The effect of berberine hydrochloride on Enterococcus faecalis biofilm formation and dispersion in vitro

Unleashing the antibacterial potential of ZIFs and their derivatives: mechanistic insights

Antibiotic resistance presents an alarming threat to global health, with bacterial infections now ranking among the leading causes of mortality. To address this escalating challenge, strategies such as antibiotic stewardship, development of antimicrobial therapies, and exploration of alternative treatment modalities are imperative. Metal-organic frameworks (MOFs), acclaimed for their outstanding biocompatibility and in vivo biodegradability, are promising avenues for the synthesis of novel antibiotic agents under mild conditions. Among these, zeolitic imidazolate frameworks (ZIFs), a remarkable subclass of MOFs, have emerged as potent antibacterial materials; the efficacy of which stems from their porous structure, metal ion content, and tunable functionalized groups. This could be further enhanced by incorporating or encapsulating metal ions, such as Cu, Fe, Ti, Ag, and others. This perspective aims to underscore the potential of ZIFs as antibacterial agents and their underlying mechanisms including the release of metal ions, generation of reactive oxygen species (ROS), disruption of bacterial cell walls, and synergistic interactions with other antibacterial agents. These attributes position ZIFs as promising candidates for advanced applications in combating bacterial infections. Furthermore, we propose a novel approach for synthesizing ZIFs and their derivatives, demonstrating exceptional antibacterial efficacy against Escherichia coli and Staphylococcus aureus. By highlighting the benefits of ZIFs and their derivatives as antibacterial agents, this perspective emphasizes their potential to address the critical challenge of antibiotic resistance.

6-Methoxyldihydrochelerythrine Chloride Inhibiting Intra and Extracellular Drug-Resistant Bacteria

Vancomycin-resistant enterococcus (VRE) is a major nosocomial pathogen that exhibits enhanced infectivity due to its robust virulence and biofilm-forming capabilities. In this study, 6-methoxyldihydrochelerythrine chloride (6-MDC) inhibited the growth of exponential-phase VRE and restored VRE's sensitivity to vancomycin. 6-MDC predominantly suppressed the de novo biosynthetic pathway of pyrimidine and purine in VRE by the RNA-Seq analysis, resulting in obstructed DNA synthesis, which subsequently weakened bacterial virulence and impeded intracellular survival. Furthermore, 6-MDC inhibited biofilm formation, eradicated established biofilms, reduced virulence, and enhanced the host immune response to prevent intracellular survival and replication of VRE. Finally, 6-MDC reduced the VRE load in peritoneal fluid and cells significantly in a murine peritoneal infection model. This paper provides insight into the potential antimicrobial target of benzophenanthridine alkaloids for the first time.

In vitro and in vivo synergistic inhibition of Malassezia furfur targeting cell membranes by Rosa rugosa Thunb. and Coptidis Rhizoma extracts

Background

Malassezia furfur (M. furfur) is a prevalent dermatophyte that significantly impairs patients' quality of life. This study aimed to evaluate the synergistic antifungal effects of combined extracts from Rosa rugosa Thunb. (MG) and Coptidis Rhizoma (HL) against M. furfur, both in vitro and in vivo.

Methods

High-performance liquid chromatography (HPLC) was used to identify the major active compounds present in MG and HL. The antifungal activity of the combined Meilian extract (ML) was assessed using the checkerboard method and time-kill curves. Microstructural alterations in the fungi were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The impact of the extracts on the fungal cell membrane was investigated through propidium iodide staining, protein concentration assays, and ergosterol quantification. Transcriptomic analysis was conducted to elucidate the molecular mechanisms underlying the effects of the extracts. Furthermore, the synergistic antifungal effects of ML were evaluated in a mouse model of seborrheic dermatitis induced by M. furfur.

Results

The study demonstrated that the combined application of MG and HL significantly affected the integrity of the M. furfur cell membrane and potentially modulated its formation processes. In the M. furfur-induced seborrheic dermatitis model, ML exhibited synergistic antifungal effects and effectively alleviated skin inflammation. These findings provide an important theoretical basis for understanding the antifungal mechanisms of ML and its potential application in dermatological therapy.

Mechanisms of action of berberine hydrochloride in planktonic cells and biofilms of Pseudomonas aeruginosa

The increasing prevalence of extensively drug-and pan-drug-resistant Pseudomonas aeruginosa is a major concern for global public health. Therefore, it is crucial to develop novel antimicrobials that specifically target P. aeruginosa and its biofilms. In the present study, we determined that berberine hydrochloride inhibited the growth of planktonic bacteria as well as prevented the formation of biofilms. Moreover, we observed downregulation in the expression of pslA and pelA biofilm-related genes. Compared with existing antibiotics, berberine hydrochloride exhibits multiple modes of action against P. aeruginosa. Our findings suggest that berberine hydrochloride exerts its antimicrobial effects by damaging bacterial cell membranes, generating reactive oxygen species (ROS), and reducing intracellular adenosine triphosphate (ATP) levels. Furthermore, berberine hydrochloride showed minimal cytotoxicity and reduced susceptibility to drug resistance. In a mouse model of peritonitis, it significantly inhibited the growth of P. aeruginosa and exhibited a strong bacteriostatic action. In conclusion, berberine hydrochloride is a safe and effective antibacterial agent that inhibits the growth of P. aeruginosa.

Strategies and mechanisms targeting Enterococcus faecalis biofilms associated with endodontic infections: a comprehensive review

Enterococcus faecalis is one of the main microorganisms that infects root canals, ranking among the most prevalent microorganisms associated with endodontic treatment failure. Given its pervasive presence in persistent endodontic infections, the successful elimination of Enterococcus faecalis is crucial for effective endodontic treatment and retreatment. Furthermore, Enterococcus faecalis can form biofilms - defense structures that microbes use to fight environmental threats. These biofilms confer resistance against host immune system attacks and antibiotic interventions. Consequently, the presence of biofilms poses a significant challenge in the complete eradication of Enterococcus faecalis and its associated disease. In response, numerous scholars have discovered promising outcomes in addressing Enterococcus faecalis biofilms within root canals and undertaken endeavors to explore more efficacious approaches in combating these biofilms. This study provides a comprehensive review of strategies and mechanisms for the removal of Enterococcus faecalis biofilms.

Exploring Plant-Based Compounds as Alternatives for Targeting Enterococcus faecalis in Endodontic Therapy: A Molecular Docking Approach

Endodontic infections pose significant challenges in dental practice due to their persistence and potential complications. Among the causative agents, Enterococcus faecalis stands out for its ability to form biofilms and develop resistance to conventional antibiotics, leading to treatment failures and recurrent infections. The urgent need for alternative treatments arises from the growing concern over antibiotic resistance and the limitations of current therapeutic options in combating E. faecalis-associated endodontic infections. Plant-based natural compounds offer a promising avenue for exploration, given their diverse bioactive properties and potential as sources of novel antimicrobial agents. In this study, molecular docking and dynamics simulations are employed to explore the interactions between SrtA, a key enzyme in E. faecalis, and plant-based natural compounds. Analysis of phytocompounds through molecular docking unveiled several candidates with binding energies surpassing that of the control drug, ampicillin, with pinocembrin emerging as the lead compound due to its strong interactions with key residues of SrtA. Comparative analysis with ampicillin underscored varying degrees of structural similarity among the study compounds. Molecular dynamics simulations provided deeper insights into the dynamic behavior and stability of protein-ligand complexes, with pinocembrin demonstrating minimal conformational changes and effective stabilization of the N-terminal region. Free energy landscape analysis supported pinocembrin's stabilizing effects, further corroborated by hydrogen bond analysis. Additionally, physicochemical properties analysis highlighted the drug-likeness of pinocembrin and glabridin. Overall, this study elucidates the potential anti-bacterial properties of selected phytocompounds against E. faecalis infections, with pinocembrin emerging as a promising lead compound for further drug development efforts, offering new avenues for combating bacterial infections and advancing therapeutic interventions in endodontic practice.

Bioprospecting and Exploration of Phytochemicals as Quorum Sensing Inhibitors against Cariogenic Dental Biofilm

Dental caries is a polymicrobial infection affecting the dental hard tissues. Excessive carbohydrate intake leads to the accumulation of acid-producing and acid-resistant microorganisms in the oral region. It is a biofilm-dependent oral infection with cariogenic pathogens and the most prevalent disease globally. The prevention and control of caries play a vital role in global health management. Periodontal diseases and subgingival plaque etiology are due to the combined action of bacterial invasion and immune reaction, resulting in the devastation of periodontal tissues, culminating in tooth loss. The compact micro colony inhabiting the dental surfaces attaches with secreted polymer, forming a biofilm. Bacterial biofilm impervious to various drugs and chemicals poses a significant challenge in therapeutic scenarios of medical and odonatological infections. The quorum-sensing signaling mechanism in bacteria controls the metabolic and physiologic properties involved in bacterial existence, pathogenesis, and virulence. Hence, studies monitoring the molecular mechanism of quorum sensing and their restricted social interactions will be highly beneficial in the treatment regimen of the modern era. Natural bioactive compounds can be exploited for their medicinal value in combating oro-dental infections. Phytochemicals are promising candidates that could provide novel strategies for fighting infections. The current review highlights the mechanism of quorum sensing, plant products’ effect in controlling quorum sensing, and biofilm-induced dental infections like Periodontitis.

Bioactive Compounds from Plant Origin as Natural Antimicrobial Agents for the Treatment of Wound Infections

The rising prevalence of drug-resistant bacteria underscores the need to search for innovative and nature-based solutions. One of the approaches may be the use of plants that constitute a rich source of miscellaneous compounds with a wide range of biological properties. This review explores the antimicrobial activity of seven bioactives and their possible molecular mechanisms of action. Special attention was focused on the antibacterial properties of berberine, catechin, chelerythrine, cinnamaldehyde, ellagic acid, proanthocyanidin, and sanguinarine against Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa. The growing interest in novel therapeutic strategies based on new plant-derived formulations was confirmed by the growing number of articles. Natural products are one of the most promising and intensively examined agents to combat the consequences of the overuse and misuse of classical antibiotics.

The antibacterial activity of berberine against Cutibacterium acnes: its therapeutic potential in inflammatory acne

Cutibacterium acnes (C. acnes) is a major pathogen implicated in the evolution of acne inflammation. Inhibition of C. acnes-induced inflammation is a prospective acne therapy strategy. Berberine (BBR), a safe and effective natural ingredient, has been proven to exhibit powerful antimicrobial and anti-inflammatory properties. However, the antimicrobial effect of BBR against C. acnes and its role in C. acnes-mediated inflammatory acne have not been explored. The objective of this investigation was to assess the antibacterial activity of BBR against C. acnes and its inhibitory effect on the inflammatory response. The results of in vitro experiments showed that BBR exhibited significant inhibition zones against four C. acnes strains, with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in the range of 6.25-12.5 μg/mL and 12.5-25 μg/mL, respectively. On the bacterial growth curve, the BBR-treated C. acnes exhibited obvious growth inhibition. Transmission electron microscopy (TEM) images indicated that BBR treatment resulted in significant morphological changes in C. acnes. High-content imaging analysis further confirmed that BBR could effectively inhibit the proliferation of C. acnes. The disruption of cell wall and cell membrane structure by BBR treatment was preliminary confirmed according to the leakage of cellular contents such as potassium (K+), magnesium (Mg2+), and alkaline phosphatase (AKP). Furthermore, we found that BBR could reduce the transcript levels of genes associated with peptidoglycan synthesis (murC, murD, mraY, and murG). Meanwhile, we investigated the modulatory ability of BBR on C. acnes-induced skin inflammation in mice. The results showed that BBR effectively reduced the number of C. acnes colonized in mice's ears, thereby alleviating ear swelling and erythema and significantly decreasing ear thickness and weight. In addition, BBR significantly decreased the levels of pro-inflammatory cytokines IL-6, IL-1β, and TNF-α in auricular tissues. These results suggest that BBR has the potential to treat inflammatory acne induced by C. acnes.

The inhibitory effect of berberine chloride hydrate on Streptococcus mutans biofilm formation at different pH values

Streptococcus mutans (S. mutans) is one of the major cariogenic bacteria of dental caries owing to its ability to adhere to tooth surfaces and biofilm formation. Berberine chloride hydrate (BH), a quaternary ammonium salt alkaloid, has diverse pharmacological efforts against microorganisms. However, the effect of BH on S. mutans biofilm has not been reported. Considering that berberine is a quaternary ammonium salt alkaloid, which needs to adapt to a large variation in pH values and the acid resistance of S. mutans, we employed three groups including pH 5 (acidic), pH 8 (alkaline), and unprocessed group (neutral) to examine the antibiofilm activities of BH against S. mutans during different pH values. In this study, we found BH effectively suppresses S. mutans biofilm formation as well as its cariogenic virulence including acid production and EPS synthesis significantly, and the inhibitory effort was reduced under acidic condition whereas elevated under alkaline condition. In addition, we preliminarily explored the influence of pH values on the structural stability and biosafety of BHas well as the underlying mechanism of inhibition of S. mutans biofilm formation with BH. Our study showed BH could maintain a good structural stability and low toxicity to erythrocytes at different pH values. And BH could downregulate the expression of srtA, spaP, and gbpC, which play critical roles in the adhesion process, promoting bacterial colonization and biofilm formation. Furthermore, comX and ldh expression levels were downregulated in BH-treated group, which might explain its inhibitory effect on acid production.IMPORTANCEDental caries is a common chronic detrimental disease, which could cause a series of oral problem including oral pain, difficulties in eating, and so on. Recently, many natural products have been considered as fundamental sources of therapeutic drugs to prevent caries. Berberine as a plant extract showed good antibiofilm abilities against microorganism. Our study focuses on its antibiofilm abilities against S. mutans, which was defined as major cariogenic bacterium and explored the role of pH values and possible underlying mechanisms in the inhibitory effect of BH on S. mutans biofilm formation. This study demonstrated a promising prospect for BH as an adjuvant drug in the prevention and management of dental caries.

In vitro antibiofilm and bacteriostatic activity of diacerein against Enterococcus faecalis

Enterococcus faecalis is one of the main pathogens that causes hospital-acquired infections because it is intrinsically resistant to some antibiotics and often is capable of biofilm formation, which plays a critical role in resisting the external environment. Therefore, attacking biofilms is a potential therapeutic strategy for infections caused by E. faecalis. Current research indicates that diacerein used in the treatment of osteoarthritis showed antimicrobial activity on strains of gram-positive cocci in vitro. In this study, we tested the MICs of diacerein using the broth microdilution method, and successive susceptibility testing verified that E. faecalis is unlikely to develop resistance to diacerein. In addition, we obtained a strain of E. faecalis HE01 with strong biofilm-forming ability from an eye hospital environment and demonstrated that diacerein affected the biofilm development of HE01 in a dose-dependent manner. Then, we explored the mechanism by which diacerein inhibits biofilm formation through qRT-PCR, extracellular protein assays, hydrophobicity assays and transcriptomic analysis. The results showed that biofilm formation was inhibited at the initial adhesion stage by inhibition of the expression of the esp gene, synthesis of bacterial surface proteins and reduction in cell hydrophobicity. In addition, transcriptome analysis showed that diacerein not only inhibited bacterial growth by affecting the oxidative phosphorylation process and substance transport but also inhibited biofilm formation by affecting secondary metabolism, biosynthesis, the ribosome pathway and luxS expression. Thus, our findings provide compelling evidence for the substantial therapeutic potential of diacerein against E. faecalis biofilms.

Bioactive compounds: a goldmine for defining new strategies against pathogenic bacterial biofilms?

Most human infectious diseases are caused by microorganisms growing as biofilms. These three-dimensional self-organized communities are embedded in a dense matrix allowing microorganisms to persistently inhabit abiotic and biotic surfaces due to increased resistance to both antibiotics and effectors of the immune system. Consequently, there is an urgent need for novel strategies to control biofilm-associated infections. Natural products offer a vast array of chemical structures and possess a wide variety of biological properties; therefore, they have been and continue to be exploited in the search for potential biofilm inhibitors with a specific or multi-locus mechanism of action. This review provides an updated discussion of the major bioactive compounds isolated from several natural sources - such as plants, lichens, algae, microorganisms, animals, and humans - with the potential to inhibit biofilm formation and/or to disperse established biofilms by bacterial pathogens. Despite the very large number of bioactive products, their exact mechanism of action often remains to be clarified and, in some cases, the identity of the active molecule is still unknown. This knowledge gap should be filled thus allowing development of these products not only as novel drugs to combat bacterial biofilms, but also as antibiotic adjuvants to restore the therapeutic efficacy of current antibiotics.

Natural products from traditional medicine as promising agents targeting at different stages of oral biofilm development

Oral cavity is an ideal habitat for more than 1,000 species of microorganisms. The diverse oral microbes form biofilms over the hard and soft tissues in the oral cavity, affecting the oral ecological balance and the development of oral diseases, such as caries, apical periodontitis, and periodontitis. Currently, antibiotics are the primary agents against infectious diseases; however, the emergence of drug resistance and the disruption of oral microecology have challenged their applications. The discovery of new antibiotic-independent agents is a promising strategy against biofilm-induced infections. Natural products from traditional medicine have shown potential antibiofilm activities in the oral cavity with high safety, cost-effectiveness, and minimal adverse drug reactions. Aiming to highlight the importance and functions of natural products from traditional medicine against oral biofilms, here we summarized and discussed the antibiofilm effects of natural products targeting at different stages of the biofilm formation process, including adhesion, proliferation, maturation, and dispersion, and their effects on multi-species biofilms. The perspective of antibiofilm agents for oral infectious diseases to restore the balance of oral microecology is also discussed.

Antifungal activity and potential mechanism of berberine hydrochloride against fluconazole-resistant Candida albicans

Introduction. The emergence of resistance to fluconazole in Candida albicans has made the clinical treatment of this microbe difficult. A potential strategy to address this problem involves diminishing fungal resistance to antimicrobial drugs.Hypothesis. Berberine hydrochloride (BH), the primary active ingredient of the traditional Chinese medicine (TCM) Coptis, inhibits the growth of fluconazole-resistant C. albicans through its action on the high-osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) pathway.Aim. To examine the effect of BH on the HOG-MAPK pathway to assess the potential molecular mechanism by which BH inhibits fluconazole-resistant C. albicans.Methodology. The minimum inhibitory concentration (MIC) of BH to fluconazole-resistant C. albicans was measured using the broth microdilution approach to determine the concentration of effective drug intervention. Changes in physiological functions regulated by the HOG-MAPK pathway in response to BH treatment were measured, as well as the expression of central signalling pathway genes and key downstream factors by qRT-PCR and Western blotting, respectively.Results. BH inhibited fluconazole-resistant C. albicans and the sensitivity to fluconazole increased after BH treatment. At a concentration of 256 and 64 μg ml^-1 BH may affect key downstream factors that regulate several physiological functions of C. albicans by upregulating the core genes expression of SLN1, SSK2, HOG1, and PBS2 in the HOG-MAPK pathway. Upregulation of GPD1, the key gene for glycerol synthesis, increased cell osmotic pressure. BH treatment increased the accumulation of reactive oxygen species by upregulating the expression of the key respiratory metabolism gene ATP11 and downregulating the expression of the superoxide dismutase gene SOD2. Furthermore, downregulation of mycelial-specific HWP1 hindered the morphological transformation of C. albicans and inhibition of the chitin synthase gene CHS3 and the β-(1,3) glucan synthase gene GSC1 impaired cytoderm integrity.Conclusion. BH affects multiple target genes in diminishing the resistance of C. albicans strains to fluconazole. This effect may be related to the action of BH on the HOG-MAPK pathway.

Antibiofilm activity of phytochemicals against Enterococcus faecalis: A literature review

Enterococcus faecalis is a leading causative pathogen of recalcitrant infections affecting heart valves, urinary tract, surgical wounds and dental root canals. Its robust biofilm formation, production of virulence factors and antibiotic resistance contribute significantly to its pathogenicity in persistent infections. The decreased effectiveness of most of antibiotics in preventing and/or eradicating E. faecalis biofilms mandates the discovery of alternative novel antibiofilm agents. Phytochemicals are potential sources of antibiofilm agents due to their antivirulence activity, diversity of chemical structure and multiple mechanisms of action. In this review, we describe the phenotypic and genetic attributes that contribute to antimicrobial tolerance of E. faecalis biofilms. We illuminate the benefits of implementing the phytochemicals to tackle microbial pathogens. Finally, we report the antibiofilm activity of phytochemicals against E. faecalis, and explain their mechanisms of action. These compounds belong to different chemical classes such as terpenes, phenylpropenes, flavonoids, curcuminoids and alkaloids. They demonstrate the ability to inhibit the formation of and/or eradicate E. faecalis biofilms. However, the exact mechanisms of action of most of these compounds are not fully understood. Therefore, the future studies should elucidate the underlying mechanisms in detail.

Self-assembly of berberine and a boron cluster for antibacterial regulation

B12H122− and BBR can quickly form rod-shaped particles in aqueous solution with enhanced reactive oxygen species (ROS) generation ability.

Hormesis Effect of Berberine against Klebsiella pneumoniae Is Mediated by Up-Regulation of the Efflux Pump KmrA

Berberine (BBR) is an effective drug for human intestinal inflammation by preventing intestinal adhesion of bacterial pathogens, while its antibacterial activity is ineffective. Although the antimicrobial mechanisms of BBR are intensively studied at high concentrations, the response of pathogens to its low concentrations remains poorly understood. Here we demonstrated that low concentrations of BBR (3 and 6 μg/mL) conferred by hormesis accelerated cell growth of an important Gram-negative pathogen, Klebsiella pneumoniae, in vitro, while higher concentrations (25 and 50 μg/mL) resulted in the opposite. Transcriptome analysis of K. pneumoniae revealed the up-regulated expression of the KmrA efflux pump and further confirmed it was hypersensitive to BBR stress. Strikingly, when cultivated in tetracycline, the growth-promoting effect of BBR became more significant, while this effect was reversed in the presence of the efflux pump inhibitor cyanide-m-chlorophenylhydrazone. The hormesis was also found in Enterobacter cloacae and Acinetobacter baumannii. More importantly, the presence of BBR at low concentrations resulted in higher minimal inhibitory concentrations of efflux-related antibiotics such as rifampicin and azithromycin. Overall, our data demonstrated the hormesis of BBR and revealed the potential risk of its applications against Gram-negative pathogens at low concentrations.

Targeting effect of berberine on type I fimbriae of Salmonella Typhimurium and its effective inhibition of biofilm

As a primary cause of food contamination and human diseases, Salmonella Typhimurium can easily form a biofilm that is difficult to remove from food surfaces, and often causes significant invisible threats to food safety. Although berberine has been widely used as an anti-infective drug in traditional medicine, some basic principles underlying its mechanism, especially the interaction between berberine and type I fimbriae genes, has not been verified yet. In this study, two strains of major fimbrial gene mutants (ΔfimA and ΔfimH) were constructed to demonstrate the possible action of berberine on type I fimbriae genes. The broth microdilution method was used to determine the antibacterial activity of berberine against selected strains (WT, ΔfimA, and ΔfimH). Cell agglutination experiments revealed that the number of S. Typhimurium type I fimbriae reduced after berberine treatment, which was consistent with transmission electron microscopy results. Quantitative real-time PCR experiments also confirmed that berberine reduced fimA gene expression, indicating a certain interaction between berberine and fimA gene. Furthermore, confocal laser scanning microscopy imaging of biofilm clearly revealed that berberine prevents biofilm formation by reducing the number of type I fimbriae. Overall, it is well speculated for us that berberine could be an excellent combating-biofilm drug in clinical microbiology and food preservation. KEY POINTS: • Reduce the number of fimbriae. • Berberine targeting fimA. • Effective biofilm inhibitor.

Antibacterial self-assembled nanodrugs composed of berberine derivatives and rhamnolipids against Helicobacter pylori

The prevalence of infections with Helicobacter pylori (H. pylori) has progressively increased worldwide, which demonstrated to be closely correlated to its biofilm formation. H. pylori biofilms protect the bacteria by significantly decreasing their sensitivity to antibiotics. Moreover, H. pylori colonizes on the gastrointestinal tract epithelium which is covered by mucus layer, acting as another barrier to prevent antibacterial agents from reaching the colonization sites. Herein, we prepared four types of versatile self-assembled nanodrugs (BD/RHL NDs) containing lipophilic alkyl berberine derivatives (BDs) and rhamnolipids (RHL) to overcome the dual obstructions of both mucus layer and biofilms. Molecular dynamics simulations estimated that the driving forces for self-assembly of BD/RHL NDs were electrostatic and hydrophobic interactions. BD/RHL NDs, characterized by appropriate size, negative charge and enhanced hydrophilicity, successfully penetrated through mucus layer without interacting with mucins. In in vitro experiments, BD/RHL NDs exhibited substantial ability to eradicate H. pylori biofilms by destroying their extracellular polymeric substances (EPS) and killing planktonic H. pylori. Furthermore, BD/RHL NDs inhibited the adherence of H. pylori on both biotic and abiotic surfaces, therefore cut off the critical step of the biofilm re-formation which was associated with the recrudescence of infections. In an H. pylori-infected mice model, C10-BD/RHL NDs group showed 40 folds less remnant H. pylori and greater mucosal protection compared with the conventional clinical triple therapy. In conclusion, BD/RHL NDs could penetrate through mucus layer and effectively eradicate H. pylori biofilms in vitro and in vivo, providing a novel strategy for clinical treatment of biofilm-related infections.

Efficacy and mechanism of actions of natural antimicrobial drugs

Microbial infections have significantly increased over the last decades, and the mortality rates remain unacceptably high. The emergence of new resistance patterns and the spread of new viruses challenge the eradication of infectious diseases. The declining efficacy of antimicrobial drugs has become a global public health problem. Natural products derived from natural sources, such as plants, animals, and microorganisms, have significant efficacy for the treatment of infectious diseases accompanied by less adverse effects, synergy, and ability to overcome drug resistance. As the Chinese female scientist Youyou Tu received the Nobel Prize for the antimalarial drug artemisinin, antimicrobial drugs developed from Traditional Chinese Medicine are expected to receive increasing attention again. This review summarizes the antimicrobial agents derived from natural products approved for nearly 20 years and describes their efficacy and mode of action. The aim of this unit is to review the current status of antimicrobial drugs from natural products in order to increase the value of natural products as a source of novel drug candidates for infectious diseases.

Biofilm formation in Acinetobacter baumannii was inhibited by PAβN while it had no association with antibiotic resistance

This study was conducted to investigate the relationship between Acinetobacter baumannii biofilm formation and antibiotic resistance. Furthermore, the effects of PAβN, a potential efflux pump inhibitor, on A. baumannii biofilm formation and dispersion were tested, and the gene expression levels of efflux pumps were determined to study the mechanisms. A total of 92 A. baumannii isolates from infected patients were collected and identified by multiplex PCR. The antimicrobial susceptibility of A. baumannii clinical isolates was tested by VITEK 2 COMPACT^® . Genotypes were determined by ERIC-2 PCR. Biofilm formation and dispersion were detected by crystal violet staining. The presence and mRNA expression of efflux pump genes were analyzed by conventional PCR and real-time PCR, respectively. More than 50% of the A. baumannii strains formed biofilm and were divided into different groups according to their biofilm-forming ability. Antibiotic resistance rates among most groups did not significantly differ. There were 7 clonal groups in 92 strains of A. baumannii and no dominant clones among the different biofilm-forming groups. PAβN inhibited A. baumannii biofilm formation and enhanced its dispersion, whereas adeB, adeJ, and adeG and the mRNA expression of adeB, abeM, and amvA showed no differences in the different biofilm-forming groups. In conclusion, there was no clear relationship between biofilm formation and antibiotic resistance in A. baumannii. The effects of PAβN on A. baumannii biofilm formation and dispersion were independent of the efflux pumps.

Analysis of Urinary Pathogen Cultures and Drug Sensitivity in Patients with Urinary Stones for Five Consecutive Years in Xiangya Hospital, China

Objective

To analyze pathogen distribution and drug sensitivity in patients with urinary calculi and thereby gain insight into the most appropriate antibacterial drugs for perioperative therapy.

Materials and Methods

From January 2014 to December 2018, the results of mid-stream urine pathogen culture and drug sensitivity tests were evaluated retrospectively for 353 patients with urinary calculi. SPSS software version 23.0 was used to analyze the data.

Results

A total of 353 strains of pathogens were isolated from urine culture. Among these, 278 (79%) strains belonged to the top 10 most frequently isolated pathogens, comprising 209 (75.2%) Gram-negative bacilli and 69 (24.8%) Gram-positive cocci. Escherichia coli was the most frequently isolated pathogen overall and the most frequently isolated Gram-negative bacillus, and Enterococcus faecalis was the most frequently isolated Gram-positive coccus. Drug sensitivity levels were effectively unchanged for less commonly used drugs, whereas drug resistance rates remained high for commonly used drugs such as ampicillin trihydrate, ampicillin/sulbactam, cefazolin, ceftriaxone, aztreonam, levofloxacin and ciprofloxacin.

Conclusion

E. coli and E. faecalis remain the most common Gram-negative bacillus and Gram-positive coccus uropathogens, respectively, in patients with urinary calculi. Mid-stream urine pathogen culture and drug sensitivity tests should be used to select appropriate antibacterial drugs before treatment, particularly for perioperative patients with urinary calculi.

Biofilm synthesis and other virulence factors in multidrug-resistant uropathogenic enterococci isolated in Northern India

Purpose

Enterococci express high degree of resistance towards wide range of antibiotics. Production of biofilm and many virulence factors along with drug resistance makes it difficult to eradicate the infection from urinary tract. The present study detected the expression of such factors including biofilm production by multidrug-resistant (MDR) enterococci.

Materials and Methods

Drug susceptibility of 103 uropathogenic enterococci was performed followed by estimation of minimum inhibitory concentration of high-level gentamicin and vancomycin by microbroth dilution method. Vancomycin-resistant genes were detected by multiplex polymerase chain reaction. Production of virulence factors such as haemagglutination, caseinase, lipase, gelatinase, haemolysin and β-lactamase was detected by phenotypic methods in MDR strains. Biofilm production was detected by calcofluor-white fluorescence staining and semi-quantitative adherence assay.

Results

45% and 18.4% of the isolates were high-level gentamicin-resistant and vancomycin-resistant enterococci (VRE), respectively. vanA gene was detected in 14 and vanB gene in 5 strains. Biofilm, caseinase and gelatinase were the most expressed virulence factor. Expression of caseinase, gelatinase and lipase was significantly higher in Enterococcus faecalis (P < 0.05). Expression of haemagglutination, gelatinase and haemolysin among the vancomycin-resistant isolates was significantly higher (P < 0.05).

Conclusion

VanA and vanB are the prevalent genotypes responsible for vancomycin resistance. The high prevalence of MDR enterococcal strains producing biofilm and virulence determinants raises concern. asa1, hyl, esp, gelE, cyl and other genes are known to express these factors and contribute to biofilm formation. Most uropathogenic enterococci expressed biofilm at moderate level and can be detected effectively by calcofluor-white staining. No correlation was noted between vancomycin resistance and biofilm production.

Type VI secretion system of Pseudomonas aeruginosa is associated with biofilm formation but not environmental adaptation

Pseudomonas aeruginosa encodes three type VI secretion systems (T6SSs), namely H1‐, H2‐, and H3‐T6SS. P. aeruginosa hemolysin‐coregulated protein (Hcp) is the effector protein and the hallmark of T6SS. Although T6SS is ubiquitous and affects ecology and human health, its general mechanism and physiological role are still not fully understood. Therefore, in this study, we investigated the impact of the P. aeruginosa T6SS on biofilm formation and environmental adaptation. To this end, we collected P. aeruginosa clinical isolates, divided them into strong biofilm formation (SBF) and nonbiofilm formation (NBF) groups based on their biofilm‐forming ability, and compared their associated clinical characteristics. The duration of hospitalization was longer in patients infected with SBF than those infected with NBF strains. The expression levels of T6SS‐related genes (hcp1 and hcp3) and a quorum‐sensing gene (lasR) were higher in the SBF group as compared to those in the NBF group. In addition, the expression level of lasR was negatively associated with that of hcp1, but was positively associated with those of hcp2 and hcp3. Moreover, we evaluated the expression of T6SS‐ and biofilm‐associated genes in planktonic and biofilm cells of the P. aeruginosa strain PAO1, and constructed strain PAO1△clpV1 to study the adaptation characteristics of H1‐T6SS. The expression levels of hcp1, hcp2, hcp3, lasR, and other biofilm‐associated genes were significantly higher in PAO1 biofilm cells as compared to those of planktonic cells. However, except for swarming ability as a vital feature for biofilm formation, there were no significant differences in the biofilm‐forming ability and expression of biofilm‐associated genes, adherence ability, growth characteristics, resistance to acid and osmotic pressure, surface structure, and morphology between the PAO1△clpV1 and PAO1 wild‐type strains. Collectively, our results suggest that T6SS might play a role in biofilm formation and that H1‐T6SS does not contribute to environmental adaptation in P. aeruginosa.

Inhibition of biofilm formation and quorum sensing mediated phenotypes by berberine in Pseudomonas aeruginosa and Salmonella typhimurium

Quorum sensing is involved in biofilm formation and modulates virulence factor production in pathogenic bacteria. Quorum sensing inhibitors can be used as novel intervention strategies for attenuating bacterial pathogenicity. Berberine is an isoquinoline alkaloid with pharmacological properties. The present study investigated the sub-inhibitory concentrations of berberine for inhibiting biofilm formation and quorum sensing regulated phenotypes in the bacterial pathogens Pseudomonas aeruginosa PA01 and Salmonella enterica serovar Typhimurium. Berberine inhibited quorum sensing regulated violacein production in C. violaceum. It reduced the pigment production in the wild type strain at 1.6 mg mL⁻¹ by 62.67%. In the opportunistic pathogen, P. aeruginosa PA01, at sub-MIC, it showed significant antibiofilm activity in by reducing biomass by 71.70% (p < 0.05). It prevented biofilm formation and inactivated biofilm maturation in bacterial pathogens at the concentration ranging from 0.019 to 1.25 mg mL⁻¹. In silico studies showed that berberine interacted with the quorum sensing signal receptors, LasR and RhlR. Furthermore, its anti-infective properties in S. Typhimurium were studied. At sub-inhibitory concentrations of 0.019 mg mL⁻¹, it reduced biofilm formation in S. Typhimurium by 31.20%. It significantly prevented invasion and adhesion of Salmonella invasion in the colonic cell, HT 29 by 55.37% and 54.68%, respectively. It was capable of reducing in vivo virulence in Caenorhabditis elegans infected with Salmonella at 0.038 mg mL⁻¹ by 65.38%. Our results suggest that berberine, previously recognised for its antimicrobial activity, could find potential application as an anti-biofilm and anti-infective agent based on its quorum sensing inhibitory activity.

Quorum sensing regulates violacein pigment production in C. violaceum.

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.