but also Bacillus spp., Listeria monocytogenes and Pseudomonas spp. which cause spoilage of dairy products and sometimes foodborne illnesses. The economic losses due to biofilm formation in the dairy industry are considerable, and scientists are constantly solicited to develop new antibiofilm strategies, especially using biocides of natural origin. Although the number of studies in this subject area has exploded in recent years, the in vivo efficacy of most novel approaches remains to be explored. Used alone or to increase the efficacy of disinfectants or antibiotics, they could allow the implementation of strategies having less impact on the environment. Their use is expected to lead to less reliance on antibiotics to treat intramammary infections in dairy farms and to the use of lower concentrations of chemical disinfectants in dairy processing plants.

Helicobacter pylori Efflux Pumps: A Double-Edged Sword in Antibiotic Resistance and Biofilm Formation

Helicobacter pylori is a major pathogen associated with various gastric diseases. Despite decades of research, the treatment of H. pylori remains challenging. One of the primary mechanisms contributing to failures of therapies targeting this bacterium is genetic mutations in drug target sites, although the growing body of scientific data highlights that efflux pumps may also take part in this process. Efflux pumps are proteinaceous transporters actively expelling antimicrobial agents from the interior of the targeted cells and reducing the intracellular concentration of these compounds. Considering that efflux pumps contribute to both antimicrobial resistance and biofilm formation, an in-depth understanding of their properties may constitute a cornerstone in the development of novel therapeutics against H. pylori. In line with this, the aim of the current review is to describe the multitude of efflux pumps produced by H. pylori and present the data describing the involvement of these proteins in tolerance and/or resistance to various classes of antimicrobial substances.

Enhancing Antibacterial Efficacy: Combining Novel Bacterial Topoisomerase Inhibitors with Efflux Pump Inhibitors and Other Agents Against Gram-Negative Bacteria

BACKGROUND

The novel bacterial topoisomerase inhibitors (NBTIs) developed in our laboratory show potent on-target enzyme inhibition but suffer from low activity against Gram-negative bacteria.

METHODS

With the aim of improving the antibacterial activity of our compounds against Gram-negative bacteria, we tested them in combination with different efflux pump inhibitors (EPIs), a strategy that showed promise in several other classes of antimicrobials. We also investigated the combined effect of NBTIs with ATP-competitive inhibitors of bacterial type II topoisomerases (ACIs), as well as the antibiofilm properties of our compounds and the combination with EPIs against early and mature Acietobacter baumannii biofilm.

RESULTS

Our results demonstrate that combinations of NBTIs with EPI Phenylalanine-arginyl-β-naphthylamide significantly reduce the corresponding NBTIs' minimal inhibitory concentration values and show potentiation of A. baumannii biofilm inhibition as compared to NBTIs alone. Although combinations of NBITs and ACIs did not show synergistic effects, the FIC index value calculations revealed additive effects for all the combinations of a selected NBTI in combination with three ACIs in all the assayed Gram-negative bacteria from the ESKAPE group.

CONCLUSIONS

These results show for the first time that combinations of NBTIs with either EPIs or a different class of the topoisomerase inhibitors may be a beneficial strategy to combat difficult-to-treat bacterial infections.

Optically accessible, 3D-printed flow chamber with integrated sensors for the monitoring of oral multispecies biofilm growth in vitro

The formation of pathogenic multispecies biofilms in the human oral cavity can lead to implant-associated infections, which may ultimately result in implant failure. These infections are neither easily detected nor readily treated. Due to high complexity of oral biofilms, detailed mechanisms of the bacterial dysbiotic shift are not yet even fully understood. In order to study oral biofilms in more detail and develop prevention strategies to fight implant-associated infections, in vitro biofilm models are sorely needed. In this study, we adapted an in vitro biofilm flow chamber model to include miniaturized transparent 3D-printed flow chambers with integrated optical pH sensors - thereby enabling the microscopic evaluation of biofilm growth as well as the monitoring of acidification in close proximity. Two different 3D printing materials were initially characterized with respect to their biocompatibility and surface topography. The functionality of the optically accessible miniaturized flow chambers was then tested using five-species biofilms (featuring the species Streptococcus oralis, Veillonella dispar, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis) and compared to biofilm growth on titanium specimens in the established flow chamber model. As confirmed by live/dead staining and fluorescence in situ hybridization via confocal laser scanning microscopy, the flow chamber setup proved to be suitable for growing reproducible oral biofilms under flow conditions while continuously monitoring biofilm pH. Therefore, the system is suitable for future research use with respect to biofilm dysbiosis and also has great potential for further parallelization and adaptation to achieve higher throughput as well as include additional optical sensors or sample materials.

The effectiveness of antimicrobial photodynamic therapy on catheter infection model

BACKGROUND/AIM

This experimental study aimed to examine the effectiveness of transdermal antimicrobial photodynamic therapy (APDT) with and without antimicrobial lock therapy (ALT), on catheter biofilms.

METHODS

S. epidermidis and C. orthopsilosis biofilms were formed within peripheral venous catheters positioned in the marginal ear veins of New Zealand white rabbits. Biofilm formation was confirmed with scanning electron microscopy in two catheters. 24 catheters with staphylococcal biofilms and 24 with fungal biofilms were treated with APDT, ALT or "APDT plus ALT" for five days. Six catheters were separated as controls. APDT was applied with a red colored LED lamp and methylene blue as the photosensitizer. Vancomycin lock solutions were used as ALT for staphylococcal biofilms and amphotericin B for fungal biofilms. The effect of treatment procedures was evaluated by intraluminal biofilm viability testing based on spectrophotometric evaluation, and a quantitative (OD) value was obtained for each catheter.

RESULTS

The mean OD values obtained by 600 nm spectrophotometric reading at 24 h (biofilm viability) after "ALT", "APDT" and "ALT plus APDT" procedures were 0.363, 0.151 and 0.128 for S. epidermidis and 0.092, 0.104 and 0.227 for C. orthopsilosis, respectively. All these OD values obtained after treatment procedures were lower than controls for both S. epidermidis (OD: 0,802) and C. orthopsilosis (OD: 0,315), although there were large fluctuations in our results.

CONCLUSIONS

Our results suggest that transdermal APDT may be an effective method for treating staphylococcal and candida biofilms formed within intravenous catheters in our rabbit ear model. The combined use of APDT and ALT might be beneficial in these staphylococcal biofilms.

Biofilm and Its Characteristics in Venous Ulcers

PURPOSE

The aim of the study was to analyze the characteristics of the biofilm of venous ulcers in terms of location and formation and to relate the presence of the biofilm to ulcer characteristics including duration, injured area, and necrotic tissue.

DESIGN

Descriptive clinical study.

MATERIALS AND METHODS

We obtained 2 biopsy fragments (tissue samples) from 44 patients with venous ulcers treated at a public outpatient clinic in a university hospital in Belo Horizonte, Brazil. Ulcers were photographed and classified according to the duration. In addition, the wound size and proportion of wound surface covered by necrotic tissue were measured. One fragment from each ulcer underwent microbiological analysis, while the other was analyzed using transmission electron microscopy. Data analysis was limited to fragments from patients with bacteria in the microbiological analysis.

RESULTS

Data analysis is based on samples obtained from 21 ulcers in 21 patients who had bacteria in their ulcer based on microbiologic analysis of a tissue sample. Most ulcers were open for 2 to 10 years, 57% (n = 12) were 16 cm2 or smaller, and the proportion of the wound bed covered by necrotic tissue coverage varied widely. Of the 21/44 patients (48%) with bacteria in their ulcers, only 3 patients had bacterial biofilm present in the transmission electron microscopy, corresponding to 7% of the 44 patients. Pseudomonas aeruginosa was the most frequent bacterium, identified in 10 fragments. The biofilm was not present on the surface but in a layer slightly below it. The detection of biofilms was not directly related to the duration of the ulcer. It was not possible to establish a correlation between the size of the lesion and the presence of these microorganisms due to the small sample size.

CONCLUSIONS

Our findings indicate that detecting biofilm in venous ulcers is challenging, as it does not uniformly occur throughout the wound bed, can occur at different depths, and is often not present on the wound surface. There is a need to develop studies that can contribute to the detection of biofilm in clinical practice.

Pseudomonas aeruginosa in the Frontline of the Greatest Challenge of Biofilm Infection-Its Tolerance to Antibiotics

P. aeruginosa biofilms are aggregates of bacteria surrounded by a self-produced matrix which binds to some antibiotics such as aminoglycosides. P. aeruginosa biofilms are tolerant to antibiotics. The treatment of biofilm infections leads to a recurrence of symptoms after finishing antibiotic treatment, although the initial clinical response to the treatment is frequently favorable. There is a concentration gradient of oxygen and nutrients from the surface to the center of biofilms. Surface-located bacteria are multiplying and metabolizing, whereas deeper located bacteria are dormant and tolerant to most antibiotics. Colistin kills dormant bacteria, and combination therapy with colistin and antibiotics which kills multiplying bacteria is efficient in vitro. Some antibiotics such as imipenem induce additional production of the biofilm matrix and of chromosomal beta-lactamase in biofilms. Biofilms present a third Pharmacokinetic/Pharmacodynamic (PK/PD) micro-compartment (first: blood, second: tissue, third: biofilm) which must be taken into consideration when calculations try to predict the antibiotic concentrations in biofilms and thereby the probability of target attainment (PTA) for killing the biofilm. Treating biofilms with hyperbaric oxygen to wake up the dormant cells, destruction of the biofilm matrix, and the use of bacteriophage therapy in combination with antibiotics are promising possibilities which have shown proof of concept in in vitro experiments and in animal experiments.

Activity of polymyxin B combined with cefepime-avibactam against the biofilms of polymyxin B-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae in in vitro and in vivo models

Bacterial biofilms, often forming on medical devices, can lead to treatment failure due to their increased antimicrobial resistance. Cefepime-avibactam (CFP-AVI) exhibits potent activities against Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) when used with polymyxin B (PMB). However, its efficacy in biofilm-related infections is unknown. The present study aimed to evaluate the activity of PMB combined with CFP-AVI against the biofilms of PMB-resistant Gram-negative bacteria. Five K. pneumoniae strains and three P. aeruginosa strains known to be PMB-resistant and prone to biofilm formation were selected and evaluated. Antimicrobial susceptibility assays demonstrated that the minimal biofilm inhibitory and eradication concentrations of PMB and CFP-AVI for biofilms formed by the eight strains were significantly higher than the minimal inhibitory concentrations of the antibiotics for planktonic cells. The biofilm formation inhibition and eradication assays showed that PMB combined with CFP-AVI cannot only suppress the formation of biofilm but also effectively eradicate the preformed mature biofilms. In a modified in vitro pharmacokinetic/pharmacodynamic biofilm model, CFP-AVI monotherapy exhibited a bacteriostatic or effective activity against the biofilms of seven strains, whereas PMB monotherapy did not have any activity at 72 h. However, PMB combined with CFP-AVI demonstrated bactericidal activity against the biofilms of all strains at 72 h. In an in vivo Galleria mellonella infection model, the 7-day survival rates of larvae infected with biofilm implants of K. pneumoniae or P. aeruginosa were 0-6.7%, 40.0-63.3%, and 46.7-90.0%, respectively, for PMB alone, CFP-AVI alone, and PMB combined with CFP-AVI; the combination therapy increased the rate by 6.7-33.3% (P < 0.05, n = 6), compared to CFP-AVI monotherapy. It is concluded that PMB combined with CFP-AVI exhibits effective anti-biofilm activities against PMB-resistant K. pneumoniae and P. aeruginosa both in vitro and in vivo, and thus may be a promising therapeutic strategy to treat biofilm-related infections.

Accelerated healing of intractable biofilm-infected diabetic wounds by trypsin-loaded quaternized chitosan hydrogels that disrupt extracellular polymeric substances and eradicate bacteria

Complex and stubborn bacterial biofilm infections significantly hinder diabetic wound healing and threaten public health. Therefore, a dressing material that effectively clears biofilms and promotes wound healing is urgently required. Herein, we introduce a novel strategy for simultaneously dispersing extracellular polymeric substances and eradicating drug-resistant bacteria. We prepared an ultrabroad-spectrum and injectable quaternized chitosan (QCS) hydrogel loaded with trypsin, which degrades biofilm extracellular proteins. Increased temperature initiated QCS gelation to form the hydrogel, enabling the sustained release of trypsin and effective adherence of the hydrogel to irregularly shaped wounds. To reproduce clinical scenarios, biofilms formed by a mixture of Staphylococcus aureus (S. aureus), Methicillin-resistant S. aureus, and Pseudomonas aeruginosa were administered to the wounds of rats with streptozotocin-induced diabetes. Under these severe infection conditions, the hydrogel efficiently suppressed inflammation, promoted angiogenesis, and enhanced collagen deposition, resulting in accelerated healing of diabetic wounds. Notably, the hydrogel demonstrates excellent biocompatibility without cytotoxicity. In summary, we present a trypsin-loaded QCS hydrogel with tremendous clinical applications potential for the treatment of chronic infected wounds.

Evaluation and Management of Pelvic Osteomyelitis in Stage IV Pressure Injuries: A Multidisciplinary Collaborative Approach

Managing pelvic osteomyelitis (POM) in the setting of stage IV pressure injuries requires multidisciplinary evaluation as well as patient and caregiver engagement and is complicated by the lack of high-evidence data to guide best practices. In this review, we describe our approach to pressure injury and POM evaluation and management through multidisciplinary collaboration and highlight areas of future research that are necessary to enhance patient outcomes, reduce healthcare costs, and improve the quality of life of those affected by POM.

Diversification of Pseudomonas aeruginosa Biofilm Populations under Repeated Phage Exposures Decreases the Efficacy of the Treatment

Phage therapy has been proposed as a therapeutic alternative to antibiotics for the treatment of chronic, biofilm-related P. aeruginosa infections. To gain a deeper insight into the complex biofilm-phage interactions, we investigated in the present study the effect of three successive exposures to lytic phages of biofilms formed by the reference strains PAO1 and PA14 as well as of two sequential clinical P. aeruginosa isolates from the sputum of a patient with cystic fibrosis (CF). The Calgary device was employed as a biofilm model and the efficacy of phage treatment was evaluated by measurements of the biomass stained with crystal violet (CV) and of the cell density of the biofilm bacterial population (CFU/mL) after each of the three phage exposures. The genetic alterations of P. aeruginosa isolates from biofilms exposed to phages were investigated by whole-genome sequencing. We show here that the anti-biofilm efficacy of the phage treatment decreased rapidly with repeated applications of lytic phages on P. aeruginosa strains with different genetic backgrounds. Although we observed the maintenance of a small subpopulation of sensitive cells after repeated phage treatments, a fast recruitment of mechanisms involved in the persistence of biofilms to the phage attack occurred, mainly by mutations causing alterations of the phage receptors. However, mutations causing phage-tolerant phenotypes such as alginate-hyperproducing mutants were also observed. In conclusion, a decreased anti-biofilm effect occurred after repeated exposure to lytic phages of P. aeruginosa biofilms due to the recruitment of different resistance and tolerance mechanisms.

Hair removal with a clipper and microbial colonisation prior to knee arthroplasty: a randomised controlled trial

Background

Despite the widely reported success of knee arthroplasty, studies show that 1.6-3 % of patients undergo revision within the first postoperative year predominantly due to infection. Preoperative skin preparation may potentially decrease the bacterial load and consequently, the risk of periprosthetic joint infections. The effects of hair removal on prosthetic joint infection are inconsistent. Our primary aim was to investigate if hair removal with a clipper influenced skin colonisation and bacterial composition.

Methods

Forty Caucasian male participants who were planned to undergo knee arthroplasty, (mean age 63.8 years), were included. Patients were randomised to hair removal in a within-person study design. As a control, the opposite leg of the patient was used. Swabs were collected prior to hair removal (baseline), immediately after hair removal (Day 0), and with follow-up after one and seven days.

Results

The intervention showed significant decrease in mean log colony-forming units per. cm2 from baseline 2.97 to 2.67 (P<0.01) immediately after hair removal and sustained at Day 1 (P=0.01). At Day 7, the mean was non-significant compared to baseline. The control group did not show any decrease of skin microbiota at follow-up on Day 0, 1 or 7.No significant differences within the bacterial composition were found between the intervention and control leg at baseline among the six most prevalent detected bacterial species: Staphylococcus epidermidis, Micrococcus luteus, S. hominis, S. capitis, S. haemolyticus and S. aureus. The study did not find any changes in the bacterial composition over time.

Conclusion

Hair removal with a clipper within 24 hours prior to surgery causes a significant non-selective reduction in skin colonisation.

Systematic review and meta-analysis of diagnostic test accuracy in chronic wound's microbiology

PURPOSE

This study aims to assess the diagnostic accuracy of non-culture-based methodologies for detecting microorganisms in chronic wounds.

METHODS

We systematically reviewed studies that evaluated the diagnostic accuracy of alternative tests in chronic wound samples, excluding studies focused on animal samples or unrelated conditions. The search encompassed PubMed, CINAHL, Scopus and Web of Science databases, employing the QUADAS-2 tool for risk of bias assessment. Our search included the PubMed, CINAHL, Scopus and Web of Science databases, and we assessed the risk of bias using the QUADAS-2 tool. A meta-analysis was conducted on polymerase chain reaction (PCR) and colorimetric methods to determine sensitivity, specificity, diagnostic odds ratio, and summary receiver-operating characteristic (sROC) curves using a random-effects model. For methods not suitable for quantitative synthesis, a narrative synthesis was performed.

RESULTS

Nineteen studies involving various types of chronic wounds were analysed, revealing diverse diagnostic methods including fluorescence, PCR, colorimetry, voltammetry, electronic nose, biosensors, enzymatic methods, staining and microscopy. Combining fluorescence with clinical signs and symptoms (CSS) versus culture showed significant accuracy. Colorimetry demonstrated low sensitivity but high specificity, with a diagnostic odds ratio of 6.3. PCR generally exhibited good accuracy, although significant heterogeneity was noted, even in subgroup analyses.

CONCLUSIONS

This study identified a broad spectrum of diagnostic approaches, highlighting the superior diagnostic accuracy achieved when microbiological analysis is combined with clinical assessments. However, the heterogeneity and methodological variations across studies present challenges in meta-analysis. Future research should aim for standardized and homogeneous study designs to enhance the assessment of diagnostic accuracy for alternative methods.

Antibiotics with antibiofilm activity - rifampicin and beyond

The management of prosthetic joint infections is a complex and multilayered process that is additionally complicated by the formation of bacterial biofilm. Foreign material provides the ideal grounds for the development of an intricate matrix that hinders treatment and creates a difficult environment for antibiotics to act. Surgical intervention is often warranted but requires appropriate adjunctive therapy. Despite available guidelines, several aspects of antibiotic therapy with antibiofilm activity lack clear definition. Given the escalating challenges posed by antimicrobial resistance, extended treatment durations, and tolerance issues, it is essential to ensure that antimicrobials with antibiofilm activity are both potent and diverse. Evidence of biofilm-active drugs is highlighted, and alternatives to classical regimens are further discussed.

In-silico and in-vitro assessment of the antibiofilm potential of azo dye, carmoisine against Pseudomonas aeruginosa

Biofilm is a community of microorganisms attached to the substrate and plays a significant role in microbial pathogenesis and medical device-related infection. Pseudomonas aeruginosa (PA) is a highly infectious gram-negative opportunistic biofilm-forming bacterium with high antibiotic resistance. Several reports underscore the antimicrobial activity of natural and synthetic food coloring agents, including carmoisine, turmeric dye, red amaranth dye, and phloxine B. However, their ability to suppress the PA biofilm is not clearly understood. Carmoisine is a red-colored synthetic azo dye containing naphthalene subunits and sulfonic groups and is widely used as a food coloring agent. This study investigated the antibiofilm potential and possible mechanism of biofilm inhibition by carmoisine against PA. Computational studies through molecular docking revealed that carmoisine strongly binds to QS regulator LasR (-12.7) and relatively less strongly but significantly with WspR (-6.9). Further analysis of the docked LasR-carmoisine complex using 100 ns MD simulation (Desmond, Schrödinger) validated the bonding strength and stability. Crystal violet assay, triphenyl tetrazolium chloride salt assay, and confocal microscopic studies were adopted for biofilm quantification, and the results indicated the dose-dependent antibiofilm activity of carmoisine against PA. We hypothesise that the carmoisine-mediated reduction of biofilm in PA is due to its interaction with LasR and interference with the QS system. The computational and biochemical analysis of another compound, 1,2-naphthoquinone-4-sulphonic acid, reiterated the role of the naphthalene ring in biofilm inhibition. Hence, this work will pave the way for the future discovery of antibiofilm drugs based on naphthalene ring-based lead compounds.Communicated by Ramaswamy H. Sarma.

Bacterial persisters: molecular mechanisms and therapeutic development

Persisters refer to genetically drug susceptible quiescent (non-growing or slow growing) bacteria that survive in stress environments such as antibiotic exposure, acidic and starvation conditions. These cells can regrow after stress removal and remain susceptible to the same stress. Persisters are underlying the problems of treating chronic and persistent infections and relapse infections after treatment, drug resistance development, and biofilm infections, and pose significant challenges for effective treatments. Understanding the characteristics and the exact mechanisms of persister formation, especially the key molecules that affect the formation and survival of the persisters is critical to more effective treatment of chronic and persistent infections. Currently, genes related to persister formation and survival are being discovered and confirmed, but the mechanisms by which bacteria form persisters are very complex, and there are still many unanswered questions. This article comprehensively summarizes the historical background of bacterial persisters, details their complex characteristics and their relationship with antibiotic tolerant and resistant bacteria, systematically elucidates the interplay between various bacterial biological processes and the formation of persister cells, as well as consolidates the diverse anti-persister compounds and treatments. We hope to provide theoretical background for in-depth research on mechanisms of persisters and suggest new ideas for choosing strategies for more effective treatment of persistent infections.

Tigecycline-Based Regimens for Complicated Urinary Tract Infections Caused by Carbapenem-Resistant Gram-Negative Bacteria: Case Series

There is existing controversy regarding the efficacy of tigecycline (TG) in treating complicated urinary tract infections (cUTIs) because of its pharmacokinetic concerns. We present three patients with cUTIs caused by carbapenem-resistant gram-negative (GN) pathogens successfully treated with high-dose tigecycline (HDT)-based regimens, as cefiderocol and aztreonam were not available in our country. The first case describes a 67-year-old patient with diabetes, prostate cancer, and double J ureteral stenting who was hospitalized with a febrile, complicated urinary tract infection (cUTI). Urine and blood cultures were positive for metallo-beta-lactamases (MBL)-producing extensively drug-resistant (XDR) Klebsiella pneumoniae (cefiderocol-susceptible). The synergy between TG and colistin using the in vitro E-test was demonstrated, and the patient was started on this regimen using HDT. Clinical and microbiological cures were achieved, and the patient was discharged home. The second case presents a 70-year-old patient with urethral pathology who was hospitalized with the diagnosis of a lower cUTI caused by an MBL-producing pan-drug-resistant (PDR) Klebsiella pneumoniae. The in vitro E-test showed synergy between TG and colistin, and our patient was successfully treated with this HDT-based combination. The third case emphasizes a 63-year-old patient with insulin-dependent diabetes, Child B cirrhosis, and a right double J ureteral stent who was hospitalized with a febrile cUTI. Urine and blood cultures were positive for carbapenem-resistant XDR Acinetobacter baumannii (susceptible to colistin and TG). Colistin was administered for only 96 hours because of stage II acute kidney injury, and we continued the treatment with HDT in monotherapy. The patient was discharged home, and no urinary tract infection relapse was seen for six months. Favorable clinical and microbiological outcomes were achieved with TG-based regimens in our cUTI cases. We highlight the role of antibiotic synergy determined by the in vitro E-test in two cases of MBL-producing XDR/PDR Klebsiella pneumoniae.

Late-Onset Reactions after Hyaluronic Acid Dermal Fillers: A Consensus Recommendation on Etiology, Prevention and Management

Hyaluronic acid (HA) dermal fillers, generally considered low-risk, can lead to rare late-onset reactions (LORs) manifesting between 3 and 4 months postinjection, occasionally even as early as 24 h postinjection. The Complication Assessment and Risk Evaluation (CARE) board was established to review these reactions. In this publication, the authors aims to explore the etiological hypotheses underlying LORs, associated risk factors, prevention, and management approaches suggested by the CARE board. The CARE board identified three etiological hypotheses contributing to LORs. Firstly, the physicochemical structure of the filler, particularly low molecular weight HA, which may trigger an immune response. Secondly, infection, potentially introduced during injection or by dormant biofilm activation. Lastly, an imbalance in the host immune system, caused by factors like autoimmune diseases or viral infections, may lead to extended foreign body reactions, delayed type IV hypersensitivity, or adjuvant-based reactions. Based on these hypotheses, the board categorized various risk factors as patient-related (e.g., recent dental treatment, current medical status, active autoimmune disease), product-related (e.g., molecular weight), and procedure-related (e.g., aseptic technique and trauma). To reduce the risk of LORs, the CARE board recommends diligent patient selection, including comprehensive medical history assessment and informed consent. Practitioners should maintain an effective aseptic technique, and choose an appropriate product and injection depth for the anatomical location. Post-procedure, patients should receive education on proper filler care. Management of LORs depends on the suspected etiology, and the CARE board has proposed an algorithm to determine the most appropriate treatment. Hyaluronidase is recommended for noninflammatory reactions in the absence of active infection, while watchful waiting and/or steroid treatment may be preferred for inflammatory reactions. Hyaluronidase is not recommended as a first-line treatment for infections, which require drainage, bacterial culture, and antibiotic treatment. However, the board emphasizes the need for individualized evaluation and treatment in all cases.

A Comprehensive Review of Microbial Biofilms on Contact Lenses: Challenges and Solutions

Contact lenses (CL) have become an immensely popular means of vision correction, offering comfort to millions worldwide. However, the persistent issue of biofilm formation on lenses raises significant problems, leading to various ocular complications and discomfort. The aim of this review is to develop safer and more effective strategies for preventing and managing microbial biofilms on CL, improving the eye health and comfort of wearers. Taking these into consideration, the present study investigates the intricate mechanisms of biofilm formation, by exploring the interplay between microbial adhesion, the production of extracellular polymeric substances, and the properties of the lens material itself. Moreover, it emphasizes the diverse range of microorganisms involved, encompassing bacteria, fungi, and other opportunistic pathogens, elucidating their implications within lenses and other medical device-related infections and inflammatory responses. Going beyond the challenges posed by biofilms on CL, this work explores the advancements in biofilm detection techniques and their clinical relevance. It discusses diagnostic tools like confocal microscopy, genetic assays, and emerging technologies, assessing their capacity to identify and quantify biofilm-related infections. Finally, the paper delves into contemporary strategies and innovative approaches for managing and preventing biofilms development on CL. In Conclusion, this review provides insights for eye care practitioners, lens manufacturers, and microbiology researchers. It highlights the intricate interactions between biofilms and CL, serving as a foundation for the development of effective preventive measures and innovative solutions to enhance CL safety, comfort, and overall ocular health. Research into microbial biofilms on CL is continuously evolving, with several future directions being explored to address challenges and improve eye health outcomes as far as CL wearers are concerned.

High efficacy treatment of murine Pseudomonas aeruginosa catheter-associated urinary tract infections using the c-di-GMP modulating anti-biofilm compound Disperazol in combination with ciprofloxacin

Persistent urinary tract infections (UTIs) in hospitalized patients constitute an important medical problem. It is estimated that 75% of nosocomial UTIs are associated with urinary tract catheters with P. aeruginosa being a species that forms biofilms on these catheters. These infections are highly resistant to standard-of-care antibiotics, and the effects of the host immune defenses, which allows for development of persistent infections. With antibiotics losing their efficacy, new treatment options against resilient infections, such as catheter-associated urinary tract infections (CAUTIs), are critically needed. Central to our anti-biofilm approach is the manipulation of the c-di-GMP signaling pathway in P. aeruginosa to switch bacteria from the protective biofilm to the unprotected planktonic mode of life. We recently identified a compound (H6-335-P1), that stimulates the c-di-GMP degrading activity of the P. aeruginosa BifA protein which plummets the intracellular c-di-GMP content and induces dispersal of P. aeruginosa biofilm bacteria into the planktonic state. In the present study, we formulated H6-335-P1 as a hydrochloride salt (Disperazol), which is water-soluble and facilitates delivery via injection or oral administration. Disperazol can work as a monotherapy, but we observed a 100-fold improvement in efficacy when treating murine P. aeruginosa CAUTIs with a Disperazol/ciprofloxacin combination. Biologically active Disperazol reached the bladder 30 min after oral administration. Our study provides proof of concept that Disperazol can be used in combination with a relevant antibiotic for effective treatment of CAUTIs.

Clinical use of 0.1% polyhexanide and propylbetaine on acute and hard-to-heal wounds: a literature review

OBJECTIVE

To summarise the findings on the effect of the clinical use of 0.1% polyhexanide-propylbetaine (PHMB/betaine) solution/gel on acute and hard-to-heal (chronic) wound healing.

METHOD

A literature search was conducted in MEDLINE, CINAHL, Embase, Scopus and the CENTRAL Trials Registry of the Cochrane Collaboration. Paired reviewers conducted title and abstract screening and full-text screening to identify experimental, quasi-experimental and observational studies. Study quality and risk of bias were not formally evaluated.

RESULTS

A total of 17 studies met the eligibility criteria. The findings from 12 studies indicated that the use of 0.1% PHMB/betaine solution/gel had: a low risk of contact sensitivity; could help debridement during wound cleansing; aided effective wound bed preparation; reduced wound size, odour and exudate; improved pain control; reduced microbial load; and enhanced wound healing. The results of three studies indicated that both 0.1% PHMB and saline solution were effective in reducing bacterial load, while another showed that adding 0.1% PHMB to tie-over dressings had no effect on reducing bacterial loads in wounds. Another study concluded that disinfection and granulation of pressure ulcers with hydrobalance dressing with 0.3% PHMB was faster and more effective than using 0.1% PHMB/betaine.

CONCLUSION

The findings of this literature review showed that 0.1% PHMB/betaine solution/gel appeared to be useful and safe for wound cleansing, was effective in removing soft debris and slough from the wound bed, and created a wound environment optimal for healing. Although these actions cannot be attributed solely to this treatment modality, these results do highlight the unique action of this combined product. However, more robust studies are needed to confirm these results.

Antibiofilm Strategies in Neonatal and Pediatric Infections

Biofilm-related infections pose significant challenges in neonatal and pediatric care, contributing to increased morbidity and mortality rates. These complex microbial communities, comprising bacteria and fungi, exhibit resilience against antibiotics and host immune responses. Bacterial species such as Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis commonly form biofilms on medical devices, exacerbating infection risks. Neonates and children, particularly those in intensive care units, are highly susceptible to biofilm-associated infections due to the prolonged use of invasive devices, such as central lines and endotracheal tubes. Enteral feeding tubes, crucial for neonatal nutritional support, also serve as potential sites for biofilm formation, contributing to recurrent microbial contamination. Moreover, Candida species, including Candida pelliculosa, present emerging challenges in neonatal care, with multi-drug resistant strains posing treatment complexities. Current antimicrobial therapies, while important in managing infections, often fall short in eradicating biofilms, necessitating alternative strategies. The aim of this review is to summarize current knowledge regarding antibiofilm strategies in neonates and in children. Novel approaches focusing on biofilm inhibition and dispersal show promise, including surface modifications, matrix-degrading enzymes, and quorum-sensing inhibitors. Prudent use of medical devices and exploration of innovative antibiofilm therapies are imperative in mitigating neonatal and pediatric biofilm infections.