African Plant-Based Natural Products with Antivirulence Activities to the Rescue of Antibiotics.

Investigation of bacterial attachment and biofilm formation of two different Pseudoalteromonas species: Comparison of different methods

Biofilm formation at oil-water interfaces is not a simple function of bacterial hydrophobicity

In addition to specific antibiotic resistance, the formation of bacterial biofilm causes another level of complications in attempts to eradicate pathogenic or harmful bacteria, including difficult penetration of drugs through biofilm structures to bacterial cells, impairment of immunological response of the host, and accumulation of various bioactive compounds (enzymes and others) affecting host physiology and changing local pH values, which further influence various biological functions. In this review article, we provide an overview on the formation of bacterial biofilm and its properties, and then we focus on the possible use of phage-derived depolymerases to combat bacterial cells included in this complex structure. On the basis of the literature review, we conclude that, although these bacteriophage-encoded enzymes may be effective in destroying specific compounds involved in the formation of biofilm, they are rarely sufficient to eradicate all bacterial cells. Nevertheless, a combined therapy, employing depolymerases together with antibiotics and/or other antibacterial agents or factors, may provide an effective approach to treat infections caused by bacteria able to form biofilms.

Infection of medical polymers is often caused by bacterial adherence and bio-film formation, and it is one of the major clinical complications causing a high rate of mortality and morbidity. In this study, it was investigated that differences of organic and inorganic antimicrobial reagents incorporated into polymers for bacterial adherence and bio-film formation. Our experimental results show adhesion of bacteria and bio-film (gram positive Staphylococcus aureus and gram negative Escherichia coli) are evidently reduced by adding organic antimicrobial reagents into PVC. However, inorganic antimicrobial reagents can not make much difference in bacterial bio-film formation on their polymers' surface. Although the surface containing inorganic antimicrobial reagents has excellent ability in killing bacteria, the amount of Escherichia coli on samples surface is no less than that on the control sample during bacterial adhesion due to both various hydrophilicity and different antibacterial mechanisms on the surface. Furthermore, bacterial bio-film formation on various hydrophilic samples is investigated, and it is observed that organic and inorganic antimicrobial compounds have much different effect on surface hydrophilicity. As a result, hydrophilicity becomes a major factor for bacterial adhesion and bio-film.

Comprehensive SummaryImplantable medical device‐associated infections (DAIs) originating from bacterial adhesion and biofilm formation have threatened to the health and life of patients. Antibacterial polymer coatings with antifouling and/or bactericidal properties have showed great potentials to combat DAI issues. In this review, we report recent advances in antibacterial polymer coatings fighting bacterial adhesion and biofilm formation on implantable biomaterial surfaces. We summarize the mechanisms of bacterial adhesion and biofilm formation, which provides guidance for the design of antibacterial coatings. We describe the polymer and coating preparation methods and discuss the structure‐property relationships of antibacterial polymer coatings. Applications of these polymer coatings in medical catheters, orthopaedic implants, and other applications are elaborated. Future challenges and prospects associated with antibacterial polymer coatings for implantable medical devices are discussed.

Biofilms play an important role in many chronic bacterial infections. Production of an extracellular mixture of sugar polymers called exopolysaccharide is characteristic and critical for biofilm formation. However, there is limited information about the mechanisms involved in the biosynthesis and modification of exopolysaccharide components and how these processes influence bacterial pathogenesis. Staphylococcus epidermidis is an important human pathogen that frequently causes persistent infections by biofilm formation on indwelling medical devices. It produces a poly-N-acetylglucosamine molecule that emerges as an exopolysaccharide component of many bacterial pathogens. Using a novel method based on size exclusion chromatography-mass spectrometry, we demonstrate that the surface-attached protein IcaB is responsible for deacetylation of the poly-N-acetylglucosamine molecule. Most likely due to the loss of its cationic character, non-deacetylated poly-acetylglucosamine in an isogenic icaB mutant strain was devoid of the ability to attach to the bacterial cell surface. Importantly, deacetylation of the polymer was essential for key virulence mechanisms of S. epidermidis, namely biofilm formation, colonization, and resistance to neutrophil phagocytosis and human antibacterial peptides. Furthermore, persistence of the icaB mutant strain was significantly impaired in a murine model of device-related infection. This is the first study to describe a mechanism of exopolysaccharide modification that is indispensable for the development of biofilm-associated human disease. Notably, this general virulence mechanism is likely similar for other pathogenic bacteria and constitutes an excellent target for therapeutic maneuvers aimed at combating biofilm-associated infection.

Biofilm Formation on Clinically Noninfected Penile Prostheses

Background and purpose Efforts to prevent infection of arthroplasties, including the use of antibiotic-loaded bone cement, are not always successful. We investigated whether the incorporation of chitosan in gentamicin-loaded bone cement increases antibiotic release, and prevents bacterial adherence and biofilm formation by clinical isolates of Staphylococcus spp. In addition, we performed mechanical and degradation tests.Methods Different amounts of chitosan were added to the powder of the gentamicin-loaded bone cement. Gentamicin release was determined using high-per-formance liquid chromatography mass spectrometry. Bacterial adherence and bacterial biofilm formation were determined using clinical isolates cultured from implants retrieved at revision hip surgery. The mechanical properties were determined as a function of degradation in accordance with ISO and ASTM standards for PMMA bone cement.Results The addition of chitosan to bone cement loaded with gentamicin reduced gentamicin release and did not increase the efficacy of the bone cement in preventing bacterial colonization and biofilm formation. Moreover, the mechanical performance of cement containing chitosan was reduced after 28 days of degradation. The compressive and bending strengths were not in compliance with the minimum ISO and ASTM requirements.Interpretation Clinically, incorporation of chitosan into gentamicin-loaded bone cement for use in joint replacement surgery has no antimicrobial benefit and the detrimental effect on mechanical properties may have an adverse effect on the longevity of the prosthetic joint.

Chamaecyparis obtusa (C. obtusa) is known to have antimicrobial effects and has been used as a medicinal plant and in forest bathing. This study aimed to evaluate the anticariogenic activity of essential oil of C. obtusa on Streptococcus mutans, which is one of the most important bacterial causes of dental caries and dental biofilm formation. Essential oil from C. obtusa was extracted, and its effect on bacterial growth, acid production, and biofilm formation was evaluated. C. obtusa essential oil exhibited concentration-dependent inhibition of bacterial growth over 0.025 mg/mL, with 99% inhibition at a concentration of 0.2 mg/mL. The bacterial biofilm formation and acid production were also significantly inhibited at the concentration greater than 0.025 mg/mL. The result of LIVE/DEAD® BacLight™ Bacterial Viability Kit showed a concentration-dependent bactericidal effect on S. mutans and almost all bacteria were dead over 0.8 mg/mL. Real-time PCR analysis showed that gene expression of some virulence factors such as brpA, gbpB, gtfC, and gtfD was also inhibited. In GC and GC-MS analysis, the major components were found to be α-terpinene (40.60%), bornyl acetate (12.45%), α-pinene (11.38%), β-pinene (7.22%), β-phellandrene (3.45%), and α-terpinolene (3.40%). These results show that C. obtusa essential oil has anticariogenic effect on S. mutans.

ObjectiveTo analyze the bacterial biofilm (BF) formation in patients with malignancy undergoing double J stent indwelling and its influencing factors.MethodsA total of 167 patients with malignant tumors who received double J stent indwelling in the hospital from January 2018 to January 2021 were included in the study. The urine and double J stent samples were collected for bacterial identification and observed for BF formation on the surface of the urinary catheter under a scanning electron microscope (SEM). Univariate and multivariate logistic regression analyses were used to analyze the influencing factors of BF.ResultsThe BF formation rate was 34.73% (58/167). The BF formation rate of positive specimens cultured in urine and double J stent was significantly higher than that of negative ones (P<0.05). Staphylococcus was the main BF bacteria in double J stent and urine culture specimens, followed by Enterococcus, Pseudomonas, Enterobacter, and Acinetobacter. Compared with the non-BF group, the number of viable bacteria in the double J stent and urine and the catheterization time in the BF group rose markedly (P<0.05). Advanced age, chemotherapy, anemia, indwelling time ≥90d, and urinary tract infection were risk factors for BF formation in patients with malignancy undergoing double J stent indwelling (P<0.05).ConclusionThere is a high rate of BF formation in patients with malignancy undergoing double J stent indwelling, with Staphylococcus as the dominant species. Treatment requires enhanced urinary catheter management and nutritional status to inhibit BF formation and lower the rate of urinary catheter-related infections.

Bacterial biofilm formation is one of the dynamic processes, which facilitates bacteria cells to attach to a surface and accumulate as a colony. With the help of biofilm formation, pathogenic bacteria can survive by adapting to their external environment. These bacterial colonies have several resistance properties with a higher survival rate in the environment. Especially, pathogenic bacteria can grow as biofilms and can be protected from antimicrobial compounds and other substances. In aquaculture, biofilm formation by pathogenic bacteria has emerged with an increased infection rate in aquatic animals. Studies show that Vibrio anguillarum, V. parahaemolyticus, V. alginolyticus, V. harveyi, V. campbellii, V. fischeri, Aeromonas hydrophila, A. salmonicida, Yersinia ruckeri, Flavobacterium columnare, F. psychrophilum, Piscirickettsia salmonis, Edwardsiella tarda, E. ictaluri, E. piscicida, Streptococcus parauberis, and S. iniae can survive in the environment by transforming their planktonic form to biofilm form. Therefore, the present review was intended to highlight the principles behind biofilm formation, major biofilm-forming pathogenic bacteria found in aquaculture systems, gene expression of those bacterial biofilms and possible controlling methods. In addition, the possibility of these pathogenic bacteria can be a serious threat to aquaculture systems.

Event Abstract Back to Event Inhibition of bacterial adhesion and biofilm formation by antimicrobial functionalized textured biomaterial surfaces Lichong Xu1, Yaqi Wo2, Mark E. Mayerhoffb2, Zhicheng Tian3, Harry Allcock3 and Christopher A. Siedlecki1, 4 1 Penn State College of Medicine, Department of Surgery, United States 2 University of Michigan, Department of Chemistry, United States 3 The Pennsylvania State University, Department of Chemistry, United States 4 Penn State College of Medicine, Department of Bioengineering, United States Introduction: Infection due to bacterial adhesion and biofilm formation represetns a major drawback to the use of blood-contacting devices. Previously we have developed textured polyurethane biomaterials for reducing bacterial adhesion and inhibiting biofilm formation. In this work, we applied the texturing pattern to functionalized polymers bearing antimicrobial properties, and show a combination of antimicrobial functionalization and physical approaches can produce additive effects on biological responses and enhance the hemocompatibility of biomaterials. Material and Methods: Carbosil polyurethane (PU, 2080A) and phosphazene polymers (trifluoroethoxy (TFE), crosslinakble trifluoroethoxy (XLTFE), and octafluoropentoxy (OFP)) were textured with ordered arrays of pillars using a soft lithography two-stage replication molding technique[1]. The Carbosil polyurethane material was doped with S-nitroso-N-acetylpenicillamine (SNAP) with different contents of SNAP in PU (5, 10, and 15 wt%) for nitric oxide (NO) release[2]. Antimicrobial properties of materials were evaluated by the optical density (OD600) of microbial cultures incubated with materials and strain S. epidermidis RP62A. Bacterial adhesion and biofilm formation on material surfaces were carried out in a multiwell plate or rotating disk system (RDS)[1] with same strain. Bacterial adhesion was counted under a fluorescent optical microscope. To observe biofilm formation, samples were in incubated in multiwell plates under static condition for 2 days or RDS system under shear for 8 days. Samples were stained with FTIC conjugated wheat germ agglutinin, and biofilm observed by fluorescence. Results and Discussion: Characterization of biomaterial surfaces: AFM images showed material surfaces textured with ordered arrays of pillars, as expected, except for TFE and XLTFE materials that were difficult to texture.Water contact angle measurements show surface hydrophobicity increased after texturing due to entrapped air. Antimicrobial properties of materials:The optical densities of culture media indicate the growth of bacteria in the presence of a variety of polymers (Fig. 1). Carbosil PU 0% SNAP and PUU films show the similar optical density as that of control (no polymers). Significant inhibition of bacterial growth was observed in the cultures for Carbosil 10% and 15% SNAP polymers, indicating NO release inhibits the growth of bacteria. A slight decrease of OD600 was observed for all phosphazene polymers. Fig. 1 Optical density of culture media indicating antimicrobial properties of polymers. Bacterial adhesion on functionalized textured polymer surfaces: Higher bacterial adhesion was observed on smooth surfaces without functionalization (Fig. 2). Surface texturing with pattern decreased bacterial adhesion on all surfaces, except for TFE and XLTFE polymers, indicating the importance of surface texturing in inhibiting adhesion. Furthermore, a significant decrease in adhesion was observed on textured PU surfaces containing 10% or 15% SNAP as well as on OFP textured surfaces, suggesting antimicrobial functionalization and texturing produce a synergistic effect on inhibiting bacterial adhesion, as the OFP polymer alone inhibited bacterial growth only slightly. Fig. 2 Bacterial adhesion on polymer surface in PBS for 1 hr at 37°C under static condition. Biofilm formation: Under static condition, biofilms were observed on Carbosil PU surfaces containing 0% SNAP and 5% SNAP after 2 days, while no biofilms were observed on surfaces containing 10% and 15% SNAP. Under shear stresses, no biofilms were observed on smooth or textured PU surfaces containing 15% SNAP after 8 days. Long term exposure experiments for biofilm formation on functionalized textured surfaces are on-going. Fig. 3 Biofilm on textured 500/500 nm patterned surfaces containing (a) 0% SNAP, (b) 15% SNAP under static condition for 2 days, and (c) 15% SNAP under shear for 8 days. Conclusion: A combination of antimicrobial functionalization of polymers and surface texturing provided an improved approach to inhibiting bacterial adhesion and biofilm formation, and thus to potentially preventing biomaterial related infections.

Human β-defensin 3 inhibits antibiotic-resistant Staphylococcus biofilm formation

S-adenosylhomocysteine nucleosidase (MTAN) is a protein that plays a crucial role in several pathways of bacteria that are essential for its survival and pathogenesis. In addition to the role of MTAN in methyl-transfer reactions, methionine biosynthesis, and polyamine synthesis, MTAN is also involved in bacterial quorum sensing (QS). In QS, chemical signaling autoinducer (AI) secreted by bacteria assists cell to cell communication and is regulated in a cell density-dependent manner. They play a significant role in the formation of bacterial biofilm. MTAN plays a major role in the synthesis of these autoinducers. Signaling molecules secreted by bacteria, i.e., AI-1 are recognized as acylated homoserine lactones (AHL) that function as signaling molecules within bacteria. QS enables bacteria to establish physical interactions leading to biofilm formation. The formation of biofilm is a primary reason for the development of multidrug-resistant properties in pathogenic bacteria like Enterococcus faecalis (E. faecalis). In this regard, inhibition of E. faecalis MTAN (EfMTAN) will block the QS and alter the bacterial biofilm formation. In addition to this, it will also block methionine biosynthesis and many other critical metabolic processes. It should also be noted that inhibition of EfMTAN will not have any effect on human beings as this enzyme is not present in humans. This review provides a comprehensive overview of the structural-functional relationship of MTAN. We have also highlighted the current status, enigmas that warrant further studies, and the prospects for identifying potential inhibitors of EfMTAN for the treatment of E. faecalis infections. In addition to this, we have also reported structural studies of EfMTAN using homology modeling and highlighted the putative binding sites of the protein.

Abstract: Biofilm formation often has detrimental effects from clinical and industrial perspectives. They are found to be resistant to antibiotics, detergents, etc., causing their treatment and cure to be onerous. Therefore, it becomes a necessity to develop novel methods to inhibit it. Iron is an essential regulator of bacterial biofilm formation. Studies suggest that by modulating iron concentration using either iron-chelating substances or iron salts, biofilm inhibition can be achieved depending on the mechanism of biofilm formation. This approach inhibits the expression of several genes responsible for adherence and colonization of bacteria. The use of nanoparticles is gaining rapid interest for biofilm inhibition. The ability of nanoparticles to act as antibacterial agents depends on their surface-to-mass ratio. Owing to their small size, certain metal nanoparticles can penetrate the EPS and inhibit bacterial adhesion and biofilm formation. Nanoparticles (NP) bring about cell lysis by interacting with cell membranes or producing Reactive Oxygen Species (ROS). Owing to the mechanical, thermal, or physiochemical properties of nanocomposite material, it is also studied for biofilm inhibition in various organisms. A widely appreciated method of NP synthesis is green synthesis, which makes use of plant extracts and microorganisms. Interestingly, plant extracts inherently are known to possess antimicrobial and anti-biofilm effects owing to their bioactive compounds. Plants synthesize secondary metabolites such as steroids, terpenoids, alkaloids, quinones, tannins, flavonoids, etc., for their defense, pollination, flavor, etc. Plant extracts made using appropriate solvents can be used to inhibit biofilm formed on various surfaces. They have been known to reduce biofilm by hindering exopolysaccharide formation and quorum sensing. In this review, we aim to describe these potential methods of biofilm inhibition.