The Enterococcus faecalis virulence factor ElrA interacts with the human Four-and-a-Half LIM Domains Protein 2

The impact of dimethylaminohexadecyl methacrylates on the physical and antibacterial properties of endodontic sealers

Objective

This study aims to incorporate contact-killing quaternary ammonium into two root canal sealers, AH Plus (DentSply Sirona, New York City, NY, USA) and BC (FKG, Le Crêt-du-Locle Switzerland) sealers to improve their antibacterial properties.

Methods

Dimethylaminohexadecyl Methacrylates (DMAHDM) were synthesized and incorporated into AH Plus and BC sealers at 5 weight percent (wt.%). The physical properties were assessed via film thickness, flow, contact angle, and solubility. The antibacterial properties were assessed by determining the number of colony-forming units (CFUs) of Enterococcus faecalis and scanning electron microscopy (SEM). Two-way ANOVA and Tukey tests were used to analyze the data.

Results

Incorporating DMAHDM at 5 wt.% increased the film thickness and reduced the flow of the AH Plus and BC sealers (P < 0.05), but the values were within clinically acceptable limits. Simultaneously, DMAHDM incorporation increased the contact angle of the sealers (P < 0.001). DMAHDM incorporation significantly (P < 0.001) inhibited the E. faecalis biofilms and resulted in complete eradication. In contrast, the AH Plus and BC control sealers had approximately 105 and 104 CFUs of bacteria, respectively. The SEM images revealed no E. faecalis colonies over the AH Plus sealers containing 5 wt.% DMAHDM, while the AH Plus control sealers were covered with a thick layer of biofilms.

Conclusions

The results of this study suggest that DMAHDM, as a contact-killing agent, could be used as an approach to prevent endodontic reinfections.

Clinical Relevance

Integrating DMAHDM into commercial sealers may enhance their antibacterial properties. These findings indicate a need for further investigation using more clinically relevant models to validate this approach.

Metabolic interplay between Proteus mirabilis and Enterococcus faecalis facilitates polymicrobial biofilm formation and invasive disease

Biofilms play an important role in the development and pathogenesis of catheter-associated urinary tract infection (CAUTI). Proteus mirabilis and Enterococcus faecalis are common CAUTI pathogens that persistently co-colonize the catheterized urinary tract and form biofilms with increased biomass and antibiotic resistance. In this study, we uncover the metabolic interplay that drives biofilm enhancement and examine the contribution to CAUTI severity. Through compositional and proteomic biofilm analyses, we determined that the increase in biofilm biomass stems from an increase in the protein fraction of the polymicrobial biofilm. We further observed an enrichment in proteins associated with ornithine and arginine metabolism in polymicrobial biofilms compared with single-species biofilms. We show that arginine/ornithine antiport by E. faecalis promotes arginine biosynthesis and metabolism in P. mirabilis, ultimately driving the increase in polymicrobial biofilm protein content without affecting viability of either species. We further show that disrupting E. faecalis ornithine antiport alters the metabolic profile of polymicrobial biofilms and prevents enhancement, and this defect was complemented by supplementation with exogenous ornithine. In a murine model of CAUTI, ornithine antiport did not contribute to E. faecalis colonization but was required for the increased incidence of urinary stone formation and bacteremia that occurs during polymicrobial CAUTI with P. mirabilis. Thus, disrupting metabolic interplay between common co-colonizing species may represent a viable strategy for reducing risk of bacteremia.IMPORTANCEChronic infections often involve the formation of antibiotic-resistant biofilm communities that include multiple different microbes, which pose a challenge for effective treatment. In the catheterized urinary tract, potential pathogens persistently co-colonize for long periods of time and the interactions between them can lead to more severe disease outcomes. In this study, we identified the metabolite L-ornithine as a key mediator of disease-enhancing interactions between two common and challenging pathogens, Enterococcus faecalis and Proteus mirabilis. Disrupting ornithine-mediated interactions may therefore represent a strategy to prevent polymicrobial biofilm formation and decrease risk of severe disease.

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.

Enrofloxacin, Effective Treatment of Pseudomonas aeruginosa and Enterococcus faecalis Infection in Oreochromis niloticus

Enrofloxacin is a broad-spectrum synthetic antimicrobial drug widely used in veterinary medicine. The present study aimed to determine the effective enrofloxacin dose for treating Pseudomonas aeruginosa and Enterococcus faecalis infection in Oreochromis niloticus. P. aeruginosa and E. faecalis isolates were verified using selective differential media and biochemically using the Vitek 2 test. Bacterial isolates were virulent for O. niloticus with LD50 equal to 2.03 × 106 and 2.22 × 107 CFU fish-1 for P. aeruginosa and E. faecalis, respectively. Infected fish suffered from decreased feed intake followed by off-food, tail erosion, darkening of the external body surface, exophthalmia, ascites, and loss of escape reflex. Internally, congested hemorrhagic hepatopancreas with engorged distended gall bladder were dominant. The posterior kidney was congested with enlarged spleen, and empty elementary tract. Pathologically, severe degenerative changes were dominant in the hepatopancreas, posterior kidney, spleen, stomach, and gills of infected fish. Antimicrobial sensitivity test indicated the high susceptibility of P. aeruginosa and E. faecalis to enrofloxacin with MIC estimated at 1 and 0.0625 µg/mL, respectively. Enrofloxacin effectively protected O. niloticus against E. faecalis and P. aeruginosa infection when used with medicated feed at doses of 10 and 20 mg kg-1 body weight.

Metagenomic and Culturomics Analysis of Microbial Communities within Surface Sediments and the Prevalence of Antibiotic Resistance Genes in a Pristine River: The Zaqu River in the Lancang River Source Region, China

Microbial communities inhabiting sedimentary environments in river source regions serve as pivotal indicators of pristine river ecosystems. While the correlation between antibiotic resistome and pathogenicity with core gut bacteria in humans is well established, there exists a significant knowledge gap concerning the interaction of antibiotic resistance genes (ARGs) and human pathogenic bacteria (HPB) with specific microbes in river source basins, often referred to as "terrestrial gut". Understanding the microbial composition, including bacteria and resident genetic elements such as ARGs, HPB, Mobile Genetic Elements (MGEs), and Virulence Factors (VFs), within natural habitats against the backdrop of global change, is imperative. To address this gap, an enrichment-based culturomics complementary along with metagenomics was conducted in this study to characterize the microbial biobank and provide preliminary ecological insights into profiling the dissemination of ARGs in the Lancang River Source Basin. Based on our findings, in the main stream of the Lancang River Source Basin, 674 strains of bacteria, comprising 540 strains under anaerobic conditions and 124 under aerobic conditions, were successfully isolated. Among these, 98 species were identified as known species, while 4 were potential novel species. Of these 98 species, 30 were HPB relevant to human health. Additionally, bacA and bacitracin emerged as the most abundant ARGs and antibiotics in this river, respectively. Furthermore, the risk assessment of ARGs predominantly indicated the lowest risk rank (Rank Ⅳ) in terms of endangering human health. In summary, enrichment-based culturomics proved effective in isolating rare and unknown bacteria, particularly under anaerobic conditions. The emergence of ARGs showed limited correlation with MGEs, indicating minimal threats to human health within the main stream of the Lancang River Source Basin.

Current Knowledge of Enterococcal Endocarditis: A Disease Lurking in Plain Sight of Health Providers

Enterococcus faecalis is a bacterial pathogen that can cause opportunistic infections. Studies indicate that initial biofilm formation plays a crucial regulatory role in these infections, as well as in colonising and maintaining the gastrointestinal tract as a commensal member of the microbiome of most land animals. It has long been thought that vegetation of endocarditis resulting from bacterial attachment to the endocardial endothelium requires some pre-existing tissue damage, and in animal models of experimental endocarditis, mechanical valve damage is typically induced by cardiac catheterisation preceding infection. This section reviews historical and contemporary animal model studies that demonstrate the ability of E. faecalis to colonise the undamaged endovascular endothelial surface directly and produce robust microcolony biofilms encapsulated within a bacterially derived extracellular matrix. This report reviews both previous and current animal model studies demonstrating the resilient capacity of E. faecalis to colonise the undamaged endovascular endothelial surface directly and produce robust microcolony biofilms encapsulated in a bacterially derived extracellular matrix. The article also considers the morphological similarities when these biofilms develop on different host sites, such as when E. faecalis colonises the gastrointestinal epithelium as a commensal member of the common vertebrate microbiome, lurking in plain sight and transmitting systemic infection. These phenotypes may enable the organism to survive as an unrecognised infection in asymptomatic subjects, providing an infectious resource for subsequent clinical process of endocarditis.

DUF916 and DUF3324 in the WxL protein cluster bind to WxL and link bacterial and host surfaces

Bacterial WxL proteins contain peptidoglycan-binding WxL domains, which have a dual Trp-x-Leu motif and are involved in virulence. It was recently shown that WxL proteins occur in gene clusters, containing typically a small WxL protein (which in the mature protein consists only of a WxL domain), a large WxL protein (which contains a C-terminal WxL domain with N-terminal host-binding domains), and a conserved protein annotated as a Domain of Unknown Function (DUF). Here we analyze this DUF and show that it contains two tandem domains-DUF916 and DUF3324-which both have an IgG-like fold and together form a single functional unit, connected to a C-terminal transmembrane helix. DUF3324 is a stable domain, while DUF916 is less stable and is likely to require a stabilizing interaction with WxL. The protein is suggested to have an important role to bind and stabilize WxL on the peptidoglycan surface, via the DUF916 domain, and to bind to host cells via the DUF3324 domain. AlphaFold2 predicts that a β-hairpin strand from DUF916 inserts into WxL adjacent to its N-terminus. We therefore propose to rename the DUF916-DUF3324 pair as WxL Interacting Protein (WxLIP), with DUF916, DUF3324 and the transmembrane helix forming the first, second and third domains of WxLIP, which we characterize as peptidoglycan binding domain (PGBD), host binding domain (HBD), and transmembrane helix (TMH) respectively.

The Role of Platelets in Infective Endocarditis

Over the last decade, the incidence of infective endocarditis (IE) has increased, with a change in the frequency of causative bacteria. Early evidence has substantially demonstrated the crucial role of bacterial interaction with human platelets, with no clear mechanistic characterization in the pathogenesis of IE. The pathogenesis of endocarditis is so complex and atypical that it is still unclear how and why certain bacterial species will induce the formation of vegetation. In this review, we will analyze the key role of platelets in the physiopathology of endocarditis and in the formation of vegetation, depending on the bacterial species. We provide a comprehensive outline of the involvement of platelets in the host immune response, investigate the latest developments in platelet therapy, and discuss prospective research avenues for solving the mechanistic enigma of bacteria-platelet interaction for preventive and curative medicine.

Bioinformatic analysis of WxL domain proteins

The WxL domain is found on the cell surface of many bacteria, most of which are commensal gut bacteria. Its functions are generally identified as being related to virulence and/or peptidoglycan attachment, but there is so far no clear function or structure for this domain. Here, a range of bioinformatics tools were used to clarify the structure and function. These indicate that WxL domains occur in cell surface-associated gene clusters that always contain a small WxL, large WxL and DUF916 domain; and that the small and large WxL proteins have distinct structure despite sharing two conserved WxL motifs. The two WxL motifs form a hydrophobic surface buried inside the protein. The likely function of the WxL domain is to attach to bacterial peptidoglycan, forming a platform to allow associated domains in the cluster to interact with host proteins.

Virulence Factors in Colorectal Cancer Metagenomes and Association of Microbial Siderophores with Advanced Stages

Colorectal cancer (CRC) is a growing public health challenge, featuring a multifactorial etiology and complex host-environment interactions. Recently, increasing evidence has pointed to the role of the gut microbiota in CRC development and progression. To explore the role of gut microbes in CRC, we retrieved metagenomic data from 156 stools from the European Nucleotide Archive database and mapped them against the VFDB database for virulence factors (VFs). GO annotations of VFs and KEGG pathways were then performed to predict the microbial functions and define functional pathways enriched in the tumor-associated microbiota. Interestingly, 306 VFs were detected in the metagenomic data. We revealed the enrichment of adenomas with VFs involved in cell adhesion, whereas in the early stages of CRC they were enriched in both adhesins and isochorismatase. Advanced stages of CRC were enriched with microbial siderophores, especially enterobactin, which was significantly associated with isochorismate synthase. We highlighted higher abundances of porins and transporters involved in antibiotic resistance and the development of biofilm in advanced stages of CRC. Most VFs detected in CRC, particularly in advanced stages, were shown to be included in siderophore biosynthesis pathways. This enrichment of predicted VFs supports the key role of the gut microbiota in the disease.

Enterococcal Endocarditis: Hiding in Plain Sight

Enterococcus faecalis is a major opportunistic bacterial pathogen of increasing clinical relevance. A substantial body of experimental evidence suggests that early biofilm formation plays a critical role in these infections, as well as in colonization and persistence in the GI tract as a commensal member of the microbiome in most terrestrial animals. Animal models of experimental endocarditis generally involve inducing mechanical valve damage by cardiac catheterization prior to infection, and it has long been presumed that endocarditis vegetation formation resulting from bacterial attachment to the endocardial endothelium requires some pre-existing tissue damage. Here we review both historical and contemporary animal model studies demonstrating the robust ability of E. faecalis to directly attach and form stable microcolony biofilms encased within a bacterially-derived extracellular matrix on the undamaged endovascular endothelial surface. We also discuss the morphological similarities when these biofilms form on other host tissues, including when E. faecalis colonizes the GI epithelium as a commensal member of the normal vertebrate microbiome - hiding in plain sight where it can serve as a source for systemic infection via translocation. We propose that these phenotypes may allow the organism to persist as an undetected infection in asymptomatic individuals and thus provide an infectious reservoir for later clinical endocarditis.

Microbiome patterns reveal the transmission of pathogenic bacteria in hilsa fish (Tenualosa ilisha) marketed for human consumption in Bangladesh

AIMS

This study conducted bacterial community, virulence and antibiogram profiling inside the hindgut and skin of freshly caught hilsa fish and those sold at markets.

METHODS AND RESULTS

The results of 16S rRNA-based high-throughput sequencing showed a higher number of bacterial genera in marketed fish samples than in fresh fish samples. The total operational taxonomic units, genus counts and diversity index were significantly higher (P > 0·05) in marketed fish, which also had abundant pathogenic bacterial groups. Skin samples had a lower profusion of pathogenic bacteria than gut samples. A total of 52 bacterial isolates from nine species were identified in this study, of which 25 were from a Chittagong market and 22 were from a Dhaka market, whereas only five were from fresh hilsa. The polymerase chain reaction amplification of 12 species-specific virulence genes in the 52 isolates, namely, aer, hly, chxA, toxB, rtxC, sfa, uge, norB, trx, toxA, ipaH, sigA and coa, indicated a high number of positive samples containing Vibrio cholerae, Aeromonas spp., Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus. Antibiogram profiling of these bacteria against 10 commercial antibiotics showed high-resistance patterns of the isolates against sulfamethoxazole, kanamycin, neomycin, ampicillin and tetracycline.

CONCLUSION

The results reveal the spread of multidrug-resistant bacteria in hilsa fish marketed for human consumption in Bangladesh.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the risk of spreading environmentally and clinically pathogenic bacteria in fish sold for human consumption in Bangladesh. Such bacteria come from aquatic pollution and poor handling, storage and transportation practices that may predispose fish to major outbreaks of infectious and waterborne diseases.

Exploration of the role of the virulence factor ElrA during Enterococcus faecalis cell infection

Enterococcus faecalis, an organism generally not pathogenic for healthy humans, has the potential to cause disease in susceptible hosts. While it seems to be equipped to interact with and circumvent host immune defense, most of the molecular and cellular mechanisms underlying the enterococcal infectious process remain elusive. Here, we investigated the role of the Enterococcal Leucine Rich protein A (ElrA), an internalin-like protein of E. faecalis also known as a virulence factor. ElrA was previously shown to prevent adhesion to macrophages. We show that ElrA does not inhibit the basic phagocytic process, but is able to prevent sensing and migration of macrophages toward E. faecalis. Presence or absence of FHL2, a eukaryotic partner of ElrA, does not affect the ElrA-dependent mechanism preventing macrophage migration. However, we highlight a partial contribution of FHL2 in ElrA-mediated virulence in vivo. Our results indicate that ElrA plays at least a dual role of which anti-phagocytic activity may contribute to dissemination of extracellular E. faecalis during infection.