Risk factors for chronic biofilm-related infection associated with implanted medical devices

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.

Chemo-photothermal therapy of bacterial infections using metal-organic framework-integrated polymeric network coatings

Surface modification of biomedical materials and devices using versatile nanocomposite coatings holds great promise for improving functionalities to defend against life-threatening bacterial infections. In this study, a one-step surface modification strategy was developed to deposit gold nanorods (AuNRs)- and curcumin (CUR)-encapsulated zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (AuNRs-ZIF-CUR NPs or AZC) onto phytic acid (PA)-ε-polylysine (Ply) network coatings. In the solution mixture of PA, Ply and AZC, PA interacted with Ply via electrostatic interactions, and can also bind to AZC via metal chelation. The as-formed AZC-PA-Ply aggregates could be deposited onto various substrates via surface adhesion of PA and gravitational effects. The physicochemical and antibacterial properties of the AZC-PA-Ply network coatings on polydimethylsiloxane (PDMS) substrates were evaluated. The sustained release of zinc ions and CUR, as well as the contact-killing ability of Ply, endowed the AZC-PA-Ply network coatings with good antibacterial chemotherapeutic effects. In addition, the embedded AuNRs in the AZC-PA-Ply network coatings exhibited excellent photothermal conversion efficiency for the ablation of bacteria. Upon near-infrared (NIR) laser irradiation, the AZC-PA-Ply-coated PDMS surfaces exhibited strong antibacterial effects by disrupting the membrane integrity and cellular functions of the adhered bacteria. Thus, the AZC-PA-Ply network coatings displayed combined antibacterial chemotherapeutic and photothermal therapeutic effects. Furthermore, the AZC-PA-Ply-coated PDMS substrates exhibited effective bacterial infection prevention and good biocompatibility in an in vivo implant model. Hence, the versatile AZC-PA-Ply network coatings are potentially useful as a multi-modal antibacterial platform to eliminate infectious bacterial pathogens in biomedical applications.

Epidemiological, clinical and microbiological characteristics of patients with biliary tract diseases with positive bile culture in a tertiary hospital

PURPOSE

The prevalence of biliary tract diseases, which are common gastrointestinal disorders, is steadily rising. If it progresses to sepsis or septic shock, it can endanger the patient's life. Therefore, it is crucial to promptly diagnose bacterial infection in individuals suffering from biliary diseases and comprehend the risk factors associated with infection. The objective of this study was to examine the types of bacteria present in the bile of patients with biliary tract diseases, assess any alterations in their susceptibility to antimicrobial agents, and identify the risk factors contributing to the development of infection in these patients.

PATIENTS AND METHODS

From June 2019 to November 2022, 317 patients of biliary tract diseases with positive bile culture were included in this hospital-based descriptive analysis. The hospital's computerized medical records were used to collect data on demographic information (including gender, age, and occupation), laboratory, and clinical findings, physical examination results, comorbidities, basic diseases, treatment history, complications, and in-hospital outcomes. The study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) principles.

RESULTS

Of the 317 patients with positive biliary tract diseases, 247 had benign diseases and 70 had malignant diseases. Patients with benign disease experienced a higher prevalence of statistically significant symptoms such as abdominal pain (81.4% vs. 57.1%, P = 0.000), nausea (31.2% vs. 14.3%, P = 0.005), vomiting (30.0% vs. 12.9%, P = 0.004), and chills (10.9% vs. 2.9%, P = 0.039), while jaundice (12.6% vs. 37.1%, P = 0.000) was more common in patients with malignant disease. At the species level, Escherichia coli (105; 40.5%), Klebsiella pneumoniae (41; 15.8%), and Pseudomonas aeruginosa (30; 11.6%) were the most commonly found Gram-negative bacterial strains in biliary tract infection. Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa were most susceptible to tigecycline, ertapenem and ceftazidime/avibactam, respectively.

CONCLUSION

Gram-negative bacteria are the most commonly isolated biliary bacteria. Clinical doctors should pay attention to patients with malignant diseases with low hemoglobin, high total bilirubin and high alkaline phosphatase. Carbapenems, tigecycline, and minocycline are the recommended antibiotics for Enterobacteriaceae. In recent years, the proportion of enterococcus has gradually increased, and clinical attention should be paid to enterococcus infection. Linezolid and vancomycin were recommended for the treatment of Enterococci infections. Overall, this work can provide reference for clinical diagnosis, treatment and effective interventions.

Screening of Lithium Substituted Ag-TiO2 Nanoparticle Coating for Antibiofilm Application

Bacterial infections and biofilm growth are common mishaps associated with medical devices, and they contribute significantly to ill health and mortality. Removal of bacterial deposition from these devices is a major challenge, resulting in an immediate necessity for developing antibacterial coatings on the surfaces of medical implants. In this context, we developed an innovative coating strategy that can operate at low temperatures (80 °C) and preserve the devices' integrity and functionality. An innovative Ag-TiO2 based coating was developed by ion exchange between silver nitrate (AgNO3) and lithium titanate (Li4Ti5O12) on glass substrates for different periods, ranging from 10 to 60 min. The differently coated samples were tested for their antibacterial and antibiofilm efficacy.

Biodegradable oxygen-evolving metalloantibiotics for spatiotemporal sono-metalloimmunotherapy against orthopaedic biofilm infections

Pathogen-host competition for manganese and intricate immunostimulatory pathways severely attenuates the efficacy of antibacterial immunotherapy against biofilm infections associated with orthopaedic implants. Herein, we introduce a spatiotemporal sono-metalloimmunotherapy (SMIT) strategy aimed at efficient biofilm ablation by custom design of ingenious biomimetic metal-organic framework (PCN-224)-coated MnO2-hydrangea nanoparticles (MnPM) as a metalloantibiotic. Upon reaching the acidic H2O2-enriched biofilm microenvironment, MnPM can convert abundant H2O2 into oxygen, which is conducive to significantly enhancing the efficacy of ultrasound (US)-triggered sonodynamic therapy (SDT), thereby exposing bacteria-associated antigens (BAAs). Moreover, MnPM disrupts bacterial homeostasis, further killing more bacteria. Then, the Mn ions released from the degraded MnO2 can recharge immune cells to enhance the cGAS-STING signaling pathway sensing of BAAs, further boosting the immune response and suppressing biofilm growth via biofilm-specific T cell responses. Following US withdrawal, the sustained oxygenation promotes the survival and migration of fibroblasts, stimulates the expression of angiogenic growth factors and angiogenesis, and neutralizes excessive inflammation. Our findings highlight that MnPM may act as an immune costimulatory metalloantibiotic to regulate the cGAS-STING signaling pathway, presenting a promising alternative to antibiotics for orthopaedic biofilm infection treatment and pro-tissue repair.

Surface modification of medical grade biomaterials by using a low-temperature-processed dual functional Ag-TiO2 coating for preventing biofilm formation

Biofilm development in medical devices is considered the major virulence component that leads to increased mortality and morbidity among patients. Removing a biofilm once formed is challenging and frequently results in persistent infections. Many current antibiofilm coating strategies involve harsh conditions causing damage to the surface of the medical devices. To address the issue of bacterial attachment in medical devices, we propose a novel antibacterial surface modification approach. In this paper, we developed a novel low-temperature based solution-processed approach to deposit silver nanoparticles (Ag NPs) inside a titanium oxide (TiO2) matrix to obtain a Ag-TiO2 nanoparticle coating. The low temperature (120 °C)-based UV annealed drop cast method is novel and ensures no surface damage to the medical devices. Various medical-grade biomaterials were then coated using Ag-TiO2 to modify the surface of the materials. Several studies were performed to observe the antibacterial and antibiofilm properties of Ag-TiO2-coated medical devices and biomaterials. Moreover, the Ag-TiO2 NPs did not show any skin irritation in rats and showed biocompatibility in the chicken egg model. This study indicates that Ag-TiO2 coating has promising potential for healthcare applications to combat microbial infection and biofilm formation.

Serratiopeptidase exhibits antibiofilm activity through the proteolytic function of N-terminal domain and versatile function of the C-terminal domain

BACKGROUND

Serratiopeptidase, a serine protease traditionally used as an oral anti-inflammatory drug has been found to show antibiofilm action. Structurally, it comprises of two distinct domains; viz-the N-terminal catalytic domain (Ncat) and a C-terminal RTX (Repeat-In-Toxin) domain (Crtx). Understanding the antibiofilm action of the serratiopeptidase molecule, as well as the antibiofilm action of each of its two domains, was the objective of this study.

RESULTS

Separate clones to express the complete recombinant serratiopeptidase protein and its variant containing a mutation in the catalytic site, the N-terminal catalytic domain and its mutant, and the C-terminal Repeat-In-Toxin domain were prepared, and the proteins were purified. The impact of these proteins on pre-existing biofilms, as well as their effect upon addition of these proteins during biofilm formation was investigated.

CONCLUSIONS

In our investigation, we have been able to analyze the antibiofilm action of serratiopeptidase in detail. Obtained results conclude that while N-terminally located proteolytic domain of serratiopeptidase conventionally acts against biofilms by hydrolytic activity, the C-terminal domain regulates or prevents biofilm formation by yet unknown mechanism in addition to its known function as an C-terminal located calcium modulated internal chaperone ensuring the proper folding and secretion of the molecule. The study's findings give new evidence that the Crtx domain plays a significant role in antibiofilm action. The proteolytic Ncat domain breaks down pre-formed biofilms. The C-terminal domain, on the other hand, acts as an inhibitor of biofilm formation by regulating or preventing biofilm development.

Copper tannate nanosheets-embedded multifunctional coating for antifouling and photothermal bactericidal applications

Implant-associated infections (IAIs), triggered by pathogenic bacteria, are a leading cause of implant failure. The design of functionalized coatings on biomedical materials is crucial to address IAIs. Herein, a multifunctional coating with good antifouling effect and antibacterial photothermal therapy (aPTT) performance was developed. The copper tannate nanosheets (CuTA NSs) were formed via coordination bonding of Cu2+ ions and tannic acid (TA). The CuTA NSs were then integrated into the TA and poly(ethylene glycol) (PEG) network to form the TCP coating for deposition on the titanium (Ti) substrates via surface adhesion of TA and gravitational effect. The resulting Ti-TCP substrate exhibited good antifouling property, reactive oxygen species (ROS) scavenging capability and cytocompatibility. The TCP coating exhibited antifouling efficacy in conjunction with aPTT, curtailing the surface adhesion and biofilm formation of pathogens, such as Staphylococcus aureus and Escherichia coli. Notably, the Ti-TCP substrate also exhibited the ability to prevent bacterial infection in vivo in a subcutaneous implantation model. The present work demonstrated a promising approach in designing high-performance antifouling and photothermal bactericidal coatings to combat IAIs.

Inorganic nanoparticles: An effective antibiofilm strategy

Biofilm is a common problem associated with human health. Pathogenicity and increase in resistance of bacteria require urgent development of effective ways for the treatment of bacterial diseases. Different strategies have been developed for the treatment of bacterial infections among which nanoparticles have shown greater prospects in battling with infections. Biofilms are resistant microbial colonies that possess resistance and, hence, cannot be killed by conventional drugs. Nanoparticles offer new avenues for treating biofilm-related infections involving multi-drug resistant organisms. They possess great antibiofilm properties, disrupting cell architecture and preventing colony formation. Green-synthesised nanoparticles are more effective and less toxic to human cells than commercially available or chemically synthesised antibiofilm nanoparticles. This review summarises the antibiofilm efficiency of plant-mediated nanoparticles and knowledge about biofilm inhibition.

In vitro models for studying implant-associated biofilms - A review from the perspective of bioengineering 3D microenvironments

Biofilm research has grown exponentially over the last decades, arguably due to their contribution to hospital acquired infections when they form on foreign body surfaces such as catheters and implants. Yet, translation of the knowledge acquired in the laboratory to the clinic has been slow and/or often it is not attempted by research teams to walk the talk of what is defined as 'bench to bedside'. We therefore reviewed the biofilm literature to better understand this gap. Our search revealed substantial development with respect to adapting surfaces and media used in models to mimic the clinical settings, however many of the in vitro models were too simplistic, often discounting the composition and properties of the host microenvironment and overlooking the biofilm-implant-host interactions. Failure to capture the physiological growth conditions of biofilms in vivo results in major differences between lab-grown- and clinically-relevant biofilms, particularly with respect to phenotypic profiles, virulence, and antimicrobial resistance, and they essentially impede bench-to-bedside translatability. In this review, we describe the complexity of the biological processes at the biofilm-implant-host interfaces, discuss the prerequisite for the development and characterization of biofilm models that better mimic the clinical scenario, and propose an interdisciplinary outlook of how to bioengineer biofilms in vitro by converging tissue engineering concepts and tools.

Material-based treatment strategies against intraosseous implant biofilm infection

Implant-associated infections present a significant clinical obstacle for orthopedic practitioners, with bacterial biofilm formation serving as a pivotal factor in the initiation, progression, and management of such infections. Conventional approaches have proven inadequate in fully eradicating biofilm-related infections. Consequently, novel material-based therapeutic strategies have been developed, encompassing the utilization of antimicrobial agents, delivery vehicles, and synergistic antibacterial systems. In this review, we provide a succinct overview of recent advancements in anti-biofilm strategies, with the aim of offering insights that may aid in the treatment of intraosseous implant infections.

Mitigating infections in implantable urological continence devices: risks, challenges, solutions, and future innovations. A comprehensive literature review

PURPOSE OF REVIEW

Stress urinary incontinence is a growing issue in ageing men, often following treatment for prostate cancer or bladder outflow obstruction. While implantable urological devices offer relief, infections are a significant concern. These infections can lead to device removal, negating the benefits and impacting patient outcomes. This review explores the risks and factors contributing to these infections and existing strategies to minimize them. These strategies encompass a multifaceted approach that considers patient-specific issues, environmental issues, device design and surgical techniques. However, despite these interventions, there is still a pressing need for further advancements in device infection prevention.

RECENT FINDINGS

Faster diagnostics, such as Raman spectroscopy, could enable early detection of infections. Additionally, biocompatible adjuncts like ultrasound-responsive microbubbles hold promise for enhanced drug delivery and biofilm disruption, particularly important as antibiotic resistance rises worldwide.

SUMMARY

By combining advancements in diagnostics, device design, and patient-specific surgical techniques, we can create a future where implantable urological devices offer men a significant improvement in quality of life with minimal infection risk.

Foregut Erosion Related to Biomedical Implants: A Scoping Review

Introduction: Biomedical devices implanted transabdominally have gained popularity over the past 50 years in the treatment of gastroesophageal reflux disease, paraesophageal hiatal hernia, and morbid obesity. Device-related foregut erosions (FEs) represent a challenging event that demands special attention owing to the potential of severe postoperative complications and death. Purpose: The aim was to provide an overview of full-thickness foregut injury leading to erosion associated with four types of biomedical devices. Methods: The study was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). PubMed, EMBASE, and Web of Science databases were queried until December 31, 2023. Eligible studies included all articles reporting data, management, and outcomes on device-related FE. Results: Overall, 132 articless were included for a total of 1292 patients suffering from device-related FE. Four different devices were included: the Angelchik antireflux prosthesis (AAP) (n = 25), nonabsorbable mesh for crural repair (n = 60), adjustable gastric banding (n = 1156), and magnetic sphincter augmentation device (n = 51). The elapsed time from device implant to erosion ranged from 1 to 480 months. Most commonly reported symptoms were dysphagia and epigastric pain, while acute presentation was reported rarely and mainly for gastric banding. The technique for device removal evolved from more invasive open approaches toward minimally invasive and endoscopic techniques. Esophagectomy and gastrectomy were mostly reported for nonabsorbable mesh FE. Overall mortality was .17%. Conclusions: Device-related FE is rare but may occur many years after AAP, nonabsorbable mesh, adjustable gastric banding, and magnetic sphincter augmentation implant. FE-related mortality is infrequent, however, increased postoperative morbidity and the need for esophagogastric resection were observed for nonabsorbable mesh-reinforced cruroplasty.

Efficacy of a Novel Intraoperative Surgical Irrigant in Preventing Periprosthetic Joint Infections in Primary Knee, Hip, and Shoulder Arthroplasties: A Retrospective Analysis

OBJECTIVE

Primary joint arthroplasty (JA) is one of the most common operating room (OR) procedures, with knee and hip arthroplasties being listed in the top five most frequent OR procedures and while not as common, shoulder arthroplasties are increasing at greater rates than knee and hip arthroplasties. Periprosthetic joint/shoulder infections (PJI/PSI) are a devastating complication of primary JAs with infection prevention deemed as the single most important strategy in combating them. The objective of this study was to retrospectively evaluate the efficacy of XPERIENCE® Advanced Surgical Irrigation (XP) in preventing PJI following primary joint arthroplasty.

METHODS

This is a retrospective study of primary knee, hip and shoulder arthroplasties that were performed by multiple orthopedic surgeons at a single hospital setting. XPERIENCE was used as an intraoperative surgical irrigant either solely, or with other intraoperative practices for prevention of infection. Incidence of acute PJI occurring within 90 days of index surgery were retrospectively collated.

RESULTS

Four hundred and twenty-three (423) primary joint replacement surgeries treated intraoperatively with XP, were evaluated for acute PJI incidence. Retrospective evaluations determined that 95% of the subjects had at least one risk factor predisposing them to PJI. There were zero PJIs diagnosed in the knee and hip arthroplasty cohorts and zero PSIs diagnosed in the shoulder arthroplasty cohorts.

CONCLUSION

The absence of PJI/PSI diagnoses in the JA cohorts treated intraoperatively with XP indicates that it could be an efficacious antimicrobial irrigant in preventing PJI, and warrants being evaluated in prospective, randomized controlled clinical trials as the sole intraoperative irrigant, as well as in combination with the other intraoperative infection prevention regimens evaluated in this retrospective study.

N-Halaminated spermidine-containing polymeric coating enables titanium to achieve dual functions of antibacterial and osseointegration

Titanium (Ti) and its alloys have been widely employed in the treatment of orthopedics and other hard tissue diseases. However, Ti-based implants are bioinert and suffer from bacterial infections and poor osseointegration in clinical applications. Herein, we successfully modified Ti with a porous N-halaminated spermidine-containing polymeric coating (Ti-SPD-Cl) through alkali-heat treatment, surface grafting and chlorination, and it has both excellent antibacterial and osteogenic abilities to significantly enhance osseointegration. The as-obtained Ti-SPD-Cl contains abundant N-Cl groups and demonstrates effective antibacterial ability against S. aureus and E. coli. Meanwhile, due to the presence of the spermidine component and construction of a porous hydrophilic surface, Ti-SPD-Cl is also beneficial for maintaining cell membrane homeostasis and promoting cell adhesion, exhibiting good biocompatibility and osteogenic ability. The rat osteomyelitis model demonstrates that Ti-SPD-Cl can effectively suppress bacterial infection and enhance bone-implant integration. Thus, Ti-SPD-Cl shows promising clinical applicability in the prevention of orthopedic implant infections and poor osseointegration.

The Impact of Smoking on Hospital Course and Postoperative Outcomes in Patients With Fracture-Related Infections

OBJECTIVES

To assess the relationship between patient smoking status and fracture-related infection (FRI) characteristics including patient symptoms at FRI presentation, bacterial species of FRI, and rates of fracture union.

METHODS

DESIGN

Retrospective cohort study.

SETTING

Urban level 1 trauma center.

PATIENT SELECTION CRITERIA

All patients undergoing reoperation for FRI from January 2013 to April 2021 were identified through manual review of an institutional database.

OUTCOME MEASURES AND COMPARISONS

Data including patient demographics, fracture characteristics, infection presentation, and hospital course were collected through review of the electronic medical record. Patients were grouped based on current smoker versus nonsmoker status. Hospital course and postoperative outcomes of these groups were then compared. Risk factors of methicillin-resistant Staphylococcus aureus (MRSA) infection, Staphylococcus epidermidis infection, and sinus tract development were evaluated using multivariable logistic regression.

RESULTS

A total of 301 patients, comprising 155 smokers (51%) and 146 nonsmokers (49%), undergoing FRI reoperation were included. Compared with nonsmokers, smokers were more likely male (69% vs. 56%, P = 0.024), were younger at the time of FRI reoperation (41.7 vs. 49.5 years, P < 0.001), and had lower mean body mass index (27.2 vs. 32.0, P < 0.001). Smokers also had lower prevalence of diabetes mellitus (13% vs. 25%, P = 0.008) and had higher Charlson Comorbidity Index 10-year estimated survival (93% vs. 81%, P < 0.001). Smokers had a lower proportion of S. epidermidis infections (11% vs. 20%, P = 0.037), higher risk of nonunion after index fracture surgery (74% vs. 61%, P = 0.018), and higher risk of sinus tracts at FRI presentation (38% vs. 23%, P = 0.004). On multivariable analysis, smoking was not found to be associated with increased odds of MRSA infection.

CONCLUSIONS

Among patients who develop a FRI, smokers seemed to have better baseline health regarding age, body mass index, diabetes mellitus, and Charlson Comorbidity Index 10-year estimated survival compared with nonsmokers. Smoking status was not significantly associated with odds of MRSA infection. However, smoking status was associated with increased risk of sinus tract development and nonunion and lower rates of S. epidermidis infection at the time of FRI reoperation.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

A Systematic Guideline by the ASPN Workgroup on the Evidence, Education, and Treatment Algorithm for Painful Diabetic Neuropathy: SWEET

Introduction

Painful diabetic neuropathy (PDN) is a leading cause of pain and disability globally with a lack of consensus on the appropriate treatment of those suffering from this condition. Recent advancements in both pharmacotherapy and interventional approaches have broadened the treatment options for PDN. There exists a need for a comprehensive guideline for the safe and effective treatment of patients suffering from PDN.

Objective

The SWEET Guideline was developed to provide clinicians with the most comprehensive guideline for the safe and appropriate treatment of patients suffering from PDN.

Methods

The American Society of Pain and Neuroscience (ASPN) identified an educational need for a comprehensive clinical guideline to provide evidence-based recommendations for PDN. A multidisciplinary group of international experts developed the SWEET guideline. The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Meeting Abstracts, and Scopus to identify and compile the evidence for diabetic neuropathy pain treatments (per section as listed in the manuscript) for the treatment of pain. Manuscripts from 2000-present were included in the search process.

Results

After a comprehensive review and analysis of the available evidence, the ASPN SWEET guideline was able to rate the literature and provide therapy grades for most available treatments for PDN utilizing the United States Preventive Services Task Force criteria.

Conclusion

The ASPN SWEET Guideline represents the most comprehensive review of the available treatments for PDN and their appropriate and safe utilization.

Upconversion 3D Bioprinting for Noninvasive In Vivo Molding

Tissue engineered bracket materials provide essential support for the physiological protection and therapeutics of patients. Unfortunately, the implantation process of such devices poses the risk of surgical complications and infection. In this study, an upconversion nanoparticles (UCNPs)-assisted 3D bioprinting approach is developed to realize in vivo molding that is free from invasive surgery. Reasonably designed UCNPs, which convert near-infrared (NIR) photons that penetrate skin tissues into blue-violet emission (300-500 nm), induce a monomer polymerization curing procedure in vivo. Using a fused deposition modeling coordination framework, a precisely predetermined trajectory of the NIR laser enables the manufacture of implantable medical devices with tailored shapes. A proof of the 3D bioprinting of a noninvasive fracture fixation scaffold is achieved successfully, thus demonstrating an entirely new method of in vivo molding for biomedical treatment.

C-terminal deletion of RelA protein is suggested as a possible cause of infective endocarditis recurrence with Enterococcus faecium

Infective endocarditis (IE) caused by Enterococcus spp. represents the third most common cause of IE, with high rates of relapse compared with other bacteria. Interestingly, late relapses (>6 months) have only been described in Enterococcus faecalis, but here we describe the first reported IE relapse with Enterococcus faecium more than a year (17 months) after the initial endocarditis episode. Firstly, by multi locus sequence typing (MLST), we demonstrated that both isolates (EF646 and EF641) belong to the same sequence type (ST117). Considering that EF641 was able to overcome starvation and antibiotic treatment conditions surviving for a long period of time, we performed bioinformatic analysis in identifying potential genes involved in virulence and stringent response. Our results showed a 13-nucleotide duplication (positions 1638-1650) in the gene relA, resulting in a premature stop codon, with a loss of 167 amino acids from the C-terminal domains of the RelA enzyme. RelA mediates the stringent response in bacteria, modulating levels of the alarmone guanosine tetraphosphate (ppGpp). The relA mutant (EF641) was associated with lower growth capacity, the presence of small colony variants, and higher capacity to produce biofilms (compared with the strain EF646), but without differences in antimicrobial susceptibility patterns according to standard procedures during planktonic growth. Instead, EF641 demonstrated tolerance to high doses of teicoplanin when growing in a biofilm. We conclude that all these events would be closely related to the long-term survival of the E. faecium and the late relapse of the IE. These data represent the first clinical evidence of mutations in the stringent response (relA gene) related with E. faecium IE relapse.

Regulating bacterial biofilms in food and biomedicine: unraveling mechanisms and Innovating strategies

Bacterial biofilm has brought a lot of intractable problems in food and biomedicine areas. Conventional biofilm control mainly focuses on inactivation and removal of biofilm. However, with robust construction and enhanced resistance, the established biofilm is extremely difficult to eradicate. According to the mechanism of biofilm development, biofilm formation can be modulated by intervening in the key factors and regulatory systems. Therefore, regulation of biofilm formation has been proposed as an alternative way for effective biofilm control. This review aims to provide insights into the regulation of biofilm formation in food and biomedicine. The underlying mechanisms for early-stage biofilm establishment are summarized based on the key factors and correlated regulatory networks. Recent developments and applications of novel regulatory strategies such as anti/pro-biofilm agents, nanomaterials, functionalized surface materials and physical strategies are also discussed. The current review indicates that these innovative methods have contributed to effective biofilm control in a smart, safe and eco-friendly way. However, standard methodology for regulating biofilm formation in practical use is still missing. As biofilm formation in real-world systems could be far more complicated, further studies and interdisciplinary collaboration are still needed for simulation and experiments in the industry and other open systems.

Surface Properties of a Biocompatible Thermoplastic Polyurethane and Its Anti-Adhesive Effect against E. coli and S. aureus

Thermoplastic polyurethane (TPU) is a polymer used in a variety of fields, including medical applications. Here, we aimed to verify if the brush and bar coater deposition techniques did not alter TPU properties. The topography of the TPU-modified surfaces was studied via AFM demonstrating no significant differences between brush and bar coater-modified surfaces, compared to the un-modified TPU (TPU Film). The effect of the surfaces on planktonic bacteria, evaluated by MTT assay, demonstrated their anti-adhesive effect on E. coli, while the bar coater significantly reduced staphylococcal planktonic adhesion and both bacterial biofilms compared to other samples. Interestingly, Pearson's R coefficient analysis showed that Ra roughness and Haralick's correlation feature were trend predictors for planktonic bacterial cells adhesion. The surface adhesion property was evaluated against NIH-3T3 murine fibroblasts by MTT and against human fibrinogen and human platelet-rich plasma by ELISA and LDH assay, respectively. An indirect cytotoxicity experiment against NIH-3T3 confirmed the biocompatibility of the TPUs. Overall, the results indicated that the deposition techniques did not alter the antibacterial and anti-adhesive surface properties of modified TPU compared to un-modified TPU, nor its bio- and hemocompatibility, confirming the suitability of TPU brush and bar coater films in the biomedical and pharmaceutical fields.

Titanium modification using bioactive titanate layer with divalent ions and coordinated ciprofloxacin - Assessment of drug distribution using FT-IR imaging

The paper presents a new method of titanium alloy (Ti6Al4V) modification using bioactive titanate layers containing various divalent ions (Ca2+, Mg2+, Sr2+, Zn2+) and surface-coordinated ciprofloxacin. Due to the coordination of ciprofloxacin (antibiotic) on the surface of the alloy, it has great application potential. In the paper, the influence of a given cation on the effectiveness of drug sorption was determined. The most effective cation was zinc and the least effective was calcium. The distribution of the antibiotic on the alloy surface was determined using FT-IR imaging. The antibiotic was evenly distributed on alloys modified with magnesium, strontium and zinc titanates. In the case of calcium titanate, the analysis could not be performed because the amount of the drug was too small. The release profiles of ciprofloxacin indicate that it can be released for as long as 3 h for strontium and zinc titanates. The biocompatibility of the obtained materials is indicated by the results of the BSA adsorption, and HA growth test. The obtained results confirm that the proposed modification can be used in the modification of titanium implants. The big advantage of this layer is that ciprofloxacin is coordinated on the surface of the material and thus will not be removed during the surgical procedure. The creation of this type of layer may in the future allow for fewer perioperative infections, and thus fewer complications.

Microbial colonization and chemically influenced selective enrichment of bacterial pathogens on polycarbonate plastic

Plastic pollution in aquatic environments poses significant concerns due to its potential to serve as a refuge for aquatic pathogens. However, the role of plastic surfaces and microbial biofilm interfaces in facilitating pathogen development remains poorly understood. In this study, a microcosm setup was employed to investigate the interactions between plastics and the microbial community and examine the differences in bacterial community composition and potential pathogen occurrences between the plastisphere-biofilm and surrounding seawater. Community composition analysis combined with SEM observations over time indicated that biofilm extracellular polymeric substance formation over 14 days had a link with the relative abundance and succession patterns of pathogen taxa. Colony clusters were observed on biofilms from day 7 and coincided with higher bacterial pathogen dominance. On day 14, pathogen abundance overall decreased with a potentially degrading biofilm. Pseudomonas and Pseudoalteromonas were the dominant potential pathogen groups observed in the microcosm. When further subjected to chemical treatment as an imposed environmental stress over time, biofilm-associated Psuedoalteromonas sharply increased in abundance after three days of exposure, but quickly diminished by 14 days in favor of genera such as Acinetobacter, Pseudomonas, and Staphylococcus. These results suggest that environmental plastisphere-biofilms can promote the early selection, enrichment, and spread of pathogenic bacteria in the aquatic environment and could be later worsened under chemical and long-term pressure. This study provided new insights into the succession of pathogens in plastisphere biofilms, contributing to the understanding of pathogen risks involved in emerging plastisphere biofilms in light of global plastic pollution.

Antibiofilm activity of marine microbial natural products: potential peptide- and polyketide-derived molecules from marine microbes toward targeting biofilm-forming pathogens

Controlling and treating biofilm-related infections is challenging because of the widespread presence of multidrug-resistant microbes. Biofilm, a naturally occurring matrix of microbial aggregates, has developed intricate and diverse resistance mechanisms against many currently used antibiotics. This poses a significant problem, especially for human health, including clinically chronic infectious diseases. Thus, there is an urgent need to search for and develop new and more effective antibiotics. As the marine environment is recognized as a promising reservoir of new biologically active molecules with potential pharmacological properties, marine natural products, particularly those of microbial origin, have emerged as a promising source of antibiofilm agents. Marine microbes represent an untapped source of secondary metabolites with antimicrobial activity. Furthermore, marine natural products, owing to their self-defense mechanisms and adaptation to harsh conditions, encompass a wide range of chemical compounds, including peptides and polyketides, which are primarily found in microbes. These molecules can be exploited to provide novel and unique structures for developing alternative antibiotics as effective antibiofilm agents. This review focuses on the possible antibiofilm mechanism of these marine microbial molecules against biofilm-forming pathogens. It provides an overview of biofilm development, its recalcitrant mode of action, strategies for the development of antibiofilm agents, and their assessments. The review also revisits some selected peptides and polyketides from marine microbes reported between 2016 and 2023, highlighting their moderate and considerable antibiofilm activities. Moreover, their antibiofilm mechanisms, such as adhesion modulation/inhibition targeting biofilm-forming pathogens, quorum sensing intervention and inhibition, and extracellular polymeric substance disruption, are highlighted herein.

Antimicrobial Surface for Devices Used in Stem Culture Manipulation and In Vitro Biofabrication of Tissues

Cell therapy and engineered tissue creation based on the use of human stem cells involves cell isolation, expansion, and cell growth and differentiation on the scaffolds. Microbial infections dramatically can affect stem cell survival and increase the risk of implant failure. To prevent these events, it is necessary to develop new materials with antibacterial properties for coating scaffold surfaces as well as medical devices, and all other surfaces at high risk of contamination. This chapter describes strategies for obtaining antibacterial blends for coating inert surfaces (polymethylmethacrylate, polycarbonate, Carbon Fiber Reinforced Polymer (CFRP)). In particular, the procedures for preparing antibacterial blends by mixing polymer resins with two types of antibacterial additives and depositing these blends on inert surfaces are described.

Biofilm antimicrobial susceptibility testing: where are we and where could we be going?

Our knowledge about the fundamental aspects of biofilm biology, including the mechanisms behind the reduced antimicrobial susceptibility of biofilms, has increased drastically over the last decades. However, this knowledge has so far not been translated into major changes in clinical practice. While the biofilm concept is increasingly on the radar of clinical microbiologists, physicians, and healthcare professionals in general, the standardized tools to study biofilms in the clinical microbiology laboratory are still lacking; one area in which this is particularly obvious is that of antimicrobial susceptibility testing (AST). It is generally accepted that the biofilm lifestyle has a tremendous impact on antibiotic susceptibility, yet AST is typically still carried out with planktonic cells. On top of that, the microenvironment at the site of infection is an important driver for microbial physiology and hence susceptibility; but this is poorly reflected in current AST methods. The goal of this review is to provide an overview of the state of the art concerning biofilm AST and highlight the knowledge gaps in this area. Subsequently, potential ways to improve biofilm-based AST will be discussed. Finally, bottlenecks currently preventing the use of biofilm AST in clinical practice, as well as the steps needed to get past these bottlenecks, will be discussed.

Biofilm formation: mechanistic insights and therapeutic targets

Biofilms are complex multicellular communities formed by bacteria, and their extracellular polymeric substances are observed as surface-attached or non-surface-attached aggregates. Many types of bacterial species found in living hosts or environments can form biofilms. These include pathogenic bacteria such as Pseudomonas, which can act as persistent infectious hosts and are responsible for a wide range of chronic diseases as well as the emergence of antibiotic resistance, thereby making them difficult to eliminate. Pseudomonas aeruginosa has emerged as a model organism for studying biofilm formation. In addition, other Pseudomonas utilize biofilm formation in plant colonization and environmental persistence. Biofilms are effective in aiding bacterial colonization, enhancing bacterial resistance to antimicrobial substances and host immune responses, and facilitating cell‒cell signalling exchanges between community bacteria. The lack of antibiotics targeting biofilms in the drug discovery process indicates the need to design new biofilm inhibitors as antimicrobial drugs using various strategies and targeting different stages of biofilm formation. Growing strategies that have been developed to combat biofilm formation include targeting bacterial enzymes, as well as those involved in the quorum sensing and adhesion pathways. In this review, with Pseudomonas as the primary subject of study, we review and discuss the mechanisms of bacterial biofilm formation and current therapeutic approaches, emphasizing the clinical issues associated with biofilm infections and focusing on current and emerging antibiotic biofilm strategies.

Immunomodulatory biomaterials against bacterial infections: Progress, challenges, and future perspectives

Bacterial infectious diseases are one of the leading causes of death worldwide. Even with the use of multiple antibiotic treatment strategies, 4.95 million people died from drug-resistant bacterial infections in 2019. By 2050, the number of deaths will reach 10 million annually. The increasing mortality may be partly due to bacterial heterogeneity in the infection microenvironment, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants. In addition, the complexity of the immune microenvironment at different stages of infection makes biomaterials with direct antimicrobial activity unsatisfactory for the long-term treatment of chronic bacterial infections. The increasing mortality may be partly attributed to the biomaterials failing to modulate the active antimicrobial action of immune cells. Therefore, there is an urgent need for effective alternatives to treat bacterial infections. Accordingly, the development of immunomodulatory antimicrobial biomaterials has recently received considerable interest; however, a comprehensive review of their research progress is lacking. In this review, we focus mainly on the research progress and future perspectives of immunomodulatory antimicrobial biomaterials used at different stages of infection. First, we describe the characteristics of the immune microenvironment in the acute and chronic phases of bacterial infections. Then, we highlight the immunomodulatory strategies for antimicrobial biomaterials at different stages of infection and their corresponding advantages and disadvantages. Moreover, we discuss biomaterial-mediated bacterial vaccines' potential applications and challenges for activating innate and adaptive immune memory. This review will serve as a reference for future studies to develop next-generation immunomodulatory biomaterials and accelerate their translation into clinical practice.

Bacterial reservoir in deeper skin is a potential source for surgical site and biomaterial-associated infections

BACKGROUND

The origin of surgical site and biomaterial-associated infection is still elusive. Micro-organisms contaminating the wound may come from the air in the operating theatre, the surgical team or the skin of the patient. The skin of patients is disinfected prior to surgery, but bacteria deeper in the skin (e.g. in sweat glands or sebaceous glands) may not be reached.

METHODS

A preliminary cohort study was performed to study the origin of surgical site and biomaterial-associated infection between May 2020 and February 2021. In order to investigate whether cutaneous microbiota colonize the wound when released from the skin upon cutting, aerobic and anaerobic bacteria were isolated, quantified and identified from the skin of 99 patients undergoing trauma surgery, before and after skin disinfection, from knife blades and from the wound directly after the first cut.

RESULTS

Ninety-nine percent of the patients were culture-positive before disinfection with chlorhexidine. Of these, 40% were still culture-positive after disinfection. Of these, 54% had a positive culture of the wound after cutting the skin. Twenty percent of the patients with a negative culture after disinfection had a positive wound culture after cutting the skin. Staphylococcus epidermidis and Cutibacterium acnes were the most commonly cultured bacterial species. In 9% of cases, more than 100 bacterial colonies were cultured from the wound; this may cause biomaterial-associated infection.

CONCLUSION

Bacteria residing in the skin and not eradicated by disinfection may enter the surgical wound upon cutting, resulting in contamination which may cause biomaterial-associated infection.

How biofilm changes our understanding of cleaning and disinfection

Biofilms are ubiquitous in healthcare settings. By nature, biofilms are less susceptible to antimicrobials and are associated with healthcare-associated infections (HAI). Resistance of biofilm to antimicrobials is multifactorial with the presence of a matrix composed of extracellular polymeric substances and eDNA, being a major contributing factor. The usual multispecies composition of environmental biofilms can also impact on antimicrobial efficacy. In healthcare settings, two main types of biofilms are present: hydrated biofilms, for example, in drains and parts of some medical devices and equipment, and environmental dry biofilms (DSB) on surfaces and possibly in medical devices. Biofilms act as a reservoir for pathogens including multi-drug resistant organisms and their elimination requires different approaches. The control of hydrated (drain) biofilms should be informed by a reduction or elimination of microbial bioburden together with measuring biofilm regrowth time. The control of DSB should be measured by a combination of a reduction or elimination in microbial bioburden on surfaces together with a decrease in bacterial transfer post-intervention. Failure to control biofilms increases the risk for HAI, but biofilms are not solely responsible for disinfection failure or shortcoming. The limited number of standardised biofilm efficacy tests is a hindrance for end users and manufacturers, whilst in Europe there are no approved standard protocols. Education of stakeholders about biofilms and ad hoc efficacy tests, often academic in nature, is thus paramount, to achieve a better control of biofilms in healthcare settings.

Chitosan hydrogel modified with lanthanum as a drug delivery system for epigallocatechin gallate: Investigation of hydrogel - drug interaction by FT-IR and Raman spectroscopy

In the presented work, chitosan hydrogel modified with lanthanum was obtained for the first time. The hydrogel was used as a carrier in the controlled release of epigallocatechin gallate. The work proved the effectiveness of drug sorption by hydrogel and controlled release in simulated body fluids. The drug was released slowly and in a controlled manner from the carrier. The research techniques used in this work (FT-IR spectroscopy and imaging, Raman spectroscopy, SEM/EDS) allowed to confirm the successful retention of EGCG on the hydrogel surface. On the basis of the EDS mapping, it was possible to confirm the even distribution of the lanthanum ions. Using FT-IR imaging, we verified that the drug was evenly distributed on the entire surface of the prepared material. The antifungal effectiveness of the material has been proven on several types of fungi. The research proved that the prepared material is capable of long-term release of the active substance and has antifungal properties. As a result, the prepared material can be successfully used as an implantable hydrogel or a coating in, e.g. titanium implants.

Development and characterization of antibacterial coatings on surgical sutures based on sodium carboxymethyl cellulose/chitosan/chlorhexidine

The layer-by-layer assembly (LBL) method was used in this work to apply antibacterial coatings to the surface of sutures. The nanofilm was created using sodium carboxymethyl cellulose, chitosan, and chlorhexidine digluconate. Polyethylene terephthalate and polyamide surgical sutures were used as the substrate. At pH 5, thin, uniform coatings with the ideal number of biopolymers in the film (10 bilayers) are produced. The pH and the shape of the polyelectrolyte macromolecules determine the film's thickness and form. The morphology of the surface and the structure of the sutures after modification become homogeneous and smooth. Both treated and untreated sutures retain their mechanical strength, and there is no significant loss of tensile strength. Nanofilms obtained on the surface of the sutures showed high antimicrobial efficacy against microorganisms Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Staphylococcus epidermidis, and Streptococcus pneumoniae. Chlorhexidine incorporated into the multilayer membrane was found to have greater antimicrobial activity than sutures treated with chlorhexidine alone. Modified surgical sutures provide antibacterial qualities that last for up to 30 days in a stable, controlled manner. The results showed the prospects of applying nanofilms based on sodium carboxymethyl cellulose/chitosan/chlorhexidine to surgical sutures that can prevent the infectious consequences of surgical interventions.

The Anti-Biofilm Potential of Linalool, a Major Compound from Hedychium larsenii, against Streptococcus pyogenes and Its Toxicity Assessment in Danio rerio

The anti-biofilm and anti-virulence potential of the essential oil (E.O.) extracted from Hedychium larsenii M. Dan & Sathish was determined against Streptococcus pyogenes. A crystal violet assay was employed to quantify the biofilm. Linalool, a monoterpene alcohol from the E.O., showed concentration-dependent biofilm inhibition, with a maximum of 91% at a concentration of 0.004% (v/v). The AlamarBlueTM assay also confirmed Linalool's non-bactericidal anti-biofilm efficacy (0.004%). Linalool treatment impeded micro-colony formation, mature biofilm architecture, surface coverage, and biofilm thickness and impaired cell surface hydrophobicity and EPS production. Cysteine protease synthesis was quantified using the Azocasein assay, and Linalool treatment augmented its production. This suggests that Linalool destabilizes the biofilm matrix. It altered the expression of core regulons covRS, mga, srv, and ropB, and genes associated with virulence and biofilm formation, such as speB, dltA, slo, hasA, and ciaH, as revealed by qPCR analysis. Cytotoxicity analysis using human kidney cells (HEK) and the histopathological analysis in Danio rerio proved Linalool to be a druggable molecule against the biofilms formed by S. pyogenes. This is the first report on Linalool's anti-biofilm and anti-virulence potential against S. pyogenes.

Horizontal Gene Transfer of Antibiotic Resistance Genes in Biofilms

Most bacteria attach to biotic or abiotic surfaces and are embedded in a complex matrix which is known as biofilm. Biofilm formation is especially worrisome in clinical settings as it hinders the treatment of infections with antibiotics due to the facilitated acquisition of antibiotic resistance genes (ARGs). Environmental settings are now considered as pivotal for driving biofilm formation, biofilm-mediated antibiotic resistance development and dissemination. Several studies have demonstrated that environmental biofilms can be hotspots for the dissemination of ARGs. These genes can be encoded on mobile genetic elements (MGEs) such as conjugative and mobilizable plasmids or integrative and conjugative elements (ICEs). ARGs can be rapidly transferred through horizontal gene transfer (HGT) which has been shown to occur more frequently in biofilms than in planktonic cultures. Biofilm models are promising tools to mimic natural biofilms to study the dissemination of ARGs via HGT. This review summarizes the state-of-the-art of biofilm studies and the techniques that visualize the three main HGT mechanisms in biofilms: transformation, transduction, and conjugation.

Pathogenic Drug Resistant Fungi: A Review of Mitigation Strategies

Fungal pathogens cause significant human morbidity and mortality globally, where there is a propensity to infect vulnerable people such as the immunocompromised ones. There is increasing evidence of resistance to antifungal drugs, which has significant implications for cutaneous, invasive and bloodstream infections. The World Health Organization (WHO) published a priority list of fungal pathogens in October 2022, thus, highlighting that a crisis point has been reached where there is a pressing need to address the solutions. This review provides a timely insight into the challenges and implications on the topic of antifungal drug resistance along with discussing the effectiveness of established disease mitigation modalities and approaches. There is also a need to elucidate the cellular and molecular mechanisms of fungal resistance to inform effective solutions. The established fungal decontamination approaches are effective for medical device processing and sterilization, but the presence of pathogenic fungi in recalcitrant biofilms can lead to challenges, particularly during cleaning. Future design ideas for implantable and reusable medical devices should consider antifungal materials and appropriates for disinfection, and where it is relevant, sterilization. Preventing the growth of mycotoxin-producing fungi on foods through the use of appropriate end-to-end processes is advisable, as mycotoxins are recalcitrant and challenging to eliminate once they have formed.

Vancomycin-nanofunctionalized peptide-enriched silk fibroin to prevent methicillin-resistant Staphylococcus epidermidis-induced femoral nonunions in rats

Introduction

Implant-related infections and infected fractures are significant burdens in orthopedics. Staphylococcus epidermidis is one of the main causes of bone infections related to biofilm formation upon implants. Current antibiotic prophylaxis/therapy is often inadequate to prevent biofilm formation and results in antibiotic resistance. The development of bioactive materials combining antimicrobial and osteoconductive properties offers great potential for the eradication of microorganisms and for the enhancement of bone deposition in the presence of infections. The purpose of this study is to prevent the development of methicillin-resistant S. epidermidis (MRSE)-infected nonunion in a rat model.

Methods

To this end, a recently developed in our laboratories bioactive material consisting of antibiotic-loaded nanoparticles based on carboxylic acid functionalized hyperbranched aliphatic polyester (CHAP) that are integrated into peptide-enriched silk fibroin sponges with osteoconductive properties (AFN-PSF) was employed, whose biocompatibility and microbiological tests provided proof of its potential for the treatment of both orthopedic and dental infections. In particular, non-critical femoral fractures fixed with plates and screws were performed in Wistar rats, which were then randomly divided into three groups: 1) the sham control (no infection, no treatment); 2) the control group, infected with MRSE and treated with peptide-enriched silk fibroin sponges incorporating non-drug-loaded functionalized nanoparticles (PSF); 3) the treated group, infected with MRSE and treated with peptide-enriched silk fibroin sponges incorporating vancomycin-loaded functionalized nanoparticles (AFN-PSF). After 8 weeks, bone healing and osteomyelitis were clinically assessed and evaluated by micro-CT, microbiological and histological analyses.

Results

The sham group showed no signs of infection and complete bone healing. The PSF group failed to repair the infected fracture, displaying 75% of altered bone healing and severe signs of osteomyelitis. The AFN-PSF treated group reached 70% of fracture healing in the absence of signs of osteomyelitis, such as abscesses in the cortical and intraosseous compartments and bone necrosis with sequestra.

Discussion

AFN-PSF sponges have proven effective in preventing the development of infected nonunion in vivo. The proposed nanotechnology for local administration of antibiotics can have a significant impact on patient health in the case of orthopedic infections.

Roles and current applications of S-nitrosoglutathione in anti-infective biomaterials

Bacterial infections can compromise the physical and biological functionalities of humans and pose a huge economical and psychological burden on infected patients. Nitric oxide (NO) is a broad-spectrum antimicrobial agent, whose mechanism of action is not affected by bacterial resistance. S-nitrosoglutathione (GSNO), an endogenous donor and carrier of NO, has gained increasing attention because of its potent antibacterial activity and efficient biocompatibility. Significant breakthroughs have been made in the application of GSNO in biomaterials. This review is based on the existing evidence that comprehensively summarizes the progress of antimicrobial GSNO applications focusing on their anti-infective performance, underlying antibacterial mechanisms, and application in anti-infective biomaterials. We provide an accurate overview of the roles and applications of GSNO in antibacterial biomaterials and shed new light on the avenues for future studies.

Multifunctional Surface Modification of PDMS for Antibacterial Contact Killing and Drug-Delivery of Polar, Nonpolar, and Amphiphilic Drugs

Medical device-associated infections pose major clinical challenges that emphasize the need for improved anti-infective biomaterials. Polydimethylsiloxane (PDMS), a frequently used elastomeric biomaterial in medical devices, is inherently prone to bacterial attachment and associated infection formation. Here, PDMS surface modification strategy is presented consisting of a cross-linked lyotropic liquid crystal hydrogel microparticle coating with antibacterial functionality. The microparticle coating composed of cross-linked triblock copolymers (diacrylated Pluronic F127) was deposited on PDMS by physical immobilization via interpenetrating polymer network formation. The formed coating served as a substrate for covalent immobilization of a potent antimicrobial peptide (AMP), RRPRPRPRPWWWW-NH2, yielding high contact-killing antibacterial effect against Staphylococcus epidermidis and Staphylococcus aureus. Additionally, the coating was assessed for its ability to selectively host polar, amphiphilic, and nonpolar drugs, resulting in sustained release profiles. The results of this study put forward a versatile PDMS modification strategy for both contact-killing antibacterial surface properties and drug-delivery capabilities, offering a solution for medical device-associated infection prevention.

Designer Liposomic Nanocarriers Are Effective Biofilm Eradicators

Drug delivery via nanovehicles is successfully employed in several clinical settings, yet bacterial infections, forming microbial communities in the form of biofilms, present a strong challenge to therapeutic treatment due to resistance to conventional antimicrobial therapies. Liposomes can provide a versatile drug-vector strategy for biofilm treatment, but are limited by the need to balance colloidal stability with biofilm penetration. We have discovered a liposomic functionalization strategy, using membrane-embedded moieties of poly[2-(methacryloyloxy)ethyl phosphorylcholine], pMPC, that overcomes this limitation. Such pMPCylation results in liposomic stability equivalent to current functionalization strategies (mostly PEGylation, the present gold-standard), but with strikingly improved cellular uptake and cargo conveyance. Fluorimetry, cryo-electron, and fluorescence microscopies reveal a far-enhanced antibiotic delivery to model Pseudomonas aeruginosa biofilms by pMPC-liposomes, followed by faster cytosolic cargo release, resulting in significantly greater biofilm eradication than either PEGylation or free drug. Moreover, this combination of techniques uncovers the molecular mechanism underlying the enhanced interaction with bacteria, indicating it arises from bridging by divalent ions of the zwitterionic groups on the pMPC moieties to the negatively charged lipopolysaccharide chains emanating from the bacterial membranes. Our results point to pMPCylation as a transformative strategy for liposomal functionalization, leading to next-generation delivery systems for biofilm treatment.

Breaching Bacterial Biofilm Barriers: Efficient Combinatorial Theranostics for Multidrug-Resistant Bacterial Biofilms with a Novel Penetration-Enhanced AIEgen Probe

The formation of microbial biofilms is acknowledged as a major virulence factor in a range of persistent local infections. Failures to remove biofilms with antibiotics foster the emergence of antibiotic-resistant bacteria and result in chronic infections. As a result, the construction of effective biofilm-inhibiting and biofilm-eradicating chemicals is urgently required. Herein, we designed a water-soluble probe APDIS for membrane-active fluorescence and broad-spectrum antimicrobial actions, particularly against methicillin-resistant Staphylococcus aureus (MRSA), which shows multidrug resistance. In vitro and in vivo experiments demonstrate its high antibacterial effects comparable to vancomycin. Furthermore, it inhibits biofilm formation by effectively killing planktonic bacteria at low inhibitory concentrations, without toxicity to mammalian cells. More importantly, this probe can efficiently penetrate through biofilm barriers and exterminate bacteria that are enclosed within biofilms and startle existing biofilms. In the mouse model of implant-related biofilm infections, this probe exhibits strong antibiofilm activity against MRSA biofilms, thus providing a novel theranostic strategy to disrupt biofilms in vivo effectively. Our results indicate that this probe has the potential to be used for the development of a combinatorial theranostic platform with synergistic enhanced effects for the treatment of multidrug-resistant bacterial infections and antibiofilm medications.

Molecular Approach for the Laboratory Diagnosis of Periprosthetic Joint Infections

The incidence of total joint arthroplasty is increasing over time since the last decade and expected to be more than 4 million by 2030. As a consequence, the detection of infections associated with surgical interventions is increasing and prosthetic joint infections are representing both a clinically and economically challenging problem. Many pathogens, from bacteria to fungi, elicit the immune system response and produce a polymeric matrix, the biofilm, that serves as their protection. In the last years, the implementation of diagnostic methodologies reduced the error rate and the turn-around time: polymerase chain reaction, targeted or broad-spectrum, and next-generation sequencing have been introduced and they represent a robust approach nowadays that frees laboratories from the unique approach based on culture-based techniques.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

Phenotypic and genotypic characterisation of thymine auxotrophy in Escherichia coli isolated from a patient with recurrent bloodstream infection

INTRODUCTION

Thymine auxotrophic in vitro mutants of Escherichia coli were first reported in the mid-20th century. Later, thymine-dependent clinical strains of E. coli as well as other Enterobacterales, Enterococcus faecalis and Staphylococcus aureus have been recognized as the cause of persistent and recurrent infections.

OBJECTIVES

The aim of this study was to characterize the phenotype and investigate the molecular basis of thymine auxotrophy in ten E. coli isolates obtained at different time points from a patient with recurrent bloodstream infection (BSI) due to a chronic aortic graft infection treated with Trimethoprim/sulfamethoxazole (TMP-SMX).

METHODS

Clinical data was obtained from hospital records. Growth characterization and antimicrobial susceptibility testing to TMP-SMX was performed on M9 agar and in MH broth with different thymine concentrations (0.5, 2, 5, 10 and 20 μg/mL), on Mueller-Hinton (MH) and blood agar. Whole genome sequencing (WGS) was performed on all E. coli isolates.

RESULTS

E. coli were isolated from ten consecutive BSI episodes from a patient with chronic aortic graft infection. Six of these isolates were resistant to TMP-SMX when assayed on blood agar. Growth experiments with added thymine confirmed that these isolates were thymine-dependent (thy-), and revealed growth defects (slower growth rate and smaller colony size) in these isolates relative to thy+ isolates (n = 4). WGS indicated that all isolates were of the same clonal lineage of sequence type 7358. Genomic analysis revealed a G172C substitution in thyA in all TMP-SMX resistant isolates, while mutations affecting genes involved in the deoxyribose salvage pathway (deoB and deoC) were identified in eight isolates.

CONCLUSION

This case highlights the risk of resistance development to TMP-SMX, especially for long-term treatment, and the possible pitfalls in detection of growth-deficient subpopulations from chronic infections, which could lead to treatment failure.

The Current Knowledge on the Pathogenesis of Tissue and Medical Device-Related Biofilm Infections

Biofilm is the trigger for the majority of infections caused by the ability of microorganisms to adhere to tissues and medical devices. Microbial cells embedded in the biofilm matrix are highly tolerant to antimicrobials and escape the host immune system. Thus, the refractory nature of biofilm-related infections (BRIs) still represents a great challenge for physicians and is a serious health threat worldwide. Despite its importance, the microbiological diagnosis of a BRI is still difficult and not routinely assessed in clinical microbiology. Moreover, biofilm bacteria are up to 100–1000 times less susceptible to antibiotics than their planktonic counterpart. Consequently, conventional antibiograms might not be representative of the bacterial drug susceptibility in vivo. The timely recognition of a BRI is a crucial step to directing the most appropriate biofilm-targeted antimicrobial strategy.

The Role of Abdominal Drain Cultures in Managing Abdominal Infections

Intra-abdominal infections (IAI) are common in hospitalized patients, both in and outside of the intensive care unit. Management principles include antimicrobial therapy and source control. Typically, these infections are polymicrobial, and intra-operative samples will guide the targeted antimicrobial therapy. Although the use of prophylactic abdominal drains in patients undergoing abdominal surgery is decreasing, the use of drains to treat IAI, both in surgical and non-surgical strategies for abdominal infection, is increasing. In this context, samples from abdominal drains are often used to assist in antimicrobial decision making. In this narrative review, we provide an overview of the current role of abdominal drains in surgery, discuss the importance of biofilm formation in abdominal drains and the mechanisms involved, and review the clinical data on the use of sampling these drains for diagnostic purposes. We conclude that biofilm formation and the colonization of abdominal drains is common, which precludes the use of abdominal fluid to reliably diagnose IAI and identify the pathogens involved. We recommend limiting the use of drains and, when present, avoiding routine microbiological sampling.

Environmental, Microbiological, and Immunological Features of Bacterial Biofilms Associated with Implanted Medical Devices

The spread of biofilms on medical implants represents one of the principal triggers of persistent and chronic infections in clinical settings, and it has been the subject of many studies in the past few years, with most of them focused on prosthetic joint infections. We review here recent works on biofilm formation and microbial colonization on a large variety of indwelling devices, ranging from heart valves and pacemakers to urological and breast implants and from biliary stents and endoscopic tubes to contact lenses and neurosurgical implants. We focus on bacterial abundance and distribution across different devices and body sites and on the role of environmental features, such as the presence of fluid flow and properties of the implant surface, as well as on the interplay between bacterial colonization and the response of the human immune system.

Evaluation of antibiofilm potential of four-domain α-amylase from Streptomyces griseus against exopolysaccharides (EPS) of bacterial pathogens using Danio rerio

Biofilm formation is a major issue in healthcare settings as 75% of nosocomial infection arises due to biofilm residing bacteria. Exopolysaccharides (EPS), a key component of the biofilm matrix, contribute to the persistence of cells in a complex milieu and defends greatly from exogenous stress and demolition. It has been shown to be vital for biofilm scaffold and pathogenic features. The present study was aimed to investigate the effectiveness of four domain-containing α-amylase from Streptomyces griseus (SGAmy) in disrupting the EPS of multidrug-resistant bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. In vitro analysis of preformed biofilm unveiled the antibiofilm efficacy of SGAmy against MRSA (85%, p < 0.05) and P. aeruginosa (82%, p < 0.05). The total carbohydrate content in the EPS matrix of MRSA and P. aeruginosa was significantly reduced to 71.75% (p < 0.01) and 74.09% (p < 0.01), respectively. The findings inferred from in vitro analysis were further corroborated through in vivo studies using an experimental model organism, Danio rerio. Remarkably, the survival rate was extended to 88.8% (p < 0.05) and 74.2% (p < 0.05) in MRSA and P. aeruginosa infected fishes, respectively. An examination of gills, kidneys, and intestines of D. rerio organs depicted the reduced level of microbial colonization in SGAmy-treated cohorts and these findings were congruent with bacterial enumeration results.

Antimicrobial coating strategy to prevent orthopaedic device-related infections: recent advances and future perspectives

The rapid development of multidrug-resistant (MDR) bacteria and biofilm-related infections (BRIs) has urgently called for new strategies to combat severe orthopaedic device-related infections (ODRIs). Antimicrobial coating has emerged as a promising strategy in halting the incidence of ODRIs and treating ODRIs in long term. With the advancement of material science and biotechnology, numerous antimicrobial coatings have been reported in literature, showing superior antimicrobial and osteogenic functions. This review has specifically discussed the currently developed antimicrobial coatings in the perspective of drug release from the coating system, focusing on their realization of controlled and on demand antimicrobial agents release, as well as multi-functionality. Acknowledging the multidisciplinary nature of antimicrobial coating, the conceptual design, the deposition method and the therapeutic effect of the antimicrobial coatings have been described in detail and discussed critically. Particularly, the challenges and opportunities on the way toward the clinical translation of antimicrobial coatings have been highlighted.