Phage-antibiotic combinations to control Pseudomonas aeruginosa-Candida two-species biofilms

Phage-antibiotic combinations to treat bacterial infections are gaining increased attention due to the synergistic effects often observed when applying both components together. Most studies however focus on a single pathogen, although in many clinical cases multiple species are present at the site of infection. The aim of this study was to investigate the anti-biofilm activity of phage-antibiotic/antifungal combinations on single- and dual-species biofilms formed by P. aeruginosa and the fungal pathogen Candida albicans. The Pseudomonas phage Motto in combination with ciprofloxacin had significant anti-biofilm activity. We then compared biofilms formed by P. aeruginosa alone with the dual-species biofilms formed by bacteria and C. albicans. Here, we found that the phage together with the antifungal fluconazole was active against 6-h-old dual-species biofilms but showed only negligible activity against 24-h-old biofilms. This study lays the first foundation for potential therapeutic approaches to treat co-infections caused by bacteria and fungi using phage-antibiotic combinations.

The discovery of an anti-Candida xanthone with selective inhibition of Candida albicans GAPDH

OBJECTIVES

This study aimed to discover novel antifungals targeting Candida albicans glyceraldehyde-3-phosphate dehydrogenase (CaGAPDH), have an insight into inhibitory mode, and provide evidence supporting CaGAPDH as a target for new antifungals.

METHODS

Virtual screening was utilized to discover inhibitors of CaGAPDH. The inhibitory effect on cellular GAPDH was evaluated by determining the levels of ATP, NAD, NADH, etc., as well as examining GAPDH mRNA and protein expression. The role of GAPDH inhibition in C. albicans was supported by drug affinity responsive target stability and overexpression experiments. The mechanism of CaGAPDH inhibition was elucidated by Michaelis-Menten enzyme kinetics and site-specific mutagenesis based on docking. Chemical synthesis was used to produce an improved candidate. Different sources of GAPDH were used to evaluate inhibitory selectivity across species. In vitro and in vivo antifungal tests, along with anti-biofilm activity, were carried out to evaluate antifungal potential of GAPDH inhibitors.

RESULTS

A natural xanthone was identified as the first competitive inhibitor of CaGAPDH. It demonstrated in vitro anti-C. albicans potential but also caused hemolysis. XP-W, a synthetic side-chain-optimized xanthone, demonstrated a better safety profile, exhibiting a 50-fold selectivity for CaGAPDH over human GAPDH. XP-W also exhibited potent anti-biofilm activity and displayed broad-spectrum anti-Candida activities in vitro and in vivo, including multi-azole-resistant C. albicans.

CONCLUSIONS

These results demonstrate for the first time that CaGAPDH is a valuable target for antifungal drug discovery, and XP-W provides a promising lead.

Bioresponsive gingerol-loaded alginate-coated niosomal nanoparticles for targeting intracellular bacteria and cancer cells

Targeting and treating intracellular pathogen infections has been long-standing challenge, particularly in light of the escalating prevalence of antimicrobial resistance. Herein, an optimum formulation of alginate (AL)-coated niosome-based carriers for delivery of herbal extract Gingerol (Gin) was developed to treat intracellular pathogen infections and cancer cells. We used Gin-Nio@AL as a model drug to assess its efficacy against Gram-negative/positive bacteria and breast cancer cell lines. Our investigation affirmed its heightened antibacterial and anticancer properties. The antibacterial activity of Gin-Nio@AL against intracellular Staphylococcus aureus (S. aureus) and pseudomonas aeruginosa (P. aeruginosa) was also tested. In the current study, the niosome nanoparticles containing herbal extract Gingerol were optimized regarding lipid content and Surfactant per Cholesterol molar ratio. The developed formulation provided potential advantages, such as smooth globular surface morphology, small diameter (240.68 nm), pH-sensitive sustained release, and high entrapment efficiency (94.85 %). The release rate of Gin from AL-coated niosomes (Gin-Nio@AL) in physiological and acidic pH is lower than uncoated nanoparticles (Gin-Nio). Besides, the release rate of Gin from niosomal formulations increased in acidic pH. The Gin-Nio@AL demonstrated good antimicrobial activity against S. aureus and P. aeruginosa, and compared to Gin-Nio, the MIC values decreased to 7.82 ± 0.00 and 1.95 ± 0.00 μg/mL, respectively. In addition, the time-kill assay results showed that the developed formulation significantly reduced the number of bacteria in both strains compared to other tested groups. The microtiter data and scanning electron microscope micrography showed that Gin-Nio@AL has a more significant inhibitory effect on biofilm formation than Gin-Nio and Gin. The cell cytotoxicity evaluation showed that Gin-Nio@AL reduced the survival rate of MDA-MB-231 cancer cells to 52.4 % and 45.2 % after 48 h and 72 h, respectively. The elimination of intracellular pathogens was investigated through a breast cancer cell infection in an in vitro model. Gin-Nio@AL exhibited an enhanced and sustained intracellular antibacterial activity against pathogens-infected breast cancer cells compared to other tested formulations. Overall, Gin-Nio@AL enables the triggered release and targeting of intra-extra cellular bacteria and cancer cells and provides a novel and promising candidate for treating intracellular pathogen infections and cancer cells.

Impact of lactic acid bacteria strains against Listeria monocytogenes biofilms on various food-contact surfaces

Listeria monocytogenes is one of the most important foodborne pathogens, causing listeriosis, a disease characterized by high mortality rates. This microorganism, commonly found in food production environments and transmitted to humans by consuming contaminated food, has the ability to form biofilms by attaching to a wide variety of surfaces. Traditional hygiene and sanitation procedures are not effective enough to completely remove L. monocytogenes biofilms from food-contact surfaces, which makes them a persistent threat to food safety. Alternative approaches to combating Listeria biofilms are needed, and the use of lactic acid bacteria (LAB) and their antimicrobial compounds shows promise. The present study investigated the effect of Lactobacillus strains, previously isolated from various foods and known to possess antimicrobial properties, on the biofilm formation of L. monocytogenes on three different food-contact surfaces. To study L. monocytogenes IVb ATCC 19115 type, culture was preferred to represent serotype IVb, which is responsible for the vast majority of listeriosis cases. The results demonstrated that cell-free supernatants (CFSs) of LAB strains inhibited biofilm formation by up to 51.57% on polystyrene, 60.96% on stainless steel, and 30.99% on glass surfaces. Moreover, these CFSs were effective in eradicating mature biofilms, with reductions of up to 78.86% on polystyrene, 73.12% on stainless steel, and 72.63% on glass surfaces. The strong inhibition rates of one strain of L. curvatus (P3X) and two strains of L. sakei (8.P1, 28.P2) used in the present study imply that they may provide an alternate technique for managing Listeria biofilms in food production environments.

Uncovering the anti-biofilm activity of Ilicicolin B against Staphylococcus aureus

The formation of bacterial biofilms reduces the entry of antibiotics into bacteria and helps bacteria tolerate otherwise lethal concentrations of antimicrobials, leading to antibiotic resistance. Therefore, clearing bacterial biofilm is an effective strategy to tackle drug resistance. Currently, there are no approved antibiotics for inhibiting bacterial biofilm formation. We found that Ilicicolin B had excellent antibacterial activity against MRSA without obvious hemolytic activity. More importantly, Ilicicolin B effectively inhibited the biofilm formation in a concentration-dependent manner by crystal violet colorimetric assay and fluorescence microscopy analysis. Exposure of Staphylococcus aureus to Ilicicolin B for 24 h reduced the protein and polysaccharide components in EPS, suggesting that Ilicicolin B disintegrated the biofilms by dissociating the EPS in a matrix. In addition, Ilicicolin B demonstrated strong antibacterial effects in a murine abscess model of S. aureus. Our findings suggest that Ilicicolin B has the potential to treat S. aureus infection by inhibiting biofilm formation.

Improved anti-biofilm activity and long-lasting effects of novel serratiopeptidase immobilized on cellulose nanofibers

Today, enzymatic treatment is a progressive field in combating biofilm producing pathogens. In this regard, serratiopeptidase, a medicinally important metalloprotease, has been recently highlighted as an enzyme with proved anti-biofilm activity. In the present study, in order to increase the long-lasting effects of the enzyme, serratiopeptidase and the novel engineered forms with enhanced anti-biofilm activity were immobilized on the surface of cellulose nanofibers (CNFs) as a natural polymer with eminent properties. For this, recombinant serratiopeptidases including the native and previously designed enzymes were produced, purified and conjugated to the CNF by chemical and physical methods. Immobilization was confirmed using different scanning and microscopic methods. The enzyme activity was assessed using casein hydrolysis test. Enzyme release analysis was performed using dialysis tube method. Anti-biofilm activity of free and immobilized enzymes has been examined on Staphylococcus aureus and Pseudomonas aeruginosa strains. Finally, cytotoxicity of enzyme-conjugated CNFs was performed by MTT assay. The casein hydrolysis results confirmed fixation of all recombinant enzymes on CNFs by chemical method; however, inadequate fixation of these enzymes was found using cold atmospheric plasma (CAP). The AFM, FTIR, and SEM analysis confirmed appropriate conjugation of enzymes on the surface of CNFs. Immobilization of enzymes on CNFs improved the anti-biofilm activity of serratiopeptidase enzymes. Interestingly, the novel engineered serratiopeptidase (T344 [8-339ss]) exhibited the highest anti-biofilm activity in both conjugated and non-conjugated forms. In conclusion, incorporation of serratiopeptidases into CNFs improves their anti-biofilm activities without baring any cytotoxicity. KEY POINTS: • Enzymes were successfully immobilized on cellulose nanofibers using chemical method. • Immobilization of enzymes on CNFs improved their anti-biofilm activity. • T344 [8-339ss] exhibited the highest anti-biofilm activity in both conjugated and non-conjugated forms.

Anti-quorum Sensing and Anti-biofilm Effect of Nocardiopsis synnemataformans RMN 4 (MN061002) Compound 2,6-Di-tert-butyl, 1,4-Benzoquinone Against Biofilm-Producing Bacteria

In this study, the anti-biofilm compound of 2,6-Di-tert-butyl, 1,4-benzoquinone was purified from Nocardiopsis synnemataformans (N. synnemataformans) RMN 4 (MN061002). To confirm the compound, various spectroscopy analyses were done including ultraviolet (UV) spectrometer, Fourier transform infrared spectroscopy (FTIR), analytical high-performance liquid chromatography (HPLC), preparative HPLC, gas chromatography-mass spectroscopy (GC-MS), liquid chromatography-mass spectroscopy (LC-MS), and 2D nuclear magnetic resonance (NMR). Furthermore, the purified compound was shown 94% inhibition against biofilm-producing Proteus mirabilis (P. mirabilis) (MN396686) at 70 µg/mL concentrations. Furthermore, the metabolic activity, exopolysaccharide damage, and hydrophobicity degradation results of identified compound exhibited excellent inhibition at 100 µg/mL concentration. Furthermore, the confocal laser scanning electron microscope (CLSM) and scanning electron microscope (SEM) results were shown with intracellular damages and architectural changes in bacteria. Consecutively, the in vivo toxicity effect of the compound against Artemia franciscana (A. franciscana) was shown to have a low mortality rate at 100 µg/mL. Finally, the molecular docking interaction between the quorum sensing (QS) genes and identified compound clearly suggested that the identified compound 2,6-Di-tert-butyl, 1,4-benzoquinone has anti-quorum sensing and anti-biofilm activities against P. mirabilis (MN396686).

Antibacterial activity and antibacterial mechanism of flavaspidic acid BB against Staphylococcus haemelyticus

BACKGROUND

Staphylococcus haemolyticus (S. haemolyticus) is the main etiological factor in skin and soft tissue infections (SSTI). S. haemolyticus infections are an important concern worldwide, especially with the associated biofilms and drug resistance. Herein, we investigated the inhibitory effect of Flavaspidic acid BB obtained from plant extractions on clinical S. haemolyticus strains and their biofilms. Moreover, we predicted its ability to bind to the protein-binding site by molecular simulation. Since the combination of Hsp70 and RNase P synthase after molecular simulation with flavaspidic acid BB is relatively stable, enzyme-linked immunosorbent assay (ELISA) was used to investigate Hsp70 and RNase P synthase to verify the potential antimicrobial targets of flavaspidic acid BB.

RESULTS

The minimum inhibitory concentrations (MIC) of flavaspidic acid BB on 16 clinical strains of S. haemolyticus was 5 ~ 480 µg/mL, and BB had a slightly higher inhibitory effect on the biofilm than MUP. The inhibitory effect of flavaspidic acid BB on biofilm formation was better with an increase in the concentration of BB. Molecular simulation verified its ability to bind to the protein-binding site. The combination of ELISA kits showed that flavaspidic acid BB promoted the activity of Hsp70 and inhibited the activity of RNase P, revealing that flavaspidic acid BB could effectively inhibit the utilization and re-synthesis of protein and tRNA synthesis, thus inhibiting bacterial growth and biofilm formation to a certain extent.

CONCLUSIONS

This study could potentially provide a new prospect for the development of flavaspidic acid BB as an antibacterial agent for resistant strains.

Antibacterial Effects of Nanocomposites on Efflux Pump Expression and Biofilm Production in Pseudomonas aeruginosa: A Systematic Review

BACKGROUND

Pseudomonas aeruginosa is an opportunistic gram-negative pathogen with multiple mechanisms of resistance to antibiotics. This systematic review aimed to study the antibacterial effects of nanocomposites on efflux pump expression and biofilm production in P. aeruginosa.

METHODS

The search was conducted from January 1, 2000, to May 30, 2022, using terms such as (P. aeruginosa) AND (biofilm) AND (antibiofilm activity) AND (anti-Efflux Pump Expression activity) AND (nanoparticles) AND (Efflux Pump Expression) AND (Solid Lipid NPS) AND (Nano Lipid Carriers). Many databases are included in the collection, including ScienceDirect, PubMed, Scopus, Ovid, and Cochrane.

RESULTS

A list of selected articles was retrieved by using the relevant keywords. A total of 323 published papers were selected and imported into the Endnote library (version X9). Following the removal of duplicates, 240 were selected for further processing. Based on the titles and abstracts of the articles, 54 irrelevant studies were excluded. Among the remaining 186 articles, 54 were included in the analysis because their full texts were accessible. Ultimately, 74 studies were selected based on inclusion/exclusion criteria.

CONCLUSION

Recent studies regarding the impact of NPs on drug resistance in P. aeruginosa found that various nanostructures were developed with different antimicrobial properties. The results of our study suggest that NPs may be a feasible alternative for combating microbial resistance in P. aeruginosa by blocking flux pumps and inhibiting biofilm formation.

A novel antimicrobial peptide YS12 isolated from Bacillus velezensis CBSYS12 exerts anti-biofilm properties against drug-resistant bacteria

Nowadays, the abuse of antibiotics has led to the rise of multi-drug-resistant bacteria. Antimicrobial peptides (AMPs), with broad-spectrum antimicrobial activity have attracted considerable attention as possible alternatives to traditional antibiotics. In this work, we aimed to evaluate the antimicrobial and anti-biofilm activity of an antimicrobial peptide designed as YS12 derived from Bacillus velezensis CBSYS12. The strain CBSYS12 was isolated from Korean food kimchi and purified followed by ultrafiltration and sequential chromatographic methodology. Hereafter, Tricine SDS-PAGE revealed a single protein band of around 3.3 kDa that was further confirmed in situ inhibitory activity of the gel. A similar molecular weight (~ 3348.4 Da) protein also appeared in MALDI-TOF confirming the purity and homogeneity of peptide YS12. Intriguingly, YS12 revealed a strong antimicrobial activity with a minimum inhibitory concentration (MIC) value ranging from 6 to 12 μg/ml for both Gram-positive and Gram-negative bacteria, such as E. coli, P. aeruginosa, MRSA 4-5, VRE 82, and M. smegmatis. We also determined the mode of action of the peptide against pathogenic microorganisms using different fluorescent dyes. In addition, the anti-biofilm assay demonstrated that peptide YS12 was able to inhibit biofilm formation  around 80% for both bacterial strains E. coli and P. aeruginosa at 80 µg/ml. Notably, YS12 exhibited a greater biofilm eradication activity than commercial antibiotics. In summary, our study proposed that peptide YS12 may be used as a promising therapeutic agent to overcome drug and biofilm-related infections.

Potential Antimicrobial and Antibiofilm Properties of Copper Oxide Nanoparticles: Time-Kill Kinetic Essay and Ultrastructure of Pathogenic Bacterial Cells

Mycosynthesis of nanoparticle (NP) production is a potential ecofriendly technology for large scale production. In the present study, copper oxide nanoparticles (CuONPs) have been synthesized from the live cell filtrate of the fungus Penicillium chrysogenum. The created CuONPs were characterized via several techniques, namely Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). Furthermore, the biosynthesized CuONPs were performed against biofilm forming Klebsiella oxytoca ATCC 51,983, Escherichia coli ATCC 35,218, Staphylococcus aureus ATCC 25,923, and Bacillus cereus ATCC 11,778. The anti-bacterial activity result was shown with the zone of inhibition determined to be 14 ± 0.31 mm, 16 ± 0.53 mm, 11 ± 0.57 mm, and 10 ± 0.57 mm respectively. Klebsiella oxytoca and Escherichia coli were more susceptible to CuONPs with minimal inhibitory concentration (MIC) values 6.25 and 3.12 µg/mL, respectively, while for Staphylococcus aureus and Bacillus cereus, MIC value was 12.5 and 25 μg/mL, respectively. The minimum biofilm inhibition concentration (MBIC) result was more evident, that the CuONPs have excellent anti-biofilm activity at sub-MIC levels reducing biofilm formation by 49% and 59% against Klebsiella oxytoca and Escherichia coli, while the results indicated that the MBIC of CuONPs on Bacillus cereus and Staphylococcus aureus was higher than 200 μg/mL and 256 μg/mL, respectively, suggesting that these CuONPs could not inhibit mature formatted biofilm of Bacillus cereus and Staphylococcus aureus in vitro. Overall, all the results were clearly confirmed that the CuONPs have excellent anti-biofilm ability against Klebsiella oxytoca and Escherichia coli. The prepared CuONPs offer a smart approach for biomedical therapy of resistant microorganisms because of its promoted antimicrobial action, but only for specified purposes.

Injectable bone cement containing carboxymethyl cellulose microparticles as a silver delivery system able to reduce implant-associated infection risk

In the challenging quest for a solution to reduce the risk of implant-associated infections in bone substitution surgery, the use of silver ions is promising regarding its broad spectrum on planktonic, sessile as well as multiresistant bacteria. In view of controlling its delivery in situ at the desired dose, we investigated its encapsulation in carboxymethyl cellulose (CMC) microparticles by spray-drying and included the latter in the formulation of a self-setting calcium phosphate bone cement. We implemented an original step-by-step methodology starting from the in vitro study of the antibacterial properties and cytotoxicity of two silver salts of different solubility in aqueous medium and then in the cement to determine the range of silver loading able to confer anti-biofilm and non-cytotoxic properties to the biomaterial. A dose-dependent efficiency of silver was demonstrated on the main species involved in bone-implant infection (S. aureus and S. epidermidis). Loading silver in microspheres instead of loading it directly inside the cement permitted to avoid undesired silver-cement interactions during setting and led to a faster release of silver, i.e. to a higher dose released within the first days combining anti-biofilm activity and preserved cytocompatibility. In addition, a combined interest of the introduction of about 10% (w/w) silver-loaded CMC microspheres in the cement formulation was demonstrated leading to a fully injectable and highly porous (77%) cement, showing a compressive strength analogous to cancellous bone. This injectable silver-loaded biomimetic composite cement formulation constitutes a versatile bone substitute material with tunable drug delivery properties, able to fight against bone implant associated infection. STATEMENT OF SIGNIFICANCE: This study is based on two innovative scientific aspects regarding the literature: i) Choice of silver ions as antibacterial agent combined with their way of incorporation: Carboxymethylcellulose has never been tested into bone cement to control its drug loading and release properties. ii) Methodology to formulate an antibacterial and injectable bone cement: original and multidisciplinary step-by-step methodology to first define, through (micro)biological tests on two silver salts with different solubilities, the targeted range of silver dose to include in carboxymethylcellulose microspheres and, then optimization of silver-loaded microparticles processing to fulfill requirements (encapsulation efficiency and size). The obtained fully injectable composite controls the early delivery of active dose of silver (from 3 h and over 2 weeks) able to fight against bone implant-associated infections.

Fabrication and characterization of thymol-loaded chitosan nanogels: improved antibacterial and anti-biofilm activities with negligible cytotoxicity

Thymol is a monoterpene phenolic derivative extracted from the Thymus vulgaris which has antimicrobial effects. In the present study, thymol-loaded chitosan nanogels were prepared and their physicochemical properties were characterized. The encapsulation efficiency of thymol into chitosan and its stability were determined. The in-vitro antimicrobial and anti-biofilm activities of thymol-loaded chitosan nanogel (Ty-CsNG), free thymol (Ty), and free chitosan nanogel (CsNG) were evaluated against both Gram-negative and Gram-positive multidrug-resistant (MDR) bacteria including Staphylococcus aureus , Acinetobacter baumanii , and Pseudomonas aeruginosa strains using the broth microdilution and crystal violet assay, respectively. After treatment of MDR strains with sub-minimum inhibitory concentration (Sub-MIC) of Ty-CsNG, free Ty and CsNG, biofilm gene expression analysis was studied. Moreover, cytotoxicity of Ty-CsNG, free Ty, and CsNG against HEK-293 normal cell line was determined using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) method. The average size of Ty-CsNG was 82.71±9.6 nm, encapsulation efficiency was 76.54 ± 0.62% with stability up to 60 days at 4 o C. Antibacterial activity test revealed that Ty-CsNG reduced the MIC by 4-6 times in comparison to free thymol. In addition, the expression of biofilm-related genes including ompA , and pgaB were significantly down-regulated after treatment of strains with Ty-CsNG ( p <0.05). In addition, free CsNG displayed negligible cytotoxicity against HEK-293 normal cell line and presented a biocompatible nanoscale delivery system. Based on the results, it can be concluded that Ty-CsNG can be considered a promising candidate for enhancing antimicrobial and anti-biofilm activities.

Chronic wound dressings - Pathogenic bacteria anti-biofilm treatment with bacterial cellulose-chitosan polymer or bacterial cellulose-chitosan dots composite hydrogels

Since the pathogenic bacteria biofilms are involved in 70% of chronic infections and their resistance to antibiotics is increased, the research in this field requires new healing agents. New composite hydrogels were designed as potential chronic wound dressings composed of bacterial cellulose (BC) with chitosan polymer (Chi) - BC-Chi and chitosan nanoparticles (nChiD) - BC-nChiD. nChiD were obtained by gamma irradiation at doses: 20, 40 and 60 kGy. Physical and chemical analyses showed incorporation of Chi and encapsulation of nChiD into BC. The BC-Chi has the highest average surface roughness. BC-nChiD hydrogels show an irradiated dose-dependent increase of average surface roughness. New composite hydrogels are biocompatible with excellent anti-biofilm potential with up to 90% reduction of viable biofilm and up to 65% reduction of biofilm height. The BC-nChiD showed better dressing characteristics: higher porosity, higher wound fluid absorption and faster migration of cells (in vitro healing). All obtained results confirmed both composite hydrogels as promising chronic wound healing agents.

Feasibility of sodium long chain polyphosphate as a potential growth promoter in broilers

The objective of this study was to evaluate in vitro antimicrobial and anti-biofilm activity of sodium long chain polyphosphate (SLCPP) and effect of dietary supplementation of SLCPP on growth performance, organ characteristics, blood metabolites, and intestinal microflora of broilers. Antimicrobial activities of SLCPP were observed against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica ser. Pullorum, Shigella sonnei, Klebsiella pneumonia, Pseudomonas aeruginosa in agar well diffusion assay. In addition, SLCPP demonstrated good anti-biofilm activity against K. pneumonia and P. aeruginosa. Furthermore, to investigate the dietary effect of SLCPP, a total of 480 1-day-old male Ross 308 broiler chicks were randomly allotted to three dietary treatment groups (4 replicates per group, 40 birds in each replicate): an antibiotic-free corn-soybean meal basal diet (NC); basal diet + enramycin 0.01% (PC); and basal diet + 0.1% SLCPP (SPP). The experiment lasted for 35 days. Results showed that birds fed with SLCPP had higher body weight (BW) and average daily gain (ADG), and lower feed conversion ratio (FCR) during the grower phase (days 7 to 21) (p < 0.05). Except for blood urea nitrogen, all other blood biochemical parameters remained unaffected by the dietary supplementation of SLCPP. Compared to the control group, lengths of the duodenum and ileum in the SPP group were significantly shorter (p < 0.05). Moreover, counts of lactic acid bacteria (LAB), total aerobes, and Streptococcus spp. in jejunum as well as LAB in cecum were increased in the SPP group than in the PC group (p < 0.05). These results suggest that dietary supplementation of SLCPP might promote the growth of broilers in their early growth phase.

Potentiating effects of leaderless enterocin DD14 in combination with methicillin on clinical methicillin-resistant Staphylococcus aureus S1 strain

Biofilm formation by pathogenic bacteria as well as their resilience to antibiotic treatments are a major health problem. Here, we sequenced and analyzed the genome of the clinical methicillin-resistant Staphylococcus aureus S1 (MRSA-S1) strain and established its sensitivity to the combination of methicillin and the leaderless two peptides enterocin DD14 (EntDD14). Such sensitivity was assessed in vitro based on the MIC/FIC values as well as on killing curves experiments. Moreover, combination of EntDD14 and methicillin was able to reduce the biofilm formation of Staphylococcus aureus S1 of about ∼30 %. Interestingly, genes thought to be involved in the virulence of MRSA-S1, like nuc and pvl which code, respectively, for nuclease and Panton-Valentine leucocidin, were shown to be downregulated following treatment with EntDD14 and methicillin. Similar effects were registered for other genes such as cflA, cflB and icaB, coding for bacterial ligands clumping factors A, B and intercellular adhesion factor respectively. All these data, suggest that combinations of bacteriocins and antibiotics are useful as a backup for treatment of bacterial infections.

Exopolysaccharides produced by Pediococcus acidilactici MT41-11 isolated from camel milk: Structural characteristics and bioactive properties

In this study, the chemical structure and bioactive properties of the EPS of Pediococcus acidilactici MT41-11 isolated from camel milk were investigated. Two polysaccharide fractions (EPS-1, EPS-2) with molecular weights about 69.0 kDa were obtained, which were purified using DEAE-Sepharose and Sephadex G-100 chromatography. Based on monosaccharide composition, FT-IR, and 1D, 2D NMR spectra, concluded that EPS-1 had a backbone composed of →2)-α-d-Manp-(1→, →3)-α-d-Manp-(1→ and with branches containing α-d-Manp-(1→, EPS-2 had a backbone composed of →6)-β-d-Glcp-(1→, and with branches containing →2)-α-l-Fucp-(1→, →3)-α-d-Glcp-(1→, →2)-α-d-Glcp-(1→, β-d-Glcp-(1→, and α-d-Glcp-(1→. Remarkably, in vitro assays showed that EPS possessed multiple bioactive properties, including stimulating Lactobacillus growth and a high DPPH free radical scavenging activity. Also, it has a good ability to anti-biofilms. Overall, the analysis of all data showed EPS from P. acidilactici MT41-11 can be used as anti-oxidant, anti-biofilm agent, and also as a potential candidate prebiotic for health food or medicine industry.

An orthodontic acrylic resin containing seaweed Ulva lactuca as a photoactive phytocompound in antimicrobial photodynamic therapy: Assessment of anti-biofilm activities and mechanical properties

BACKGROUND

Uncontrolled accumulation of microbial plaque and formation of biofilm on the surface orthodontic acrylic removable appliances increases the risk of enamel decalcification and periodontal diseases. The purpose of the present study was to evaluate antimicrobial activities, anti-virulence potencies, and mechanical properties of orthodontic acrylic resin containing different concentrations of Ulva lactuca (a green marine macroalga) following photo-activation against Streptococcus mutans.

MATERIALS AND METHODS

Minimum inhibitory concentration (MIC) of U. lactuca was determined against S. mutans. Acrylic resin specimens with different concentrations of U. lactuca (0.2 %, 0.5 %, 1%, 2.5 %, 5%, and 10 % weight/weight) were fabricated. Flexural strength values, antimicrobial effects, and anti-biofilm activities of samples were assessed in comparison with original acrylic resin as the control group. Also, the expression of the virulence-associated genes was assessed by quantitative real-time polymerase chain reaction.

RESULTS

U. lactuca at concentrations of 1-10% significantly reduced the S. mutans growth rate by 20.3%-63.3% in comparison to the control group (P < 0.05). Therefore, the concentration of 1% of U. lactuca was considered as a MIC. The highest and lowest flexural strength values were observed in the control group (43.5 ± 2.4 MPa) and the group with a 10 % concentration of U. lactuca (19.2 ± 1.8 MPa), respectively. Flexural strength values decreased in samples containing 2.5 %, 5%, and 10 % concentrations of U. lactuca in comparison to the control group significantly (P > 0.05). In the disc agar diffusion test, the growth inhabitation zones around samples containing different concentrations of photo-activated U. lactuca ranged from 13 mm to 25 mm in diameter. Interestingly, the anti-biofilm activity of U. lactuca-mediated aPDT against S. mutans was dose-dependent. Additionally, the sub-MIC dose of U. lactuca (0.5 %) following photo-activation could significantly decrease the expression levels of gtfB, gtfC, and gtfD to 4.1-, 5.3-, and 7.4-fold, respectively.

CONCLUSIONS

Adding photo-activated U. lactuca to the orthodontic acrylic resin at a concentration of 1% increases its antibacterial and anti-biofilm activities besides not detrimentally affects its flexural strength.

Investigation on the biofilm eradication potential of selected medicinal plants against methicillin-resistant Staphylococcus aureus

Biofilms are multi-species bacterial communities with complex structures that create antibiotic resistance, cause life-threatening infections, thereby considerable economic loss; needed new approaches. Medicinal plants are focused as new alternatives for their therapeutic and antimicrobial effects. Our present study, Azadirachta indica, Moringa oleifera, Murraya koenigii, and Psidium guajava extracts were investigated against MRSA. The preliminary antimicrobial study showed pet. ether extract of A. indica and ethanolic extract of P. guajava showed a MIC value of 125 μg/mL and MBC value of 500 μg/mL. These extracts showed biofilm inhibition in the range of 60.0-83.9 % and did not possess any hemolytic activity to the human erythrocytes. The plant species investigated in this study had different degrees of antibiofilm activity against MRSA. However, we suggest that A. indica and P. guajava are promising candidates and further investigation is needed to isolate the antimicrobial compounds for the management of MRSA and its mechanism of activity.

Preparative HPLC fraction of Hibiscus rosa-sinensis essential oil against biofilm forming Klebsiella pneumoniae

Recent years Klebsiella pneumoniae (K. pneumoniae) biofilm formation (BF) is emerging thread worldwide. For tackling this problem, we have chosen Hibiscus rosa-. pneumoniae. The HPLC purified essential oils (EOs sinensis (H. rosa-sinensis) (HRS) to inhibit the BF K) of H. rosa-sinensis was performed against BF K. pneumoniae and showed concentration dependent biofilm inhibition. At the MBIC of EOs (90 µg/ml), the biofilm inhibition was showed at 92% against selected BF K. Pneumoniae. The biofilm metabolic assay, exopolysaccharide quantification and hydrophobicity index variation results exhibited with 88%, 92% and 89% reduction at 90 μg/mL was observed respectively. In addition, the morphological modification of MBIC treated K. pneumoniae was clearly viewed by scanning electron microscope (SEM). Overall, all the invitro experiments result were confirmed that the MBIC of H. rosa-sinensis EOs was very effective against BF K. pneumonia.

The impact that β-citronellol isomers have on the biofilm formation of Candida yeasts

Infections associated with biofilms developed by Candida spp. are becoming a great problem due to its resistance against the immune response of the host and the action of antifungal agents. Hence, finding substances that can inhibit the development of biofilms increases the likelihood that these compounds one day can become good antifungals applied in the clinic. The aim of this study was to evaluate the effect of β-citronellol enantiomers on the biofilm formation by Candida albicans and Candida tropicalis isolated from bloodstream infections. Inhibition was evaluated by reading microplates treated with different concentrations of R-(+)-β-citronellol, S-(-)-β-citronellol and amphotericin B, compared to negative control, in spectrophotometer at 590 nm. All tested concentrations of β-citronellol enantiomers inhibited the biofilm formation of Candida. However, it is still necessary to evaluate the behavior of these isomers on mature biofilms, so that they can become more viable as antifungal therapeutical agents.

Rhamnolipid exhibits anti-biofilm activity against the dermatophytic fungi Trichophyton rubrum and Trichophyton mentagrophytes

Dermatophytes are responsible for a majority of fungal infections in humans and other vertebrates, causing dermatophytosis. Treatment failures are often associated with biofilm formation, making dermatophytes resistant to antifungals. In this study, effects of a rhamnolipid (RL-SS14) produced by Pseudomonas aeruginosa SS14 on planktonic cells of Trichophyton rubrum and Trichophyton mentagrophytes, their biofilm formation, and disruption of mature biofilms were assessed. The composition of RL-SS14 was analysed using FTIR, HPLC-ESI-MS, and GC-MS. Minimum inhibitory concentrations against the planktonic forms of T. rubrum and T. mentagrophytes were 0.5 mg/mL and 0.125 mg/mL, respectively. Crystal-violet (biofilm biomass) and safranin (extracellular matrix) staining revealed that RL-SS14 significantly inhibited biofilm formation and also reduced preformed biofilms in a dose-dependent manner. Microscopic visualization of treated biofilms via SEM, AFM, and CLSM revealed marked morphological damage, cell death, and reduced extracellular matrix. The results indicate the potential of RL-SS14 as an anti-biofilm agent against dermatophytes.

Single step production of high-purity copper oxide-titanium dioxide nanocomposites and their effective antibacterial and anti-biofilm activity against drug-resistant bacteria

In the present research work, copper oxide-titanium dioxide nanocomposites were synthesized for the first time using advanced pulsed laser ablation in liquid (PLAL) technique for disinfection of drug-resistant pathogenic waterborne biofilm-producing bacterial strains. For this, a series of copper oxide-titanium dioxide nanocomposites were synthesized by varying the composition of copper oxide (5%, 10%, and 20%) with titanium dioxide. The pure titanium dioxide and copper oxide-titanium dioxide nanocomposites were characterized by advanced instrumental techniques. XRD, TEM, FE-SEM, EDX, elemental mapping and XPS analysis results consistently revealed the successful formation of copper oxide-titanium dioxide nanocomposites using PLAL technique. The antibacterial and antibiofilm activities of pure titanium dioxide and copper oxide-titanium dioxide nanocomposites were investigated against biofilm-producing strains of Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa by various methods. Our results revealed that the PLAL synthesized copper oxide-titanium dioxide nanocomposites showed enhanced anti-biofilm and antibacterial activity compared to pure titanium dioxide in a dose-dependent manner against targeted pathogens. Furthermore, the effects of pure titanium dioxide and copper oxide-titanium dioxide nanocomposites on bacterial morphology, biofilm formation, aggregation and their colonization by targeted pathogens were also examined using scanning electron microscopy. Microscopic images clearly showed that the cell envelope of almost all the cells were rumples, rough, had irregularities and abnormal appearance with the major damage being characterized by the formation of "pits". Many depressions and indentations were also seen in their cell envelope and the original shape of Pseudomonas aeruginosa cells changed from normal rod to swollen, large and elongated which indicates the loss of membrane integrity and damage of cell wall and membrane. The findings suggested that PLAL synthesized copper oxide-titanium dioxide nanocomposites have good potential for removal of biofilm or killing of pathogenic bacteria in water distribution network and for wastewater treatment, hospital and environmental applications. In addition, cytotoxic activity of pure TiO₂ and PLAL synthesized copper oxide-titanium dioxide nanocomposites against normal and healthy cells (HEK-293) and cancerous cells (HCT-116) were also evaluated by MTT assay. The MTT assay results showed no cytotoxic effects on HEK-293 cells, which suggest TiO₂ and PLAL synthesized copper oxide-titanium dioxide nanocomposites are non-toxic to the normal cells.

Anticandidal and synergistic effect of essential oil fractions from three aromatic plants used in Cameroon

Despite the use of conventional antifungal drugs, Candida spp resistance, especially mediated by biofilms formation remains recurrent. Therefore, new drugs to treat fungal infections are urgently needed. In this line, our study aimed to determine the anticandidal activity and the synergistic effect of essential oil fractions from Syzygium aromaticum, Cymbopogon citratus and Aeollanthus heliotropioides harvested in Cameroon using a combination approach. Essential oils have been obtained by hydrodistillation and their chemical composition was analysed by GC/MS. Antifungal activity was evaluated by the determination of minimum inhibitory concentration (MIC) using a micro-dilution method. The sorbitol and ergosterol binding ability and anti-biofilm activity were also assessed in order to evaluate the mode of action. The crude essential oils showed a good anticandidal activity, most probably due to the eugenol, linalool and citral content. The combination of two fractions F7 and F10 showed an improved growth inhibition of Candida spp compared to the crude essential oils. The inhibitory effect could be related with the presence of γ-dodecalactone and citronellol as main compounds. The best synergistic combination F7F10 inhibited biofilm formation at ten time reduced combination MIC. The active fractions targeted different fungal cell structures, including cell wall and membrane. Our study showed that the combination of selected essential oils fractions exhibited an increased antifungal activity against Candida spp compared to the crude essential oils. The combination approach of inner compound groups may be used as a promising strategy for the development of efficient recombined micro-essential oils as antifungal agents to face Candida resistance.

strain Sh10 against Proteus mirabilis

BACKGROUND AND OBJECTIVES

Biofilm formed by Proteus mirabilis strains is one of the most important medical problems especially in the case of device-related urinary tract infections. This study was conducted to evaluate the bacteriocin produced by a marine isolate of Bacillus sp. Sh10, for it's in vitro inhibitory activity against pre-formed biofilm and in interference with the biofilm-forming of two biofilm-producing bacteria (P. mirabilis UCa4 and P. mirabilis UCe1).

MATERIALS AND METHODS

Sensitivity of two biofilm-producing bacteria (P. mirabilis UCa4 and P. mirabilis UCe1) to bacteriocin, was investigated in planktonic and biofilm states by cell viability and crystal violet assay, respectively. Scanning electron microscopy (SEM) was also performed to determine the effect of bacteriocin on the morphology of the cells associated with biofilm.

RESULTS

It was found that bacteriocin possessed bactericidal activity to biofilm-forming isolates in the planktonic state. However, bacteriocin interferes with the formation of biofilms and disrupts established biofilms. Bacteriocin reduced biofilm formation in the isolates of P. mirabilis UCa4 and P. mirabilis UCe1 with SMIC₅₀ of 32 and 128 μg/mL, desirable SMIC₅₀ of bacteriocin for biofilm disruption were 128 and 256 μg/mL, respectively. The SEM results indicated that bacteriocin affected the cell morphology of biofilm-associated cells.

CONCLUSION

The present findings indicated that bacteriocin from Bacillus sp. Sh10 has bactericidal properties against biofilm-forming isolates of P. mirabilis UCa4 and P. mirabilis UCe1 and has the ability to inhibit the formation of biofilm and disrupt established biofilm.

In vitro antibacterial activity of medicinal plants against biofilm-forming methicillin-resistant Staphylococcus aureus: efficacy of Moringa stenopetala and Rosmarinus officinalis extracts

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) is slowly rising in Ethiopia for the past few decades. Therefore, novel classes of antibiotics are indispensable to combat the increased incidence of newly emerging multidrug-resistant bacteria like MRSA. Terrestrial flora is considered as a reservoir of novel bioactive secondary metabolites as they have provided us with the largest array of natural products. In this background, the present study is intended to evaluate the in-vitro antibacterial efficacy of five medicinal plants (Ocimum lamiifolium Hochst. ex Benth., Rosmarinus officinalis L, Catharanthus roseus Linn., Azadirachta indica A. Juss and Moringa stenopetala Bac) against a panel of seven biofilm-forming MRSA. The leaves of the plants were extracted in organic solvents of varying polarity and the resultant crude extracts of respective medicinal plants were inspected for their antimicrobial activity by well diffusion technique. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the plant extracts against MRSA were determined by the broth dilution method. Besides, an anti-biofilm assay of the most potent plant extract was also performed, after which its chemical constituents were delineated by combined Gas Chromatographic and Mass Spectroscopic profiling (GC-MS). The results revealed that, of the five plants, three species including M. stenopetala, R. officinalis, and O. lamifolium exhibited significant antibacterial activity. Organic solvents with high and medium polarity were excellent in extracting antimicrobials compared to nonpolar solvents. The broadest and highest rank of activity was observed in the crude ethanolic extract of M. stenopetala. Based on the MIC/MBC ratio, the crude ethanolic extract of M. stenopetala was determined to be bacteriostatic. Anti-biofilm assay showed that the extract of M. stenopetala fairly inhibited the growth of MRSA in the preformed biofilm matrix. The GC-MS analysis of M. stenopetala revealed the presence of twelve compounds with antimicrobial activity. The present study provides new insight into the development of novel drug leads to the management of MRSA.

Antimicrobial and biochemical characterization of a C-type lectin isolated from pearl spot (Etroplus suratensis)

The present study reveals purification and characterization of a C-type lectin from the serum of pearl spot, Etroplus suratensis (Es-Lec). The Es-Lec was purified by affinity chromatography with mannose coupled sepharose CL-4B column and it exhibits single band with a molecular weight of 75 kDa in SDS-PAGE. The surface morphology of purified Es-Lec displays the homogeneous nature of protein. A distinct peak with a retention time of 2.958 min was appeared in high performance liquid chromatography (HPLC), X-ray diffraction (XRD) analysis expresses a single peak at 31.8372̊ and MALDI-TOF peaks which shows the purity and crystalline nature of the protein respectively. Functional analysis of purified Es-Lec exhibits yeast agglutination activity against Saccharomyces cerevisiae and has the ability to agglutinate the human erythrocytes, which was observed by light microscopy and haemagglutination inhibition was also done. In addition, purified Es-Lec showed the broad spectrum of antibacterial activity against Gram negative Vibrio parahaemolyticus and Aeromonas hydrophila. Antibiofilm potential of purified Es-Lec against selected Gram-negative bacteria exhibited the disruption of biofilm architecture at the concentration of 50 μg ml^-1 and also it exhibited antiviral and anticancer activity.

Anti-biofilm Activity Against Gram-Positive Bacteria by Biologically Synthesized Silver Nanoparticles Using Curcuma longa

OBJECTIVE

To assess the biofilm inhibition activity of biosynthesized silver nanoparticles (AgNPs) using Curcuma longa.

METHOD

Characterizations of these biogenic nanoparticles were done by UV-Vis spectroscopy, TEM, EDX and nanoparticles tracking analyzer. The antibiofilm activity of AgNPs against S. aureus and S. pneumoniae was carried out by 96 well plate method. Further, the combined effect of AgNPs with the antibiotic was studied against S. aureus and S. pneumoniae.

RESULTS

UV-spectroscopic analysis showed a surface plasmon resonance peak at 415nm. The shape of AgNPs is spherical with an average size of 20-40 nm while the elemental silver was confirmed by EDX analysis. These biosynthesized AgNPs have anti-biofilm activity against S. aureus and S. pneumoniae. Furthermore, the combined effect of AgNPs with an antibiotic, showed enhanced anti-biofilm activity against both the strains under study.

CONCLUSION

C. longa mediated AgNPs showed potent anti-biofilm activity.

Chemical composition of Pistacia vera L. oleoresin and its antibacterial, anti-virulence and anti-biofilm activities against oral streptococci, including Streptococcus mutans

OBJECTIVE

The aim of this study was to characterize the chemical composition of oleoresin of Pistacia vera L. and to determine its antimicrobial and anti-virulence activity versus selected oral streptococci.

DESIGN

A gaschromatografic analysis of the oleoresin was performed. The antimicrobial and anti-virulence activity of the oleoresin and its fractions was evaluated by the Minimum Inhibitory Concentration (MIC) and/or Minimum Bactericidal Concentration (MBC), biofilm production and haemolytic activity inhibition experiments.

RESULTS

The oleoresin MBCs were ≥1024 μg/mL for all tested strains; the neutral and acidic fraction MBCs ranged from 128 to 2048 μg/mL. Essential oil's MBCs (from 256 to 2048 μg/mL) were almost identical to MICs, suggesting a bactericidal effect. P. vera oleoresin at sub-lethal concentrations significantly reduced biofilm production by Streptococcus mutans (up to 49.4%) and by Streptococcus sanguinis (up to 71.2%). In addition, the acidic fraction showed a specific anti-biofilm activity against S. mutans (up to 41.3% reduction). A significant dose-dependent reduction in the haemolytic activity of S. mutans (up to 65.9%) and of S. anginosus (up to 78.3%) was observed after growth in the presence of oleoresin at sub-lethal concentrations. The acidic fraction reduced haemolytic activity (up to 54.3% at 64 μg/mL) of S. mutans only.

CONCLUSIONS

Given the anti-virulence activity of the P. vera oleoresin and its acidic fraction against S. mutans, our findings suggest their potential use in oral hygiene. These data represent the first step in the exploitation of P. vera L. oleoresin.

Plasma-activated water: antibacterial activity and artifacts?

Broad biological activities of "plasma-activated water" (PAW) have drawn great attentions recently. Treatment of water using gas discharge plasma led to acidic solutions with excellent and broad antibacterial activity. Because PAW caused severe membrane damages in bacteria and diffused freely in extracellular matrix, PAW also demonstrated good anti-biofilm activity. However, further studies revealed that trace amounts of metal ions (mainly copper and zinc) in PAW brought by plasma treatment played key roles in bacteria inactivation. The contribution of metal ions to the antibacterial activity varied among PAWs from different working gases. However, solution acidification caused by reactive species in plasma was essential. The experimental results demonstrated that potential artifacts in reported biological activities of PAWs should be considered.

Effect of resveratrol and Regrapex-R-forte on Trichosporon cutaneum biofilm

Microorganisms that cause chronic infections exist predominantly as surface-attached stable communities known as biofilms. Microbial cells in biofilms are highly resistant to conventional antibiotics and other forms of antimicrobial treatment; therefore, modern medicine tries to develop new drugs that exhibit anti-biofilm activity. We investigated the influence of a plant polyphenolic compound resveratrol (representative of the stilbene family) on the opportunistic pathogen Trichosporon cutaneum. Besides the influence on the planktonic cells of T. cutaneum, the ability to inhibit biofilm formation and to eradicate mature biofilm was studied. We have tested resveratrol as pure compound, as well as resveratrol in complex plant extract-the commercially available dietary supplement Regrapex-R-forte, which contains the extract of Vitis vinifera grape and extract of Polygonum cuspidatum root. Regrapex-R-forte is rich in stilbenes and other biologically active substances. Light microscopy imaging, confocal microscopy, and crystal violet staining were used to quantify and visualize the biofilm. The metabolic activity of biofilm-forming cells was studied by the tetrazolium salt assay. Amphotericin B had higher activity against planktonic cells; however, resveratrol and Regrapex-R-forte showed anti-biofilm effects, both in inhibition of biofilm formation and in the eradication of mature biofilm. The minimum biofilm eradicating concentration (MBEC₈₀) for Regrapex-R-forte was found to be 2222 mg/L (in which resveratrol concentration is 200 mg/L). These methods demonstrated that Regrapex-R-forte can be employed as an anti-biofilm agent, as it has similar effect as amphotericin B (MBEC₈₀ = 700 mg/L), which is routinely used in clinical practice.

Chitosans as new tools against biofilms formation on the surface of silicone urinary catheters

Urinary catheters contamination by microorganisms is a major cause of hospital acquired infections and represents a limitation for long-term use. In this work, biofilms of Klebsiella pneumoniae and Escherichia coli clinical isolates were developed on urinary catheters for 48 and 72 h in artificial urine medium (AUM) with different molecular weight chitosans (AUM-CS solutions) at pH 5.0. The number of viable bacteria was determined by standard plate count agar while crystal violet (CV) staining was carried out to assess biomass production (optical density at 570 nm) in the mentioned conditions. Re-growth of each strain was also evaluated after 24 h re-incubation of the treated catheters. Significant decreases of log CFU/catheter and biomass production were observed for all the biofilms developed in AUM-CS compared with the controls in AUM. The percentages of biofilm removal were slightly higher for E. coli biofilms (up to 90.4%) than those of K. pneumoniae (89.7%); in most cases, the complete inhibition of bacterial re-growth on treated catheter pieces was observed. Contact time influenced chitosan efficacy rather than its molecular weight or the biofilms age. The results confirmed the potentiality of chitosans as a biomacromolecule tool to contrast biofilm formation and reduce bacterial re-growth on urinary catheters.

The optimal ethanol lock therapy regimen for treatment of biofilm-associated catheter infections: an in-vitro study

BACKGROUND

Ethanol-based lock therapy (LT) solutions are used as an alternative to antibiotics for the conservative management of catheter-related bloodstream infection. However, no clear consensus on regimen or dose has been reached.

AIM

To find the ethanol-based lock solution containing a sufficiently low concentration of ethanol for reduction of the metabolic activity of bacterial and fungal biofilms.

METHODS

Using an in-vitro model, three concentrations of ethanol (25%, 40%, 70%) were tested, with and without 60 IU of heparin, at six different time-points and against 24 h preformed biofilms of Staphylococcus aureus ATCC29213, Staphylococcus epidermidis (clinical isolate), Enterococcus faecalis ATCC33186, Candida albicans ATCC14058, and Escherichia coli ATCC25922. The reduction in the metabolic activity of the biofilm was measured using the tetrazolium salt assay and LT was considered to be successful when metabolic activity fell by >90%. Regrowth inhibition was then tested within 24 h and seven days after each LT regimen only at the ethanol concentration of the most successful LT regimen.

FINDINGS

The most successful LT was achieved with 40% ethanol + 60 IU of heparin only at 24, 72, and 24 h for seven-day regimens (P < 0.05). However, none of the regimens reached 45% RI within seven days of therapy.

CONCLUSION

According to our in-vitro data, an ethanol-based lock solution with 40% ethanol + 60 IU heparin administered daily for 72 h is sufficient to almost eradicate the metabolic activity of bacterial and fungal biofilms. Future studies are needed to study cell regrowth after LT.

Screening of Anti-Biofilm Compounds from Marine-Derived Fungi and the Effects of Secalonic Acid D on Staphylococcus aureus Biofilm

Biofilm formation of Staphylococcus aureus is one of its mechanisms of drug resistance. Antibiofilm screening of 106 compounds from marine-derived fungi displayed that 12 compounds inhibited S. aureus biofilm formation by >50% at the concentration of 100 μg/ml, and only secalonic acid D (SAD) and B inhibited by >90% at 6.25 μg/ml without inhibiting cell growth after 24-h incubation. Meanwhile, it was found that the double bond between C-1 and C-10 of citrinin derivatives and the C-C connection position of two chromone monomers may be important for their anti-biofilm activities. Moreover, SAD slightly facilitated biofilm eradication and influenced its architecture. Furthermore, SAD slowed the cell growth rate in the preceding 18-h incubation and differentially regulated transcriptional expression of several genes, such as agr, isaA, icaA, and icaD, associated with biofilm formation in planktonic and biofilm cells, which may be the reason for the anti-biofilm activity of SAD. Finally, SAD acted synergistically against S. aureus growth and biofilm formation with other antibiotics. These findings indicated that various natural products from marine-derived fungi, such as SAD, could be used as a potential biofilm inhibitor against S. aureus.

In vitro assessment of the anti-biofilm activity of ethanol alone and in combination with enoxaparin 60IU

INTRODUCTION

Catheter-related bloodstream infection (C-RBSI) can sometimes be managed without catheter removal by combining systemic therapy with catheter lock therapy. Most antiseptic lock solutions are made up of ethanol combined with an anticoagulant. However, data regarding the anti-biofilm activity of ethanol combined with enoxaparin are scarce. We aimed to assess the efficacy of ethanol at different concentrations combined with enoxaparin 60IU as a lock solution for eradication of the biofilm of different microorganisms.

METHODS

Using a static 96-well plate in vitro model, we tested 30%, 35%, and 40% ethanol alone and combined with 60IU of enoxaparin against 24-h-old biofilm from the following microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, and Candida albicans. Time of exposure was assessed during a 2-h and 24-h regimen. We analysed the percentage reduction in metabolic activity using the XTT assay. We considered therapy to be successful when metabolic activity was reduced by >90%.

RESULTS

In the 2-h regimen, the therapy was successful against all microorganisms at 35% and 40% ethanol without enoxaparin (p<0.001). In the 24-h regimen, the therapy was successful against all microorganisms at all ethanol solutions without enoxaparin (p<0.001). When ethanol was combined with enoxaparin, the therapy was only successful in the 24-h regimen in biofilms of S. epidermidis, C. albicans and E. coli at all concentrations of ethanol assessed.

CONCLUSIONS

Our in vitro model demonstrated that when ethanol is combined with enoxaparin in a lock solution, it negatively affects ethanol anti-biofilm activity after both short and long exposures.

The effect of emodin on Staphylococcus aureus strains in planktonic form and biofilm formation in vitro

Staphylococcus aureus (S. aureus) is a Gram-positive pathogen and forms biofilm easily. Bacteria inside biofilms display an increased resistance to antibiotics and disinfectants. The objective of the current study was to assess the antimicrobial activities of emodin, 1,2,8-trihydroxy-6-methylanthraquinone, an anthraquinone derivative isolated from Polygonum cuspidatum and Rheum palmatum, against S. aureus CMCC26003 grown in planktonic and biofilm cultures in vitro. In addition, a possible synergistic effect between emodin and berberine chloride was evaluated. As quantified by crystal violet method, emodin significantly decreased S. aureus biofilm growth in a dose-dependent manner. The above findings were further supported by scanning electron microscopy. Moreover, the present study demonstrated that sub-MICs emodin obviously intervened the release of extracellular DNA and inhibited expression of the biofilm-related genes (cidA, icaA, dltB, agrA, sortaseA and sarA) by real-time RT-PCR. These results revealed a promising application for emodin as a therapeutic agent and an effective strategy to prevent S. aureus biofilm-related infections.

LL-37-derived membrane-active FK-13 analogs possessing cell selectivity, anti-biofilm activity and synergy with chloramphenicol and anti-inflammatory activity

Although the human-derived antimicrobial peptide (AMP) LL-37 has potent antimicrobial and anti-inflammatory activities, its therapeutic application is limited by its low cell selectivity and high production cost due to its large size. To overcome these problems, we tried to develop novel LL-37-derived short α-helical AMPs with improved cell selectivity and without a significant loss of anti-inflammatory activity relative to that of parental LL-37. Using amino acid substitution, we designed and synthesized a series of FK13 analogs based on the sequence of the 13-meric short FK13 peptide (residues 17-29 of LL-37) that has been identified as the region responsible for the antimicrobial activity of LL-37. Among the designed FK13 analogs, FK-13-a1 and FK-13-a7 showed high cell selectivity and retained the anti-inflammatory activity. The therapeutic index (a measure of cell selectivity) of FK-13-a1 and FK-13-a7 was 6.3- and 2.3-fold that of parental LL-37, respectively. Furthermore, FK-13-a1 and FK-13-a7 displayed more potent antimicrobial activity against antibiotic-resistant bacteria including MRSA, MDRPA, and VREF, than did LL-37. In addition, FK-13-a1 and FK-13-a7 exhibited greater synergistic effects with chloramphenicol against MRSA and MDRPA and were more effective anti-biofilm agents against MDRPA than LL-37 was. Moreover, FK-13-a1 and FK-13-a7 maintained their activities in the presence of physiological salts and human serum. SYTOX green uptake, membrane depolarization and killing kinetics revealed that FK13-a1 and FK13-a7 kills microbial cells by permeabilizing the cell membrane and damaging membrane integrity. Taken together, our results suggest that FK13-a1 and FK13-a7 can be developed as novel antimicrobial/anti-inflammatory agents.

Gold-nanoparticles coated with the antimicrobial peptide esculentin-1a(1-21)NH2 as a reliable strategy for antipseudomonal drugs

Naturally occurring antimicrobial peptides (AMPs) hold promise as future therapeutics against multidrug resistant microorganisms. Recently, we have discovered that a derivative of the frog skin AMP esculentin-1a, Esc(1-21), is highly potent against both free living and biofilm forms of the bacterial pathogen Pseudomonas aeruginosa. However, bringing AMPs into clinics requires to overcome their low stability, high toxicity and inefficient delivery to the target site at high concentrations. Importantly, peptide conjugation to gold nanoparticles (AuNPs), which are among the most applied inorganic nanocarriers in biomedical sciences, represents a valuable strategy to solve these problems. Here we report that covalent conjugation of Esc(1-21) to soluble AuNPs [AuNPs@Esc(1-21)] via a poly(ethylene glycol) linker increased by ∼15-fold the activity of the free peptide against the motile and sessile forms of P. aeruginosa without being toxic to human keratinocytes. Furthermore, AuNPs@Esc(1-21) resulted to be significantly more resistant to proteolytic digestion and to disintegrate the bacterial membrane at very low concentration (5nM). Finally, we demonstrated for the first time the capability of peptide-coated AuNPs to display a wound healing activity on a keratinocytes monolayer. Overall, these findings suggest that our engineered AuNPs can serve as attractive novel biological-derived material for topical treatment of epithelial infections and healing of the injured tissue.

STATEMENT OF SIGNIFICANCE

Despite conjugation of AMPs to AuNPs represents a worthwhile solution to face some limitations for their development as new therapeutics, only a very limited number of studies is available on peptide-coated AuNPs. Importantly, this is the first report showing that a covalent binding of a linear AMP via a poly(ethylene glycol) linker to AuNPs highly enhances antipseudomonal activity, preserving the same mode of action of the free peptide, without being harmful. Furthermore, AuNPs@Esc(1-21) are expected to accelerate recovery of an injured skin layer. All together, these findings suggest our peptide-coated AuNPs as attractive novel nanoscale formulation to treat bacterial infections and to heal the injured tissue.

Methods for Investigating Biofilm Inhibition and Degradation by Antimicrobial Peptides

Multidrug-resistant bacteria are a growing problem worldwide. One extensively studied resistance mechanism is biofilm colonization-microbial colonies formed by many Gram-positive and Gram-negative bacteria species. Cationic antimicrobial peptides (AMPs) are innate immune system molecules serving as a first line of defense in fighting invading pathogens. The AMPs' underlying mechanism and biophysical properties required for anti-biofilm activity are not fully known. Here we present protocols for investigating AMPs' biological activity against major stages of biofilm life cycle, namely, planktonic stage (MIC assay), initial adhesion to surfaces (bacterial attachment assay), and formation or degradation of sessile microcolonies (biofilm formation and degradation assays). Furthermore, we demonstrate experiments that allow determination and comparison between peptide biophysical properties (secondary structure, hydrophobicity, and oligomerization) and how they affect their mechanism (peptide-binding assays) of anti-biofilm activity.

Characterization of potential lytic bacteriophage against Vibrio alginolyticus and its therapeutic implications on biofilm dispersal

Vibrio alginolyticus is a leading cause of vibriosis, presenting opportunistic infections to humans associated with raw seafood contamination. At present, phage therapy that acts as an alternative sanitizing agent is explored for targeting V. alginolyticus. The study outcome revealed that the phage VP01 with its extreme lytic effect showed a high potential impact on the growth of V. alginolyticus as well as biofilm formation. Electron microscopy revealed the phage resemblance to Myoviridae, based on its morphology. Further study clarified that the phage VP01 possesses a broad host spectrum and amazing phage sensitivity at different pH, high thermal stability, and high burst size of 415 PFU/cell. In addition, the investigation of phage co-culturing against this pathogen resulted in a significant growth reduction even at less MOIs 0.1 and 1. These results suggest that the phage could be a promising candidate for the control of V. alginolyticus infections.

Pyrazole derived ultra-short antimicrobial peptidomimetics with potent anti-biofilm activity

In this study, we report on the first chemical synthesis of ultra-short pyrazole-arginine based antimicrobial peptidomimetics derived from the newly synthesized N-alkyl/aryl pyrazole amino acids. Through the systematic tuning of hydrophobicity, charge, and peptide length, we identified the shortest peptide Py11 with the most potent antimicrobial activity. Py11 displayed greater antimicrobial activity against antibiotic-resistant bacteria, including MRSA, MDRPA, and VREF, which was approximately 2-4 times higher than that of melittin. Besides its higher selectivity (therapeutic index) toward bacterial cells than LL-37, Py11 showed highly increased proteolytic stability against trypsin digestion and maintained its antimicrobial activity in the presence of physiological salts. Interestingly, Py11 exhibited higher anti-biofilm activity against MDRPA compared to LL-37. The results from fluorescence spectroscopy and transmission electron microscopy (TEM) suggested that Py11 kills bacterial cells possibly by integrity disruption damaging the cell membrane, leading to the cytosol leakage and eventual cell lysis. Furthermore, Py11 displayed significant anti-inflammatory (endotoxin-neutralizing) activity by inhibiting LPS-induced production of nitric oxide (NO) and TNF-α. Collectively, our results suggest that Py11 may serve as a model compound for the design of antimicrobial and antisepsis agents.

The lipopeptide 6-2 produced by Bacillus amyloliquefaciens anti-CA has potent activity against the biofilm-forming organisms

Both the whole cells and protoplasts of Pseudomonas aeruginosa PAO1 and Bacillus cereus, two biofilm-forming bacteria, were disrupted by the lipopeptide 6-2 produced by Bacillus amyloliquefaciens anti-CA. The lipopeptide 6-2 could also effectively inhibit the formation of biofilms and disperse pre-formed biofilms. Live/dead staining of the biofilms grown in the absence or presence of the lipopeptide 6-2 showed that more dead bacterial cells in the presence of the lipopeptide than those in the absence of the lipopeptide and biofilm formation was greatly reduced by the lipopeptide 6-2. Expression of the PslC gene related to exopolysaccharides in P. aeruginosa PAO1 was also inhibited. All these results demonstrated that the lipopeptide 6-2 produced by B. amyloliquefaciens anti-CA had a high activity against biofilm-forming bacteria. The lipopeptide 6-2 also killed the larvae of Balanus amphitrite and inhibit the germination of Laminaria japonica spore and growth of protozoa, all of which were the fouling organisms in marine environments.

Enhanced efficacy and anti-biofilm activity of novel nanoemulsions against skin burn wound multi-drug resistant MRSA infections

Multi-drug resistant MRSA (methicillin-resistant Staphylococcus aureus) is a global problem for human health, especially skin burn wound patients. Therefore, we estimated the antibacterial and anti-biofilm activity of a chlorhexidine acetate nanoemulsion (CNE) by previously ourselves designed against skin burn wound MRSA infections. Compared with its water solution (CHX), CNE showed a better and faster action against MRSA both in vitro and in vivo. Importantly, CNE was more effective at inhibiting biofilm formation and clearing the biofilm. We also found that the cell walls and membranes of MRSA were severely disrupted after treatment with CNE. Moreover, the relative electrical conductivity and the leakage of alkaline phosphates, K(+), Mg(2+), DNA and protein obviously increased because the cell wall and membrane were damaged. These data show that novel CNE is a promising potential antimicrobial candidate, especially for skin burn wound MRSA infections.

D-Amino acids incorporation in the frog skin-derived peptide esculentin-1a(1-21)NH2 is beneficial for its multiple functions

Naturally occurring antimicrobial peptides (AMPs) represent promising future antibiotics. We have previously isolated esculentin-1a(1-21)NH2, a short peptide derived from the frog skin AMP esculentin-1a, with a potent anti-Pseudomonal activity. Here, we investigated additional functions of the peptide and properties responsible for these activities. For that purpose, we synthesized the peptide, as well as its structurally altered analog containing two D-amino acids. The peptides were then biophysically and biologically investigated for their cytotoxicity and immunomodulating activities. The data revealed that compared to the wild-type, the diastereomer: (1) is significantly less toxic towards mammalian cells, in agreement with its lower α-helical structure, as determined by circular dichroism spectroscopy; (2) is more effective against the biofilm form of Pseudomonas aeruginosa (responsible for lung infections in cystic fibrosis sufferers), while maintaining a high activity against the free-living form of this important pathogen; (3) is more stable in serum; (4) has a higher activity in promoting migration of lung epithelial cells, and presumably in healing damaged lung tissue, and (5) disaggregates and detoxifies the bacterial lipopolysaccharide (LPS), albeit less than the wild-type. Light scattering studies revealed a correlation between anti-LPS activity and the ability to disaggregate the LPS. Besides shedding light on the multifunction properties of esculentin-1a(1-21)NH2, the D-amino acid containing isomer may serve as an attractive template for the development of new anti-Pseudomonal compounds with additional beneficial properties. Furthermore, together with other studies, incorporation of D-amino acids may serve as a general approach to optimize the future design of new AMPs.

Silver nanoparticles with antimicrobial activities against Streptococcus mutans and their cytotoxic effect

Microbial resistance represents a challenge for the scientific community to develop new bioactive compounds. The goal of this research was to evaluate the antimicrobial activity of silver nanoparticles (AgNPs) against a clinical isolate of Streptococcus mutans, antibiofilm activity against mature S. mutans biofilms and the compatibility with human fibroblasts. The antimicrobial activity of AgNPs against the planktonic clinical isolate was size and concentration dependent, with smaller AgNPs having a lower minimum inhibitory concentration. A reduction of 2.3 log in the number of colony-forming units of S. mutans was observed when biofilms grown in a CDC reactor were exposed to 100 ppm of AgNPs of 9.5±1.1 nm. However, AgNPs at high concentrations (>10 ppm) showed a cytotoxic effect upon human dermal fibroblasts. AgNPs effectively inhibited the growth of a planktonic S. mutans clinical isolate and killed established S. mutans biofilms, which suggests that AgNPs could be used for prevention and treatment of dental caries. Further research and development are necessary to translate this technology into therapeutic and preventive strategies.

Anti-biofilm and cytotoxicity activity of impregnated dressings with silver nanoparticles

Infections arising from bacterial adhesion and colonization on chronic wounds are a significant healthcare problem. Silver nanoparticles (AgNPs) impregnated in dressing have attracted a great deal of attention as a potential solution. The goal of the present study was to evaluate the anti-biofilm activities of AgNPs impregnated in commercial dressings against Pseudomonas aeruginosa, bacteria isolated of chronic wounds from a hospital patient. The antimicrobial activity of AgNPs was tested within biofilms generated under slow fluid shear conditions using a standard bioreactor. A 2-log reduction in the number of colony-forming units of P. aeruginosa was recorded in the reactor on exposure to dressing impregnated with 250ppm of AgNPs, diameter 9.3±1.1nm, and also showed compatibility to mammalian cells (human fibroblasts). Our study suggests that the use of dressings with AgNPs may either prevent or reduce microbial growth in the wound environment, and reducing wound bioburden may improve wound-healing outcomes.

Enhanced antibacterial and anti-biofilm activities of silver nanoparticles against Gram-negative and Gram-positive bacteria

Silver nanoparticles (AgNPs) have been used as antibacterial, antifungal, antiviral, anti-inflammtory, and antiangiogenic due to its unique properties such as physical, chemical, and biological properties. The present study was aimed to investigate antibacterial and anti-biofilm activities of silver nanoparticles alone and in combination with conventional antibiotics against various human pathogenic bacteria. Here, we show that a simple, reliable, cost effective and green method for the synthesis of AgNPs by treating silver ions with leaf extract of Allophylus cobbe. The A. cobbe-mediated synthesis of AgNPs (AgNPs) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the antibacterial and anti-biofilm activity of antibiotics or AgNPs, or combinations of AgNPs with an antibiotic was evaluated using a series of assays: such as in vitro killing assay, disc diffusion assay, biofilm inhibition, and reactive oxygen species generation in Pseudomonas aeruginosa, Shigella flexneri, Staphylococcus aureus, and Streptococcus pneumonia. The results suggest that, in combination with antibiotics, there were significant antimicrobial and anti-biofilm effects at lowest concentration of AgNPs using a novel plant extract of A. cobbe, otherwise sublethal concentrations of the antibiotics. The significant enhancing effects were observed for ampicillin and vancomycin against Gram-negative and Gram-positive bacteria, respectively. These data suggest that combining antibiotics and biogenic AgNPs can be used therapeutically for the treatment of infectious diseases caused by bacteria. This study presented evidence of antibacterial and anti-biofilm effects of A. cobbe-mediated synthesis of AgNPs and their enhanced capacity against various human pathogenic bacteria. These results suggest that AgNPs could be used as an adjuvant for the treatment of infectious diseases.

Spectroscopic identification and anti-biofilm properties of polar metabolites from the medicinal plant Helichrysum italicum against Pseudomonas aeruginosa

Two new acylated styrylpyrones, one 5-methoxy-1(3H)-isobenzofuranone glucoside and a hydroxymethyl-orcinol derivative, along with sixteen known aromatic metabolites, including lignans, quinic acid derivatives low-molecular weight phenol glucosides, have been isolated from the methanol extract of Helichrysum italicum, a medicinal plant typical of the Mediterranean vegetation. The structures of these compounds have been elucidated on the basis of extensive 2D-NMR spectroscopic analyses, including COSY, TOCSY, HSQC, CIGAR-HMBC, H2BC and HSQC-TOCSY, along with Q-TOF HRMS(2) analysis. Selected compounds were evaluated for their anti-biofilm properties against Pseudomonas aeruginosa.

Inhibitory effect of N-ethyl-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide on Haemophilus spp. planktonic or biofilm-forming cells

During this study, we have investigated in vitro activity of N-substituted-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide derivatives with N-ethyl, N-(4-metoxyphenyl) and N-cyclohexyl substituents against Gram-negative Haemophilus influenzae and H. parainfluenzae bacteria. A spectrophotometric assay was used in order to determine the bacterial growth and biofilm formation using a microtiter plate to estimate minimal inhibitory concentration (MIC) and minimal biofilm inhibitory concentration (MBIC). Among the tested N-substituted pyrazole derivatives, only N-ethyl-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide showed a significant in vitro activity against both planktonic cells of H. parainfluenzae (MIC = 0.49-31.25 μg ml^-1) and H. influenzae (MIC = 0.24-31.25 μg ml^-1) as well as biofilm-forming cells of H. parainfluenzae (MBIC = 0.24-31.25 μg ml^-1) and H. influenzae (MBIC = 0.49 to ≥31.25 μg ml^-1). The pyrazole compound exerted higher inhibitory effect both on the growth of planktonic cells and biofilm formation by penicillinase-positive and penicillinase-negative isolates of H. parainfluenzae than the activity of commonly used antibiotics such as ampicillin. No cytotoxicity of the tested compound in vitro at concentrations used was found. The tested pyrazole N-ethyl derivative could be considered as a compound for the design of agents active against both pathogenic H. influenzae and opportunistic H. parainfluenzae, showing also anti-biofilm activity. This appears important because biofilms are determinants of bacterial persistence in long-term and recurrent infections recalcitrant to standard therapy.