Preventing Pseudomonas aeruginosa Biofilms on Indwelling Catheters by Surface-Bound Enzymes

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

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

Study on PTFE superhydrophobic coating modified by IC@dMSNs and its enhanced antibacterial effect

INTRODUCTION

Vascular catheter-related infections and thrombosis are common and may lead to serious complications after catheterization. Reducing the incidence of such infections has become a significant challenge.

OBJECTIVES

This study aims to develop a super hydrophobic nanocomposite drug-loaded vascular catheter that can effectively resist bacterial infections and blood coagulation.

METHODS

In this study, a SiO2 nanocoated PTFE (Polytetrafluoroethylene) catheter (PTFE-SiO2) was prepared and further optimized to prepare a SiO2 nanocoated PTFE catheter loaded with imipenem/cilastatin sodium (PTFE-IC@dMSNs). The catheters were characterized for performance, cell compatibility, anticoagulant performance, in vitro and in vivo antibacterial effect and biological safety.

RESULTS

PTFE-IC@dMSNs catheter has efficient drug loading performance and drug release rate and has good cell compatibility and anticoagulant effect in vitro. Compared with the PTFE-SiO2 catheter, the inhibition ring of the PTFE-IC@dMSNs catheter against Escherichia coli increased from 3.98 mm2 to 4.56 mm2, and the antibacterial rate increased from about 50.8 % to 56.9 %, with a significant difference (p < 0.05). The antibacterial zone against Staphylococcus aureus increased from 8.63 mm2 to 11.74 mm2, and the antibacterial rate increased from approximately 83.5 % to 89.3 %, showing a significant difference (p < 0.05). PTFE-IC@dMSNs catheter also has good biocompatibility in vivo. Furthermore, the PTFE-IC@dMSNs catheter can reduce the adhesion of blood cells and have excellent anticoagulant properties, and even maintain these properties even with the addition of imipenem/cilastatin sodium.

CONCLUSION

Compared with PTFE, PTFE-SiO2 and PTFE-IC@dMSNs catheters have good characterization performance, cell compatibility, and anticoagulant properties. PTFE SiO2 and PTFE-IC@dMSNs catheters have good antibacterial performance and tissue safety against E. coli and S. aureus. Relatively, PTFE-SiO2 and PTFE-IC@dMSNs catheter has better antibacterial properties and histocompatibility and has potential application prospects in anti-bacterial catheter development and anticoagulation.

Chemical multiscale robotics for bacterial biofilm treatment

A biofilm constitutes a bacterial community encased in a sticky matrix of extracellular polymeric substances. These intricate microbial communities adhere to various host surfaces such as hard and soft tissues as well as indwelling medical devices. These microbial aggregates form a robust matrix of extracellular polymeric substances (EPSs), leading to the majority of human infections. Such infections tend to exhibit high resistance to treatment, often progressing into chronic states. The matrix of EPS protects bacteria from a hostile environment and prevents the penetration of antibacterial agents. Modern robots at nano, micro, and millimeter scales are highly attractive candidates for biomedical applications due to their diverse functionalities, such as navigating in confined spaces and targeted multitasking. In this tutorial review, we describe key milestones in the strategies developed for the removal and eradication of biofilms using robots of different sizes and shapes. It can be seen that robots at different scales are useful and effective tools for treating bacterial biofilms, thus preventing persistent infections, the loss of costly implanted medical devices, and additional costs associated with hospitalization and therapies.

Fluoride anodic films on stainless-steel fomites to reduce transmission infections

The growing concern arising from viruses with pandemic potential and multi-resistant bacteria responsible for hospital-acquired infections and outbreaks of food poisoning has led to an increased awareness of indirect contact transmission. This has resulted in a renewed interest to confer antimicrobial properties to commonly used metallic materials. The present work provides a full characterization of optimized fluoride anodic films grown in stainless steel 304L as well as their antimicrobial properties. Antibacterial tests show that the anodic film, composed mainly of chromium and iron fluorides, reduces the count and the percentage of the area covered by 50% and 87.7% for Pseudomonas aeruginosa and Stenotrophomonas maltophilia, respectively. Virologic tests show that the same treatment reduces the infectivity of the coronavirus HCoV-229E-GFP, in comparison with the non-anodized stainless steel 304L.IMPORTANCEThe importance of environmental surfaces as a source of infection is a topic of particular interest today, as many microorganisms can survive on these surfaces and infect humans through direct contact. Modification of these surfaces by anodizing has been shown to be useful for some alloys of medical interest. This work evaluates the effect of anodizing on stainless steel, a metal widely used in a variety of applications. According to the study, the fluoride anodic layers reduce the colonization of the surfaces by both bacteria and viruses, thus reducing the risk of acquiring infections from these sources.

Synergistic and Additive Effects of Menadione in Combination with Antibiotics on Multidrug-Resistant Staphylococcus aureus: Insights from Structure-Function Analysis of Naphthoquinones

Antimicrobial resistance (AMR) interferes with the effective treatment of infections and increases the risk of microbial spread and infection-related illness and death. The synergistic activities of combinations of antimicrobial compounds offer satisfactory approaches to some extent. Structurally diverse naphthoquinones (NQs) including menadione (-CH3 group at C2) exhibit substantial antimicrobial activities against multidrug-resistant (MDR) pathogens. We explored the combinations of menadione with antibiotic ciprofloxacin or ampicillin against Staphylococcus aureus and its biofilms. We found an additive (0.590 %) were also observed. However, preformed biofilms were not affected. Dent formation was also evident in S. aureus treated with the test compounds. The structure-function relationship (SFR) of NQs was used to determine and predict their activity pattern against pathogens. Analysis of 10 structurally distinct NQs revealed that the compounds with -Cl, -Br, -CH3 , or -OH groups displayed the lowest MICs (32-256 μg/mL). Furthermore, 1,4-NQs possessing a halogen or -CH3 moiety showed elevated ROS activity, whereas molecules with an -OH group affected cell integrity. Improved activity of antimicrobial combinations and SFR approaches are significant in antimicrobial therapies.

Pseudomonas aeruginosa biofilm exopolysaccharides: assembly, function, and degradation

The biofilm matrix is a fortress; sheltering bacteria in a protective and nourishing barrier that allows for growth and adaptation to various surroundings. A variety of different components are found within the matrix including water, lipids, proteins, extracellular DNA, RNA, membrane vesicles, phages, and exopolysaccharides. As part of its biofilm matrix, Pseudomonas aeruginosa is genetically capable of producing three chemically distinct exopolysaccharides - alginate, Pel, and Psl - each of which has a distinct role in biofilm formation and immune evasion during infection. The polymers are produced by highly conserved mechanisms of secretion, involving many proteins that span both the inner and outer bacterial membranes. Experimentally determined structures, predictive modelling of proteins whose structures are yet to be solved, and structural homology comparisons give us insight into the molecular mechanisms of these secretion systems, from polymer synthesis to modification and export. Here, we review recent advances that enhance our understanding of P. aeruginosa multiprotein exopolysaccharide biosynthetic complexes, and how the glycoside hydrolases/lyases within these systems have been commandeered for antimicrobial applications.

Extracellular matrix-degrading enzymes as a biofilm control strategy for food-related microorganisms

Biofilm is one of the major problems in food industries and is difficult to be removed or prevented by conventional sanitizers. In this review, we discussed the extracellular matrix-degrading enzymes as a strategy to control biofilms of foodborne pathogenic and food-contaminating bacteria. The biofilms can be degraded by using the enzymes targeting proteins, polysaccharides, extracellular DNA, or lipids which mainly constitute the extracellular polymeric substances of biofilms. However, the efficacy of enzymes varies by the growth medium, bacterial species, strains, or counterpart microorganisms due to a high variation in the composition of extracellular polymeric substances. Several studies demonstrated that the combined treatment using conventional sanitizers or multiple enzymes can synergistically enhance the biofilm removal efficacies. In this review, the application of the immobilized enzymes on solid substrates is also discussed as a potential strategy to prevent biofilm formation on food contact surfaces.

Drug delivery strategies for antibiofilm therapy

Although new antibiofilm agents have been developed to prevent and eliminate pathogenic biofilms, their widespread clinical use is hindered by poor biocompatibility and bioavailability, unspecific interactions and insufficient local concentrations. The development of innovative drug delivery strategies can facilitate penetration of antimicrobials through biofilms, promote drug dispersal and synergistic bactericidal effects, and provide novel paradigms for clinical application. In this Review, we discuss the potential benefits of such emerging techniques for improving the clinical efficacy of antibiofilm agents, as well as highlighting the existing limitations and future prospects for these therapies in the clinic.

Understanding and Implementing Diagnostic Stewardship: A Guide for Resident Physicians in the Era of Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a significant global health challenge, exacerbated by the COVID-19 pandemic. Antimicrobial stewardship programs (ASPs) are crucial in managing this crisis, with diagnostic stewardship (DS) emerging as a key component. DS refers to the appropriate use of diagnostic tests to optimize patient outcomes, improve antimicrobial use, and combat multi-drug-resistant (MDR) organisms. Despite its potential, understanding and application of DS remain ambiguous in multiple respects, which, however, do not directly implicate the implementation of such initiatives. DS is particularly important for resident physicians who are often at the forefront of patient care and can significantly influence future AMR strategies. This review provides a comprehensive overview of DS, discussing its importance, potential challenges, and future directions. It emphasizes the need for resident physicians to understand DS principles and integrate them into their clinical practice from the beginning of their careers. The review also highlights the role of various stakeholders in implementing DS and the importance of continuous education and training. Ultimately, DS is not just a clinical tool but a philosophy of care, essential for a more responsive, humane, and effective healthcare system.

Hydrogen peroxide from L-amino acid oxidase of king cobra (Ophiophagus hannah) venom attenuates Pseudomonas biofilms

Because of the high incidence of Pseudomonas aeruginosa biofilms-related nosocomial infections, venoms from common Thai snakes were tested. Although venoms from king cobra (Ophiophagus hannah; OH) and green pit viper (Trimeresurus albolabris) showed the broadest antibacterial spectrum, OH venom demonstrated more profound anti-biofilm activities against P. aeruginosa. Additionally, purified L-amino acid oxidase from OH venom (OH-LAAO), using a three-step chromatography and protein identification, reduced biofilm mass as indicated by the downregulation of several genes, including the genes for biofilm synthesis (algD and pslB) and biofilm regulators (algU, gacA, and siaD). Moreover, OH-LAAO disrupted Pseudomonas-preformed biofilms via upregulation of several genes for biofilm dispersion (nbdA, bdlA, and dipA) and biofilm degradation (endA and pslG), resulting in a reduction of the biofilm biomass. Due to the antimicrobial effects and anti-biofilm activities (reduced production plus increased dispersion) neutralized by catalase, a hydrogen peroxide (H₂O₂)-degrading enzyme, the enhanced H₂O₂ by OH venom might be one of the anti-biofilm mechanisms. Hence, OH-LAAO was proposed as a novel agent against Pseudomonas biofilms for either treatment or prevention. More studies are interesting.

How Three Self-Secreted Biofilm Exopolysaccharides of Pseudomonas aeruginosa, Psl, Pel, and Alginate, Can Each Be Exploited for Antibiotic Adjuvant Effects in Cystic Fibrosis Lung Infection

In cystic fibrosis (CF), pulmonary infection with Pseudomonas aeruginosa is a cause of increased morbidity and mortality, especially in patients for whom infection becomes chronic and there is reliance on long-term suppressive therapies. Current antimicrobials, though varied mechanistically and by mode of delivery, are inadequate not only due to their failure to eradicate infection but also because they do not halt the progression of lung function decline over time. One of the reasons for this failure is thought to be the biofilm mode of growth of P. aeruginosa, wherein self-secreted exopolysaccharides (EPSs) provide physical protection against antibiotics and an array of niches with resulting metabolic and phenotypic heterogeneity. The three biofilm-associated EPSs secreted by P. aeruginosa (alginate, Psl, and Pel) are each under investigation and are being exploited in ways that potentiate antibiotics. In this review, we describe the development and structure of P. aeruginosa biofilms before examining each EPS as a potential therapeutic target for combating pulmonary infection with P. aeruginosa in CF, with a particular focus on the current evidence for these emerging therapies and barriers to bringing these therapies into clinic.

Enzymatic Dispersion of Biofilms: An Emerging Biocatalytic Avenue to Combat Biofilm-Mediated Microbial Infections

Drug resistance by pathogenic microbes has emerged as a matter of great concern to mankind. Microorganisms such as bacteria and fungi employ multiple defense mechanisms against drugs and the host immune system. A major line of microbial defense is the biofilm, which comprises extracellular polymeric substances that are produced by the population of microorganisms. Around 80% of chronic bacterial infections are associated with biofilms. The presence of biofilms can increase the necessity of doses of certain antibiotics up to 1000-fold to combat infection. Thus, there is an urgent need for strategies to eradicate biofilms. Although a few physicochemical methods have been developed to prevent and treat biofilms, these methods have poor efficacy and biocompatibility. In this review, we discuss the existing strategies to combat biofilms and their challenges. Subsequently, we spotlight the potential of enzymes, in particular, polysaccharide degrading enzymes, for biofilm dispersion, which might lead to facile antimicrobial treatment of biofilm-associated infections.