Methicillin-resistant Staphylococcus Aureus Biofilm Research Articles

Callistemon citrinus bioactive metabolites as new inhibitors of methicillin-resistant Staphylococcus aureus biofilm formation

Ethnopharmacological relevanceThe development of new inhibitors of bacterial virulence factors from natural origin has recently received significant attention. Callistemon citrinus Skeels is an important plant of great medicinal value. Its antimicrobial activity is well documented. Although several compounds were isolated from this plant, the actual bioactive compounds responsible for its antimicrobial activity are still unrevealed. Aim of the studyTo evaluate the effect of C. citrinus crude extract and isolated compounds on methicillin-resistant and sensitive Staphylococcus aureus. Materials and methodsThe methylene chloride-methanol extract (MME) of C. citrinus leaves was prepared by Soxhlet apparatus. Biologically guided fractionation of MME was accomplished using several normal and reversed phase silica gel columns. The potency of MME and its isolated compounds against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) was evaluated. In addition, the mechanism of resistance was studied using three virulence factors; antibiofilm activity, inhibition of staphyloxanthin biosynthesis and effect on acid tolerance. Ultrastructural changes in MRSA and MSSA were observed by TEM to understand mode of action of these compounds. ResultsPulverulentone A (C1), 8- desmethyl eucalyptin (C2) and eucalyptin (C3) were isolated from the most bioactive fraction of MME. Confocal scanning laser microscopy images revealed that C. citrinus isolated compounds destroyed the intact architecture of biofilm, thickness and reduced its biomass. Pulverulentone A (C1) showed the most potent anti-biofilm activity up to 71% and 62.3% against MRSA and MSSA, respectively. It also exhibited the highest inhibition of staphyloxanthin biosynthesis of MRSA and MSSA by 55.6% and 54.5%, respectively. The bacterial cell membrane was compromised, losing its integrity and releasing important cellular constituents when exposed to C1-C3 ConclusionsC. citrinus phenolics and acylphloroglucinols may serve as potential source of plant-based antibacterials and thus could be implicated to control MRSA biofilm formation.

Amphiphilic Cationic Macromolecules Highly Effective Against Multi-Drug Resistant Gram-Positive Bacteria and Fungi With No Detectable Resistance.

The ever increasing threats of Gram-positive superbugs such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), and vancomycin-resistant Enterococccus faecium (VRE) are serious matter of concern worldwide toward public health. Such pathogens cause repeated recurrence of infections through the formation of biofilms which consist of metabolically inactive or slow growing dormant bacterial population in vast majority. Concurrently, dispersal of biofilms originates even more virulent dispersed cells responsible for pathogenesis. Along with this, fungal infections most commonly associated with Candida albicans also created a major complicacy in human healthcare. Moreover, concomitant survival of C. albicans and MRSA in a multispecies biofilms created extremely complicated polymicrobial infections. Surprisingly, infections associated with single species biofilm as well as multiple species biofilm (co-existence of MRSA and C. albicans) are almost untreatable with conventional antibiotics. Therefore, the situation demands an urgent development of antimicrobial agent which would tackle persistent infections associated with bacteria, fungi and their biofilms. Toward this goal, herein we developed a new class of branched polyethyleneimine based amphiphilic cationic macromolecules (ACMs) bearing normal alkyl, alkyl ester and alkyl amide moieties. An optimized compound with dual activity against drug-resistant bacteria (MIC = 2–4 μg/mL) and fungi (MIC = 4–8 μg/mL) was identified with minimal toxicity toward human erythrocytes (HC50 = 270 μg/mL). The lead compound, ACM-AHex (12) displayed rapid bactericidal and fungicidal kinetics (>5 log CFU/mL reduction within 1–4 h). It also killed metabolically dormant stationary (MRSA and VRE) and persister (S. aureus) cells. Moreover, this compound was able to disrupt the preformed biofilm of MRSA and reduced the bacterial burden related to the dispersed cells. It showed significant proficiencies to eliminate polymicrobial biofilms of MRSA and C. albicans. Bacteria also could not develop any resistant against this class of membrane active molecules even after 15 days of successive passages. Taken together this class of macromolecule can be developed further as a dual therapeutic agent to combat infections associated with bacterial and fungal co-existence.

Antibacterial Efficacy of Two Commercially Available Bacteriophage Formulations, Staphylococcal Bacteriophage and PYO Bacteriophage, Against Methicillin-Resistant Staphylococcus aureus: Prevention and Eradication of Biofilm Formation and Control of a Systemic Infection of Galleria mellonella Larvae.

Sessile bacteria growing on surfaces are more resistant to standard antibiotics than their planktonic counterpart. Due to their antimicrobial properties, bacteriophages have re-emerged as a promising approach to treat bacterial biofilm-associated infections. Here, we evaluated the ability of two commercially available phage formulations, Staphylococcal bacteriophage (containing the monophage Sb-1) and PYO bacteriophage (a polyphage), in preventing and eradicating an in vitro biofilm of methicillin-resistant Staphylococcus aureus (MRSA) by isothermal microcalorimetry and high-resolution confocal laser scanning microscopy (CLSM). Moreover, to assess the potential in vivo efficacy of both phage preparations, a Galleria mellonella model of MRSA systemic infection was used. Microcalorimetry measurement showed that 107 PFU/ml (the highest tested titer) of both phage formulations were able to inhibit planktonic growth in a concentration-dependent manner. However, MRSA biofilm was eradicated only by co-incubation of 5–7 days with the highest phage titers, respectively. In the experiments of biofilm prevention, isothermal microcalorimetry revealed that the heat production was completely abolished in the presence of sub-inhibitory titers (104 PFU/ml) of phages. These data were also confirmed by confocal laser scanning microscopy. Both phage formulations increased the survival of G. mellonella larvae preventing or treating MRSA infection compared to untreated control. In conclusion, tested phage formulations are promising for preventing device colonization and killing biofilm bacteria attached on a surface. Novel strategies for direct coating and release of phages from material should be investigated.

Inhibition of methicillin-resistant Staphylococcus aureus (MRSA) biofilm by cationic poly (D, L-lactide-co-glycolide) nanoparticles

The emergent need for new treatment methods for multi-drug resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) has focused attention on novel potential tools like nanoparticles (NPs). In the present study, a drug-free cationic nanoparticles (CNPs) system was developed and its anti-MRSA effects were firstly investigated. The results showed that CNPs (261.7 nm, 26.1 mv) showed time- and concentration-dependent activity against MRSA growth, killing ∼ 90% of planktonic bacterial cells in 3 h at 400 μg ml−1, and completely inhibiting biofilm formation at 1000 μg ml−1. Moreover, CNPs at 400 μg ml−1 reduced the minimum inhibitory concentration (MIC) of vancomycin on inhibition of planktonic MRSA growth (∼ 25%) and biofilm formation (∼ 50%). The CNPs–bacteria interaction force was up to 22 nN. Overall, these data suggest that CNPs have a good potential in clinical applications for the prevention and treatment of MRSA infection.

In situ Treatment With Novel Microbiocide Inhibits Methicillin Resistant Staphylococcus aureus in a Murine Wound Infection Model.

Increased prevalence of antibiotic resistance in skin and soft tissue infections is a concerning public health challenge currently facing medical science. A combinatory, broad spectrum biocidal antiseptic has been developed (“ASP”) as a topically applied solution to potential resistant and polymicrobial infected wounds that may be encountered in this context. The ASP-105 designate was evaluated in vitro by determining the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), against different strains of methicillin-resistant Staphylococcus aureus (MRSA), resulting estimates of which approximated the positive control (bacitracin). To evaluate in vivo microbicide efficacy, we utilized a murine full thickness wound model to study bacterial infection and wound healing kinetics. Mice were experimentally wounded dorsally and infected with bioluminescent MRSA. The infected wound was splinted, dressed and treated topically with either ASP-105, vehicle (-control), or bacitracin. Bacterial burden and wound healing was monitored using an in vivo imaging system and evaluation of biofilm formation using scanning electron microscopy of wound dressing. Treatment with ASP-105 significantly reduced bacterial burdens in the first 3 days of infection and inhibited MRSA biofilm formation on the surgical dressing. Notably, treatment with ASP-105 resulted in a sterilizing effect of any detectable MRSA in nearly all (80%; 4/5) of treatment group. All mice receiving vehicle control developed highly MRSA-luminescent and purulent wound beds as a result of experimental infection. The ASP-105 therapy facilitated natural healing in the absence of MRSA infection. Results of this study suggests that that the novel “ASP” combinatory topical antiseptic can be used directly in wounds as a potent, broad-spectrum microbicide against drug resistant S. aureus without injury to the wound bed and impediment of natural restorative processes associated with wound healing. Further studies are warranted to test the effectiveness of this biocidal formulation against other recalcitrant bacterial and fungal pathogens in the context of serious wound infections, and to assess utility of use in both clinical and self-treat scenarios.

Inhibition mechanism of cardamom essential oil on methicillin-resistant Staphylococcus aureus biofilm

In recent years, studies have found that in addition to nosocomial infections, methicillin-resistant Staphylococcus aureus (MRSA) can even cause community-associated infections, and MRSA spreads through food and animal that produce products in the community. In addition, MRSA can colonize the surface of food and food container and form biofilms by secreting extracellular polymers, leading to cross-infection. Cardamom essential oil has been found to be highly active against MRSA. Therefore, this study aimed to investigate the inhibitory effect of cardamom essential oil on MRSA biofilm and its mechanism. The semi-quantitative test results of crystal violet and the removal of MRSA biofilm on different food container materials show that cardamom essential oil can effectively remove MRSA biofilm and can be applied to the surface of food container materials. Meanwhile, the inhibition mechanism of cardamom essential oil on MRSA biofilm was studied by measuring the metabolic activity, extracellular polymer content and relative expression of MRSA biofilm formation related genes. Based on results, it is presumed that cardamom essential oil can function to scavenge MRSA biofilm by inhibiting the metabolic activity of bacteria, inhibiting the formation of extracellular polymers, and regulating the expression of genes involved in biofilm formation.

Activity of pulmonary vancomycin exposures versus planktonic and biofilm isolates of methicillin-resistant Staphylococcus aureus from cystic fibrosis sputum

Vancomycin is commonly used to treat methicillin-resistant Staphylococcus aureus (MRSA) infections in patients with cystic fibrosis (CF) lung disease. However, there are limited data to support the in vitro activity of this agent against MRSA isolated from CF sputum. The primary objective of this study was to evaluate the activity of vancomycin at pulmonary concentrations (intravenous and inhaled) against four clinical MRSA CF sputum isolates in planktonic and biofilm time-kill (TK) experiments. Vancomycin minimum inhibitory concentrations (MICs) were determined for these isolates at standard inoculum (SI) (~106 CFU/mL) and high inoculum (HI) (~108 CFU/mL) as well as in biofilms cultivated using physiological medium representing the microenvironment of the CF lung. Vancomycin concentrations of 10, 25, 100 and 275 µg/mL were evaluated in TK experiments against planktonic MRSA at varying inocula and versus biofilm MRSA. Vancomycin MICs increased from 0.5 µg/mL when tested at SI to 8-16 µg/mL at HI. Vancomycin MICs were further increased to 16-32 µg/mL in biofilm studies. In TK experiments, vancomycin displayed bactericidal activity (≥3 log10 killing at 24 h) against 1/4 and 0/4 planktonic MRSA isolates at SI and HI, respectively, whereas vancomycin was bactericidal against 0/4 isolates against MRSA biofilms. Based on these findings, vancomycin monotherapy appears unlikely to eradicate MRSA from the respiratory tract of patients with CF, even at high concentrations similar to those observed with inhaled therapy. Novel vancomycin formulations with enhanced biofilm penetration or combination therapy with other potentially synergistic agents should be explored.

Thymol Inhibits Biofilm Formation, Eliminates Pre-Existing Biofilms, and Enhances Clearance of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Mouse Peritoneal Implant Infection Model.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common human pathogen that causes several difficult-to-treat infections, including biofilm-associated infections. The biofilm-forming ability of S. aureus plays a pivotal role in its resistance to most currently available antibiotics, including vancomycin, which is the first-choice drug for treating MRSA infections. In this study, the ability of thymol (a monoterpenoid phenol isolated from plants) to inhibit biofilm formation and to eliminate mature biofilms, was assessed. We found that thymol could inhibit biofilm formation and remove mature biofilms by inhibiting the production of polysaccharide intracellular adhesin (PIA) and the release of extracellular DNA (eDNA). However, cotreatment with thymol and vancomycin was more effective at eliminating MRSA biofilms, in a mouse infection model, than monotherapy with vancomycin. Comparative histopathological analyses revealed that thymol reduced the pathological changes and inflammatory responses in the wounds. Assessments of white blood cell counts and serum TNF-α and IL-6 levels showed reduced inflammation and an increased immune response following treatment with thymol and vancomycin. These results indicate that combinatorial treatment with thymol and vancomycin has the potential to serve as a more effective therapy for MRSA biofilm-associated infections than vancomycin monotherapy.

Orostachys japonicus ethyl acetate fraction suppresses MRSA biofilm formation

Objective: To investigate the effect of Orostachys (O.) japonicus, a perennial herbaceous plant of the Family Crassulaceae, on biofilm formed by methicillin-resistant Staphylococcus aureus (MRSA). Methods: Powdered O. japonicus was extracted by 95% methanol, concentrated, and then, systematically fractionated with n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc), n-butanol, and H2O according to polarity. Among them, the flavonoid-rich EtOAc fraction demonstrated the highest antibacterial activity and was used in this study. Using the biofilm inhibition assay, cell-surface attachment assay, confocal laser scanning microscopy, latex agglutination assay, and real time qRT-PCR, we examined whether the EtOAc fraction inhibited the formation of MRSA biofilm. Results: The EtOAc fraction exhibited distinct activity against biofilm formation and cell-surface attachment of MRSA up to 1 mg/mL through down-regulating the expression of mecA gene and the production and agglutination of penicillin-binding protein 2a as solidly observed in biofilm inhibition assay, cell-suface attachment assay, confocal laser scanning microscopy, latex agglutination assay, and real time qRT-PCR analysis. Conclusions: These results suggest that O. japonicus could be utilized as a potential resource for the development of new anti-biofilm formation of MRSA and antibacterial agents in the future.

Camel milk whey hydrolysate inhibits growth and biofilm formation of Pseudomonas aeruginosa PAO1 and methicillin-resistant Staphylococcus aureus

Pseudomonas aeruginosa PAO1 and Methicillin-Resistant Staphylococcus aureus (MRSA) are amongst the most virulent pathogens, causing chronic and life-threatening human infections. Thus, novel natural compounds able to inhibit these pathogens, reduce and/or eradicate their biofilms are in high demand. Camel milk has been demonstrated to contain many functional and bioactive molecules and has consequently been considered in various therapeutic applications. This study aimed to assess the antibacterial and antibiofilm activities of the camel milk whey proteins after hydrolysis by papain, and the obtained fractions from size exclusion chromatography (SEC) against PAO1 and MRSA. Antibacterial activity of camel milk whey against PAO1 and MRSA was enhanced by hydrolysis with papain. Size-exclusion fraction 2 (SEC-F2) had significantly (P < 0.01) the highest antibacterial activity against PAO1 and MRSA with a minimum inhibitory concentration of 0.156 and 0.3125 mg/mL, respectively. Additionally, SEC-F2 significantly (P < 0.01) decreased the biofilm biomass by 60.45% and 85.48% for PAO1 and MRSA, respectively. Moreover, SEC-F2 potentially reduced the PAO1 and MRSA biofilms depending on its concentrations. Scanning electron microscopy showed that the SEC-F2 fraction caused potential morphological changes in both PAO1 and MRSA, mostly represented in cell elongation and leakage of cytoplasmic content. In conclusion, this study has demonstrated that hydrolysis of camel milk whey with papain generates robust antibacterial and antibiofilm small-peptides against PAO1 and MRSA.

Synergistic combinations of antimicrobial peptides against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on polystyrene and medical devices

ObjectivesAntimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections such as those caused by methicillin-resistant Staphylococcus aureus (MRSA). In this regard, antimicrobial peptides (AMPs) appear to be a promising solution. The aim of the present study was to investigate the potential activity of temporin A, citropin 1.1, CA(1–7)M(2–9)NH2 and Pal-KGK-NH2 in synergistic activity against MRSA biofilms developed on polystyrene surface (PSS) and central venous catheter (CVC). MethodsThe study was subdivided into distinct phases to assess the ability of AMPs to inhibit biofilm formation, to identify possible synergy between AMPs, and to eradicate preformed biofilms on PSS and CVC using AMPs alone or in combination. ResultsActivity of the AMPs was particularly evident in the inhibition of biofilm formation on PSS and CVC, whilst the eradication of preformed biofilms was more difficult and was reached only after 24h of contact. The synergistic activity of AMP combinations, selected by their fractional inhibitory concentration index (FICI), led to an improvement in the performance of all of the molecules in the removal of different biofilms. ConclusionOverall, AMPs could represent the next generation of antimicrobial agents for a prophylactic or therapeutic tool to control biofilms of antibiotic-resistant bacteria and/or biofilm-associated infections on different medical devices.

The Droplet-Size Effect Of Squalene@cetylpyridinium Chloride Nanoemulsions On Antimicrobial Potency Against Planktonic And Biofilm MRSA.

BackgroundIt is important to explore the interaction between antibacterial nanoparticles and microbes for understanding bactericidal activity and developing novel applications. It is possible that the nanoparticulate size can govern the antibacterial potency.PurposeThe purpose of this study was to evaluate the antimicrobial and antibiofilm properties of cetylpyridinium chloride (CPC)–decorated nanoemulsions against methicillin-resistant Staphylococcus aureus (MRSA).MethodsThe droplet size could be adjusted by varying the percentage of squalene, the main ingredient of the oily core.ResultsWe fabricated cationic nanoemulsions of three different sizes, 55, 165, and 245 nm. The nanoemulsions showed greater storage stability than the self-assembled CPC micelles. The tested nanoemulsions exhibited more antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria and fungi. The killing of MRSA was mainly induced by direct cell-membrane damage. This rupture led to the leakage of cytoplasmic DNA and proteins. The nanoemulsions might also degrade the DNA helix and disturb protein synthesis. The proteomic analysis indicated the significant downregulation of DNA-directed RNA polymerase (RNAP) subunits β and β’. The antibacterial effect of nanoemulsions increased with decreasing droplet size in the biofilm MRSA but not planktonic MRSA. The small-sized nanoemulsions had potent antibiofilm activity that showed a colony-forming unit (CFU) reduction of 10-fold compared with the control. The loss of total DNA concentration also negatively correlated with the nanoemulsion size.ConclusionThe present report established a foundation for the development of squalene@CPC nanosystems against drug-resistant S. aureus.

Transcriptional Analysis of the Effects of Gambogic Acid and Neogambogic Acid on Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a major threat to human health, as this bacterium has developed resistance to a variety of conventional antibiotics. This is especially true of MRSA biofilms, which not only exhibit enhanced pathogenicity but also are resistant to most antibiotics. In this work, we demonstrated that two natural products with antitumor activity, namely, gambogic acid (GA) and neogambogic acid (NGA), have significant inhibitory activity toward MRSA. GA and NGA can not only effectively inhibit planktonic MRSA strains in vivo and in vitro, but also have strong inhibitory effects on MRSA biofilms formation. By transcriptome sequencing, Q-RT-PCR and PRM, we found that GA and NGA could reduce the expression of S. aureus virulence factors by inhibiting the saeRS two-component, thus achieving inhibition of MRSA. We found that GA and NGA had anti-MRSA activity in vivo and in vitro and identified saeRS to be the target, indicating that saeRS inhibitors may be used to treat biofilm-related infections.

3D bioprinting of mature bacterial biofilms for antimicrobial resistance drug testing

The potential to bioprint and study 3D bacterial biofilm constructs could have great clinical significance at a time when antimicrobial resistance is rising to dangerously high levels worldwide. In this study, clinically relevant bacterial species including Escherichia coli, Staphylococcus aureus (MSSA), Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa were 3D bioprinted using a double-crosslinked alginate bioink to form mature bacteria biofilms, characterized by confocal laser scanning microscopy (CLSM) and fluorescent staining. Solid and porous bacteria-laden constructs were reproducibly bioprinted with thicknesses ranging from 0.25 to 4 mm. We demonstrated 3D bioprinting of thicker biofilms (>4 mm) than found in currently available in vitro models. Bacterial viability was excellent in the bioprinted constructs, with CLSM observation of bacterial biofilm production and maturation possible for at least 28 d in culture. Importantly, we observed the complete five-step biofilm life cycle in vitro following 3D bioprinting for the first time, suggesting the formation of mature 3D bioprinted biofilms. Bacterial growth was faster in thinner, more porous constructs whilst constructs crosslinked with BaCl2 concentrations of above 10 mM had denser biofilm formation. 3D MRSA and MSSA biofilm constructs were found to show greater resistance to antimicrobials than corresponding two-dimensional (2D) cultures. Thicker 3D E. coli biofilms had greater resistance to tetracycline than thinner constructs over 7 d of treatment. Our methodology allowed for the precise 3D bioprinting of self-supporting 3D bacterial biofilm structures that developed biofilms during extended culture. 3D biofilm constructs containing bacterial biofilms produce a model with much greater clinical relevance compared to 2D culture models and we have demonstrated their use in antimicrobial testing.

Efficacy of partial purified bacteriocin of Pseudomonas aeruginosa on Methicillin-resistant Staphylococcus aureus biofilm

Biofilms are microbial communities that cause serious chronic infections in the environment by enhancing antimicrobial resistance. Bacteria in the biofilm can be up to a thousand times more resistant to antibiotics than the same bacteria circulating in a planktonic state. The emergence of antibiotic-resistant microorganism has led to the exploration of different therapeutic agents like ribosomally synthesized microorganism peptides referred to as bacteriocins. In this study, bacteriocin producing bacteria Pseudomonas aeruginosa isolated from a soil sample. It was found to be effective against Methicillin-resistant Staphylococcus aureus (MRSA). Furthermore the bacteriocin was partial purified by ammonium sulfate, the precipitate has highly effective against MRSA (400AU/mL). MRSA cells were treated with precipitated culture supernatant of P. aeruginosa TA6 was analyzed by FT-IR. The treated and untreated MRSA showed band variations at 682.59 and 3442.15cm-1 corresponding to the alkyl and amide group respectively. Bacteriocin showed marked inhibition activity against the biofilm of MRSA. About 0.05% and 0.02% attachment of biofilm was observed in the presence of 1X MIC (10 μg/mL) and 2X MIC (20 g/mL) respectively. Our results recommend that bacteriocins that make stable pores on biofilm cells are extremely potent for the treatment of MRSA biofilm infections.

Photothermal inactivation of methicillin-resistant Staphylococcus aureus: anti-biofilm mediated by a polypyrrole-carbon nanocomposite.

Widespread resistance to antibiotics amongst pathogens has become a tremendous challenge of high morbidity and mortality rates which increases the needs to exploring novel methods of treatment. An efficient antimicrobial procedure to root out pathogenic bacteria is photothermal therapy. In this study, antimicrobial effects of a polypyrrole-carbon nanocomposite (PPy-C) upon laser irradiation in order to destroy the pathogenic gram-positive bacterium, methicillin-resistant Staphylococcus aureus (MRSA) were assessed. The bacterial cells were incubated with 500, 750 and 1000 μg ml-1 concentrations of PPy-C and irradiated with an 808-nm laser at a power density of 1.0 W cm-2. To indicate the biocompatibility and toxic effect of the nanocomposite without and with laser irradiation, the authors counted the number of CFUs and compared it to an untreated sample. Antibacterial mechanisms of PPy-C were assessed through temperature increment, reactive oxygen species production, and protein and DNA leakages. Photothermal heating assay showed that 26°C temperature increases in the presence of 1000 µg ml-1 PPy-C led to >98% killing of MRSA. Furthermore, 20 min radiation of near-infrared light to PPy-C in different concentrations indicated destruction and reduction in the MRSA biofilm formation. Therefore, PPy-C was introduced as a photothermal absorber with a bactericidal effect in MRSA.

Phenylthiazoles with nitrogenous side chain: An approach to overcome molecular obesity

A novel series of phenylthiazoles bearing cyclic amines at the phenyl-4 position was prepared with the objective of decreasing lipophilicity and improving the overall physicochemical properties and pharmacokinetic profile of the compounds. Briefly, the piperidine ring (compounds 10 and 12) provided the best ring size in terms of antibacterial activity when tested against 16 multidrug-resistant clinical isolates. Both compounds were superior to vancomycin in the ability to eliminate methicillin-resistant Staphylococcus aureus (MRSA), residing within infected macrophages and to disrupt mature MRSA biofilm. Additionally, compounds 10 and 12 exhibited a fast-bactericidal mode of action in vitro. Furthermore, the new derivatives were 160-times more soluble in water than the previous lead compound 1b. Consequently, compound 10 was orally bioavailable with a highly-acceptable pharmacokinetic profile in vivo that exhibited a half-life of 4 h and achieved a maximum plasma concentration that exceeded the minimum inhibitory concentration (MIC) values against all tested bacterial isolates.

In vitro inhibitory activity of N-acetylcysteine on tympanostomy tube biofilms from methicillin-resistant Staphylococcus aureus and quinolone-resistant Pseudomonas aeruginosa

ObjectivesBiofilm formation in tympanostomy tubes causes persistent and refractory otorrhea. In the present study, we investigated the in vitro antibiofilm activity of N-acetylcysteine (NAC) against biofilm formation by methicillin-resistant Staphylococcus aureus (MRSA) and quinolone-resistant Pseudomonas aeruginosa (QRPA). MethodsWe examined the antibiofilm activity of NAC against biofilms produced by MRSA and QRPA strains using in vitro biofilm formation assay, adhesion assay, and biofilm eradication assay. Additionally, the antibiofilm activity of different concentrations of NAC against tympanostomy-tube biofilms from MRSA and QRPA strains was compared using a scanning electron microscope. ResultsThe adhesion of MRSA and QRPA strains decreased significantly in a concentration-dependent manner after treatment with varying amounts of NAC. Treatment with NAC inhibited biofilm formation of both MRSA and QRPA strains and increased eradication of preformed mature biofilm produced by MRSA and QRPA. Besides, NAC exhibited significant eradication-activity against tympanostomy-tube biofilms produced by MRSA and QRPA strains. ConclusionsOur results show potent inhibition of MRSA and QRPA biofilm after treatment with NAC. NAC shows potential for the treatment of biofilms and refractory post-tympanostomy tube otorrhea resulting from MRSA and QRPA infection.

The Pathogenicity and Transcriptome Analysis of Methicillin-Resistant Staphylococcus aureus in Response to Water Extract of Galla chinensis.

Aim Antibiotic abuse contributes to the emergence of methicillin-resistant Staphylococcus aureus (MRSA). It is increasingly important to screen new antimicrobial agents for the management of MRSA infections. G. chinensis, a nontoxic Chinese herbal medicine, is considered a potential antibacterial agent. The aim of this study was to investigate the bactericidal effects of the aqueous extracts of G. chinensis on MRSA. The potential mechanisms of G. chinensis aqueous extract inhibition of the pathogenicity of MRSA in vivo are also discussed. Methods G. chinensis aqueous extract was prepared and its antimicrobial activities were examined by determining its minimum inhibitory concentration (MIC). Biofilm biomass was determined by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). RNA sequencing (RNA-seq) was used to evaluate differentially expressed functional pathways in MRSA treated with G. chinensis aqueous extract. We validated the role of G. chinensis aqueous extract in the invasive ability and pathogenicity of MRSA in vivo using a rat infectious model. Results The results indicated that MRSA was sensitive to the G. chinensis aqueous extracts at concentration of 31.25μg/mL. G. chinensis extract led to a reduction in dextran-dependent aggregation and biofilm formation in MRSA. Based on the transcriptome analysis, G. chinensis aqueous extracts significantly downregulated the gene expression related to biofilm formation and carbohydrate metabolism. G. chinensis aqueous extract inhibited the invasive ability and the pathogenicity of MRSA in vivo. Conclusion The antimicrobial properties of G. chinensis aqueous extract are likely related to its modulation of MRSA biofilm formation and carbohydrate metabolism. G. chinensis aqueous extract is a promising supplementary therapy to lessen or eliminate the use of antibiotics and is a potential tool for the management of MRSA infections.

Comparative efficacy of linezolid and vancomycin for endotracheal tube MRSA biofilms from ICU patients

PurposeTo compare the efficacy of systemic treatment with linezolid (LNZ) versus vancomycin (VAN) on methicillin-resistant Staphylococcus aureus (MRSA) burden and eradication in endotracheal tube (ETT) biofilm and ETT cuff from orotracheally intubated patients with MRSA respiratory infection.MethodsProspective observational clinical study was carried out at four European tertiary hospitals. Plasma and endotracheal aspirate (ETA) levels of LNZ and VAN were determined 72 h after treatment initiation through high-performance liquid chromatography or bioassay. LNZ or VAN concentration in the ETT biofilm and MRSA burden and eradication was determined upon extubation. The minimum inhibitory concentration (MIC) for LNZ and VAN was assessed by E-test strips (Biomerieux®). Scanning electron microscopy images were obtained, and ETT biofilm thickness was compared between groups.ResultsTwenty-five patients, 15 treated with LNZ and 10 with VAN, were included in the study. LNZ presented a significantly higher concentration (μg/mL) than VAN in ETT biofilm (72.8 [1.3–127.1] vs 0.4 [0.4–1.3], p < 0.001), although both drugs achieved therapeutic plasma levels 72 h after treatment initiation. Systemic treatment with LNZ achieved lower ETT cuff MRSA burdens than systemic treatment with VAN. Indeed, LNZ increased the MRSA eradication rate in ETT cuff compared with VAN (LNZ 75%, VAN 20%, p = 0.031).ConclusionsIn ICU patients with MRSA respiratory infection intubated for long periods, systemic treatment with LNZ obtains a greater beneficial effect than VAN in limiting MRSA burden in ETT cuff.