Biofilm consortia on biomedical and biological surfaces: delivery and targeting strategies

Evaluation of Antibiofilm and Antiquorum Sensing Activities of Fucoidan Characterized from Padina boryana against Nosocomial Pathogens

Modern functional chemicals that can be employed in biotechnology, pharmaceutics, and food science are a sustainable source to be found in seaweeds. The bioactivity of the majority of these marine compounds has received scant research. Fucoidan is a highly sulfated polysaccharide with a range of bioactivities, including an antipathogenic effect. There is still much to learn about the relationship between fucoidan structure and its function in pathogen infections. By employing microwave and probe sonication to create crude fucoidan, DEAE-cellulose anion-exchange chromatography was used to further purify the substance. Purified fucoidan was structurally characterized using UV-Visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and NMR analysis. The results of the structural analysis demonstrate that sulfates and hydroxyl groups are present in the isolated fucoidan. There are fucose residues, according to the NMR data. The present study investigates the bioactivity of fucoidan, a polysaccharide derived from the brown algae Padina boryana, as a potent weapon against the known nosocomial diseases Proteus vulgaris and Salmonella enterica. Fluorescence microscopy was used to show that fucoidan antibiofilm action is totally effective against Proteus vulgaris and Salmonella enterica biofilm formations as well as planktonic cell growths at dosages over 25 g/mL. Here, using in vitro investigations of the possible inactivation of molecules that are regulated by acyl-homoserine lactone (AHL) in both bacterial species, we explore the antiquarum sensing and antibiofilm capabilities of fucoidan. According to the present study, extracted fucoidan from Padina boryana can be used to generate antibacterial compounds and operate as a quorum-sensing inhibitor to combat side effects and antibiotic resistance.

Pseudomonas aeruginosa Biofilm Formation and Its Control

Microbes are hardly seen as planktonic species and are most commonly found as biofilm communities in cases of chronic infections. Biofilms are regarded as a biological condition, where a large group of microorganisms gets adhered to a biotic or abiotic surface. In this context, Pseudomonas aeruginosa, a Gram-negative nosocomial pathogen is the main causative organism responsible for life-threatening and persistent infections in individuals affected with cystic fibrosis and other lung ailments. The bacteria can form a strong biofilm structure when it adheres to a surface suitable for the development of a biofilm matrix. These bacterial biofilms pose higher natural resistance to conventional antibiotic therapy due to their multiple tolerance mechanisms. This prevailing condition has led to an increasing rate of treatment failures associated with P. aeruginosa biofilm infections. A better understanding of the effect of a diverse group of antibiotics on established biofilms would be necessary to avoid inappropriate treatment strategies. Hence, the search for other alternative strategies as effective biofilm treatment options has become a growing area of research. The current review aims to give an overview of the mechanisms governing biofilm formation and the different strategies employed so far in the control of biofilm infections caused by P. aeruginosa. Moreover, this review can also help researchers to search for new antibiofilm agents to tackle the effect of biofilm infections that are currently imprudent to conventional antibiotics.

Emerging Antibacterial Strategies with Application of Targeting Drug Delivery System and Combined Treatment

At present, some bacteria have developed significant resistance to almost all available antibiotics. One of the reasons that cannot be ignored is long-term exposure of bacteria to the sub-minimum inhibitory concentration (MIC) of antibiotics. Therefore, it is necessary to develop a targeted antibiotic delivery system to improve drug delivery behavior, in order to delay the generation of bacterial drug resistance. In recent years, with the continuous development of nanotechnology, various types of nanocarriers that respond to the infection microenvironment, targeting specific bacterial targets, and targeting infected cells, and so on, are gradually being used in the delivery of antibacterial agents to increase the concentration of drugs at the site of infection and reduce the side effects of drugs in normal tissues. Here, this article describes in detail the latest research progress on nanocarriers for antimicrobial, and commonly used targeted antimicrobial strategies. The advantages of the combination of nanotechnology and targeting strategies in combating bacterial infections are highlighted in this review, and the upcoming opportunities and remaining challenges in this field are rationally prospected.

Antibacterial, Antibiofilm and Anticancer Activity of Biologically Synthesized Silver Nanoparticles Using Seed Extract of Nigella sativa

Silver nanoparticle (AgNP) based approaches using plant materials have been accepted as biomedical applications. The current study aimed to test the antibacterial, antibiofilm, and anticancer activity of silver nanoparticles synthesized by seed extract of Nigella sativa (Ns) as stabilizing and reducing agents. Characterization was done through UV–visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) analyses. UV-Vis spectroscopy showed a specific silver plasmon peak at 400 nm and a quick color change was observed in the bio-reaction medium. Electron microscopic images of Ns-AgNPs identified as spherical in shape with varied size ranged between 8 and 80 nm and zeta potential analysis evidenced the particles stability and polydisperity. Antibiofilm activity of Ns-AgNPs was evident as at 12.5 µg/mL Ns-AgNps restricted the biofilm formation by 88.42% for Enterococcus faecalis, 84.92% for E. coli, 81.86% for Klebsiella pneumonia, 82.84% for Staphylococcus aureus, and 49.9% for Pseudomonas aeruginosa, respectively. Furthermore, biologically synthesized AgNPs showed the significant bacteriostatic and bactericidal activity. Even the lowest concentration of Ns-AgNps restricted the highest rate of inhibition against S. aureus (6.5 and 15 µg/mL) and E. faecalis (6.5 and 15 µg/mL). Antimicrobial activity of S. aureus and E. fecalis was more prominent than E. coli (15 and 30 µg/mL), K. pneumonia (15 and 30 µg/mL) and P. aeruginosa (30 and 60 µg/mL) respectively. Moreover, Ns-AgNPs revealed significant cytotoxic ability and substantially killed human breast cancer cell (HCC-712) viability. The results of current study advocate that Ns-AgNps may be considered as a potential option in biomedical applications, alternative therapy, designing anti-biofilm agents, treating multi drug resistance bacterial infection, and anti-cancer therapy.

Cyclic Changes in the Amide Bands Within Escherichia coli Biofilms Monitored Using Real-Time Infrared Attenuated Total Reflection Spectroscopy (IR-ATR)

Contrary to the planktonic state of bacteria, their biofilm form represents severe complications in areas such as human medicine or food industry due to the increasing resistance against harsh conditions and treatment. In the present study, infrared attenuated total reflection (IR-ATR) spectroscopy has been applied as an analytic tool studying Escherichia coli ( E. coli) biofilm formation close to real time. We report on IR spectroscopic investigations on the biofilm formation via ATR waveguides probing the biofilm in the spectral window of 1800-900 cm^-1 at dynamic flow conditions, which facilitated monitoring the growth dynamics during several days. Key IR bands are in the range 1700-1590 cm^-1 (amide I), 1580-1490 cm^-1 (amide II), and 1141-1006 cm^-1 extracellular polymeric substances (EPS), which were evaluated as a function of time. Cyclic fluctuations of the amide I and amide II bands and a continuous increase of the EPS band were related to the starvation of bottom-layered bacteria caused by the nutrient gradient. Potential death of bacteria may then result in cannibalistic behavior known for E. coli colonies. Observing this behavior via IR spectroscopy allows revealing these cyclical changes in bottom-layered bacteria within the biofilm under continuous nutrient flow, in molecular detail, and during extended periods for the first time.

Current Trends in Development of Liposomes for Targeting Bacterial Biofilms

Biofilm targeting represents a great challenge for effective antimicrobial therapy. Increased biofilm resistance, even with the elevated concentrations of very potent antimicrobial agents, often leads to failed therapeutic outcome. Application of biocompatible nanomicrobials, particularly liposomally-associated nanomicrobials, presents a promising approach for improved drug delivery to bacterial cells and biofilms. Versatile manipulations of liposomal physicochemical properties, such as the bilayer composition, membrane fluidity, size, surface charge and coating, enable development of liposomes with desired pharmacokinetic and pharmacodynamic profiles. This review attempts to provide an unbiased overview of investigations of liposomes destined to treat bacterial biofilms. Different strategies including the recent advancements in liposomal design aiming at eradication of existing biofilms and prevention of biofilm formation, as well as respective limitations, are discussed in more details.

Encapsulation of Bacteriophage in Liposome Accentuates Its Entry in to Macrophage and Shields It from Neutralizing Antibodies

Phage therapy has been a centre of attraction for biomedical scientists to treat infections caused by drug resistant strains. However, ability of phage to act only on extracellular bacteria and probability of interference by anti-phage antibodies in vivo is considered as a important limitation of bacteriophage therapy. To overcome these hurdles, liposome were used as delivery vehicle for phage in this study. Anti-phage antibodies were raised in mice and pooled serum was evaluated for its ability to neutralize free and liposome entrapped phage. Further, ability of phage and liposome-entrapped phage to enter mouse peritoneal macrophages and kill intracellular Klebsiella pneumoniae was compared. Also, an attempt to compare the efficacy of free phage and liposome entrapped phage, alone or in conjunction with amikacin in eradicating mature biofilm was made. The entrapment of phage in liposome provided 100% protection to phage from neutralizing antibody. On the contrary un-entrapped phage got neutralized within 3 h of its interaction with antibody. Compared to the inability of free phage to enter macrophages, the liposome were able to deliver entrapped phage inside macrophages and cause 94.6% killing of intracellular K. pneumoniae. Liposome entrapped phage showed synergistic activity along with amikacin to eradicate mature biofilm of K. pneumoniae. Our study reinforces the growing interest in using phage therapy as a means of targeting multidrug resistant bacterial infections as liposome entrapment of phage makes them highly effective in vitro as well as in vivo by overcoming the majority of the hurdles related to clinical use of phage.

Urinary catheter indwelling clinical pathogen biofilm formation, exopolysaccharide characterization and their growth influencing parameters

Self-reproducing microbial biofilm community mainly involved in the contamination of indwelling medical devices including catheters play a vital role in nosocomial infections. The catheter-associated urinary tract infection (CA-UTI) causative Staphylococcus aureus, Enterobacter faecalis, and Pseudomonas aeruginosa were selectively isolated, their phenotypic as well as genotypic biofilm formation, production and monomeric sugar composition of EPS as well as sugar, salt, pH and temperature influence on their in vitro biofilm formation were determined. From 50 culture positive urinary catheters S. aureus (24%), P. aeruginosa (18%), E. faecalis (14%) and others (44%) were isolated. The performed assays revealed their varying biofilm forming ability. The isolated S. aureus ica, E. faecalis esp, and P. aeruginosa cup A gene sequencing and phylogenetic analysis showed their close branching and genetic relationship. The analyzed sugar, salt, pH, and temperature showed that the degree of CA-UTI isolates biofilm formation is an environmentally sensitive process. EPS monosaccharide HPLC analysis showed the presence of neutral sugars (ng/μl) as follows: glucose (P. aeruginosa: 44.275; E. faecalis: 4.23), lactose (P. aeruginosa: 7.29), mannitol (P. aeruginosa: 2.53; S. aureus: 2.62; E. faecalis: 2.054) and maltose (E. faecalis: 7.0042) revealing species-specific presence and variation. This study may have potential clinical relevance for the easy diagnosis and management of CA-UTI.

Potential effect of cationic liposomes on interactions with oral bacterial cells and biofilms

CONTEXT

Although oral infectious diseases have been attributed to bacteria, drug treatments remain ineffective because bacteria and their products exist as biofilms. Cationic liposomes have been suggested to electrostatically interact with the negative charge on the bacterial surface, thereby improving the effects of conventional drug therapies. However, the electrostatic interaction between oral bacteria and cationic liposomes has not yet been examined in detail.

OBJECTIVE

The aim of the present study was to examine the behavior of cationic liposomes and Streptococcus mutans in planktonic cells and biofilms.

MATERIALS AND METHODS

Liposomes with or without cationic lipid were prepared using a reverse-phase evaporation method. The zeta potentials of conventional liposomes (without cationic lipid) and cationic liposomes were -13 and 8 mV, respectively, and both had a mean particle size of approximately 180 nm. We first assessed the interaction between liposomes and planktonic bacterial cells with a flow cytometer. We then used a surface plasmon resonance method to examine the binding of liposomes to biofilms. We confirmed the binding behavior of liposomes with biofilms using confocal laser scanning microscopy.

RESULTS

The interactions between cationic liposomes and S. mutans cells and biofilms were stronger than those of conventional liposomes. Microscopic observations revealed that many cationic liposomes interacted with the bacterial mass and penetrated the deep layers of biofilms.

DISCUSSION AND CONCLUSION

In this study, we demonstrated that cationic liposomes had higher affinity not only to oral bacterial cells, but also biofilms than conventional liposomes. This electrostatic interaction may be useful as a potential drug delivery system to biofilms.

Antibiofilm and quorum sensing inhibitory activity of Achyranthes aspera on cariogenic Streptococcus mutans: an in vitro and in silico study

CONTEXT

Traditionally, many cultures use chewing sticks for oral hygiene maintenance. When properly used, these chewing sticks are found to be efficient due to the combined effect of mechanical cleaning, enhanced salivation and the antimicrobial action of leached out plant compounds.

OBJECTIVE

Achyranthes aspera L. (Amaranthaceae), an ethanomedicinal herb was evaluated for its potential to inhibit growth and biofilm formation by cariogenic isolate Streptococcus mutans as an alternative means of caries management by quorum quenching (QQ).

MATERIALS AND METHODS

Biofilm forming cariogenic isolates were isolated and their susceptibility to the petroleum ether, benzene, methanol, aqueous extracts of A. aspera was evaluated. Gas chromatography-mass spectrometry (GC-MS), phytochemical analyses and structure-based virtual screening for their quorum sensing (QS) inhibitory activities, drug-likeness and bioavailability were also carried out.

RESULTS

The biofilm inhibition percentage obtained for methanol, benzene, petroleum ether and aqueous extracts (125 µg/mL) were ≤94%, ≤74%, ≤62% ≤42%, respectively. GC-MS analyses indicated 61 compounds, of which betulin recorded efficient interaction exhibiting comparable binding energy of -8.72 with S. mutans glycosyltransferase (GTF-SI) whereas 3,12-oleandione exhibited binding energy -5.92 with OmpR subfamily QS regulatory DNA-binding response regulator. Computer-assisted molecular descriptor and Lipinski's rule violation calculation uncovered the presence of more drug-like compounds.

DISCUSSION AND CONCLUSION

Anticaries bioactive compounds of A. aspera with higher QS response regulator binding energy, low toxicity and optimal pharmacokinetic properties were revealed. These compounds with possible QQ ability hold the potential for use as anticaries drug leads and antibiofilm preventative medicine.

Learning from bacteriophages - advantages and limitations of phage and phage-encoded protein applications

The emergence of bacteria resistance to most of the currently available antibiotics has become a critical therapeutic problem. The bacteria causing both hospital and community-acquired infections are most often multidrug resistant. In view of the alarming level of antibiotic resistance between bacterial species and difficulties with treatment, alternative or supportive antibacterial cure has to be developed. The presented review focuses on the major characteristics of bacteriophages and phage-encoded proteins affecting their usefulness as antimicrobial agents. We discuss several issues such as mode of action, pharmacodynamics, pharmacokinetics, resistance and manufacturing aspects of bacteriophages and phage-encoded proteins application.

Investigating the effect of polymeric approaches on circulation time and physical properties of nanobubbles

PURPOSE

A challenge in the field of nanobubbles, including lipobubbles and polymeric nanobubbles, is identification of formulation approaches to enhance circulation time or "bubble life" in the specific organ to allow for organ visualization. The aim of this study was to investigate the potential of two specific preparation approaches, polymeric surface modification to lipobubbles and a one-step approach for the preparation of ionotropically originated polymeric hydrogel nanobubbles for the production of biocompatible, biodegradable, and sufficiently echogenic ('flexible') bubbles, preferably within the nanometer range, that possess an enhanced in vivo lifetime compared to an unmodified lipobubble to allow visualization of the lymph node vasculature.

METHODS

In the first approach, formed liposomes (basic and polymerically enhanced) were sequentially layered with appropriate cationic and anionic polyelectrolytes followed by transformation into polymer-coated nanobubbles. In addition, a one-step approach was employed for the fabrication of ionotropically originated polymeric hydrogel bubbles.

RESULTS

Bubble lifetime was marginally enhanced by self-deposition of polyelectrolytes onto the normal lipobubble, however, not significantly (P = 0.0634). In general, formulations possessing a higher ratio of anionic:cationic coats and highly anionic overall surface charge (-20.62 mV to -17.54 mV) possessed an enhanced lifetime. The improvement in bubble lifetime was significant when a purely polymeric polyionic hydrogel bubble shell was instituted compared to a normal unmodified lipobubble (P = 0.004). There was enhanced persistence of these systems compared to lipobubbles, attributed to the highly flexible, interconnected hydrogel shell which minimized gas leakage. The prolonged contrast signal may also be attributed to a degree of polymeric deposition/endothelial attachment.

CONCLUSIONS

This study identified the relevance of polymeric modifications to nanobubbles for an improved circulating lifetime, which would be essential for application of these systems in passive drug or gene targeting via the enhanced permeability and retention effect.

A comparison of the in vitro antimicrobial activity of liposomes containing meropenem and gentamicin

The antimicrobial activity of eight cationic, two neutral and three anionic liposome compositions containing meropenem and gentamicin was tested in vitro in broth and serum medium. The cationic formulations showed better antibacterial efficacy against both Gram-positive and Gram-negative bacteria than the anionic and neutral ones, regardless of the encapsulated drug. The most effective formulations were the cationic PC/DOPE/DOTAP 3:4:3 and PC/Chol/DOTAP 3:4:3, as the MICs with meropenem were 2 to 4 times lower than those of the free drug.

Mannosylated liposomes for bio-film targeting

Vesicular systems in general are investigated to achieve bacterial bio-film targeting as their architecture mimics bio-membranes in terms of structure and bio-behavior. This paper elaborates upon the role of the inherent characteristics of the carrier system and further envisages the role of anchored ligands in navigating the contents in the vicinity of bio-films. Vesicles in the present study were coated with hydrophobic derivatives of mannan (cholesteryl mannan and sialo-mannan). The prepared vesicles were characterized for size, shape, percentage entrapment and ligand binding specificity and results were compared with the uncoated versions. Using a set of in vitro and in vivo models, the bio-film targeting potential of plain and mannosylated liposomal formulations were compared. Results suggested that mannosylated vesicles could be effectively targeted to the model bacterial bio-films, compared with plain vesicles. Moreover, the sialo-mannan coated liposomes recorded superior targetability as reflected in the significantly higher percentage growth inhibition when compared with cholesteryl mannan coated liposomes. The engineered systems thus have the potential use for the delivery of anti-microbial agents to the bio-films.

Microbiological quality assurance of purified water by ozonization of storage and distribution system

Purified water storage and distribution systems at ambient temperature are highly susceptible to microbial contamination and formation of biofilm. The impact of two disinfection regimens with ozone as a function of time, the heterotrophic plate counts (HPC), and the concentration of total organic compounds (TOC) in purified water were investigated over a period of 4 years. We have established that concentrations of ozone of 70 +/- 20 ppb in the production regimen and 250 +/- 50 ppb in the disinfection regimen are sufficient to maintain a low bioburden and low TOC in a recirculating distribution system. The purified water that entered into the distribution system has low HPC (0.01 CFU/mL), indicating a reduction by ozone in the storage tank by up to approximately 120-fold. Over 4 years, 94-98% of the microbial counts were in the category 0-5 CFU/mL, and none in category > or =50 CFU/mL. In spite of increased TOC in the inlet water, up to 40 ppb, the microbial counts in purified water in the distribution loop were unaffected. The study emphasizes that the critical points regarding microbial contamination of the purified water system are user point valves and the tubes used for transferring water to equipment. The specified ozone level prevents microbial growth and formation of biofilm in the distribution system that might otherwise endanger the water quality by sporadic release of microbes.

Bactericidal effects of plasma-generated cluster ions

Air purification by plasma-generated cluster ions (PCIs) relies on a novel technology producing hydrated positive and negative ions. Phenomenological tests have shown strong evidence of lethal effects of the PCIs on various micro-organisms. However, the mechanisms of PCI action are still widely unknown. The aim was thus to test the bactericidal efficacy of PCI technology on common indoor micro-organisms and to explore possible PCI mechanisms of action. According to time/dose-dependent experiments with Staphylococcus, Enterococcus, Micrococcus and Bacillus, the inhibiting effects became apparent within the first few minutes of PCI exposure and led to an irreversible 99.9% destruction within the following 2-8 h of exposure. The destructive effect of the PCIs corresponded to membrane damage of the bacteria. Use of the techniques of both SDS PAGE and 2D PAGE revealed changes in the bacterial surface protein composition induced by the PCIs. In contrast, neither DNA nor cytoplasm protein damage was detected electrophoretically. The antimicrobial action of the PCIs seems to occur because of chemical modification of the surface proteins of bacteria. In situ hydroxyl radical formation on the surface of bacteria was proposed as the leading mechanism of the protein damage caused by the PCIs. At the same time, DNA damage seems not to be involved in the antibacterial action of the PCIs. The data obtained would broaden the knowledge concerning the antibacterial effects of air-born plasma-generated cluster ions and help to produce more efficient air-cleaning devices.

In vitro antimicrobial activity of liposomal meropenem against Pseudomonas aeruginosa strains

Twelve lipid formulations of liposomal meropenem were tested on six drug-susceptible and two drug-resistant Pseudomonas aeruginosa strains to determine their antibacterial activity. Cationic liposomes, especially PC/DOPE/SA 4:4:2 and PC/DOTAP/Chol 5:2:3, were more effective than anionic ones against sensitive isolates as the MICs of those formulations were two to four times lower than those of the free drug. None of the studied liposomal forms of meropenem exhibited bactericidal activity against isolates, which are drug-resistant due to low permeability. Even Fluidosomes (liposomes made of DPPC/DMPG 18:1), which demonstrated fusion with P. aeruginosa membranes, showed 4-16 times higher MICs for sensitive and resistant strains than did the free meropenem.