Characterization of biofilm formation by Enterococcus faecalis isolates derived from urinary tract infections in China

Molecular characterization and biofilm formation ability of Enterococcus faecium and Enterococcus faecalis bloodstream isolates from a Chinese tertiary hospital in Beijing

To investigate the molecular characteristics and biofilm-forming ability of 116 Enterococcus faecium (Efm) and 72 Enterococcus faecalis (Efs) isolates obtained from patients with bloodstream infections (BSI) at a Chinese hospital between July 2011 and March 2018. The presence of glycopeptide resistance genes and five virulence genes (esp, gelE, asa1, hyl, and cylA) was screened using two multiplex PCR. MLST was used to assess the clonality. Crystal violet staining was used to detect biofilms. Vancomycin resistance was detected in 30.1% of Efm and 2.8% of Efs isolates, respectively. All VRE strains carried the vanA gene. The esp, gelE, asa1, and cylA genes in 72 Efs strains were detected at 62.5%, 84.7%, 84.7%, and 69.4%, respectively. Among the 116 Efm isolates, 74.1% and 25.8% carried esp and hyl, respectively. The esp gene was significantly associated with vancomycin-resistant Efm (VREfm) compared to vancomycin-susceptible Efm (VSEfm). In total, 91.7% of Efs and 20.0% of Efm produced biofilms. Twenty-six STs were identified among the 72 Efs isolates, with ST4 (29.2%) being the predominant. In total, 116 Efm strains were grouped into 26 STs, with ST78 (46.6%) being the predominant. Both VREfm (41.7%) and VSEfm (48.8%) were dominant in ST78. There is no clear evidence suggesting that some STs are associated with vancomycin resistance or biofilm formation. Both Efm and Efs BSI isolates showed a polyclonal pattern with a dominant clone and many unique types, implying the coexistence of clonal dissemination and an influx of new clones. The horizontal transmission of resistance genes may play a more important role in VREfm prevalence than clonal expansion.

The Synergistic Activity of Rhamnolipid Combined with Linezolid against Linezolid-Resistant Enterococcus faecium

Enterococci resistance is increasing sharply, which poses a serious threat to public health. Rhamnolipids are a kind of amphiphilic compound used for its bioactivities, while the combination of nontraditional drugs to restore linezolid activity is an attractive strategy to treat infections caused by these pathogens. This study aimed to investigate the activity of linezolid in combination with the rhamnolipids against Enterococcus faecium. Here, we determined that the rhamnolipids could enhance the efficacy of linezolid against enterococci infections by a checkerboard MIC assay, a time-kill assay, a combined disk test, an anti-biofilm assay, molecular simulation dynamics, and mouse infection models. We identified that the combination of rhamnolipids and linezolid restored the linezolid sensitivity. Anti-biofilm experiments show that our new scheme can effectively inhibit biofilm generation. The mouse infection model demonstrated that the combination therapy significantly reduced the bacterial load in the feces, colons, and kidneys following subcutaneous administration. This study showed that rhamnolipids could play a synergistic role with linezolid against Enterococcus. Our combined agents could be appealing candidates for developing new combinatorial agents to restore antibiotic efficacy in the treatment of linezolid-resistant Enterococcus infections.

Evaluation of anti-biofilm effect of antimicrobial sonodynamic therapy-based periodontal ligament stem cell-derived exosome-loaded kojic acid on Enterococcus faecalis biofilm

Introduction. Antimicrobial sonodynamic therapy (aSDT) is an approach that uses ultrasound waves (UWs) and a sonosensitizer to generate reactive oxygen species (ROS) to damage microbial cells in biofilms. Using nano-carriers, such as exosomes (Exos), to deliver the sonosensitizer can potentially enhance the effectiveness of aSDT.Hypothesis/Gap Statement. aSDT can downregulate the expression of gelE and sprE genes, increasing the production of endogenous ROS and degradation of pre-formed Enterococcus faecalis biofilms.Aim. This study investigated the anti-biofilm effect of aSDT-based periodontal ligament stem cell-derived exosome-loaded kojic acid (KA@PDL-Exo) on pre-formed E. faecalis biofilms in root canals.Methodology. Following the isolation and characterization of PDL-Exo, KA@PDL-Exo was prepared and confirmed. The minimal biofilm inhibitory concentration (MBIC) of KA, PDL-Exo, KA@PDL-Exo and sodium hypochlorite (NaOCl) was determined, and their anti-biofilm effects were assessed with and without UWs. The binding affinity of KA with GelE and SprE proteins was evaluated using in silico molecular docking. Additionally, the study measured the generation of endogenous ROS and evaluated changes in the gene expression levels of gelE and sprE.Results. The results revealed a dose-dependent decrease in the viability of E. faecalis cells within biofilms. KA@PDL-Exo was the most effective, with an MBIC of 62.5 µg ml-1, while NaOCl, KA and PDL-Exo had MBIC values of 125, 250 and 500 µg ml-1, respectively. The use of KA@PDL-Exo-mediated aSDT resulted in a significant reduction of the E. faecalis biofilm (3.22±0.36 log10 c.f.u. ml-1; P<0.05). The molecular docking analysis revealed docking scores of -5.3 and -5.2 kcal mol-1 for GelE-KA an SprE-KA, respectively. The findings observed the most significant reduction in gene expression of gelE and sprE in the KA@PDL-Exo group, with a decrease of 7.9- and 9.3-fold, respectively, compared to the control group (P<0.05).Conclusion. The KA@PDL-Exo-mediated aSDT was able to significantly reduce the E. faecalis load in pre-formed biofilms, decrease the expression of gelE and srpE mRNA, and increase the generation of endogenous ROS. These findings imply that KA@PDL-Exo-mediated aSDT could be a promising anti-biofilm strategy that requires additional in vitro and in vivo investigations.

Resistance Profiles and Virulence Determinants in Biofilm-Forming Enterococcus faecium Isolated from Raw Seafood in Bangladesh

Pathogenic, antibiotic-resistant, and biofilm-forming bacteria can be transferred to humans through the consumption of contaminated seafood. The present study was carried out to determine antibiotic resistance profiles and virulence determinants in biofilm-forming Enterococcus faecium isolated from seafood in Bangladesh. A total of 150 seafood samples, including shrimp (n = 50), crabs (n = 25), and marine fish (n = 75), were screened using cultural, staining, biochemical, polymerase chain reaction (PCR), Congo red (CR), and disk diffusion (DD) assays. In PCR, E. faecium was detected in 27.3% (41/150; CI95% 20.8; 34.9) of samples, where marine fish (34.7%, CI95% 24.9; 45.9) had the highest prevalence (p < 0.05) compared to crabs (32%, CI95% 17.2; 51.6) and shrimp (14%, CI95% 7.0; 26.1). Thirty-two (78.1%, CI95% 63.3; 88.0) of the E. faecium isolates were determined to be biofilm formers in the CR test, where 43.9% (18/41, CI95% 29.9; 59.0) and 34.2% (14/41, CI95% 21.6; 49.5) of the isolates were strong and intermediate biofilm formers, respectively. In PCR, virulence genes, i.e., pil (100%), ace (92.7%), agg (68.3%), fsrA (65.9%), gelE (63.4%), sprE (53.7%), fsrB (51.2%), and fsrC (43.9%), were detected in E. faecium isolates. All the E. faecium isolates were phenotypically resistant to ≥3 antimicrobial categories and ≥3 antibiotics, including WHO-classified reserve antibiotics linezolid (70.7%) and fosfomycin (19.5%). Moreover, the multiple antibiotic resistance index ranged up to 0.8, showing resistance to ten antibiotics and eight antibiotic classes. In this study, the prevalence of virulence genes and antibiotic resistance was significantly greater (p < 0.05) in strong biofilm-forming E. faecium strains as compared to strains with intermediate and non-biofilm-forming abilities. As far as we know, this study, for the first time in Bangladesh, determined antibiotic resistance and detected virulence genes in biofilm-forming E. faecium isolated from seafood samples. The data from this study could play a significant role in evaluating potential health hazards linked to the ingestion of uncooked or minimally processed seafood.

Progress in the application of Enterococcus faecium in animal husbandry

As a probiotic, enterococcus faecium (E. faecium) has the characteristics of high temperature resistance, gastric acid resistance, bile salt resistance, etc. It can also effectively improve animal performance and immunity and improve the animal's intestinal environment, so in recent years it has been more widely used in the livestock industry. However, due to the improper use of antibiotics and the growing environmental stress of strains, the drug resistance of enterococcus faecium has become more and more serious, and because some enterococcus faecium carry virulence genes, leading to the emergence of pathogenic strains, its safety issues have been widely concerned. This paper focuses on the biological characteristics of enterococcus faecium, the application of this bacterium in animal husbandry and the safety issues in its use, with a view to providing a reference for the application of enterococcus faecium in the development of animal husbandry.

A New Approach for Explaining and Treating Dry Sockets: A Pilot Retrospective Study

Objective Dry socket, a common complication following a tooth extraction, is characterized by severe and radiating pain that typically begins one to four days after the extraction. Despite several risk factors, the exact cause and underlying mechanisms of dry sockets remain unclear. This study aims to propose a novel pathogenesis and management approach for dry sockets based on an infectious process. Methods The study was conducted by reviewing medical records, at a private dental clinic, of patients who fit the inclusion criteria; these patients appeared to have come between April 2022 and April 2023. The study included all patients with age ≥17 years diagnosed with dry socket that was resistant to conventional topical treatment, and who received treatment with ciprofloxacin 500 mg three times per day during the study period. Results Out of 15 patients who received treatment with ciprofloxacin 500 mg three times per day during the study period, 11 patients (73.3%) were completely relieved of symptoms within 24 hours, with no need for additional painkillers or nonsteroidal anti-inflammatory drugs (NSAIDs). In addition, two patients (13.3%) had a partial response after 48 hours, where their pain was ameliorated from severe to moderate with the use of conventional painkillers (including paracetamol and NSAIDs) and steroidal anti-inflammatory drugs such as dexamethasone (8 mg IM daily) to have total relief. On the other hand, the other two patients (13.3%) had a negative response to the treatment and were out of reach for follow-up. Conclusion These clinical outcomes, coupled with previous laboratory data, could explain all clinical aspects of dry sockets and provide substantial support for the hypothesis that an infectious mechanism plays the principal role in the pathophysiology of dry sockets.

Differences in Virulence Factors and Antimicrobial Susceptibility of Uropathogenic Enterococcus spp. Strains in a Rural Area of Uganda and a Spanish Secondary Hospital

Enterococcus faecalis and Enterococcus faecium have become two of the most important agents of nosocomial diseases due to their constantly growing resistance. Enterococcal infections are associated with biofilms, which are intrinsically sensitive to antimicrobials. The main goal of this study was to compare and relate their capacity to form biofilm and their antimicrobial sensitivity, as well as their virulence factors and their implicated genes, of strains isolated from patients with urinary tract infection (UTI) in a rural hospital in Uganda and a secondary hospital in Spain. A prospective study was conducted with 104 strains of E. faecalis and E. faecium isolated from patients with suspected UTI and who presented leukocyturia at the Saint Joseph Kitgum hospital (Uganda) and at the Hospital Universitario Principe de Asturias (Spain). All microorganisms were identified in Spain by MALDI-TOF mass spectrometry. Antimicrobial susceptibility studies were carried out using the Vitek^® 2 system (Biomériux, France). The biofilm formation capacity was studied by photospectrometry. Phenotypic and genotypic virulence factors were studied in all cases by PCR or expression techniques. In Uganda, we found a higher incidence of E. faecium (65.3%, n = 32), contrary to the situation found in Spain where most of the bacteria found belonged to E. faecalis (92.7%, n = 51). All E. faecalis strains were found to have very low levels of resistance to ampicillin, imipenem, and nitrofurantoin. However, E. faecium exhibited more than 25% resistance to these antibiotics. Although the esp gene has been shown in the results obtained to be an important initial agent in biofilm formation, we have also demonstrated in this study the intervention of other genes when esp is not present, such as the ace1 gene. No statistically significant relationships were found between the presence of agg and gelE genes and increased biofilm formation. The significant difference between the incidence of E. faecalis and E. faecium and biofilm formation, between samples from Spain and Uganda, shows us very different profiles between countries.

An Enzybiotic Cocktail Effectively Disrupts Preformed Dual Biofilm of Staphylococcus aureus and Enterococcus faecalis

Multidrug-resistant bacterial infections are on the rise around the world. Chronic infections caused by these pathogens through biofilm mediation often complicate the situation. In natural settings, biofilms are often formed with different species of bacteria existing synergistically or antagonistically. Biofilms on diabetic foot ulcers are formed predominantly by two opportunistic pathogens, Staphylococcus aureus and Enterococcus faecalis. Bacteriophages and phage-based proteins, including endolysins, have been found to be active against biofilms. In this study, we evaluated the activity of two engineered enzybiotics either by themselves or as a combination against a dual biofilm formed by S. aureus and E. faecalis in an inert glass surface. An additive effect in rapidly disrupting the preformed dual biofilm was observed with the cocktail of proteins, in comparison with mono treatment. The cocktail-treated biofilms were dispersed by more than 90% within 3 h of treatment. Apart from biofilm disruption, bacterial cells embedded in the biofilm matrix were also effectively reduced by more than 90% within 3 h of treatment. This is the first instance where a cocktail of engineered enzybiotics has been effectively used to impede the structural integrity of a dual biofilm.

Bactericidal synergism between phage endolysin Ply2660 and cathelicidin LL-37 against vancomycin-resistant Enterococcus faecalis biofilms

Antibiotic resistance and the ability to form biofilms of Enterococcus faecalis have compromised the choice of therapeutic options, which triggered the search for new therapeutic strategies, such as the use of phage endolysins and antimicrobial peptides. However, few studies have addressed the synergistic relationship between these two promising options. Here, we investigated the combination of the phage endolysin Ply2660 and the antimicrobial peptide LL-37 to target drug-resistant biofilm-producing E. faecalis. In vitro bactericidal assays were used to demonstrate the efficacy of the Ply2660-LL-37 combination against E. faecalis. Larger reductions in viable cell counts were observed when Ply2660 and LL-37 were applied together than after individual treatment with either substance. Transmission electron microscopy revealed that the Ply2660-LL-37 combination could lead to severe cell lysis of E. faecalis. The mode of action of the Ply2660-LL-37 combination against E. faecalis was that Ply2660 degrades cell wall peptidoglycan, and subsequently, LL-37 destroys the cytoplasmic membrane. Furthermore, Ply2660 and LL-37 act synergistically to inhibit the biofilm formation of E. faecalis. The Ply2660-LL-37 combination also showed a synergistic effect for the treatment of established biofilm, as biofilm killing with this combination was superior to each substance alone. In a murine peritoneal septicemia model, the Ply2660-LL-37 combination distinctly suppressed the dissemination of E. faecalis isolates and attenuated organ injury, being more effective than each treatment alone. Altogether, our findings indicate that the combination of a phage endolysin and an antimicrobial peptide may be a potential antimicrobial strategy for combating E. faecalis.

Situational analysis on fluoroquinolones use and characterization of high-level ciprofloxacin-resistant Enterococcus faecalis by integrated broiler operations in South Korea

Fluoroquinolones are classified as "critically important antimicrobials for human medicine"; however, their extensive use in livestock poses a significant health risk to humans as it leads to the rapid spread of antimicrobial resistance. This study confirmed that 40.0%-71.4% of the farms in three of the five integrated broiler operations were administered ciprofloxacin (CIP). Moreover, preventive purposes (60.9%), veterinarian prescriptions (82.6%), drinking water route (100%), and 1 to 3 days (82.6%) of age were significantly highest (P < 0.05). 194 high-level ciprofloxacin-resistant (HLCR) Enterococcus faecalis (E. faecalis) were found in 65 of 74 farms, and of which, the prevalence of qnrA (63.9%), tetM (60.3%), ermB (64.9%), blaz (38.7%), and catA (34.0%) was significantly highest (P < 0.05). 154 (79.4%) isolates showed MDR, and the distribution of MDR was significantly differences among the operations (P < 0.05). All HLCR E. faecalis possessed double mutations in gyrA and parC, and S83I/S80I (90.7%) mutations were most commonly identified. Interestingly, the distribution of isolates with MICs ≥ 512 for both CIP and moxifloxacin was significantly higher in CIP-administered farms (56.5%) than in non-CIP-administered farms (41.4%) (P < 0.05). Also, the prevalence of strong or moderate biofilm formers in HLCR E. faecalis was significantly higher than that of weak and no biofilm formers (P < 0.05). HLCR E. faecalis were heavily distributed in the broiler farms in Korea; therefore, it is necessary to minimize the prevalence of resistant bacteria via structural management regulations such as cleaning and disinfection of farm environments.

Promising applications of D-amino acids in periprosthetic joint infection

Due to the rise in our aging population, a disproportionate demand for total joint arthroplasty (TJA) in the elderly is forecast. Periprosthetic joint infection (PJI) represents one of the most challenging complications that can occur following TJA, and as the number of primary and revision TJAs continues to rise, an increasing PJI burden is projected. Despite advances in operating room sterility, antiseptic protocols, and surgical techniques, approaches to prevent and treat PJI remain difficult, primarily due to the formation of microbial biofilms. This difficulty motivates researchers to continue searching for an effective antimicrobial strategy. The dextrorotatory-isoforms of amino acids (D-AAs) are essential components of peptidoglycan within the bacterial cell wall, providing strength and structural integrity in a diverse range of species. Among many tasks, D-AAs regulate cell morphology, spore germination, and bacterial survival, evasion, subversion, and adhesion in the host immune system. When administered exogenously, accumulating data have demonstrated that D-AAs play a pivotal role against bacterial adhesion to abiotic surfaces and subsequent biofilm formation; furthermore, D-AAs have substantial efficacy in promoting biofilm disassembly. This presents D-AAs as promising and novel targets for future therapeutic approaches. Despite their emerging antibacterial efficacy, their role in disrupting PJI biofilm formation, the disassembly of established TJA biofilm, and the host bone tissue response remains largely unexplored. This review aims to examine the role of D-AAs in the context of TJAs. Data to date suggest that D-AA bioengineering may serve as a promising future strategy in the prevention and treatment of PJI.

Diverse Enterococcus faecalis strains show heterogeneity in biofilm properties

Biofilm formation is important for Enterococcus faecalis to cause healthcare-associated infections. It is unclear how E. faecalis biofilms vary in parameters such as development and composition. To test the hypothesis that differences in biofilms exist among E. faecalis strains, we evaluated in vitro biofilm formation and matrix characteristics of five genetically diverse E. faecalis lab-adapted strains and clinical isolates (OG1RF, V583, DS16, MMH594, and VA1128). Biofilm formation of all strains was repressed in TSB+10% FBS. However, DMEM+10% FBS enhanced biofilm formation of clinical isolate VA1128. Crystal violet staining and fluorescence microscopy of biofilms grown on Aclar membranes demonstrated differences between OG1RF and VA1128 in biofilm development over a 48-h time course. None of the biofilms were dispersed by single treatments of sodium (meta)periodate, DNase, or Proteinase K alone, but the biofilm biomass of both OG1RF and DS16 was partially removed by a sequential treatment of sodium (meta)periodate and DNase. Reversing the treatment order was not effective, suggesting that the extracellular DNA targeted by DNase was obscured by carbohydrates that are susceptible to sodium (meta)periodate degradation. Fluorescent staining of biofilm matrix components further demonstrated that more carbohydrates bound by wheat germ agglutinin comprise OG1RF biofilms compared to VA1128 biofilms. This study highlights the existence of heterogeneity in biofilm properties among diverse E. faecalis strains, which may have implications for the design of novel anti-biofilm treatment strategies.

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.

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.

In vitro activities of licochalcone A against planktonic cells and biofilm of Enterococcus faecalis

This study aims to evaluate the in vitro antibacterial and anti-biofilm activities of licochalcone A on Enterococcus faecalis and to investigate the possible target genes of licochalcone A in E. faecalis. This study found that licochalcone A had antibacterial activities against E. faecalis, with the MIC50 and MIC90 were 25 μM. Licochalcone A (at 4 × MIC) indicated a rapid bactericidal effect on E. faecalis planktonic cells, and killed more E. faecalis planktonic cells (at least 3-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 2, 4, and 6 h of the time-killing test. Licochalcone A (at 10 × MIC) significantly reduced the production of E. faecalis persister cells (at least 2-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 24, 48, 72, and 96 h of the time-killing test. Licochalcone A (at 1/4 × MIC) significantly inhibited the biofilm formation of E. faecalis. The RNA levels of biofilm formation-related genes, agg, esp, and srtA, markedly decreased when the E. faecalis isolates were treated with licochalcone A at 1/4 × MIC for 6 h. To explore the possible target genes of licochalcone A in E. faecalis, the licochalcone A non-sensitive E. faecalis clones were selected in vitro by induction of wildtype strains for about 140 days under the pressure of licochalcone A, and mutations in the possible target genes were detected by whole-genome sequencing. This study found that there were 11 nucleotide mutations leading to nonsynonymous mutations of 8 amino acids, and among these amino acid mutations, there were 3 mutations located in transcriptional regulator genes (MarR family transcriptional regulator, TetR family transcriptional regulator, and MerR family transcriptional regulator). In conclusion, this study found that licochalcone A had an antibacterial effect on E. faecalis, and significantly inhibited the biofilm formation of E. faecalis at subinhibitory concentrations.

Antimicrobial Peptides Active in In Vitro Models of Endodontic Bacterial Infections Modulate Inflammation in Human Cardiac Fibroblasts

Endodontic and periodontal disease are conditions of infectious origin that can lead to tooth loss or develop into systemic hyperinflammation, which may be associated with a wide variety of diseases, including cardiovascular. Endodontic and periodontal treatment often relies on antibiotics. Since new antimicrobial resistances are a major threat, the use of standard antibiotics is not recommended when the infection is only local. Antimicrobial peptides were recently demonstrated to be valid alternatives for dental treatments. The antimicrobial peptide M33D is a tetrabranched peptide active against Gram-negative and Gram-positive bacteria. It has a long life, unusual for peptides, because its branched form provides resistance to proteases. Here the efficacy of M33D and of its analog M33i/l as antibiotics for local use in dentistry was evaluated. M33D and M33i/l were active against reference strains and multidrug-resistant clinical isolates of Gram-negative and Gram-positive species. Their minimum inhibitory concentration against different strains of dental interest was between 0.4 and 6.0 μM. Both peptides acted rapidly on bacteria, impairing membrane function. They also disrupted biofilm effectively. Disinfection of the root canal is crucial for endodontic treatments. M33D and M33i/l reduced E. faecalis colonies to one-twentieth in a dentin slices model reproducing root canal irrigation. They both captured and neutralized lipopolysaccharide (LPS), a bacterial toxin responsible for inflammation. The release of IL-1β and TNFα by LPS-stimulated murine macrophages was reduced by both peptides. Human cardiac fibroblasts respond to different insults with the release of proinflammatory cytokines, and consequently, they are considered directly involved in atherogenic cardiovascular processes, including those triggered by infections. The presence of M33D and M33i/l at MIC concentration reduced IL6 release from LPS- stimulated human cardiac fibroblasts, hence proving to be promising in preventing bacteria-induced atherogenesis. The two peptides showed low toxicity to mammalian cells, with an EC50 one order of magnitude higher than the average MIC and low hemolytic activity. The development of antimicrobial peptides for dental irrigations and medication is a very promising new field of research that will provide tools to fight dental infections and their severe consequences, while at the same time protecting standard antibiotics from new outbreaks of antimicrobial resistance.

Detection of optrA and poxtA genes in linezolid resistant Enterococcus isolates from fur animals in China

The emergence of linezolid-resistant (LR) enterococci found in food of animal origin arouses attention, but little is known about LR enterococci in fur animals. A total of 342 E. faecalis and 265 E. faecium strains isolated from fur animals in China from 2015 to 2017 were investigated to determine if linezolid-resistant (LR) enterococci (≥16 μg ml^-1 ) are present. Overall, two E. faecalis and twelve E. faecium among these isolates were resistant to linezolid. In addition, all LR isolates were classified as multidrug-resistant (MDR) isolates. We further explore the resistance genes of the LR enterococci, four E. faecalis and two E. faecium isolates contained optrA gene. Two of them co-harbored optrA and poxtA genes. We detected virulence genes in LR enterococci were the following: asa1, cylA, esp, gelE and hyl, among which the highest carrying rate gene was asa1. Besides, all of the LR enterococci we tested had the biofilm-forming ability. It is worth noting that we detected a novel ST type ST2010 from E. faecium 82-2. These data show LR enterococci exist in fur animals and have unique characteristics.

Virulence Mechanisms of Common Uropathogens and Their Intracellular Localisation within Urothelial Cells

A recurrent urinary tract infection (UTI) is a common debilitating condition whereby uropathogens are able to survive within the urinary tract. In this study, we aimed to determine if the common uropathogens Escherichia coli, Enterococcus faecalis, and Group B Streptococcus possessed virulence mechanisms that enable the invasion of urothelial cells. Urothelial cells were isolated from women with detrusor overactivity and recurrent UTIs; the intracellular localisation of the uropathogens was determined by confocal microscopy. Uropathogens were also isolated from women with acute UTIs and their intracellular localisation and virulence mechanisms were examined (yeast agglutination, biofilm formation, and haemolysis). Fluorescent staining and imaging of urothelial cells isolated from women with refractory detrusor overactivity and recurrent UTIs demonstrated that all three uropathogens were capable of intracellular colonisation. Similarly, the bacterial isolates from women with acute UTIs were also seen to intracellularly localise using an in vitro model. All Enterococcus and Streptococcus isolates possessed a haemolytic capacity and displayed a strong biofilm formation whilst yeast cell agglutination was unique to Escherichia coli. The expression of virulence mechanisms by these uropathogenic species was observed to correlate with successful urothelial cell invasion. Invasion into the bladder urothelium was seen to be a common characteristic of uropathogens, suggesting that bacterial reservoirs within the bladder contribute to the incidence of recurrent UTIs.

Heme cross-feeding can augment Staphylococcus aureus and Enterococcus faecalis dual species biofilms

The contribution of biofilms to virulence and as a barrier to treatment is well-established for Staphylococcus aureus and Enterococcus faecalis, both nosocomial pathogens frequently isolated from biofilm-associated infections. Despite frequent co-isolation, their interactions in biofilms have not been well-characterized. We report that in combination, these two species can give rise to augmented biofilms biomass that is dependent on the activation of E. faecalis aerobic respiration. In E. faecalis, respiration requires both exogenous heme to activate the cydAB-encoded heme-dependent cytochrome bd, and the availability of O₂. We determined that the ABC transporter encoded by cydDC contributes to heme import. In dual species biofilms, S. aureus provides the heme to activate E. faecalis respiration. S. aureus mutants deficient in heme biosynthesis were unable to augment biofilms whereas heme alone is sufficient to augment E. faecalis mono-species biofilms. Our results demonstrate that S. aureus-derived heme, likely in the form of released hemoproteins, promotes E. faecalis biofilm formation, and that E. faecalis gelatinase activity facilitates heme extraction from hemoproteins. This interspecies interaction and metabolic cross-feeding may explain the frequent co-occurrence of these microbes in biofilm-associated infections.

Characterization and anti-biofilm activity of bacteriophages against urinary tract Enterococcus faecalis isolates

Strong biofilm-forming Enterococcus feacalis urinary tract pathogens (n = 35) were used to determine the lytic spectrum of six bacteriophages isolated from sewage samples. Only 17 Enterococcus feacalis isolates gave lytic zones with the tested bacteriophages from which five isolates were susceptible to all of them. The isolated enterococcal phages are characterized by wide range of thermal (30–90 °C) and pH (3–10) stability. They belong to order Caudovirales, from which four bacteriophages (EPA, EPB, EPD, EPF) belong to family Myoviridae and two (EPC, EPE) belong to family Siphoviridae. In addition, they have promising antibiofilm activity against the tested strong-forming biofilm E. faecalis isolates. The enterococcal phages reduced the formed and preformed biofilms to a range of 38.02–45.7% and 71.0–80.0%, respectively, as compared to the control. The same promising activities were obtained on studying the anti-adherent effect of the tested bacteriophages on the adherence of bacterial cells to the surface of urinary catheter segments. They reduced the number of adherent cells to a range of 30.8–43.8% and eradicated the pre-adherent cells to a range of 48.2–71.1%, as compared to the control. Overall, the obtained promising antibiofilm activity makes these phages good candidates for application in preventing and treating biofilm associated Enterococcus faecalis infections.

Development of 4-[4-(Anilinomethyl)-3-phenyl-pyrazol-1-yl] Benzoic Acid Derivatives as Potent Anti-Staphylococci and Anti-Enterococci Agents

From a library of compounds, 11 hit antibacterial agents have been identified as potent anti-Gram-positive bacterial agents. These pyrazole derivatives are active against two groups of pathogens, staphylococci and enterococci, with minimum inhibitory concentration (MIC) values as low as 0.78 μg/mL. These potent compounds showed bactericidal action, and some were effective at inhibiting and eradicating Staphylococcus aureus and Enterococcus faecalis biofilms. Real-time biofilm inhibition by the potent compounds was studied, by using Bioscreen C. These lead compounds were also very potent against S. aureus persisters as compared to controls, gentamycin and vancomycin. In multiple passage studies, bacteria developed little resistance to these compounds (no more than 2 × MIC). The plausible mode of action of the lead compounds is the permeabilization of the cell membrane determined by flow cytometry and protein leakage assays. With the detailed antimicrobial studies, both in planktonic and biofilm contexts, some of these potent compounds have the potential for further antimicrobial drug development.

Antibiofilm activity of green synthesized silver nanoparticles against biofilm associated enterococcal urinary pathogens

Biofilm-formed enterococcal urinary tract clinical isolates (n = 92) were used for studying the antibiofilm activity of cinnamon, ginger, and chemical AgNPs. The average particle sizes of cinnamon, ginger, and chemical AgNPs were 8.7, 41.98, and 55.7 nm, respectively. The results of Fourier transform infrared analysis revealed that phytocompounds, such as cinnamaldehyde and gingerol, were the main compounds incorporated in the synthesis of cinnamon and ginger AgNPs, respectively. The purity and crystalline nature of the AgNPs have been confirmed by energy dispersive X-ray and X-ray Diffraction analysis. The results of antimicrobial activity showed that MIC of ginger, cinnamon, and chemical AgNPs were 37.64, 725.7, and 61.08 μg/ml, respectively. On studying the antibiofilm activity of AgNPs at sub-MIC values (1/2, 1/4, and 1/8 MIC), the results revealed that it was concentration dependent. Therefore, further studies were carried out to evaluate the antibiofilm activity of AgNPs at a concentration of 18 μg/ml. The results showed that ginger and chemical AgNPs reduced the formed biofilm to 39.14% and 65.32% and the number of adherent cells on the urinary catheter surface to 42.73% and 69.84%, respectively, as compared to that of the control, while cinnamon AgNPs showed no significant activity. Accordingly, ginger AgNPs had the most potent antibacterial and antiadherent activity against biofilm-associated enterococcal isolates.

Mechanism of cooperative N-glycan processing by the multi-modular endoglycosidase EndoE

Bacteria produce a remarkably diverse range of glycoside hydrolases to metabolize glycans from the environment as a primary source of nutrients, and to promote the colonization and infection of a host. Here we focus on EndoE, a multi-modular glycoside hydrolase secreted by Enterococcus faecalis, one of the leading causes of healthcare-associated infections. We provide X-ray crystal structures of EndoE, which show an architecture composed of four domains, including GH18 and GH20 glycoside hydrolases connected by two consecutive three α-helical bundles. We determine that the GH20 domain is an exo-β-1,2-N-acetylglucosaminidase, whereas the GH18 domain is an endo-β-1,4-N-acetylglucosaminidase that exclusively processes the central core of complex-type or high-mannose-type N-glycans. Both glycoside hydrolase domains act in a concerted manner to process diverse N-glycans on glycoproteins, including therapeutic IgG antibodies. EndoE combines two enzyme domains with distinct functions and glycan specificities to play a dual role in glycan metabolism and immune evasion.

EndoE is a multi-domain glycoside hydrolase of the human pathogen Enterococcus faecalis. Here, the authors present crystal structures of EndoE and provide biochemical insights into the molecular basis of EndoE’s substrate specificity and catalytic mechanism.

Development of Antibiofilm Therapeutics Strategies to Overcome Antimicrobial Drug Resistance

A biofilm is a community of stable microorganisms encapsulated in an extracellular matrix produced by themselves. Many types of microorganisms that are found on living hosts or in the environment can form biofilms. These include pathogenic bacteria that can serve as a reservoir for persistent infections, and are culpable for leading to a broad spectrum of chronic illnesses and emergence of antibiotic resistance making them difficult to be treated. The absence of biofilm-targeting antibiotics in the drug discovery pipeline indicates an unmet opportunity for designing new biofilm inhibitors as antimicrobial agents using various strategies and targeting distinct stages of biofilm formation. The strategies available to control biofilm formation include targeting the enzymes and proteins specific to the microorganism and those involved in the adhesion pathways leading to formation of resistant biofilms. This review primarily focuses on the recent strategies and advances responsible for identifying a myriad of antibiofilm agents and their mechanism of biofilm inhibition, including extracellular polymeric substance synthesis inhibitors, adhesion inhibitors, quorum sensing inhibitors, efflux pump inhibitors, and cyclic diguanylate inhibitors. Furthermore, we present the structure–activity relationships (SAR) of these agents, including recently discovered biofilm inhibitors, nature-derived bioactive scaffolds, synthetic small molecules, antimicrobial peptides, bioactive compounds isolated from fungi, non-proteinogenic amino acids and antibiotics. We hope to fuel interest and focus research efforts on the development of agents targeting the uniquely complex, physical and chemical heterogeneous biofilms through a multipronged approach and combinatorial therapeutics for a more effective control and management of biofilms across diseases.

Antibacterial, antibiofilm, anti-inflammatory, and wound healing effects of nanoscale multifunctional cationic alternating copolymers

Infectious diseases caused by new or unknown bacteria and viruses, such as anthrax, cholera, tuberculosis and even COVID-19, are a major threat to humanity. Thus, the development of new synthetic compounds with efficient antimicrobial activity is a necessity. Herein, rationally designed novel multifunctional cationic alternating copolymers were directly synthesized through a step-growth polymerization reaction using a bivalent electrophilic cross-linker containing disulfide bonds and a diamine heterocyclic ring. To optimize the activity of these alternating copolymers, several different diamines and cross-linkers were explored to find the highest antibacterial effects. The synthesized nanopolymers not only displayed good to excellent antibacterial activity as judged by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Escherichia coli, but also reduced the number of biofilm cells even at low concentrations, without killing mammalian cells. Furthermore, in vivo experiments using infected burn wounds in mice demonstrated good antibacterial activity and stimulated wound healing, without causing systemic inflammation. These findings suggest that the multifunctional cationic nanopolymers have potential as a novel antibacterial agent for eradication of multidrug resistant bacterial infections.

Characterization and Comparison of Enterococcus spp. Isolates from Feces of Healthy Dogs and Urine of Dogs with UTIs

Simple Summary

Infections caused by Enterococcus spp. represent a serious threat to human and animal health due to difficulties in treatment. Indeed, these bacteria are a very able “trafficker” of antimicrobial resistance genes and for this reason they are often resistant to many antimicrobials. In this study we explored the role of pet dogs as possible carriers and targets of antimicrobial resistant and virulent enterococci. Isolates collected from feces of healthy animals and urine of dogs suffering with UTIs were characterized and compared. Strains resulted as resistant to many of the antimicrobials tested and almost of them were multidrug-resistant. Diffuse resistance was recorded for compounds routinely employed in human and pet therapy. Genes responsible for antimicrobial resistance were widely detected. E. faecalis and E. faecium resulted as equally distributed in stool samples, while E. faecalis prevailed among UTI isolates; virulence genes were more often detected in bacteria belonging to this species. Our data confirm that enterococci inhabitant of the gut flora probably represent the main source of UTI in dogs. Furthermore, healthy and sick pet dogs could be spreaders of antimicrobial and virulent enterococci, representing a possible hazard for other animals and owners.

Abstract

Enterococcus spp. are opportunistic pathogens of both humans and animals characterized by high resistance to antimicrobials. Dogs could be intestinal carriers or suffer from Enterococcus infections, mainly urinary tract infections (UTIs). This study aimed to analyze and compare Enterococcus spp. isolated from healthy dog stools and sick dog urine. Overall, 51 isolates (29 from stools and 22 from UTI) were characterized at species level and tested for antimicrobial resistance, biofilm production and presence of resistance and virulence genes. E. faecium and E. faecalis resulted as equally distributed in stools samples, while E. faecalis predominated among UTI isolates. HLAR phenotype was detected in 47.1% isolates; 64.7% isolates were resistant to ampicillin (47.1% with a MIC ≥ 64 µg/mL). High levels of resistance were recorded for fluoroquinolones (enrofloxacin 74.5%, ciprofloxacin 66.7%), clindamycin (84.3%), tetracycline (78.4%) and quinupristin–dalfopristin (78.4%). No vancomycin resistant strains were detected. All but one isolate were multidrug-resistant. Most detected resistance genes were tetM (70.5%), pbp4 (52.9%) and aph(3′)-IIIa (39.2%). All isolates were able to produce biofilm, but isolates from UTIs and belonging to E. faecalis more frequently resulted in strong biofilm producers. Most detected virulence genes were asa1 (52.9%), gelE (41.2%), cylA (37.3%) and esp (35.3%); all of them resulted as more frequently associated to E. faecalis. No particular differences emerged between isolates from feces and UTI, considering all evaluated aspects. Our results confirm pet dogs as carriers of multidrug-resistant enterococci; stool microflora could be considered as the most probable source of enterococcal UTI and E. faecalis carried by dogs seems to be more virulent than E. faecium, justifying its more frequent involvement in urinary tract infections.

Lipid-Polymer Hybrid Nanoparticles Enhance the Potency of Ampicillin against Enterococcus faecalis in a Protozoa Infection Model

Enterococcus faecalis (E. faecalis) biofilms are implicated in endocarditis, urinary tract infections, and biliary tract infections. Coupled with E. faecalis internalization into host cells, this opportunistic pathogen poses great challenges to conventional antibiotic therapy. The inability of ampicillin (Amp) to eradicate bacteria hidden in biofilms and intracellular niches greatly reduces its efficacy against complicated E. faecalis infections. To enhance the potency of Amp against different forms of E. faecalis infections, Amp was loaded into Lipid-Polymer hybrid Nanoparticles (LPNs), a highly efficient nano delivery platform consisting of a unique combination of DOTAP lipid shell and PLGA polymeric core. The antibacterial activity of these nanoparticles (Amp-LPNs) was investigated in a protozoa infection model, achieving a much higher multiplicity of infection (MOI) compared with studies using animal phagocytes. A significant reduction of total E. faecalis was observed in all groups receiving 250 μg/mL Amp-LPNs compared with groups receiving the same concentration of free Amp during three different interventions, simulating acute and chronic infections and prophylaxis. In early intervention, no viable E. faecalis was observed after 3 h LPNs treatment whereas free Amp did not clear E. faecalis after 24 h treatment. Amp-LPNs also greatly enhanced the antibacterial activity of Amp at late intervention and boosted the survival rate of protozoa approaching 400%, where no viable protozoa were identified in the free Amp groups at the 40 h postinfection treatment time point. Prophylactic effectiveness with Amp-LPNs at a concentration of 250 μg/mL was exhibited in both bacteria elimination and protozoa survival toward subsequent infections. Using protozoa as a surrogate model for animal phagocytes to study high MOI infections, this study suggests that LPN-formulated antibiotics hold the potential to significantly improve the therapeutic outcome in highly complicated bacterial infections.

Prevalence of Virulence Genes and Antibiotic Resistance Pattern in Enterococcus Faecalis Isolated from Urinary Tract Infection in Shahrekord, Iran

Background

This study aims to specify the antimicrobial resistance pattern and virulence genes of Enterococcus faecalis isolated from urinary tract infections in Shahrekord, Iran.

Methods

Urine samples of 1000 people suspected of having urinary tract infections referred to Shahrekord medical diagnostic laboratories were examined. Biofilm assays were performed by microtiter plate test through reading the OD490. Polymerase Chain Reaction (PCR) was applied to study the virulence factors.

Results

Enterococcus faecalis was detected in 60 samples. After performing microbiological tests, all samples were positive in the molecular analysis. Strong, moderate and weak biofilm reactions reported 66.67%, 25%, and 8.33% respectively. The most resistance reported to cotrimoxazole, vancomycin and amikacin and the lowest resistance to nitrofurantoin (8.33%) was reported. Statistical analysis with Fisher's exact test showed a statistically significant relationship between biofilm production and resistance to cotrimoxazole, vancomycin and cefotaxime. Prevalence of efe A, ace, gel E, esp, cyl M, agg, cyl A and cyl B in strong biofilm formation isolates was reported 100%, 87.5%, 82%, 62.5%, 55%, 37.5% 25% and 22.5% respectively. There was a significant relationship between the frequency of efa A and strong biofilm reaction.

Conclusion

The presence of E. faecalis strains resistant to co-trimoxazole and vancomycin and present of some virulence factors is alarming the researchers. Since antibiotic resistance genes are probably transmitted among enterococci, and Staphylococci, controlling infections made by enterococci as well as the appropriate administration of antibiotics could treat the nosocomial infections effectively.

New Insights into the Virulence Traits and Antibiotic Resistance of Enterococci Isolated from Diverse Probiotic Products

The GRAS (generally recognized as safe) status of Enterococcus has not yet been authenticated, but enterococci, as probiotics, have been increasingly applied in human healthcare and animal husbandry, for instance as a dietary supplement, feed additive, or growth promotor. The food chain is the important route for introducing enterococci into the human gut. The pathogenicity of Enterococcus from probiotic products requires investigation. In the study, 110 commercial probiotic products used for human, animal, aquaculture, and plants were examined, among which 36 enterococci were identified, including 31 from Enterococcus faecium, 2 from E. faecalis, 2 from E. casseliflavus, and 1 from E. gallinarum. Strikingly, 28 of the 36 enterococci isolated from probiotics here did not mention the presence of Enterococcus in the labeled ingredients, and no Enterococcus isolates were found from 5 animal probiotics that were labeled with the genus. In total, 35 of the 110 products exhibited hemolysis, including 5 (10.6%) human probiotics, 14 (41.2%) animal probiotics, 8 (57.1%) aquaculture probiotics, and 8 (53.3%) plant probiotics. The detection rates of virulence factors associated with adhesion, antiphagocytosis, exoenzyme, biofilm, and other putative virulence markers (PVM) in 36 enterococci were 94.4%, 91.7%, 5.6%, 94.4% and 8.3%. Twenty-six of the 36 isolated strains exhibited biofilm formation ability, where 25 strains (69.4%) and one (2.8%) were strong and weak biofilm producers, respectively. We analyzed the resistance rates against erythromycin (97%), vancomycin and ciprofloxacin (8%), tetracycline (3%), and high-level aminoglycosides (0%), respectively. High detection rates of msrC/lsaA (86%) and aac(6')-Ii (86%) were observed, followed by vanC (8%), tetM (3%). The Tn5801-tetM-like integrative conjugative element (ICE) was identified in E. gallinarum, exhibiting resistance to tetracycline (64 μg/mL). Seven probiotic E. faecalis and E. faecium, as active ingredients in human probiotics, shared the same STs (sequence types) and were distinct from the STs of other contaminated or mislabeled enterococci, indicating that two particular STs belonged to native probiotic isolates. These findings advocate appropriate assessments of enterococci when used in probiotics.

Comparison of Enterococcus faecalis Biofilm Removal Efficiency among Bacteriophage PBEF129, Its Endolysin, and Cefotaxime

Enterococcus faecalis is a Gram-positive pathogen which colonizes human intestinal surfaces, forming biofilms, and demonstrates a high resistance to many antibiotics. Especially, antibiotics are less effective for eradicating biofilms and better alternatives are needed. In this study, we have isolated and characterized a bacteriophage, PBEF129, infecting E. faecalis. PBEF129 infected a variety of strains of E. faecalis, including those exhibiting antibiotic resistance. Its genome is a linear double-stranded DNA, 144,230 base pairs in length. Its GC content is 35.9%. The closest genomic DNA sequence was found in Enterococcus phage vB_EfaM_Ef2.3, with a sequence identity of 99.06% over 95% query coverage. Furthermore, 75 open reading frames (ORFs) were functionally annotated and five tRNA-encoding genes were found. ORF 6 was annotated as a phage endolysin having an L-acetylmuramoyl-l-alanine amidase activity. We purified the enzyme as a recombinant protein and confirmed its enzymatic activity. The endolysin’s host range was observed to be wider than its parent phage PBEF129. When applied to bacterial biofilm on the surface of in vitro cultured human intestinal cells, it demonstrated a removal efficacy of the same degree as cefotaxime, but much lower than its parent bacteriophage.

Linezolid Resistance in Enterococcus faecalis Associated With Urinary Tract Infections of Patients in a Tertiary Hospitals in China: Resistance Mechanisms, Virulence, and Risk Factors

Background:Enterococcus faecalis has been commonly considered as one of the major pathogens of the urinary tract infection (UTI) in human host worldwide, whereas the molecular characteristics of E. faecalis clinical isolates from the patients with UTI in China remains seldomly reported. This study aimed to investigate the resistance mechanism, molecular characteristics and risk factors of E. faecalis clinical isolates from patients with UTI in China.

Methods: A total of 115 non-duplicated E. faecalis clinical isolates from patients with UTI were retrospectively collected in a tertiary hospital in China and their clinical data was further analyzed. The linezolid and tedizolid susceptibility were determined by agar dilution. The resistance genes, including erm(A), erm(B), erm(C), tet(M), optrA, cfr, cfr(B), poxtA, and MLST-based housekeeping genes were investigated by PCR.

Results: In 115 non-duplicated E. faecalis clinical isolates from the patients with UTI in this hospital setting, the frequency of linezolid or tedizolid-resistant/intermediate isolates were 22.61 and 13.04%, respectively, and the frequency of linezolid-resistant/intermediate E. faecalis clinical isolates carrying with erm(A) were 86%. Among the five linezolid-resistant E. faecalis strains found in this study, three optrA-positive isolates and the other two linezolid-resistant strains were G2576U genetic mutations in the V domain of the 23S rRNA genes. The ST clonality analysis indicated that 31.42% (11/35) of ST16 E. faecalis UTI isolates were not susceptible to linezolid. Moreover, the univariable analysis indicated that the high risk factors of linezolid-resistant/intermediate E. faecalis infections involved the indwelling catheter, trachea cannula catheter and the carriage of erm(A) or optrA. Furthermore, the indwelling catheter and trachea cannula catheter were demonstrated as the independent predictors of linezolid-resistant/intermediate E. faecalis strains in patients with UTI by multivariable analysis.

Conclusion: Linezolid-resistant/intermediate E. faecalis associated with urinary tract infections of patients in this hospital setting from China might be explained by the high carriage frequency of optrA genes and moreover, indwelling catheter and trachea cannula should be considered as the independent predictors of linezolid-resistant/intermediate E. faecalis infections. The transmission mechanism of linezolid-resistant/intermediate E. faecalis in this hospital setting should be further studied.

Phenotypic and genotypic characterization of Enterococcus spp. from yolk sac infections in broiler chicks with a focus on virulence factors

Bacterial infections of yolk sacs contribute to increased mortality of chicks, chronic infections during their rearing, or increased selection in the flock, which in turn leads to high economic losses in poultry production worldwide. The aim of this study was a phenotypic and genotypic characterization of enterococci isolated from yolk sac infections (YSI) of broiler chickens from Poland and the Netherlands. Biochemical, matrix-assisted laser desorption/ionization (MALDI)–time-of-flight (TOF) MS, and rpoA gene sequencing identification was performed. Moreover, phenotypic and genotypic characterization of virulence factors and analysis of the clonal relationship of isolates by MALDI-TOF MS and enterobacterial repetitive intergenic consensus—polymerase chain reaction (ERIC-PCR) were performed. The biochemical test identified 70 isolates as Enterococcus faecalis and 6 as Enterococcus mundtii. The results of MALDI-TOF MS were 100% concordant with those obtained by rpoA gene sequencing, and all 76 isolates were identified as E. faecalis. Differences were noted in the β-glucuronidase, β-glucosidase, α-galactosidase, phosphatase, melibiose, lactose, and raffinose tests that is going about the results of biochemical identification. None of the isolates were beta-hemolytic on blood agar in aerobic conditions, but all but one were gelatinase positive. Among biofilm-forming isolates (30/76; 39.5%), as many as 66.7% (20/30) were Polish E. faecalis strains. Most of the isolates carried virulence genes, that is gelE, ace, asa1, efaAfs, fsrA, fsrB, fsrC, cob, cpd, and ccf, but none had the hyl gene. Some isolates harbored cyl operon genes. One Polish strain (ST16) had all of the tested cyl genes and the esp gene, considered clinically important, and showed the highest biofilm-forming ability. Nearly 50% of the isolates showed close genetic relatedness in ERIC typing. In contrast with MALDI-TOF MS cluster analysis, ERIC-PCR results did not show a relationship with the origin of the strains. Using MALDI-TOF MS, 7 peaks were found in Polish and Dutch isolates, which may type them as species-specific biomarkers in E. faecalis from YSI.

Phenotypic and Molecular Characterization of Plasmid-Mediated Virulence and Antimicrobial Resistance Traits among Multidrug Resistant Enterococcus spp. in Egypt

Enterococcus spp. are remarkable multidrug resistant (MDR) bacteria that are causing serious healthcare-associated infections. The current study investigated the frequency of Enterococcus spp., antimicrobial susceptibility, biofilm formation and the presence of some plasmid-mediated virulence characters and antimicrobial resistance determinants in enterococcal isolates from Egyptian hospitals in Cairo. Enterococcus bacterial isolates were recovered from different clinical specimens and identified using biochemical testing and KB005A HiStrep™ identification kit. Kirby-Bauer disc diffusion method and/or broth microdilution method were used to determine the antimicrobial susceptibility patterns. Phenotypic assays were performed to study biofilm formation and cytolysin and gelatinase production. PCR assays targeting the plasmid-carried genes aac(6’)-aph(2’), aph(3)-IIIa, vanA, agg and cylA were performed. In this study, 50 isolates of diverse Enterococcus spp. were identified with E. faecium was the most frequently isolated one. High resistance profiles were determined against tested antimicrobials and all isolates were MDR. Moderate biofilm formation was detected in 20% of isolates, 18% showed complete blood hemolysis and 12% produced gelatinase. All isolates carried the tested aminoglycosides resistance genes, while vanA was found only in 4 isolates (8%). The virulence genes agg and cylA were detected in 4% and 32% of isolates, respectively. In conclusion, E. faecium was the most prevalent species. The entire isolates set were MDR and the plasmid-carried aminoglycoside resistance genes were extensively disseminated among MDR isolates. Thus, regular surveillance studies, from the area of study or other geographical regions in Egypt, and strict infection control measures are required to monitor the emerging MDR enterococci.

Molecular Investigations of Linezolid Resistance in Enterococci OptrA Variants from a Hospital in Shanghai

Purpose

The OptrA protein is a member of ATP-binding cassette (ABC) transporters, a transporter family which can confer resistance to oxazolidinone antibiotics by transferring plasmid. We aim to describe the distribution of optrA-harbored Enterococcus in Huashan hospital in 2017 and to address the effects of optrA mutations on the susceptibility of linezolid antibiotic drug.

Methods

Linezolid-resistance-related genes were tested for Enterococcus by polymerase chain reaction (PCR) and then sequenced for amino acid substitution site analysis. Broth microdilution and agar dilution test were applied to determine the minimal inhibitory concentration (MIC) of linezolid for Enterococcus containing optrA. Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to evaluate the genotypes of optrA-positive isolates. To verify the functions of two main optrA variants, optrA over-expressing strains were constructed.

Results

Among 20 optrA-positive strains, only two were resistant to linezolid. No amino acid substitution existed in 23S rRNA V domain among Enterococcus faecalis. None had cfr, cfr(B) or cfr(C) genes. F101L and G4D/K/R or T150A were the main substitutions of ribosomal protein L4, L3, respectively. We found one Enterococcus faecium isolate co-contained optrA and poxtA and another E. faecalis isolate co-contained optrA and cfr(D), but they were not resistant to linezolid. Among 20 optrA-positive strains, ST-16 was the main type. Two main optrA variants KD (T112K, Y176D) and RDK (I104R, Y176D, E256K) slightly raised enterococci's MIC of linezolid.

Conclusion

OptrA exists in linezolid non-resistant enterococci with diverse amino acid substitutions. The variants play different roles in changing the MIC of linezolid.

Radezolid Is More Effective Than Linezolid Against Planktonic Cells and Inhibits Enterococcus faecalis Biofilm Formation

The aim of this study was to compare the effects of radezolid and linezolid on planktonic and biofilm cells of Enterococcus faecalis. A total of 302 E. faecalis clinical isolates were collected, and the minimum inhibitory concentrations (MICs) of radezolid and linezolid were determined by the agar dilution method. Changes in the transcriptome of a high-level, in vitro-induced linezolid-resistant isolate were assessed by RNA sequencing and RT-qPCR, and the roles of efflux pump-related genes were confirmed by overexpression analysis. Biofilm biomass was evaluated by crystal violet staining and the adherent cells in the biofilms were quantified according to CFU numbers. The MIC₅₀/MIC₉₀ values of radezolid (0.25/0.50 mg/L) against the 302 E. faecalis clinical isolates were eightfold lower than those of linezolid (2/4 mg/L). The radezolid MICs against the high-level linezolid-resistant isolates (linezolid MICs ≥ 64 mg/L) increased to ≥ 4 mg/L with mutations in the four copies of the V domain of the 23S rRNA gene. The mRNA expression level of OG1RF_12220 (mdlB2, multidrug ABC superfamily ATP-binding cassette transporter) increased in the high-level linezolid-resistant isolates, and radezolid and linezolid MICs against the linezolid-sensitive isolate increased with overexpression of OG1RF_12220. Radezolid (at 1/4 or 1/8× the MIC) inhibited E. faecalis biofilm formation to a greater extent than linezolid, which was primarily achieved through the inhibition of ahrC, esp, relA, and relQ transcription in E. faecalis. In conclusion, radezolid is more effective than linezolid against planktonic E. faecalis cells and inhibits biofilm formation by this bacterium.

Antibiotic Susceptibility and Virulence Genes in Enterococcus Isolates from Wild Mammals Living in Tuscany, Italy

Drug resistance is of great importance to human and animal health, but wild environments are still poorly understood in terms of their function as reservoirs of dangerous microbes and resistance determinants. The aim of the study was to determine the antibiotic susceptibility and virulence factors of Enterococcus bacteria from wildlife in Tuscany, Italy. Of the 36 mammalian fecal samples, 52 isolates were derived and classified as Enterococcus faecium (46% of isolates), Enterococcus hirae (19%), Enterococcus faecalis (13%), Enterococcus gallinarum (8%), Enterococcus casseliflavus (6%), Enterococcus durans (4%), Enterococcus mundtii (2%), and Enterococcus canintestini (2%) using both matrix-assisted laser desorption/ionization-time of flight mass spectrometry and methods based on analysis of genetic material. The isolates tested showed the most frequent resistance to tetracycline (36.5% isolates), ciprofloxacin (36.5%), and erythromycin (25%). Three isolates showed high level of resistance (minimal inhibitory concentration ≥1,024 μg/mL) to vancomycin and teicoplanin, and 15% of the isolates demonstrated multidrug resistance. No isolate resistant to ampicillin, linezolid, or streptomycin was found. Among resistance genes, aac(6)-Ii (50% isolates), msrA/B (48%), msrC (42%), and tetM (31%) were identified most frequently. All E. faecium and E. faecalis isolates were positive for the efaAfm and efaAfs genes, respectively. Other virulence-associated genes, that is, gelE, cylA, asa1, esp, ace, orf1481, ptsD, and sgrA, were found in the majority of E. faecalis and several E. faecium isolates. Multilocus sequence typing analysis performed for selected isolates revealed three new sequence types. The results obtained indicate that wild mammals might act as reservoirs of resistance and virulence determinants that could be transferred between different ecosystems.

Emergence of multidrug resistance and extensive drug resistance among enterococcal clinical isolates in Egypt

Introduction

Enterococci commonly inhabit the gastrointestinal tract of both human and animals; however, they have emerged as a leading cause of several infections with substantial morbidity and mortality. Their ability to acquire resistance combined with intrinsic resistance to various antimicrobials makes treatment of enterococcal infections challenging.

Materials and methods

The aim of the study was to evaluate the antimicrobial resistance pattern, and assess the prevalence of multidrug resistance (MDR) and extensive drug resistance (XDR) among enterococcal isolates, collected from different clinical sources, in Mansoura University Hospitals, Egypt.

Results

Antibiotic sensitivity testing revealed elevated levels of resistance among enterococcal clinical isolates (N=103). All E. faecium (N=32) and 74.6% of E. faecalis isolates(N=71) were MDR, while two E. faecalis and four E. faecium isolates were XDR. High level gentamicin resistance was detected in 79.6%, most of them carried the aac(6’)-Ie-aph(2’’)-Ia gene. High level streptomycin resistance was seen in 36.9%, of which 52.6% carried the ant(6’)-Ia gene. Resistance to macrolides and lincosamides were mediated by ermB (92.2%) and msrA/B (42.7%). tetK, tetL, andtetM genes were detected among tetracyclines resistant isolates. Resistance to vancomycin was detected in 15.5%, where vanB and vanC₁ gene clusters were detected in VRE isolates. Ten isolates (9.7%) were resistant to linezolid, eight of which harbored the optrA gene. Vancomycin and linezolid resistant enterococci were more likely to exhibit strong/moderate biofilm formation than vancomycin and linezolid sensitive ones.

Conclusion

Elevated levels of resistance to different classes of antimicrobial agents and emergence of MDR and XDR strains pose a major threat with limited therapeutic options for infections caused by this emerging pathogen.

Incidence of Virulence Determinants Among Enterococcal Clinical Isolates in Egypt and Its Association with Biofilm Formation

Background: Although Enterococci compromise an essential part of normal gut microbiota of both animals and humans, they have emerged as a leading opportunistic pathogen causing infections. The pathogenesis of enterococci is attributed to an array of virulence determinants. Objectives: This study aims to explore the prevalence and characteristics of enterococcal clinical isolates collected from Mansoura University Hospitals, Egypt, assess their ability to form biofilm, and the correlation with virulence determinants and antimicrobial resistance. Materials and Methods: A total of 70 Enterococcal clinical isolates were collected from different clinical sources between June and December 2016. Biofilm formation capacity was assessed, and characterization of virulence factors and antibiotic susceptibility was performed. Clonal relatedness between isolates was assessed using enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) approach. Results and Conclusion: The molecular analysis demonstrated high genetic diversity among enterococcal clinical isolates. The gelE was the most frequently detected gene (91.4%), followed by asa1 (70%), esp (65.7%), and cylA (17.1%), while hyl was not detected in any isolate. Gelatinase activity was detected in 35.7%, while hemolysin and lipase activity was detected in 12.9% and 78.5%, respectively. Most of the enterococcal isolates were biofilm producers, of which 67.1% were strong/moderate biofilm producers. All linezolid-resistant isolates exhibited strong/moderate biofilm formation capacity. Strong/moderate biofilm formation was more frequently observed among esp-positive (esp+) and gelatinase nonproducing (gelatinase-) enterococcal isolates. Multiple regression analysis denoted that esp (odds ratio [OR] 5.371, p = 0.003) and gelatinase production (OR 0.264, p = 0.015) were associated with strong/moderate biofilm formation capacity. These findings suggest that esp gene positivity and gelatinase production may affect biofilm formation capacity among enterococcal clinical isolates.

Quantitative Proteomics Analysis of Membrane Proteins in Enterococcus faecalis With Low-Level Linezolid-Resistance

Despite increasing reports of low-level linezolid-resistant enterococci worldwide, the mechanism of this resistance remains poorly understood. Previous transcriptome studies of low-level linezolid-resistant Enterococcus faecalis isolates have demonstrated a number of significantly up-regulated genes potentially involved in mediation of drug resistance. However, whether the transcriptome faithfully reflects the proteome remains unknown. In this study, we performed quantitative proteomics analysis of membrane proteins in an E. faecalis isolate (P10748) with low-level linezolid-resistance in comparison with two linezolid-susceptible strains 3138 and ATCC 29212, all of which have been previously investigated by whole transcriptome analysis. A total of 8,197 peptides associated with 1,170 proteins were identified in all three isolates with false discovery rate (FDR) at 1% and P < 0.05. There were 14 significantly up-regulated and 6 significantly down-regulated proteins in strain P10748 compared to strains 3138 and ATCC 29212, which were in general positively correlated with transcription levels revealed in previous transcriptome studies. Our analysis suggests that the low-level linezolid-resistance in E. faecalis is conferred primarily by the ATP-binding cassette protein OptrA through ribosomal protection and, possibly, also by the enterococcal surface protein (Esp) and other proteins through biofilm formation. The genetic transfer of optrA is potentially regulated by the surface exclusion protein Sea1, conjugal transfer protein TraB, replication protein RepA and XRE family transcription regulator protein. This report represents the first investigation of the mechanisms of linezolid-resistance in E. faecalis by a quantitative proteomics approach.