Recent insights into the physicochemical properties, bioactivities and their relationship of tea polysaccharides.

Tea polysaccharides (TPS) is receiving global concern in past years due to their therapeutic effects in many diseases such as obesity and diabetes. Many publications imply that the unique physicochemical properties and bioactivities of TPS are prerequisites for its use as a biofilm, drug carrier and emulsifier. Despite numerous healthy benefits, studies on the in-deep structure-activity relationship of TPS still not well explored and explained yet. The main reasons for the research limitation are attributed mainly to the unbreakable advanced structural research technology and the formation of TPS conjugates. The present review also summarizes some similar parameters in primary structure of TPS with better bioactivities, discusses the relationships between their physicochemical properties and bioactivities, and suggests that function-specific TPS would be obtained in the future if the links between preparation methods, physicochemical properties and bioactivities of TPS could be well understood and established.

Introduce a novel post-biotic against Pseudomonas aeruginosa biofilm formation using Escherchia coli Nissle1917 outer membrane vesicles.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that can cause acute infections as well as chronic ones in humans. The expression of algD and PpyR genes involved in biofilm formation in clinical isolates of P. aeruginosa in the presence of Escherichia coli Nissle1917 outer membranes vesicles (EcN OMVs) was evaluated. All isolates were tested for biofilm formation. qPCR and disk diffusion were used to identify the expression of algD and PpyR genes, and antimicrobial resistance, respectively. EcN OMVs caused a more significant loss of algD and PpyR expression, compared with the control group. EcN OMVs contain a variety of biomolecules that are capable of influencing the biofilm formation genes. EcN OMVs treatment reduced P. aeruginosa biofilm formation significantly, which emphasizes their positive role in inhibiting biofilm formation. As a result, EcN OMVs can be used as new therapeutic strategies for inhibiting P. aeruginosa biofilm formation.

The regulation of carbon dioxide on food microorganisms: A review.

This review presents a survey of two extremely important technologies about CO2 with the effectiveness of controlling microorganisms - atmospheric pressure CO2-based modified atmosphere packaging (MAP) and high pressure CO2 non-thermal pasteurization (HPCD). CO2-based MAP is effectively in delaying the lag and logarithmic phases of microorganisms by replacing the surrounding air, while HPCD achieved sterilization by subjecting food to either subcritical or supercritical CO2 for some time in a continuous, batch or semi-batch way. In addition to the advantages of healthy, eco-friendly, quality-preserving, effective characteristic, some challenges such as the high drip loss and packaging collapse associated with higher concentration of CO2, the fuzzy mechanisms of oxidative stress, the unproven specific metabolic pathways and biomarkers, etc., in CO2-based MAP, and the unavoidable extraction of bioactive compounds, the challenging application in solid foods with higher efficiency, the difficult balance between optimal sterilization and optimal food quality, etc., in HPCD still need more efforts to overcome. The action mechanism of CO2 on microorganisms, researches in recent years, problems and future perspectives are summarized. When dissolved in solution medium or cellular fluids, CO2 can form carbonic acid (H2CO3), and H2CO3 can further dissociate into bicarbonate ions (HCO3-), carbonate (CO32-) and hydrogen cations (H+) ionic species following series equilibria. The action mode of CO2 on microorganisms may be relevant to changes in intracellular pH, alteration of proteins, enzyme structure and function, alteration of cell membrane function and fluidity, and so on. Nevertheless, the effects of CO2 on microbial biofilms, energy metabolism, protein and gene expression also need to be explored more extensively and deeply to further understand the action mechanism of CO2 on microorganisms.

Strategy to combat biofilms: a focus on biofilm dispersal enzymes.

Bacterial biofilms, which consist of three-dimensional extracellular polymeric substance (EPS), not only function as signaling networks, provide nutritional support, and facilitate surface adhesion, but also serve as a protective shield for the residing bacterial inhabitants against external stress, such as antibiotics, antimicrobials, and host immune responses. Biofilm-associated infections account for 65-80% of all human microbial infections that lead to serious mortality and morbidity. Tremendous effort has been spent to address the problem by developing biofilm-dispersing agents to discharge colonized microbial cells to a more vulnerable planktonic state. Here, we discuss the recent progress of enzymatic eradicating strategies against medical biofilms, with a focus on dispersal mechanisms. Particularly, we review three enzyme classes that have been extensively investigated, namely glycoside hydrolases, proteases, and deoxyribonucleases.

Erythritol alters gene transcriptome signatures, cell growth, and biofilm formation in Staphylococcus pseudintermedius.

BACKGROUND: Erythritol was found to inhibit the growth of microorganisms. The present study aimed to demonstrate the growth inhibition of Staphylococcus pseudintermedius by erythritol and to define the changes in gene transcription signatures induced by erythritol. Changes in the gene transcription profiles were analysed by RNA sequencing and quantitative reverse transcription PCR. Gene ontology analysis was performed to assign functional descriptions to the genes. RESULTS: Erythritol inhibited S. pseudintermedius growth in a dose-dependent manner. We then performed a transcriptome analysis of S. pseudintermedius with and without 5% (w/w) erythritol exposure to validate the mechanism of growth inhibition. We revealed that erythritol induced up-regulation of three genes (ptsG, ppdK, and ppdkR) that are related to the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS). Glucose supplementation restored the up-regulation of the PTS-related genes in response to erythritol. In addition, erythritol down-regulated eleven genes that are located in a single pur-operon and inhibited biofilm formation of S. pseudintermedius. CONCLUSIONS: These findings indicated that erythritol antagonistically inhibits PTS-mediated glucose uptake, thereby exerting a growth inhibitory effect on S. pseudintermedius. Moreover, erythritol inhibits the 'de novo' IMP biosynthetic pathway that may contribute to biofilm synthesis in S. pseudintermedius.

Bioactive Compounds from P. pertomentellum That Regulate QS, Biofilm Formation and Virulence Factor Production of P. aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen responsible for many nosocomial infections. This bacterium uses Quorum Sensing (QS) to generate antimicrobial resistance (AMR) so its disruption is considered a novel approach. The current study describes the antibiofilm and QS inhibitory potential of extract and chemical components from Piper pertomentellum. The methodo- logy included the phytochemical study on the aerial part of the species, the determination of QS inhibition efficacy on Chromobacterium violaceum and the evaluation of the effect on biofilm formation and virulence factors on P. aeruginosa. The phytochemical study led to the isolation and identification of a new piperamide (ethyltembamide 1), together with four known amides (tembamide acetate 2, cepharadione B 3, benzamide 4 and tembamide 5). The results indicated that the ethanolic extract and some fractions reduced violacein production in C. violaceum, however, only the ethanolic extract caused inhibition of biofilm formation of P. aeruginosa on polystyrene microtiter plates. Finally, the investigation determined that molecules (1-5) inhibited the formation of biofilms (50% approximately), while compounds 2-4 can inhibit pyocyanin and elastase production (30-50% approximately). In this way, the study contributes to the determination of the potential of extract and chemical constituents from P pertomentellum to regulate the QS system in P. aeruginosa.

Isolation, characterization and application of a lytic phage vB_VspM_VS1 against Vibrio splendidus biofilm.

Vibrio splendidus is a common pathogen in the ocean that infects Apostichopus japonicus, Atlantic salmon and Crassostrea gigas, leading to a variety of diseases. In this study, a virulent phage vB_VspM_VS1, which infects V. splendidus, was isolated from aquaculture ponds in Dalian, China, and it belongs to the family Straboviridae in the order Caudoviricetes. vB_VspM_VS1 had an adsorption rate of 96% in 15 min, a latent period of 65 min, and a burst size of 140 ± 6 PFU/cell. The complete genome of phage vB_VspM_VS1 consists of a linear double-stranded DNA that is 248,270 bp in length with an average G + C content of 42.5% and 389 putative protein-coding genes; 116 genes have known functions. There are 4 tail fiber genes in the positive and negative strands of the phage vB_VspM_VS1 genome. The protein domain of the phage vB_VspM_VS1 tail fibers was obtained from the Protein Data Bank and the SMART (http://smart.embl.de) database. Bacterial challenge tests revealed that the growth of V. splendidus HS0 was apparently inhibited (OD600 < 0.01) in 12 h at an MOI of 10. In against biofilms, we also showed that the OD570 value of the vB_VspM_VS1-treated group (MOI = 1) decreased significantly to 0.04 ± 0.01 compared with that of the control group (0.48 ± 0.08) at 24 h. This study characterizes the genome of the phage vB_VspM_VS1 that infects the pathogenic bacterium V. splendidus of A. japonicus.

High antipersister activity of a promising new quinolone drug candidate in eradicating uropathogenic Escherichia coli persisters and persistent infection in mice.

AIMS: To develop more potent drugs that eradicate persister bacteria and cure persistent urinary tract infections (rUTIs). METHODS AND RESULTS: We synthesized eight novel clinifloxacin analogs and measured minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the time-kill curves in uropathogenic Escherichia coli (UPEC) UTI89, and applied the candidate drugs and combinations against biofilm bacteria in vitro and in mice. Transcriptomic analysis was performed for UPEC after candidate drug treatment to shed light on potential mechanism of action. We identified Compound 2, named Qingdafloxacin (QDF), which was more potent than clinafloxacin and clinically used levofloxacin and moxifloxacin, with an MIC of < 0.04 µg ml-1 and an MBC of 0.08∼0.16 µg ml-1. In drug combination studies, QDF + gentamicin + nitrofuran combination but not single drugs completely eradicated all stationary phase bacteria containing persisters and biofilm bacteria, and all bacteria in a persistent UTI mouse model. Transcriptome analysis revealed that the unique antipersister activity of QDF was associated with downregulation of genes involved in bacterial stress response, DNA repair, protein misfolding repair, pyrimidine metabolism, glutamate, and glutathione metabolism, and efflux. CONCLUSIONS: QDF has high antipersister activity and its drug combinations proved highly effective against biofilm bacteria in vitro and persistent UTIs in mice, which may have implications for treating rUTIs.

Lysine lactylation regulates metabolic pathways and biofilm formation in Streptococcus mutans.

In eukaryotes, lactate produced during glycolysis is involved in regulating multiple metabolic processes through lysine lactylation (Kla). To explore the potential link between metabolism and Kla in prokaryotes, we investigated the distribution of Kla in the cariogenic bacterium Streptococcus mutans during planktonic growth in low-sugar conditions and in biofilm-promoting, high-sugar conditions. We identified 1869 Kla sites in 469 proteins under these two conditions, with the biofilm growth state showing a greater number of lactylated sites and proteins. Although high sugar increased Kla globally, it reduced lactylation of RNA polymerase subunit α (RpoA) at Lys173. Lactylation at this residue inhibited the synthesis of extracellular polysaccharides, a major constituent of the cariogenic biofilm. The Gcn5-related N-acetyltransferase (GNAT) superfamily enzyme GNAT13 exhibited lysine lactyltransferase activity in cells and lactylated Lys173 in RpoA in vitro. Either GNAT13 overexpression or lactylation of Lys173 in RpoA inhibited biofilm formation. These results provide an overview of the distribution and potential functions of Kla and improve our understanding of the role of lactate in the metabolic regulation of prokaryotes.

Antibiotic-Potentiating Effect of Some Bioactive Natural Products against Planktonic Cells, Biofilms, and Virulence Factors of Pseudomonas aeruginosa.

Background: Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections that are mediated by both virulence factor production and biofilm formation. In addition, many antibiotics are increasingly losing their efficacy due to the development of resistance. The screening of potentially bioactive natural compounds that have both antivirulence and antibiofilm activities to enhance antibiotic efficacy and reverse antibiotic resistance is a good strategy to overcome these issues. In this study, the antibacterial, antibiofilm, and antivirulence factor activities of some bioactive natural products in combination with conventional antibiotics were evaluated against clinical isolates of P. aeruginosa. Methods: The broth microdilution method was used to determine the antibacterial and antibiofilm activities. The checkerboard method was used to evaluate the combination interactions. Spectrophotometric and agar plate techniques were used to assess the effect of the combination on the pyocyanin production and the motility in P. aeruginosa ATCC 27853 strain. Results: Out of the eighteen combinations tested, ten exhibited synergistic effects against planktonic cells, seven against biofilm inhibition, and five against the eradication of mature biofilm of P. aeruginosa biofilm. The best synergistic effect was the association of amikacin and sinapic acid against planktonic cells (FICI = 0.08) with a 70-fold reduction in the MIC value of amikacin. The same combination showed significant synergistic inhibition of biofilm formation (FICI = 0.1) and biofilm eradication (FICI = 0.15) reducing the MBIC and MBEC of amikacin by 32-fold. Some selected synergistic combinations showed statistically significant differences (p < 0.01 or p < 0.001) in the inhibition of virulence factors compared to the antimicrobials alone. Conclusion: In summary, this study revealed sinapic acid as an antibiotic adjuvant and antivirulence compound to overcome P. aeruginosa infections. This finding indicates that the combinations of amikacin plus sinapic acid, ceftazidime plus thymol, and norfloxacin plus curcumin could be considered promising candidates for the development of combination therapies targeting virulence factors against P. aeruginosa infections.

The non-attached biofilm aggregate.

Biofilms have conventionally been perceived as dense bacterial masses on surfaces, following the five-step model of development. Initial biofilm research focused on surface-attached formations, but detached aggregates have received increasing attention in the past decade due to their pivotal role in chronic infections. Understanding their nature sparked fervent discussions in biofilm conferences and scientific literature. This review consolidates current insights on non-attached aggregates, offering examples of their occurrence in nature and diseases. We discuss their formation and dispersion mechanisms, resilience to antibiotics and immune-responses, drawing parallels to surface-attached biofilms. Moreover, we outline available in vitro models for studying non-attached aggregates.

Raman Spectroscopic and Microbial Study of Biofilms Hosted Gypsum Deposits in the Hypersaline Wetlands: Astrobiological Perspective.

Gypsum (CaSO4·2H2O) has been identified at the surface of Mars, by both orbiters and rovers. Because gypsum mostly forms in the presence of liquid water as an essential element for sustaining microbial life and has a low porosity, which is ideal for preserving organic material, it is a promising target to look for signs of past microbial life. In this article, we studied organic matter preservation within gypsum that precipitates in a salt flat or a so-called coastal sabkha located in Qatar. Sabkha's ecosystem is considered a modern analog to evaporitic environments that may have existed on early Mars. We collected the sediment cores in the areas where gypsum is formed and performed DNA analysis to characterize the community of extremophilic microorganisms that is present at the site of gypsum formation. Subsequently, we applied Raman spectroscopy, a technique available on several rovers that are currently exploring Mars, to evaluate which organic molecules can be detected through the translucent gypsum crystals. We showed that organic material can be encapsulated into evaporitic gypsum and detected via Raman microscopy with simple, straightforward sample preparation. The molecular biology data proved useful for assessing to what extent complex Raman spectra can be linked to the original microbial community, dominated by Halobacteria and methanogenic archaea, providing a reference for a signal that may be detected on Mars.

Identification, proteolytic activity quantification and biofilm-forming characterization of Gram-positive, proteolytic, psychrotrophic bacteria isolated from cold raw milk.

Psychrotrophic bacteria of raw milk face the dairy industry with significant spoilage and technological problems due to their ability to produce heat-resistant enzymes and biofilms. Despite extensive information about Gram-negative psychrotrophic bacteria in milk, little is known about Gram-positive psychrotrophic bacteria in milk, and their proteolytic activity and biofilm-forming characteristics. In the present study, Gram-positive, proteolytic, psychrotrophic bacteria of cold raw milk were identified, and their proteolytic activity and biofilm-forming capacity were quantified. In total, 12 genera and 22 species were represented among the bacterial isolates, however 50% belonged to three genera, namely Staphylococcus (19.4%), Bacillus (16.7%), and Enterococcus (13.9%). Different levels of proteolytic activity were detected in the identified isolates, even among the strains belonging to the same species. In addition, proteolytic activity was significantly higher at 25°C than at 7°C for all isolates. The crystal violet staining assay in polystyrene microtitre plates revealed a high level of variation in the biofilm-forming capacity at 7°C. After 72 hours of incubation, 11.1% of the strains did not produce a biofilm, while 27.8%, 52.8%, and 8.3% produced low, moderate, and high amounts of biofilm on polystyrene, respectively. The psychrotrophic bacteria were also able to produce biofilms on the surface of stainless steel coupons in ultra-high temperature milk after 72 h of incubation at 7°C; the number of attached cells ranged from 1.34 to 5.11 log cfu/cm2. These results expand the knowledge related to the proteolytic activity and biofilm-forming capacity of Gram-positive psychrotrophic milk bacteria.

Antibacterial activity of menadione alone and in combination with oxacillin against methicillin-resistant Staphylococcus aureus and its impact on biofilms.

Introduction. Antibiotic resistance is a major threat to public health, particularly with methicillin-resistant Staphylococcus aureus (MRSA) being a leading cause of antimicrobial resistance. To combat this problem, drug repurposing offers a promising solution for the discovery of new antibacterial agents.Hypothesis. Menadione exhibits antibacterial activity against methicillin-sensitive and methicillin-resistant S. aureus strains, both alone and in combination with oxacillin. Its primary mechanism of action involves inducing oxidative stress.Methodology. Sensitivity assays were performed using broth microdilution. The interaction between menadione, oxacillin, and antioxidants was assessed using checkerboard technique. Mechanism of action was evaluated using flow cytometry, fluorescence microscopy, and in silico analysis.Aim. The aim of this study was to evaluate the in vitro antibacterial potential of menadione against planktonic and biofilm forms of methicillin-sensitive and resistant S. aureus strains. It also examined its role as a modulator of oxacillin activity and investigated the mechanism of action involved in its activity.Results. Menadione showed antibacterial activity against planktonic cells at concentrations ranging from 2 to 32 µg ml-1, with bacteriostatic action. When combined with oxacillin, it exhibited an additive and synergistic effect against the tested strains. Menadione also demonstrated antibiofilm activity at subinhibitory concentrations and effectively combated biofilms with reduced sensitivity to oxacillin alone. Its mechanism of action involves the production of reactive oxygen species (ROS) and DNA damage. It also showed interactions with important targets, such as DNA gyrase and dehydroesqualene synthase. The presence of ascorbic acid reversed its effects.Conclusion. Menadione exhibited antibacterial and antibiofilm activity against MRSA strains, suggesting its potential as an adjunct in the treatment of S. aureus infections. The main mechanism of action involves the production of ROS, which subsequently leads to DNA damage. Additionally, the activity of menadione can be complemented by its interaction with important virulence targets.

A mini-review on indigenous microbial biofilm from various wastewater for heavy-metal removal - new trends.

Biofilm, as a form of the microbial community in nature, represents an evolutionary adaptation to the influence of various environmental conditions. In nature, the largest number of microorganisms occur in the form of multispecies biofilms. The ability of microorganisms to form a biofilm is one of the reasons for antibiotic resistance. The creation of biofilms resistant to various contaminants, on the other hand, improves the biological treatment process in wastewater treatment plants. Heavy metals cannot be degraded, but they can be transformed into non-reactive and less toxic forms. In this process, microorganisms are irreplaceable as they interact with the metals in a variety of ways. The environment polluted by heavy metals, such as wastewater, is also a source of undiscovered microbial diversity and specific microbial strains. Numerous studies show that biofilm is an irreplaceable strategy for heavy metal removal. In this review, we systematize recent findings regarding the bioremediation potential of biofilm-forming microbial species isolated from diverse wastewaters for heavy metal removal. In addition, we include some mechanisms of action, application possibilities, practical issues, and future prospects.

In vitro efficacy of synthetic lawsone derivative disinfectant solution on removing dual-species biofilms and effect on acrylic denture surface properties.

Candida albicans (C. albicans) and Streptococcus mutans (S. mutans) biofilms involve in denture stomatitis. This study compared compound 1 to 2% chlorhexidine gluconate (CHX), Polident, and distilled water (DW) in biofilms reduction and effect on polymethylmethacrylate acrylic (PMMA) properties. The structure of lawsone (naphthoquinone derivative) was modified by the addition of an alkylnyloxy group to yield compound 1. Dual-species biofilms of C. albicans and S. mutans were developed on PMMA discs. The colony-forming unit count measured the number of residual biofilm cells after exposure to the test agents. PMMA discs were examined for color stability, surface roughness, hardness, and chemical structure after 28 days. At 3 min, compound 1 was less effective than CHX in reducing C. albicans (p = 0.004) and S. mutans (p = 0.034) but more effective than Polident in reducing C. albicans (p = 0.001). At 15 min, no viable cells were detectable for compound 1 and its effectiveness was comparable to CHX (p = 0.365). SEM showed fungal cell surface damages in CHX, compound 1 and Polident groups. Only color change was affected by time (p < 0.001) and type of test agent (p = 0.008), and only CHX reached a clinical perception level. Compound 1 is a promising agent for removing biofilm from the PMMA surface without substantially degrading surface properties.

Synergistic Role of Biofilm-Associated Genes and Efflux Pump Genes in Tigecycline Resistance of Acinetobacter baumannii.

BACKGROUND Previous research reported that the resistance mechanism of Acinetobacter baumannii resistance to tigecycline was mainly related to the overexpression of the AdeABC efflux pump system. Biofilm formation is a notable pathogenesis of A. baumannii infections and antibiotic resistance. Our study explores the latent relevance of biofilm-associated genes and efflux pump genes in A. baumannii tigecycline resistance. MATERIAL AND METHODS A total of 78 clinical samples were collected from October 2018 to October 2019. Seventy-two clinically isolated A. baumannii strains were divided into a tigecycline-resistant Acinetobacter baumannii (TR-AN) group and tigecycline-sensitive Acinetobacter baumannii (TS-AN) group by tigecycline minimum inhibitory concentration tests. The biofilm formation of the 2 groups was observed using crystal violet staining. Furthermore, biofilm-related genes and efflux pump genes were analyzed by RT-PCR. RESULTS The biofilm-forming rate of the TR-AN group was 82.2%, and that of the TS-AN group was 14.8%. The biofilm synthesis gene bfs was 91.3% positive in the TR-AN group, significantly higher than in the TS-AN group at the transcription level (P<0.05). The minimum inhibitory concentration of tigecycline was higher in the TR-AN group with biofilm formation than in the TR-AN group without biofilm formation (P<0.05). The efflux pump AdeB gene was 95.2% positive in the TR-AN group with biofilm formation and 38.7% positive in the TR-AN group without biofilm formation. CONCLUSIONS The biofilm formation of A. baumannii may be positively related to tigecycline resistance ability because of the co-expression of the bfs gene and the AdeB efflux pump gene. The enhanced transcription level of bfs and AdeB promotes biofilm formation to improve the resistance of A. baumannii to tigecycline.

Uncovering the role of algal organic matter biocoating on Navicula incerta cell deposition and biofilm formation.

Spontaneous natural biofilm concentrates microalgal biomass on solid supports. However, the biofilm is frequently susceptible to exfoliation upon nutrient deficiency, particularly found in aged biofilm. Therefore, this study highlights a novel biofilm cultivation technique by pre-depositing the algal organic matters from marine diatom, Navicula incerta onto microporous polyvinylidene fluoride membrane to further strengthen the biofilm developed. Due to the improvement in membrane surface roughness and hydrophobicity, cells adhered most abundantly to soluble extrapolymeric substances-coated (sEPS) (76×106±16×106 cells m-2), followed by bounded EPS-coated (57.67×106±0.33×106 cells m-2), internally organic matter (IOM)-coated (39.00×106±5.19×106 cells m-2), and pristine control the least (6.22×106±0.77×106 cells m-2) at 24th h. Surprisingly, only bEPS-coated membrane demonstrated an increase in cell adhesion toward the end of the experiment at 72 h. The application of the bio-coating has successfully increased the rate of cell attachment by at least 45.3% upon inoculation and achieved as high as 89.9% faster attachment at 72 hours compared to the pristine control group. Soluble polysaccharides and proteins might be carried along by the cells adhering onto membranes hence resulting in a built up of EPS hydrophobicity (>70% in average on bio-coated membranes) over time as compared with pristine (control) that only recorded an average of approximately 50% hydrophobicity. Interestingly, cells grown on bio-coated membranes accumulated more internally bounded polysaccharides, though bio-coating had no discernible impact on the production of both externally and internally bounded protein. The collective findings of this study reveal the physiological alterations of microalgal biofilms cultured on bio-coated membranes.

In vitro activity of exebacase against methicillin-resistant Staphylococcus aureus biofilms on orthopedic Kirschner wires.

Orthopedic foreign body-associated infection can be difficult to treat due to the formation of biofilms protecting microorganisms from both antimicrobials and the immune system. Exebacase is an antistaphylococcal lysin (cell wall hydrolase) under consideration for local treatment for biofilm-based infections caused by methicillin-resistant Staphylococcus aureus (MRSA). To determine the activity of exebacase, we formed MRSA biofilms on orthopedic Kirschner wires and exposed them to varying concentrations (0.098, 0.98, 9.8 mg/ml) of exebacase and/or daptomycin over 24 h. The biofilm consisted of 5.49 log10 colony forming units (cfu)/K-wire prior to treatment and remained steady throughout the experiment. Exebacase showed significant biofilm reduction at all timepoints (up to 5.78 log10 cfu/K-wire; P < 0.0495) compared to the controls at all concentrations and all time points with bactericidal activity (> 3 log10 cfu/K-wire reduction) observed for up to 12 h for the 0.098 and 0.98 mg/ml concentrations and at 24 h for 9.8 mg/ml. Daptomycin showed significant biofilm reduction, although non-bactericidal, at all time points for 0.98 and 9.8 mg/ml and at 4 and 8 h with 0.098 mg/ml (P < 0.0495). This study supports further evaluation of local administration of exebacase as a potential treatment for orthopedic implant infections.

Novel photoactivated Indole-pyridine chemotherapeutics with strong antimicrobial and antibiofilm activity toward Staphylococcus aureus.

The challenge of antibiotic resistance worldwide has brought an urgent need to explore novel drugs for bacterial infections. Antimicrobial photodynamic therapy has been proven to be a potential antimicrobial modality but is limited by biofilms. In this study, we synthesized three cationic photosensitizers with strong photoinduced antimicrobial and antibiofilm activities toward gram-positive Staphylococcus aureus. The indole-pyridine compounds illustrated multiple type I/II photosensitization and coenzyme NAD(P)H photocatalytic activity upon excitation. A mechanistic study showed that intracellular reactive oxygen generation and NAD(P)H oxidation caused membrane damage, leading to protein/nucleus acid leakage. This research provides insights into the development of novel chemotherapeutics with synergetic photodynamic and photocatalytic reactivity.