Virulence of enterococci

Genome analysis reveals a biased distribution of virulence and antibiotic resistance genes in the genus Enterococcus and an abundance of safe species

Enterococci are lactic acid bacteria (LAB) that, as their name implies, often are found in the gastrointestinal tract of animals. Like many other gut-dwelling LAB, for example, various lactobacilli, they are frequently found in other niches as well, including plants and fermented foods from all over the world. In fermented foods, they contribute to flavor and other organoleptic properties, help extend shelf life, and some even possess probiotic properties. There are many positive attributes of enterococci; however, they have been overshadowed by the occurrence of antibiotic-resistant and virulent strains, often reported for the two species, Enterococcus faecalis and Enterococcus faecium. More than 40,000 whole-genome sequences covering 64 Enterococcus type species are currently available in the National Center for Biotechnology Information repository. Closer inspection of these sequences revealed that most represent the two gut-dwelling species E. faecalis and E. faecium. The remaining 62 species, many of which have been isolated from plants, are thus quite underrepresented. Of the latter species, we found that most carried no potential virulence and antibiotic resistance genes, an observation that is aligned with these species predominately occupying other niches. Thus, the culprits found in the Enterococcus genus mainly belong to E. faecalis, and a biased characterization has resulted in the opinion that enterococci do not belong in food. Since enterococci possess many industrially desirable traits and frequently are found in other niches besides the gut of animals, we suggest that their use as food fermentation microorganisms is reconsidered.IMPORTANCEWe have retrieved a large number of Enterococcus genome sequences from the National Center for Biotechnology Information repository and have scrutinized these for the presence of virulence and antibiotic resistance genes. Our results show that such genes are prevalently found in the two species Enterococcus faecalis and Enterococcus faecium. Most other species do not harbor any virulence and antibiotic resistance genes and display great potential for use as food fermentation microorganisms or as probiotics. The study contributes to the current debate on enterococci and goes against the mainstream perception of enterococci as potentially dangerous microorganisms that should not be associated with food and health.

A novel thermostable lytic phage vB_EF_Enf3_CCASU-2024-3 against clinical Enterococcus faecium and Enterococcus faecalis

Enterococci, Gram-positive bacteria, have become a major concern in healthcare settings due to their significant virulence and antibiotic resistance. This research focuses on isolating, phenotypic, and genotypic analysis of enterococci-specific lytic phages to be used as potential candidates in combating multidrug-resistant (MDR) Enterococcus clinical isolates. The virulence of Enterococcus isolates was analyzed by testing for gelatinase and biofilm formation. The phage(s) was isolated from a sewage sample, then purified, propagated, and physiochemically analyzed. The phage was examined using transmission electron microscopy, and the whole genome sequence (WGS) was performed. Sixety-five clinical enterococci including, 27 (41.5%), 33 (50.7%) 3 (4.6%), and 2 (3%) E. faecalis, E. faecium, E. avium, and E. durans, respectively were isolated. Linezolid, teicoplanin, chloramphenicol, and vancomycin exhibited the lowest resistance. Twenty-five (38.5%) isolates were both gelatinase- and biofilm-producers. A novel lytic vB_EF_Enf3 phage belonging to Caudoviricetes class, characterized by an icosahedral head with a diameter of 100 ± 5 nm and a tail measuring 70 ± 5 nm in length was isolated. The phage demonstrated good thermal stability, and viability across various pH levels and exhibited a broad- spectrum of activity against E. faecium and E. faecalis. The vB_EF_Enf3 phage (36,202 bp length) harbored 36 open reading frames (ORFs) with a GC content of 34.4% (GenBank accession, PP747318). In conclusion, a novel thermostable lytic bacteriophage vB_EF_Enf3, belonging to class Caudoviricetes, was isolated from sewage showing broad-spectrum potent lytic activity against E. faecium and E. faecalis and maintained stability under various extreme conditions, including temperature, and pH fluctuations.

Detection of Enterococcus faecalis and the red complex bacteria analyzed by the Checkerboard technique for DNA-DNA hybridization in endodontic infections: A systematic review and meta-analysis

Endodontic infections include conditions such as pulp necrosis, apical periodontitis, abscesses, granulomas, and periapical cysts. Detection of pathogenic microorganisms responsible for these diseases is essential for accurate diagnosis and future therapy. Enterococcus faecalis, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola were analyzed qualitatively and quantitatively using the Checkerboard methodology for DNA-DNA hybridizations as a bacterial identification tool. Clinical investigations have shown a significant frequency of these microorganisms. The present systematic review and meta-analysis aimed to determine the prevalence of E. faecalis and red complex bacteria (RCB) (P. gingivalis, T. forsythia, and T. denticola) analyzed by the Checkerboard DNA-DNA hybridization technique in endodontic infections. This systematic literature review followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines-electronic databases: PubMed, Scopus, ScienceDirect, Web of Science, and Google Scholar. Statistical analysis was performed using STATA V.15 software. Seventeen articles were included, of which a total of 620 samples were evaluated. Five hundred sixty-seven samples were taken from infected root canals, 34 samples from periradicular tissues, and 27 samples from periapical abscesses of infected teeth. The prevalence of E. faecalis in endodontic infections in all studies was 74 %, of P. gingivalis was 63 %, of T. forsythia 46 %, and of T. denticola 58 %. The presence of bacteria such as E. faecalis reduces the efficiency of endodontic therapy and leads to recurring infections. It is recognized that "RCB" can be identified in endodontic lesions; however, they are not usually prominent. The DNA-DNA hybridization approach is critical for identifying bacteria and detecting difficult-to-culture microorganisms, making it a helpful and cost-effective tool for directing personalized endodontic treatments.

Prophylactic phage administration provides a time window for delayed treatment of vancomycin-resistant Enterococcus faecalis in a murine bacteremia model

Introduction

Vancomycin-resistant Enterococcus faecalis (VRE) poses a significant challenge in clinical settings due to its resistance to multiple antibiotics. Phage therapy offers a promising alternative to address this resistance crisis. However, critical gaps remain regarding optimal dosing, therapeutic design, and treatment timing for phage therapy targeting VRE-induced bacteremia.

Methods

The biological and genomic characteristics of a novel lytic phage specific to VRE were investigated. Its in vitro bactericidal and antibiofilm activities were evaluated, along with its synergy with antimicrobial agents. In vitro safety and protective efficacy were assessed using a mouse bacteremia model. The impact of phage therapy on gut microbiota was examined through 16S rDNA gene sequencing.

Results

We isolated and characterized a novel lytic phage, vB_EfaS-1017, specific to vancomycin-resistant E. faecalis. This phage features a circular, double-stranded DNA genome (40,766 bp), sharing 91.19% identity and 79% coverage with Enterococcus phage vB_EfaS_SRH2. vB_EfaS-1017 exhibited robust bactericidal and antibiofilm activity in vitro and demonstrated synergy with levofloxacin. Safety assessments confirmed its non-toxicity to mammalian cells and lack of hemolytic activity. In a mouse bacteremia model, phage treatment alone rescued 60% of infected mice, while combining phage with levofloxacin increased survival to 80%. Prophylactic administration of phage 24 hours prior to infection failed to prevent mortality. However, a combination of prophylactic phage administration and delayed treatment rescued 60% of mice, compared to 100% mortality in the delayed treatment alone group. Additionally, phage therapy helped maintain or restore gut microbiota balance.

Discussion

These findings underscore the potential of phage-antibiotic combinations as a superior therapeutic strategy against VRE infections. The observed synergy between phages and antibiotics highlights a promising approach to overcoming bacterial resistance and improving clinical outcomes. Furthermore, prophylactic phage administration may provide a critical time window for effective delayed treatment. Further preclinical research is essential to refine phage therapy protocols for clinical application.

A mouse model of immunosuppression facilitates oral Candida albicans biofilms, bacterial dysbiosis and dissemination of infection

Opportunistic pathogens are a major threat to people, especially those with impaired immune systems. Two of the most important microbes in this category are the fungus Candida albicans and Gram-positive bacteria of the genus Enterococcus, which share overlapping niches in the oral cavity, gastrointestinal and urogenital tracts. The clinical importance of oral C. albicans biofilm and its interaction with the host under immunosuppressive conditions remains largely understudied. Here, we used a mouse model of oropharyngeal candidiasis (OPC) with cortisone acetate injection on alternate days and a continuous supply of C. albicans in drinking water for three days, resulting in immunosuppression. Results showed abundant growth of resident oral bacteria and a strong C. albicans biofilm on the tongue consisting of hyphae which damaged papillae, the epidermal layer, and invaded tongue tissue with the accumulation of inflammatory cells as demonstrated by Grocott's methenamine silver and hematoxylin and eosin staining, respectively. The dispersed microbes from the oral biofilm colonized the gastrointestinal (GI) tract and damaged its integrity, disseminating microbes to other organs. Although no visible damage was observed in the kidney and liver, except increased lipid vacuoles in the liver cells, C. albicans was found in the liver homogenate. Intriguingly, we found co-occurrence of Enterococcus faecalis in the tongue, liver, and stool of immunosuppressed control and C. albicans infected organs. Targeted 16S rRNA and ITS2 amplicon sequencing of microbes from the fecal samples of mice confirmed the above results in the stool samples and revealed an inverse correlation of beneficial microbes in the dysbiosis condition. Our study shows that mucosal-oral infection of C. albicans under immunosuppressed conditions causes tissue damage and invasion in local and distant organs; the invasion may be aided by the overgrowth of the resident endogenous Enterobacteriaceae and other members, including the opportunistic pathogen Enterococcus faecalis.

From Isolation to Application: Utilising Phage-Antibiotic Synergy in Murine Bacteremia Model to Combat Multidrug-Resistant Enterococcus faecalis

Enterococcus species, natural inhabitants of the human gut, have become major causes of life-threatening bloodstream infections (BSIs) and the third most frequent cause of hospital-acquired bacteremia. The rise of high-level gentamicin resistance (HLGR) in enterococcal isolates complicates treatment and revives bacteriophage therapy. This study isolated and identified forty E. faecalis clinical isolates, with 30% exhibiting HLGR. The HLGR5 isolate, resistant to fosfomycin, vancomycin, and linezolid, was used to isolate the vB_EfaS_SZ1 phage from effluent water. This phage specifically lysed 42% of HLGR isolates. vB_EfaS_SZ1 demonstrated beneficial traits, including thermal stability, acid-base tolerance, a short latent period, and a large burst size. The phage genome comprises a 40,942 bp linear double-stranded DNA with 65 open reading frames (ORFs). The genome closely resembled Enterococcus phages, classifying it within the Efquatrovirus genus. Phage-antibiotic synergy was assessed using checkerboard assays and time-killing analyses, revealing enhanced bacteriolytic activity of ampicillin and fosfomycin, with significant reductions in minimum inhibitory concentration values. In a mouse bacteremia model, phage-antibiotic combinations significantly reduced E. faecalis liver burden compared to monotherapies. Histopathological analysis confirmed therapeutic synergy, showing reduced inflammation and improved hepatocyte regeneration. These findings underscore the potential of phage vB_EfaS_SZ1 as an adjunct to antibiotic therapy for resistant enterococcal bacteremia.

Increasing prevalence of bacteriocin carriage in a 6-year hospital cohort of E. faecium

Vancomycin-resistant enterococci (VRE) are important pathogens in hospitalized patients; however, the factors involved in VRE colonization of hospitalized patients are not well characterized. Bacteriocins provide a competitive advantage to enterococci in experimental models of colonization, but little is known about bacteriocin content in samples derived from humans and even less is known about their dynamics in the clinical setting. To identify bacteriocins which may be relevant in the transmission of VRE, we present a systematic analysis of bacteriocin content in the genomes of 2,248 patient-derived E. faecium isolates collected over a 6-year period from a single hospital system. We used computational methods to broadly search for bacteriocin structural genes and a functional assay to look for phenotypes consistent with bacteriocin expression. We identified homology to 15 different bacteriocins, with 2 having a high presence in this clinical cohort. Bacteriocin 43 (bac43) was found in a total of 58% of isolates, increasing from 8% to 91% presence over the 6-year collection period. There was little genetic variation in the bac43 structural or immunity genes across isolates. The enterocin A structural gene was found in 98% of isolates, but only 0.3% of isolates had an intact enterocin A gene cluster and displayed a bacteriocin-producing phenotype. This study presents a wide survey of bacteriocins from hospital isolates and identified bac43 as highly conserved, increasing in prevalence, and phenotypically functional. This makes bac43 an interesting target for future investigation for a potential role in E. faecium transmission.IMPORTANCEWhile enterococci are a normal inhabitant of the human gut, vancomycin-resistant E. faecalis and E. faecium are urgent public health threats responsible for hospital-associated infections. Bacteriocins are ribosomally synthesized antimicrobial proteins and are commonly used by bacteria to provide a competitive advantage in polymicrobial environments. Bacteriocins have the potential to be used by E. faecium to invade and dominate the human gut leading to a greater propensity for transmission. In this work, we explore bacteriocin content in a defined clinically derived population of E. faecium using both genetic and phenotypic studies. We show that one highly active bacteriocin is increasing in prevalence over time and demonstrates great potential relevance to E. faecium transmission.

Antimicrobial Efficacy of Single-Walled Carbon Nanotubes and Their Combinations Against Enterococcus faecalis Assessed Using the Agar Diffusion Method: An In Vitro Study

INTRODUCTION

This study aimed to evaluate the antimicrobial efficacy of single-walled carbon nanotubes when combined with the commonly used intracanal medicaments by checking their zone of inhibition against Enterococcus faecalis.

MATERIALS AND METHODS

The test materials were divided into five different groups, namely, Group I: single-walled carbon nanotubes; Group II: calcium hydroxide; Group III: chlorhexidine; Group IV: single-walled carbon nanotubes + calcium hydroxide; and Group V: single-walled carbon nanotubes + chlorhexidine. Five sterile Petri plates per group were inoculated with Enterococcus faecalis (E. faecalis); wells were made in the plates, one on each side, and a volume of 50 microliters of each solution was dispensed into individual wells using a pipette. The specimens were placed in an incubator at 37°C for a duration of 48 hours. The area of inhibition surrounding each well was documented and assessed. The statistical analysis was conducted using the Kruskal-Wallis test and the Kolmogorov-Smirnov test.

RESULTS

Single-walled carbon nanotubes combined with chlorhexidine have shown the highest antimicrobial efficacy against Enterococcus faecalis in comparison to all the test groups.

CONCLUSION

This study showcases the antimicrobial effectiveness of a blend of single-walled carbon nanotubes and chlorhexidine solution. It may be developed as a potent intracanal medicament in the future.

Optimized protocol for collecting root canal biofilms for in vitro studies

Endodontic retreatment is often necessitated by several factors, including the persistence of microorganisms in the root canal system (RCS). Their complex organization in biofilms increases their pathogenic potential, necessitating new disinfection strategies. This study aimed to standardize a new in vitro protocol for collecting biofilm from the RCS. Thirty-four bovine incisors were used in the study, divided into two experimental groups with two collection steps each: (a) biofilm collection protocol and (b) absorbent paper points protocol. Twelve specimens from each group were selected for counting colony-forming units (CFUs), while eight specimens were prepared for scanning electron microscopy (SEM). Two additional specimens served as sterilization controls to ensure that experiments were free of contamination. The coronal region was removed and standardized at 15 mm. After preparation with ProTaper up to F5, the apical foramen was sealed with composite resin, and the roots were stabilized with acrylic resin in 1.5-mL Eppendorf tubes. The specimens were sterilized and inoculated with Enterococcus faecalis NTCT 775 every 24 h for 21 days. After this period, each group underwent biofilm collection protocols, and CFU and scanning electron microscopy (SEM) data were analyzed. The Shapiro-Wilk test was performed to assess the normality of log-transformed data, and the results indicated a normal distribution for all groups, allowing parametric testing. The Levene test was used to evaluate the equality of variances. The proposed biofilm collection method yielded significantly higher CFU counts compared with the absorbent paper points method, particularly when analyzed on a log₁₀ scale. An independent samples t-test confirmed a statistically significant difference between the two methods (p < 0.0001). The proposed protocol achieved an efficiency rate of 95.85 % ± 1.15 %, whereas the absorbent paper points protocol yielded a lower efficiency of 5.46 % ± 1.37 %. Therefore, the biofilm collection protocol proposed in this study proved to be more effective for biofilm removal from the RCS.

Enterococcal-host interactions in the gastrointestinal tract and beyond

The gastrointestinal tract (GIT) is typically considered the natural niche of enterococci. However, these bacteria also inhabit extraintestinal tissues, where they can disrupt organ physiology and cause life-threatening infections. Here, we discuss how enterococci, primarily Enterococcus faecalis, interact with the intestine and other host anatomical locations such as the oral cavity, heart, liver, kidney, and vaginal tract. The metabolic flexibility of these bacteria allows them to quickly adapt to new environments, promoting their persistence in diverse tissues. In transitioning from commensals to pathogens, enterococci must overcome harsh conditions such as nutrient competition, exposure to antimicrobials, and immune pressure. Therefore, enterococci have evolved multiple mechanisms to adhere, colonize, persist, and endure these challenges in the host. This review provides a comprehensive overview of how enterococci interact with diverse host cells and tissues across multiple organ systems, highlighting the key molecular pathways that mediate enterococcal adaptation, persistence, and pathogenic behavior.

Recent advances in environmental antibiotic resistance genes detection and research focus: From genes to ecosystems

Antibiotic resistance genes (ARGs) persistence and potential harm have become more widely recognized in the environment due to its fast-paced research. However, the bibliometric review on the detection, research hotspot, and development trend of environmental ARGs has not been widely conducted. It is essential to provide a comprehensive overview of the last 30 years of research on environmental ARGs to clarify the changes in the research landscape and ascertain future prospects. This study presents a visualized analysis of data from the Web of Science to enhance our understanding of ARGs. The findings indicate that solid-phase extraction provides a reliable method for extracting ARG. Technological advancements in commercial kits and microfluidics have facilitated the efficacy of ARGs extraction with significantly reducing processing times. PCR and its derivatives, DNA sequencing, and multi-omics technology are the prevalent methodologies for ARGs detection, enabling the expansion of ARG research from individual strains to more intricate microbial communities in the environment. Furthermore, due to the development of combination, hybridization and mass spectrometer technologies, considerable advancements have been achieved in terms of sensitivity and accuracy as well as lowering the cost of ARGs detection. Currently, high-frequency terms such as "Antibiotic Resistance, Antibiotics, and Metagenomics" are the center of attention for study in this area. Prominent topics include the investigation of anthropogenic impacts on environmental resistance, as well as the dynamics of migration, dissemination, and adaptation of environmental ARGs, etc. The research on environmental ARGs has made significant advancements in the fields of "Microbiology" and "Biotechnology Applied Microbiology". Over the past decade, there has been a notable increase in the fields of "Environmental Sciences Ecology" and "Engineering" with a similar growth trend observed in "Water Resources". These three domains are expected to continue driving extensive study within the realm of environmental ARGs.

Identification of Enterococcus spp. from food sources by matrix-assisted laser desorption ionization-time of flight mass spectrometry and characterization of virulence factors, antibiotic resistance, and biofilm formation

The continuous detection of multi-drug-resistant enterococci in food source environments has aroused widespread concern. In this study, 198 samples from chicken products, animal feces, raw milk, and vegetables were collected in Japan and Egypt to investigate the prevalence of enterococci and virulence characterization. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was employed for species identification and taxonomic analysis of the isolates. The results showed that the rates of most virulence genes (efaA, gelE, asa1, ace, and hyl) in the Japanese isolates were slightly higher than those in the Egyptian isolates. The rate of efaA was the highest (94.9 %) among seven virulence genes detected, but the cylA gene was not detected in all isolates, which was in accordance with γ-type hemolysis phenotype. In Enterococcus faecalis, the rate of kanamycin-resistant strains was the highest (84.75 %) among the antibiotics tested. Moreover, 78 % of E. faecalis strains exhibited multi-drug resistance. Four moderately vancomycin-resistant strains were found in Egyptian isolates, but none were found in Japanese isolates. MALDI-TOF MS analysis correctly identified 98.5 % (68/69) of the Enterococcus isolates. In the principal component analysis dendrogram, strains isolated from the same region with the same virulence characteristics and similar biofilm-forming abilities were characterized by clustered distribution in different clusters. This finding highlights the potential of MALDI-TOF MS for classifying E. faecalis strains from food sources.

Enterococcus Phage vB_EfaS_HEf13 as an Anti-Biofilm Agent Against Enterococcus faecalis

Enterococcus faecalis is a Gram-positive bacterium that is frequently found in the periapical lesion of patients with apical periodontitis. Its biofilm formation in root canal is closely related to the development of refractory apical periodontitis by providing increased resistance to endodontic treatments. Phage therapy has recently been considered as an efficient therapeutic strategy in controlling various periodontal pathogens. We previously demonstrated the bactericidal capacities of Enterococcus phage vB_EfaS_HEf13 (phage HEf13) against clinically-isolated E. faecalis strains. Here, we investigated whether phage HEf13 affects biofilm formation and pre-formed biofilm of clinically-isolated E. faecalis, and its combinatory effect with endodontic treatments, including chlorhexidine (CHX) and penicillin. The phage HEf13 inhibited biofilm formation and disrupted pre-formed biofilms of E. faecalis in a dose- and time-dependent manner. Interestingly, phage HEf13 destroyed E. faecalis biofilm exopolysaccharide (EPS), which is known to be a major component of bacterial biofilm. Furthermore, combined treatment of phage HEf13 with CHX or penicillin more potently inhibited biofilm formation and disrupted pre-formed biofilm than either treatment alone. Confocal laser scanning microscopic examination demonstrated that these additive effects of the combination treatments on disruption of pre-formed biofilm are mediated by relatively enhanced reduction in thickness distribution and biomass of biofilm. Collectively, our results suggest that the effect of phage HEf13 on E. faecalis biofilm is mediated by its EPS-degrading property, and its combination with endodontic treatments more potently suppresses E. faecalis biofilm, implying that phage HEf13 has potential to be used as a combination therapy against E. faecalis infections.

Increasing prevalence of bacteriocin carriage in a six-year hospital cohort of E. faecium

Vancomycin resistant enterococci (VRE) are important pathogens in hospitalized patients, however, the factors involved in VRE colonization of hospitalized patients are not well characterized. Bacteriocins provide a competitive advantage to enterococci in experimental models of colonization, but little is known about bacteriocin content in samples derived from humans and even less is known about their dynamics in the clinical setting. To identify bacteriocins which may be relevant in the transmission of VRE, we present a systematic analysis of bacteriocin content in the genomes of 2,428 patient derived E. faecium isolates collected over a six-year period from a single hospital system. We used computational methods to broadly search for bacteriocin structural genes and a functional assay to look for phenotypes consistent with bacteriocin expression. We identified homology to 15 different bacteriocins with two having high presence in this clinical cohort. Bacteriocin 43 (bac43) was found in a total of 58% of isolates, increasing from 8% to 91% presence over the six-year collection period. There was little genetic variation in the bac43 structural or immunity genes across isolates. The enterocin A structural gene was found in 98% of isolates but only 0.3% of isolates had an intact enterocin A gene cluster and displayed a bacteriocin producing phenotype. This study presents a wide survey of bacteriocins from hospital isolates and identified bac43 as highly conserved, increasing in prevalence, and phenotypically functional. This makes bac43 an interesting target for future investigation for a potential role in E. faecium transmission.

Importance

While enterococci are a normal inhabitant of the human gut, vancomycin-resistant E. faecalis and E. faecium are urgent public health threats responsible for hospital associated infections. Bacteriocins are ribosomally synthesized antimicrobial proteins and are commonly used by bacteria to provide a competitive advantage in polymicrobial environments. Bacteriocins have the potential be used by E. faecium to invade and dominate the human gut leading to a greater propensity for transmission. In this work, we explore bacteriocin content in a defined clinically derived population of E. faecium using both genetic and phenotypic studies. We show that one highly active bacteriocin is increasing in prevalence over time and demonstrates great potential relevance to E. faecium transmission.

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.

Bad to the bone? - Genomic analysis of Enterococcus isolates from diverse environments reveals that most are safe and display potential as food fermentation microorganisms

Enterococci comprise a group of lactic acid bacteria (LAB) with considerable potential to serve as food fermentation microorganisms. Unfortunately, enterococci have received a lot of negative attention, due to the occurrence of pathogenic and multidrug resistant strains. In this study, we used genomics to select safe candidates among the forty-four studied enterococcal isolates. The genomes of the forty-four strains were fully sequenced and assessed for presence of virulence and antibiotic resistance genes. Nineteen isolates belonging to the species Enterococcus lactis, Enterococcus faecium, Enterococcus durans, and Enterococcus thailandicus, were deemed safe from the genome analysis. The presence of secondary metabolite gene clusters for bacteriocins was assessed, and twelve candidates were found to secrete antimicrobial compounds effective against Listeria monocytogenes isolated from cheese and Staphylococcus aureus. Physiological characterization revealed nineteen industrial potentials; all strains grew well at 42 °C and acidified 1.5 hours faster than their mesophilic counterpart Lactococcus lactis, with which they share metabolism and flavor forming ability. We conclude that a large fraction of the examined enterococci were safe and could serve as excellent food fermentation microorganisms with inherent bioprotective abilities.

In vitro evaluation of anti-microbial efficacy of Trigonella foenum-graecum and its constituents on oral biofilms

Background and Objective

The extracts obtained from the leaves and seeds of Trigonella foenum-graecum (Fenugreek) are effective against various microbial infections. The phytoconstituents of Trigonella foenum-graecum have shown promising effects as anti-diabetics, anti-helmentic, anti-microbial, antifungal, and antipyretic, but its impact on oral pathogens is yet to be established. Therefore, the present study aimed to explore the antimicrobial efficacy of phytoconstituents of Trigonella foenum-graecum as compared to 0.2% chlorhexidine (CHX).

Materials and Methods

The methanolic extracts of Trigonella foenum-graecum i.e., fenugreek absolute (FA), diosgenin (DIO), and furanone (FU) were used in this study. The antimicrobial efficacy of these extracts was evaluated by testing the minimal inhibitory concentration, minimal bactericidal concentration (MBC), agar well-diffusion assay, colony-forming unit (CFU) count, and also by using confocal laser scanning microscopy (CLSM) against Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 35218, and Pseudomonas aeruginosa ATCC 27853.

Results

The results of the study demonstrated that Trigonella foenum-graecum has anti-microbial activity comparable to 0.2% CHX. Well-diffusion assay and CFU count assay of the extracts showed statistically significant (P < 0.001) results. MIC and MBC values were observed for FA, DIO, and FU compared to CHX against these selected test organisms. These results were confirmed by visual validation with CLSM.

Conclusion

The use of herbal alternatives in periodontics might prove to be advantageous. Trigonella foenum-graecum can be used as a promising alternative to CHX against S. aureus, E. faecalis, E. coli, and P. aeruginosa for the management of oral and periodontal infections.

Comparative evaluation of the antibacterial activity of curcumin-coated gutta-percha versus nanocurcumin-coated gutta-percha against Escherichia coli: An in vitro study

Introduction

Due to its biological and antibacterial qualities, many plants, including curcumin, are used as phytomedicines in dentistry. They are primarily used as intracanal medication in endodontics to prevent probable chemical side effects and also to address antimicrobial resistance. Curcumin nanoformulations have improved antibacterial activity and improved dispersion, making them the superior form of curcumin. The purpose of this study was to assess curcumin and nanocurcumin's antibacterial properties. As a gutta-percha coating, they are to be tested against Escherichia coli.

Materials and Methods

The study employs the standard strain of E. coli, ATCC 25922. The antibacterial activity of gutta-percha cones against E. coli is assessed after coating them with suspensions of curcumin and nanocurcumin. Scanning electron microscopy is utilized to evaluate the coatings' continuity.

Results

The gutta-percha cones that are untreated, coated with curcumin, and coated with nanocurcumin exhibit significantly different levels of antibacterial activity. There is statistically significant variation in their antibacterial activity.

Conclusion

(1) Compared to curcumin-coated and untreated gutta-percha cones, those coated with nanocurcumin exhibit a stronger antibacterial activity. (2) Compared to uncoated gutta-percha cones, gutta-percha cones coated with curcumin exhibit more antibacterial action.

In vitro antibiofilm effect of different irradiation doses in infected root canal model

BACKGROUND

Eradication of endodontic biofilms from the infected root canal system is still the main concern in endodontics. In this study, the role of the power density parameter in the efficacy of antimicrobial photodynamic therapy (PDT) with toluidine blue O (TBO) and phycocyanin (PC) activated by a 635 nm diode laser (DL) against Enterococcus faecalis biofilm in the root canal model was investigated.

MATERIALS AND METHODS

The E. faecalis biofilm in the root canal was treated with TBO and PC with different power densities (636, 954, 1273, and 1592 W/cm2). The untreated biofilm represented the control group. After the treatments, the biofilms were analyzed based on the number of colonies per milliliter.

RESULTS

TBO and PC activated with 635 nm DL with a power density of 1592 W/cm2 were more efficient in removing E. faecalis biofilms within the root canals than those with a power density of 636 W/cm2 (p = 0.00).

CONCLUSION

The light power density optimized the bacterial reduction of E. faecalis biofilms in the root canal spaces. These results provide information on the decisive parameters for performing PDT on intracanal biofilms.

Probiotic characterization of Bacillus smithii: Research advances, concerns, and prospective trends

Bacillus smithii is a thermophilic Bacillus that can be isolated from white wine, hot spring soil, high-temperature compost, and coffee grounds, with various biofunctions and wide applications. It is resistant to both gastric acid and high temperature, which makes it easier to perform probiotic effects than traditional commercial probiotics, so it can maintain good vitality during food processing and has great application prospects. This paper starts with the taxonomy and genetics and focuses on aspects, including genetic transformation, functional enzyme production, waste utilization, and application in the field of food science as a potential probiotic. According to available studies during the past 30 years, we considered that B. smithii is a novel class of microorganisms with a wide range of functional enzymes such as hydrolytic enzymes and hydrolases, as well as resistance to pathogenic bacteria. It is available in waste degradation, organic fertilizer production, the feed and chemical industries, the pharmaceutical sector, and food fortification. Moreover, B. smithii has great potentials for applications in the food industry, as it presents high resistance to the technological processes that guarantee its health benefits. It is also necessary to systematically evaluate the safety, flavor, and texture of B. smithii and explore its biological mechanism of action, which is of great value for further application in multiple fields, especially in food and medicine.

The pathogenicity of vancomycin-resistant Enterococcus faecalis to colon cancer cells

BACKGROUND

The aim of this study was to investigate the pathogenicity of vancomycin-resistant Enterococcus faecalis (VREs) to human colon cells in vitro.

METHODS

Three E. faecalis isolates (2 VREs and E. faecalis ATCC 29212) were cocultured with NCM460, HT-29 and HCT116 cells. Changes in cell morphology and bacterial adhesion were assessed at different time points. Interleukin-8 (IL-8) and vascular endothelial growth factor A (VEGFA) expression were measured via RT-qPCR and enzyme-linked immunosorbent assay (ELISA), respectively. Cell migration and human umbilical vein endothelial cells (HUVECs) tube formation assays were used for angiogenesis studies. The activity of PI3K/AKT/mTOR signaling pathway was measured by Western blotting.

RESULTS

The growth and adhesion of E. faecalis at a multiplicity of infection (MOI) of 1:1 were greater than those at a MOI of 100:1(p < 0.05). Compared to E. faecalis ATCC 29212, VREs showed less invasive effect on NCM460 and HT-29 cells. E. faecalis promoted angiogenesis by secreting IL-8 and VEGFA in colon cells, and the cells infected with VREs produced more than those infected with the standard strain (p < 0.05). Additionally, the PI3K/AKT/mTOR signaling pathway was activated in E. faecalis infected cells, with VREs demonstrating a greater activation compared to E. faecalis ATCC 29212 (p < 0.05).

CONCLUSION

VREs contribute to the occurrence and development of CRC by promoting angiogenesis and activating the PI3K/AKT/mTOR signaling pathway.

Bacteraemia caused by non-faecalis and non-faecium Enterococcus species-a retrospective study of incidence, focus of infection, and prognosis

BACKGROUND/AIM

Enterococcus faecalis and Enterococcus faecium cause human infections including bacteraemia and infective endocarditis (IE). Only few studies describing non-faecalis and non-faecium Enterococcus (NFE) infections have been conducted. We aimed to describe the incidence, prognosis, and focus of infection of bacteraemia with NFE.

METHODS

This retrospective population-based study included all episodes of patients having a blood culture with growth of NFE between 2012 and 2019 in Region Skåne, Sweden. Information was collected from medical records. Episodes of bacteraemia caused by NFE were compared to episodes of bacteraemia caused by E. faecalis and E. faecium.

RESULTS

During the study period, 136 episodes with NFE bacteraemia were identified corresponding to an incidence of NFE bacteraemia of 16 cases per 1,000,000 person-years among adults. Enterococcus casseliflavus (n=45), Enterococcus gallinarum (n=34), and Enterococcus avium (n=29) were the most common species. The most common foci of infection were biliary tract infections (n=17) followed by gastrointestinal infections (n=7). Urinary tract infections were not commonly caused by NFE (n=1), and no episodes of IE were caused by NFE. Polymicrobial bacteraemia was more common with NFE (73%) than with E. faecalis (35%) and E. faecium (42%). Community acquired infections were more common in bacteraemia with NFE compared to E. faecium. 30- and 90-day survival rates were 76% and 68%, respectively, and recurrent NFE bacteraemia was seen after 3% of the episodes.

CONCLUSION

Bacteraemia caused by NFE is rare and is often polymicrobial. Biliary tract focus is common in NFE bacteraemia whereas IE and urinary tract focus are uncommon.

Microbiome Dysbiosis, Dietary Intake and Lifestyle-Associated Factors Involve in Epigenetic Modulations in Colorectal Cancer: A Narrative Review

Background: Colorectal cancer is the second cause of cancer mortality and the third most commonly diagnosed cancer worldwide. Current data available implicate epigenetic modulations in colorectal cancer development. The health of the large bowel is impacted by gut microbiome dysbiosis, which may lead to colon and rectum cancers. The release of microbial metabolites and toxins by these microbiotas has been shown to activate epigenetic processes leading to colorectal cancer development. Increased consumption of a 'Westernized diet' and certain lifestyle factors such as excessive consumption of alcohol have been associated with colorectal cancer.Purpose: In this review, we seek to examine current knowledge on the involvement of gut microbiota, dietary factors, and alcohol consumption in colorectal cancer development through epigenetic modulations.Methods: A review of several published articles focusing on the mechanism of how changes in the gut microbiome, diet, and excessive alcohol consumption contribute to colorectal cancer development and the potential of using these factors as biomarkers for colorectal cancer diagnosis.Conclusions: This review presents scientific findings that provide a hopeful future for manipulating gut microbiome, diet, and alcohol consumption in colorectal cancer patients' management and care.

Characterization of Lactococcus lactis 11/19-B1 Isolated from Kiwi Fruit as a Potential Probiotic and Paraprobiotic

Probiotics are live bacteria used as food additives that are beneficial to human health. Lactococcus lactis 11/19-B1 strain isolated from kiwi fruit stimulates innate immunity in silkworms. Intake of yogurt containing the living 11/19-B1 strain significantly decreases the level of low-density lipoproteins (LDLs) in high-LDL volunteers and improves atopic dermatitis in humans. In this study, the probiotic properties of the 11/19-B1 strain, such as sensitivity to antimicrobial compounds, biogenic amine production, some virulence genes for human health, antimicrobial activity, tolerance to gastric acid and bile acids, and ability to adhere to the intestinal mucosa, were evaluated. The 11/19-B1 strain did not show resistance to the tested antimicrobial compounds except cefoxitin and fosfomycin. In addition, no production of amines that can harm humans, the antimicrobial activity required for probiotics, and the absence of adhesion to Caco-2 cells suggest that it is unlikely to attach to the intestinal epithelium. The 11/19-B1 strain grew in 0.3% but not in 1% bile salt. In the presence of 2% skim milk, the survival rate of the 11/19-B1 strain under simulated gastrointestinal tract conditions was 67% even after 4 h. These results indicate that the 11/19-B1 strain may function as a probiotic or paraprobiotic to be utilized in the food industry.

Isolation, characterization of Enterococcus phages and their application in control of E. faecalis in milk

AIMS

Isolation and characterization of Enterococcus phages and application of phage cocktail to control E. faecalis in milk.

METHODS AND RESULTS

For phage isolations, double layer agar method was used. Host range of the phages were determined by the spot test. Twelve phages with varying host ranges were isolated. Phages PEF1, PEF7b, and PEF9 with different host ranges and lytic activities were selected for phage cocktails. Compared to two-phages cocktails tested, the cocktail containing all the three phages displayed stronger antibacterial and biofilm removal activities. The cocktail treatment reduced viable E. faecalis in biofilm by 6 log within 6 h at both 30°C and 4°C. In milk, the cocktail gradually reduced the viable count of E. faecalis and the count reached below the lower limit of detection at 48 h at 4°C.

CONCLUSION

The strong bactericidal and biofilm removal activities of the phage cocktail suggest the potential of this cocktail as a natural biocontrol agent for combating E. faecalis in milk.

Distribution and association of antimicrobial resistance and virulence characteristics in Enterococcus spp. isolates from captive Asian elephants in China

Enterococcus spp., as an opportunistic pathogen, are widely distributed in the environment and the gastrointestinal tracts of both humans and animals. Captive Asian elephants, popular animals at tourist attractions, have frequent contact with humans. However, there is limited information on whether captive Asian elephants can serve as a reservoir of antimicrobial resistance (AMR). The aim of this study was to characterize AMR, antibiotic resistance genes (ARGs), virulence-associated genes (VAGs), gelatinase activity, hemolysis activity, and biofilm formation of Enterococcus spp. isolated from captive Asian elephants, and to analyze the potential correlations among these factors. A total of 62 Enterococcus spp. strains were isolated from fecal samples of captive Asian elephants, comprising 17 Enterococcus hirae (27.4%), 12 Enterococcus faecalis (19.4%), 8 Enterococcus faecium (12.9%), 7 Enterococcus avium (11.3%), 7 Enterococcus mundtii (11.3%), and 11 other Enterococcus spp. (17.7%). Isolates exhibited high resistance to rifampin (51.6%) and streptomycin (37.1%). 50% of Enterococcus spp. isolates exhibited multidrug resistance (MDR), with all E. faecium strains demonstrating MDR. Additionally, nine ARGs were identified, with tet(M) (51.6%), erm(B) (24.2%), and cfr (21.0%) showing relatively higher detection rates. Biofilm formation, gelatinase activity, and α-hemolysin activity were observed in 79.0, 24.2, and 14.5% of the isolates, respectively. A total of 18 VAGs were detected, with gelE being the most prevalent (69.4%). Correlation analysis revealed 229 significant positive correlations and 12 significant negative correlations. The strongest intra-group correlations were observed among VAGs. Notably, we found that vancomycin resistance showed a significant positive correlation with ciprofloxacin resistance, cfr, and gelatinase activity, respectively. In conclusion, captive Asian elephants could serve as significant reservoirs for the dissemination of AMR to humans.

Volatile anesthetic isoflurane exposure facilitates Enterococcus biofilm infection

Enterococcus faecalis (E. faecalis) is one of the major pathogenic bacteria responsible for surgical site infections. Biofilm infections are major hospital-acquired infections. Previous studies suggested that ions could regulate biofilm formation in microbes. Volatile anesthetics, frequently administered in surgical setting, target ion channels. Here, we investigated the role of ion channels/transporters and volatile anesthetics in the biofilm formation by E. faecalis MMH594 strain and its ion transporter mutants. We found that a chloride transporter mutant significantly reduced biofilm formation compared to the parental strain. Downregulation of teichoic acid biosynthesis in the chloride transporter mutant impaired biofilm matrix formation and cellular adhesion, leading to mitigated biofilm formation. Among anesthetics, isoflurane exposure enhanced biofilm formation in vitro and in vivo. The upregulation of de novo purine biosynthesis pathway by isoflurane exposure potentially enhanced biofilm formation, an essential process for DNA, RNA, and ATP synthesis. We also demonstrated that isoflurane exposure to E. faecalis increased cyclic-di-AMP and extracellular DNA production, consistent with the increased purine biosynthesis. We further showed that isoflurane enhanced the enzymatic activity of phosphoribosyl pyrophosphate synthetase (PRPP-S). With the hypothesis that isoflurane directly bound to PRPP-S, we predicted isoflurane binding site on it using rigid docking. Our study provides a better understanding of the underlying mechanisms of E. faecalis biofilm formation and highlights the potential impact of an ion transporter and volatile anesthetic on this process. These findings may lead to the development of novel strategies for preventing E. faecalis biofilm formation and improving patient outcomes in clinical settings.

Biocidal activity of multifunctional cuprite-doped anion exchanger - Influence of bacteria type and medium composition

The study presents unconventional, bifunctional, heterogeneous antimicrobial agents - Cu2O-loaded anion exchangers. The synergetic effect of a cuprous oxide deposit and polymeric support with trimethyl ammonium groups was studied against the reference strains of Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853. Biological testing (minimum bactericidal concentration, MBC), time- and dose-dependent bactericidal effect (under different conditions - medium composition and static/dynamic culture) demonstrated promising antimicrobial activity and confirmed its multimode character. The standard values of MBC, for all studied hybrid polymers and bacteria, were similar (64-128 mg/mL). However, depending on the medium conditions, due to the copper release into the bulk solution, bacteria were actively killed even at much lower doses of the hybrid polymer (25 mg/mL) and low Cu(II) concentrations in solution (0.01 mg/L). Simultaneously, confocal microscopic studies confirmed the effective inhibition of bacterial adhesion and biofilm formation on their surface. The studies conducted under different conditions showed also the influence of the structure and physical properties of studied materials on the biocidal efficacy and an antimicrobial action mechanism was proposed that could be significantly affected by electrostatic interactions and copper release to the solution. Although the antibacterial activity was also dependent on various strategies of bacterial cell resistance to heavy metals present in the aqueous medium, the studied hybrid polymers are versatile and efficient biocidal agents against bacteria of both types, Gram-positive and Gram-negative. Therefore, they can be a convenient alternative for point-of-use water disinfection systems providing water quality in medical devices such as dental units, spa equipment, and aesthetic devices used in the cosmetic sector.

Prevalence of Enterococcus species in adults with periodontal health or with periodontitis: a systematic review

The aim of this study was to evaluate the prevalence of Enterococcus species in the mouth of adults with periodontal health and periodontitis. A systematic search was made in databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search for articles was conducted in Medline/PubMed, Latin American and Caribbean Health Sciences Literature Database (LILACS), Cochrane Library, Scopus, Embase, Web of Science databases and in the System of Information on Grey Literature in Europe (SINGLE) and included articles published in English up to April 25th, 2021. Observational studies in humans with and without periodontitis were evaluated to identify the prevalence of Enterococcus species. Articles that met the inclusion criteria were analyzed and classified to determine the quality rating in good, fair, and poor. A new detailed checklist for quality assessment was developed based on the information required for applicable data extraction in reviews. The study design, sample size, demographic data, periodontal clinical parameters, microbial analysis method, biological sample, prevalence of Enterococcus spp., and correlations with periodontal clinical parameters were assessed. After screening and full-text reading, 8 articles met the inclusion criteria. All selected studies showed a significantly higher prevalence of Enterococcus spp. in patients with periodontitis compared with periodontally healthy patients. Thus, the present systematic review suggests that the prevalence of Enterococcus faecalis in the mouth of periodontitis individuals is higher than that of periodontally healthy individuals.

Antimicrobial Resistance Profiles, Virulence Determinants, and Biofilm Formation in Enterococci Isolated from Rhesus Macaques (Macaca mulatta): A Potential Threat for Wildlife in Bangladesh?

Enterococci are commensal bacteria that inhabit the digestive tracts of animals and humans. The transmission of antibiotic-resistant genes through human-animal contact poses a potential public health risk worldwide, as zoonoses from wildlife reservoirs can occur on every continent. The purpose of this study was to detect Enterococcus spp. in rhesus macaques (Macaca mulatta) and to investigate their resistance patterns, virulence profiles, and biofilm-forming ability. Conventional screening of rectal swabs (n = 67) from macaques was followed by polymerase chain reaction (PCR). The biofilm-forming enterococci were determined using the Congo red agar plate assay. Using the disk diffusion test (DDT), antibiogram profiles were determined, followed by resistance and virulence genes identification by PCR. PCR for bacterial species confirmation revealed that 65.7% (44/67) and 22.4% (15/67) of the samples tested positive for E. faecalis and E. faecium, respectively. All the isolated enterococci were biofilm formers. In the DDT, enterococcal isolates exhibited high to moderate resistance to penicillin, rifampin, ampicillin, erythromycin, vancomycin, and linezolid. In the PCR assays, the resistance gene bla_TEM was detected in 61.4% (27/44) of E. faecalis and 60% (9/15) of E. faecium isolates. Interestingly, 88.63 % (39/44) of E. faecalis and 100% (15/15) of E. faecium isolates were phenotypically multidrug-resistant. Virulence genes (agg, fsrA, fsrB, fsrC, gelE, sprE, pil, and ace) were more frequent in E. faecalis compared to E. faecium; however, isolates of both Enterococcus spp. were found negative for the cyl gene. As far as we know, the present study has detected, for the first time in Bangladesh, the presence of virulence genes in MDR biofilm-forming enterococci isolated from rhesus macaques. The findings of this study suggest employing epidemiological surveillance along with the one-health approach to monitor these pathogens in wild animals in Bangladesh, which will aid in preventing their potential transmission to humans.

Phylogeny, Virulence, and Antimicrobial Resistance Gene Profiles of Enterococcus faecium Isolated from Australian Feedlot Cattle and Their Significance to Public and Environmental Health

The extent of similarity between E. faecium strains found in healthy feedlot beef cattle and those causing extraintestinal infections in humans is not yet fully understood. This study used whole-genome sequencing to analyse the antimicrobial resistance profile of E. faecium isolated from beef cattle (n = 59) at a single feedlot and compared them to previously reported Australian isolates obtained from pig (n = 60) and meat chicken caecal samples (n = 8), as well as human sepsis cases (n = 302). The E. faecium isolated from beef cattle and other food animal sources neither carried vanA/vanB responsible for vancomycin nor possessed gyrA/parC and liaR/liaS gene mutations associated with high-level fluoroquinolone and daptomycin resistance, respectively. A small proportion (7.6%) of human isolates clustered with beef cattle and pig isolates, including a few isolates belonging to the same sequence types ST22 (one beef cattle, one pig, and two human isolates), ST32 (eight beef cattle and one human isolate), and ST327 (two beef cattle and one human isolate), suggesting common origins. This provides further evidence that these clonal lineages may have broader host range but are unrelated to the typical hospital-adapted human strains belonging to clonal complex 17, significant proportions of which contain vanA/vanB and liaR/liaS. Additionally, none of the human isolates belonging to these STs contained resistance genes to WHO critically important antimicrobials. The results confirm that most E. faecium isolated from beef cattle in this study do not pose a significant risk for resistance to critically important antimicrobials and are not associated with current human septic infections.

Antimicrobial Efficacy of Two Different Calcium Hydroxide Endodontic Dressings on the Eradication of Enterococcus faecalis in Single-Rooted Canals: An In Vitro Study

INTRODUCTION

Bacterial pulp infections are considered the most common cause of endodontic treatment failure. Enterococcus faecalis was isolated from most cases of failure of endodontic treatment. Therefore, using the appropriate intra-canal dressing is essential for successful treatment. The improved formula used in calcium hydroxide PLUS points ensures more calcium hydroxide is released over a longer period and more space to release calcium hydration. This in vitro research aimed to evaluate the differences in the efficacy between Ca(OH)₂ paste and PLUS points as an endodontic dressing in eradicating E. faecalis growth inside infected single-rooted canals.

MATERIALS AND METHODS

Thirty mandibular first premolars with single canals were extracted for orthodontic reasons and were prepared after cutting their crowns to standardize the length of the roots to 17 mm, root preparation, and isolating E. faecalis. The infected sample root canals were contaminated with the prepared bacterial suspension, and the sample was incubated in the incubator under air conditions at 37°C for seven days, counting the bacteria colonies. Then, the bacterial units were counted before applying the drug, applying Ca(OH)₂ paste in the first group and Ca(OH)₂ PLUS points in the second group. The bacterial units were counted, and the number of bacteria was compared between the two substances applied to the samples, measuring the intracanal dressings' effectiveness. Wilcoxon signed-rank tests were used to detect significant differences.  Results: The results showed a statistically significant difference in the bacterial count of E. faecalis before and after applying the dressing of Ca(OH)₂ paste from a mean of 11.89 to a mean of 3.18 (p=0.003) and no statistical difference in applying Ca(OH)₂ PLUS points from mean 11.98 to mean 10.50 (p>0.05).

CONCLUSION

Within the limits of the current in vitro study, the Ca(OH)₂ paste cones were more effective than Ca(OH)₂ PLUS points in eradicating E. faecalis growth inside the infected single-rooted canals.

Therapeutic and prophylactic effects of oral administration of probiotic Enterococcus faecium Smr18 in Salmonella enterica-infected mice

Salmonella enterica serotype Typhi causes chronic enteric fever known as typhoid. Prolonged treatment regimen used for the treatment of typhoid and indiscriminate use of antibiotics has led to the emergence of resistant strains of S. enterica that has further increased the severity of the disease. Therefore, alternative therapeutic agents are urgently required. In this study, probiotic and enterocin-producing bacteria Enterococcus faecium Smr18 was compared for both its prophylactic and therapeutic efficacy in S. enterica infection mouse model. E. faecium Smr18 possessed high tolerance to bile salts and simulated gastric juice, as treatment for 3 and 2 h resulted in 0.5 and 0.23 log₁₀ reduction in the colony forming units, respectively. It exhibited 70% auto aggregation after 24 h of incubation and formed strong biofilms at both pH 5 and 7. Oral administration of E. faecium in BALB/c mice infected with S. enterica significantly (p < 0.05) reduced the mortality of the infected mice and prevented the weight loss in mice. Administration of E. faecium prior to infection inhibited the translocation of S. enterica to liver and spleen, whereas, its administration post-infection completely cleared the pathogen from the organs within 8 days. Further, in both pre- and post-E. faecium-treated infected groups, sera levels of liver enzymes were restored back to normal; whereas the levels of creatinine, urea and antioxidant enzymes were significantly (p < 0.05) reduced compared to the untreated-infected group. E. faecium Smr18 administration significantly increased the sera levels of nitrate by 1.63-fold and 3.22-fold in pre- and post-administration group, respectively. Sera levels of interferon-γ was highest (tenfold) in the untreated-infected group, whereas the levels of interleukin-10 was highest in the post-infection E. faecium-treated group thereby indicating the resolution of infection in the probiotic-treated group, plausibly due to the increased production of reactive nitrogen intermediates.

Isolation, identification and safety evaluation of OTA-detoxification strain Pediococcus acidilactici NJB421 and its effects on OTA-induced toxicity in mice

Ochratoxin A (OTA) is a potent mycotoxin found in foods and feeds, posing a health risk to animals and humans. Biological detoxification of OTA is considered a promising method, and some bacteria and fungi which can degrade OTA are isolated. However, research on safety and alleviating toxic effects are scarce. This study aims to isolate OTA-detoxification probiotics from natural samples and evaluate their safety and protective effects in mice. Here, a new OTA-detoxification strain named Pediococcus acidilactici NJB421 (P. acidilactici NJB421) was isolated from cow manure, which exhibited a removal rate of OTA at 48.53% for 48 h. P. acidilactici NJB421 exhibited high temperature resistance, acid tolerance, 0.3% bile salt and 1.4% trypsin resistance. The safety evaluation showed that P. acidilactici NJB421 at 2 × 10⁸ CFU/per mouse had no abnormalities in body weight, organ indices, ALT, AST and ALP activities, BUN, CRE and TP contents. And P. acidilactici NJB421 alleviated the decreases in body weight, organ indices and small intestinal length, and alleviated intestinal injury, liver injury and kidney injury. These results suggest P. acidilactici NJB421 is safe and has protection against OTA poisoning, which provides a new OTA-detoxification strain for livestock and food industries.

The Regulations of Essential WalRK Two-Component System on Enterococcus faecalis

Enterococcus faecalis (E. faecalis) is a Gram-positive, facultative anaerobic bacterium that is highly adaptable to its environment. In humans, it can cause serious infections with biofilm formation. With increasing attention on its health threat, prevention and control of biofilm formation in E. faecalis have been observed. Many factors including polysaccharides as well as autolysis, proteases, and eDNA regulate biofilm formation. Those contributors are regulated by several important regulatory systems involving the two-component signal transduction system (TCS) for its adaptation to the environment. Highly conserved WalRK as one of 17 TCSs is the only essential TCS in E. faecalis. In addition to biofilm formation, various metabolisms, including cell wall construction, drug resistance, as well as interactions among regulatory systems and resistance to the host immune system, can be modulated by the WalRK system. Therefore, WalRK has been identified as a key target for E. faecalis infection control. In the present review, the regulation of WalRK on E. faecalis pathogenesis and associated therapeutic strategies are demonstrated.

Vancomycin Resistance in Enterococcus and Staphylococcus aureus

Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus are both common commensals and major opportunistic human pathogens. In recent decades, these bacteria have acquired broad resistance to several major classes of antibiotics, including commonly employed glycopeptides. Exemplified by resistance to vancomycin, glycopeptide resistance is mediated through intrinsic gene mutations, and/or transferrable van resistance gene cassette-carrying mobile genetic elements. Here, this review will discuss the epidemiology of vancomycin-resistant Enterococcus and S. aureus in healthcare, community, and agricultural settings, explore vancomycin resistance in the context of van and non-van mediated resistance development and provide insights into alternative therapeutic approaches aimed at treating drug-resistant Enterococcus and S. aureus infections.

Role of the fsr Quorum-Sensing System in Enterococcus faecalis Bloodstream Infection

Enterococcus faecalis is an important intestinal colonizing bacteria and can cause various tissue infections, including invasive blood infection (BI). The annual incidence of E. faecalis BI has been estimated to be ~4.5 per 100,000, with a fatality rate that can reach 20%. However, whether bacterial colonization or invasive infections are tissue based has not been thoroughly studied. In this study, we analyzed 537 clinical isolates from 7 different tissues to identify the key genomic elements that facilitate the colonization and invasive infection of E. faecalis. Comparative genomic analysis revealed that the BI E. faecalis isolates had the largest genome size but the lowest GC content, fsr quorum-sensing system genes were enriched in the BI E. faecalis, and the fsr gene cluster could enhance biofilm formation and serum resistance ability. Our findings also provide deep insight into the genomic differences between different tissue isolates, and the fsr quorum-sensing systems could be a key factor promoting E. faecalis invasion into the blood. IMPORTANCE First, we conducted an advanced study on the genomic differences between colonizing and infecting E. faecalis, which provides support and evidence for early and accurate diagnoses. Second, we discovered that fsr was significantly associated with blood infections, which also provides additional information for studies exploring the invasiveness of E. faecalis. Most importantly, we found that fsr played an important role in both biofilm formation and serum resistance ability in E. faecalis.

A novel approach for combining the metagenome, metaresistome, metareplicome and causal inference to determine the microbes and their antibiotic resistance gene repertoire that contribute to dysbiosis

The use of whole metagenomic data to infer the relative abundance of all its microbes is well established. The same data can be used to determine the replication rate of all eubacterial taxa with circular chromosomes. Despite their availability, the replication rate profiles (metareplicome) have not been fully exploited in microbiome analyses. Another relatively new approach is the application of causal inferencing to analyse microbiome data that goes beyond correlational studies. A novel scalable pipeline called MeRRCI (Metagenome, metaResistome, and metaReplicome for Causal Inferencing) was developed. MeRRCI combines efficient computation of the metagenome (bacterial relative abundance), metaresistome (antimicrobial gene abundance) and metareplicome (replication rates), and integrates environmental variables (metadata) for causality analysis using Bayesian networks. MeRRCI was applied to an infant gut microbiome data set to investigate the microbial community's response to antibiotics. Our analysis suggests that the current treatment stratagem contributes to preterm infant gut dysbiosis, allowing a proliferation of pathobionts. The study highlights the specific antibacterial resistance genes that may contribute to exponential cell division in the presence of antibiotics for various pathogens, namely Klebsiella pneumoniae, Citrobacter freundii, Staphylococcus epidermidis, Veilonella parvula and Clostridium perfringens. These organisms often contribute to the harmful long-term sequelae seen in these young infants.

Aerobic Vaginitis Caused by Enterococcus Faecalis - Clinical Features and Treatment

Bckground

Aerobic vaginitis is an imbalance of the vaginal flora and the main characteristic is an abnormal vaginal flora that contains aerobic and intestinal pathogens with varying degrees of vaginal inflammation. The frequency of AV varies from 12% to 23.7% in symptomatic women who are not pregnant and 4 to 8% during pregnancy and has an increased risk for sexually transmitted diseases (STI). The causative agents of AV are: Enterococcus faecalis (E. faecalis), Esherichia coli, group B streptococcus and Staphylococcus aureus.

Objective

The aim of this review was to present the most important features of aerobic vaginitis regarding description of this frequent clinical problems within population in Bosnia and Herzegovina and also worlfwide.

Methods

Author analized aerobic vaginitis based on scientific literature by searching published papers in important indexed databases.

Results and Discussion

The most frequently isolated AV pathogen is E. faecalis in about 31%. New works indicate the presence of the HPV 16 gene and genome in E. faecalis in the biopsied material of cervical cancer, as well as the ability that HPV 16 genes can be translated and transcribed in these bacteria, and that the HPV gene can form viral particles in these bacteria leads to certain connection that can be a risk factor in the progression of cervical lesions to cancer. A decrease in the number of lactobacilli in the vaginal secretion reduces the defense ability and changes the pH value of the vaginal environment, which favors the development of bacterial inflammation. AV positive for E. faecalis leads to a change in the pH value of the vaginal environment above 5, and the increased pH value of the vaginal environment in HPV positive women can be an association for cervical intraepithelial lesion (CIN). A dominant pathogen in AV such as E. faecalis can reduce the protective effect of lactobacilli by causing inflammation, as well as an increase in IL-6, IL-8 and TNF, increasing the risk of HPV 16 infection resulting in CIN and cervical cancer. In cervical cancer research, the presence of genes and genomes (except E1) of human papillomavirus (HPV) type 16 was found in bacteria such as: E. faecalis and Staphylococcus aureus from cervical cancer biopsies. Intensive treatment of AV could be a very important factor in preventing the onset of precancerous lesions and cervical cancer. The recommended treatment of AV includes a combination of therapy such as: antibacterial (antiseptic and antibiotic), hormonal, non-steroidal anti-inflammatory and/or probiotics, which can be prescribed in the form of local or systemic therapy.

Conclusion

There is no generally accepted clinical strategy for the treatment of AV caused by E. faecalis. Most authors suggest that therapy be based on microscopic or microbiological findings using a topical antibiotic for the infectious agent, a topical steroid to reduce inflammation, and estrogen to treat atrophy.

Determination of Enterococcus faecalis and Enterococcus faecium Antimicrobial Resistance and Virulence Factors and Their Association with Clinical and Demographic Factors in Kenya

Background

Enterococci are clinically significant because of their increasing antibiotic resistance and their ability to cause severe infections due to an arsenal of virulence genes. Few studies in the developing world have examined virulence factors that may significantly impact patient outcomes. This study describes the antimicrobial resistance profiles and prevalence of five key Enterococcal virulence genes gelE, asa, cylA, esp, and hyl in forty-four clinical Enterococcus faecalis and E. faecium isolates in Kenya and their association with patients' demographic and clinical characteristics.

Results

All E. faecium isolates were obtained from hospital-acquired skin and soft tissue infections. While E. faecalis was associated with community-acquired urinary tract infections. All isolates were resistant to erythromycin, whereas 11/44 (27.5%), 25/44 (56.8%), 28/44 (63.6%), 37/44 (84.1%), 40/44 (90.0%), and 43/44 (97.5%) were susceptible to tetracycline, levofloxacin, gentamicin, ampicillin, nitrofurantoin, and teicoplanin, respectively. All isolates were susceptible to tigecycline, vancomycin, and linezolid. There was little difference in the antibiotic resistance profiles between E. faecalis and E. faecium. The prevalence of the virulence genes among the 44 isolates were 27 (61.4%) for gelE, 26 (59.1%) for asa1, 16 (36.3%) for esp, 11 (25.0%) for cylA, and 1 (2.3%) for hyl. 72.9% of E. faecalis isolates had multiple virulence genes compared to 57% of E. faecium isolates with no virulence genes. The hyl gene was only detected in E. faecium, while cylA and asa1 were only detected in E. faecalis. A significant correlation was observed between the presence of asa1 and esp virulence genes and tetracycline resistance (P=0.0305 and 0.0363, respectively). A significant correlation was also observed between the presence of virulence genes gelE and asa1 and nitrofurantoin resistance (P=0.0175 and 0.0225, respectively) and ampicillin resistance (P=0.0005 and 0.0008, respectively).

Conclusion

The study highlights the high levels of erythromycin resistance in E. faecalis and E. faecium, the demographic factors influencing the species distribution among patients, and the accumulation of multiple virulence genes in E. faecalis. The significant association of gelE, asa1, and esp virulence genes with drug resistance could explain the pathogenic success of E. faecalis and provides a guide for future studies.

Evaluation of Safety and Probiotic Potential of Enterococcus faecalis MG5206 and Enterococcus faecium MG5232 Isolated from Kimchi, a Korean Fermented Cabbage

The purpose of this study was to evaluate the genotypic and phenotypic toxicity of Enterococcus faecalis MG5206 and Enterococcus faecium MG5232 isolated from kimchi (fermented vegetable cabbage). In this study, the genotypic toxicity of the strains MG5206 and MG5232 was identified through whole-genome sequencing analysis, and phenotypic virulence, such as susceptibility to antibiotics, hemolytic activity, and gelatinase and hyaluronidase activities, was also evaluated. In addition, the in vivo toxicity of both strains was evaluated using an acute oral administration test in Sprague–Dawley rats. In all the tests, both the strains were determined to be safety by confirming that they did not show antibiotic resistance or virulence factors. In addition, these strains exhibited a low level of autoaggregation ability (37.2–66.3%) and hydrophobicity, as well as a high survival rate in gastrointestinal condition in vitro. Therefore, the safety and high gastrointestinal viability of E. faecalis MG5206 and E. faecium MG5232 suggests that both the strains could be utilized in food as potential probiotics in the future.

Unusual Presentation of Infective Endocarditis Following a Prostatic Urethral Lift

Infective endocarditis is a serious inflammation of the inner lining of the heart. It is caused by pathogens entering the bloodstream and infecting the endocardium. We demonstrate a unique presentation of infective endocarditis following a prostatic urethral lift. The low index of suspicion and atypical symptoms prevented early diagnosis of the disease, leading to life-threatening complications and valve replacement surgery. Understanding unusual presentations of infective endocarditis can increase the index of suspicion in outpatient settings, leading to early diagnosis and preventing fatal complications.

Anti-microbial efficacy of Vanilla planifolia leaf extract against common oral micro-biomes: A comparative study of two different antibiotic sensitivity tests

Introduction

Over the past century, several antibiotics have been discovered and used to treat various microbial diseases. However, over the past few decades, with the emergence of anti-microbial resistant strains of microbiomes, it has become increasingly necessary to discover and develop alternative anti-microbial agents. Herbal formulations have shown promising results in the past decade. However, many herbal formulations remain unexplored. The present study aims to explore the anti-microbial properties of a newly prepared Vanilla planifolia extract.

Methodology

Vanilla planifolia leaves were collected, shade-dried, and then powdered. The powdered leaves of Vanilla planifolia (100 gm) were extracted by the cold percolation method with 300 ml ethanol at room temperature for 72 hours. The extracts were then tested for its constituent anti-microbial activity by the agar well method and disk diffusion method against different commonly found oral micro-biomes. The zones of inhibition were noted and measured, and the results were derived. Statistical analysis was performed using the Student t-test (P <_ 0.001). Based on the statistical analysis, conclusions were drawn.

Results

The ethanolic extracts of Vanilla planifolia on the agar plates showed considerable anti-microbial activity in both the test methods against Staphylococcus aureus, Streptococcus mutans, and Enterococcus. However, no effect was found against Candida albicans. There was no significant difference in the results obtained by the two test methods (P >_ 0.001).

Conclusions

This experimental study presents a medicinal plant, an orchid Vanilla planifolia, which demonstrates the presence of essential anti-microbial agents in it, making it a potent, potential dental biomaterial with a positive and benefitting effect on the oral micro-environment.

Enterococcus faecium and Pediococcus acidilactici deteriorate Enterobacteriaceae-induced depression and colitis in mice

Gut dysbiosis is closely associated with the outbreak of inflammatory bowel disease (IBD) and psychiatric disorder. The Enterobacteriaceae population was higher in the feces of patients with inflammatory bowel disease (IBD-F) than in those of healthy control volunteers (HC-F). The Enterococcaceae and Lactobacillaceae populations were higher in the feces of IBD patients with depression (IBD/D+-F) vs. the feces of IBD patients without depression (IBD/D--F). Therefore, we examined the effects of Klebsiella oxytoca, Escherichia coli, Cronobacter sakazakii, Enterococcus faecium, and Pediococcus acidolactici overpopulated in IBD/D+-F and their byproducts LPS and exopolysaccharide (EPS) on the occurrence of depression and colitis in mice. Oral gavages of Klebsiella oxytoca, Escherichia coli, and Cronobacter sakazakii belonging to Enterobacteriaceae, singly or together, caused dose-dependently colitis and depression-like behaviors in germ-free and specific-pathogen-free mice. Although Enterococcus faecium and Pediococcus acidolactici did not significantly cause colitis and depression-like behaviors, they significantly deteriorated Klebsiella oxytoca- or Escherichia coli-induced colitis, neuroinflammation, and anxiety/depression-like behaviors and increased blood LPS, corticosterone, and IL-6 levels. The EPSs from Enterococcus faecium and Pediococcus acidolactici also worsened Klebsiella oxytoca LPS-induced colitis, neuroinflammation, and depression-like behaviors in mice and increased the translocation of fluorescein isothiocyanate-conjugated LPS into the hippocampus. However, Bifidobacterium longum, which was lower in IBD/D+-F vs. IBD/D--F, or its EPS suppressed them. In conclusion, Enterococcus faecium and Pediococcus acidolactici, known as a probiotic strain, and their EPSs may be a risk factor for the outbreak of depression and IBD.

Scientists’ Assessments of Research on Lactic Acid Bacterial Bacteriocins 1990–2010

The antimicrobial activity of bacteriocins from lactic acid bacteria has constituted a very active research field within the last 35 years. Here, we report the results of a questionnaire survey with assessments of progress within this field during the two decades of the 1990s and the 2000s by 48 scientists active at that time. The scientists had research positions at the time ranging from the levels of Master’s and Ph.D. students to principal investigators in 19 Asian, European, Oceanian and North American countries. This time period was evaluated by the respondents to have resulted in valuable progress regarding the basic science of bacteriocins, whereas this was not achieved to the same degree with regard to their applications. For the most important area of application, food biopreservation, there were some success stories, but overall the objectives had not been entirely met due to a number of issues, such as limited target spectrum, target resistance, poor yield as well as economic and regulatory challenges. Other applications of bacteriocins such as enhancers of the effects of probiotics or serving as antimicrobials in human clinical or veterinary microbiology, were not evaluated as having been implemented successfully to any large extent at the time. However, developments in genomic and chemical methodologies illustrate, together with an interest in combining bacteriocins with other antimicrobials, the current progress of the field regarding potential applications in human clinical microbiology and food biopreservation. In conclusion, this study illuminates parameters of importance not only for R&D of bacteriocins, but also for the broader field of antimicrobial research.

Preparation of a Novel Nanocomposite and Its Antibacterial Effectiveness against Enterococcus faecalis-An In Vitro Evaluation

The interest in the use of green-mediated synthesis of nanoparticles (NPs) is shown to have increased due to their biocompatibility and reduction of overall production costs. The current study aimed to evaluate a novel nanocomposite (NC) prepared by using a combination of zinc oxide, silver and chitosan with lemon extract as a cross-linking agent and assessed its antimicrobial effectiveness against Enterococcus faecalis (E. faecalis). The NPs and NC were prepared individually using a modification of previously established methods. Ananalys is of the physiochemical properties of the NC was conducted using ultraviolet-visible spectroscopy (UV-Vis) (Shimadzu Corporation, Kyoto, Japan). and transmission electron microscopy (TEM) imaging(HR-TEM; JEOL Ltd., Akishima-shi, Japan. The microbial reduction with this novel NC was evaluated by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a tube assay analytic technique. A time-kill assay analysis was conducted to evaluate the kinetic potential against E. faecalis at different time intervals. The novel NC showed a homogenous nanoparticle size under TEM imaging and under UV-Vis established an absorption range of 350−420 nm making it similar to its individual counterparts. The MIC and MIB were measured at 62.5 ± 20 mg/L (p < 0.05) and 250 ± 72 mg/L (p < 0.05), respectively. A time-kill assay analysis for the NC showed 5 h was required to eradicate E. faecalis. Based on the achieved results, it was seen that the novel NC using a combination of silver, zinc oxide and chitosan showed improved antimicrobial action against E. faecalis compared with its individual components under laboratory conditions. A complete eradication of 108 log units of E. faecalis at 250 mg/L occurred after a total of 5 h. These preliminary results establish the use of lemon extract-mediated silver, zinc and chitosan-based NC had an antibacterial effectiveness against E. faecalis similar to the individual counterparts used for its production under laboratory conditions.

Antibacterial Effects of Recombinant Endolysins in Disinfecting Medical Equipment: A Pilot Study

Nosocomial infections caused by multidrug-resistant (MDR) bacteria are severe life-threatening factors. Endolysins (lysins) degrade the bacterial cell wall peptidoglycan and may help control pathogens, especially MDR bacteria prevalent in hospital settings. This study was conducted to verify the potential of lysin as disinfectant to kill bacteria contaminating medical devices that cause hospital infections. Eight catheters removed from hospitalized patients were collected and tested for their ability to kill bacteria contaminating the catheters using two lysins, LysSS and CHAP-161. Catheter-contaminating bacterial species were isolated and identified by 16s rRNA sequencing. From the eight catheters, bacteria were cultured from seven catheters, and five bacterial species (Bacillus megaterium, Bacillus muralis, Corynebacterium striatum, Enterococcus faecium, and Staphylococcus epidermidis) were identified. LysSS could inhibit catheter-contaminating bacteria, including C. striatum and S. epidermidis, compared with untreated controls but could not inhibit the growth of E. faecium. CHAP-161 showed more bactericidal effects than LysSS, but could not inhibit the growth of S. epidermidis. This study showed the potential of lysin as an alternative disinfectant for hazardous chemical disinfectants used in hospitals.

Bacterial effluxome as a barrier against antimicrobial agents: structural biology aspects and drug targeting

Antimicrobial resistance (AMR) is fast becoming a medical crisis affecting the entire global population. The bacterial membrane is the first layer of defense for the bacteria against antimicrobial agents (AMA), specifically transporters in the membrane efflux these AMA out of the bacteria and plays a significant role in the AMR development. Understanding the structure and the functions of these efflux transporters is essential to overcome AMR. This review discusses efflux transporters (primary, secondary, and tripartite), their domain architectures, substrate specificities, and efflux pump inhibitors (EPI). Special emphasis on nosocomial ESKAPEE (Enterococcus faecium., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli) pathogens, their multidrug efflux targets and inhibitors are discussed. Deep knowledge about the functioning of efflux pumps and their structural aspects will open up opportunities for developing new EPI, which could be used along with AMA as combination therapy to overcome the emerging AMR crisis.

Enterococcus innesii sp. nov., isolated from the wax moth Galleria mellonella

Four bacterial strains were isolated from two different colony sources of the wax moth Galleria mellonella. They were characterized by a polyphasic approach including 16S rRNA gene sequence analysis, core-genome analysis, average nucleotide identity (ANI) analysis, digital DNA-DNA hybridization (dDDH), determination of G+C content, screening of antibiotic resistance genes, and various phenotypic analyses. Initial analysis of 16S rRNA gene sequence identities indicated that strain GAL7^T was potentially very closely related to Enterococcus casseliflavus and Enterococcus gallinarum, having 99.5-99.9 % sequence similarity. However, further analysis of whole genome sequences revealed a genome size of 3.69 Mb, DNA G+C content of 42.35 mol%, and low dDDH and ANI values between the genomes of strain GAL7^T and closest phylogenetic relative E. casseliflavus NBRC 100478^T of 59.0 and 94.5 %, respectively, indicating identification of a putative new Enterococcus species. In addition, all novel strains encoded the atypical vancomycin-resistance gene vanC-4. Results of phylogenomic, physiological and phenotypic characterization confirmed that strain GAL7^T represented a novel species within the genus Enterococcus, for which the name Enterococcus innesii sp. nov. is proposed. The type strain is GAL7^T (=DSM 112306^T=NCTC 14608^T).