Multiple-drug resistant enterococci: the nature of the problem and an agenda for the future

Identification of drug-resistant phenotypes and resistance genes in Enterococcus faecalis isolates from animal feces originating in Xinjiang, People’s Republic of China

This study examined the presence and the antibiotic resistance patterns of Enterococcus faecalis isolated from the feces of 285 animals. Polymerase chain reaction tests verified the presence of E. faecalis from 49 pigs, 20 cows, 174 sheep, 17 horses, 21 chickens, and four dung beetles. Bacterial strains from different animals showed differences in susceptibility and resistance to the tested antimicrobials. The isolates exhibited resistance to ampicillin (6.32%), ciprofloxacin (40.00%), nitrofurantoin (1.40%), erythromycin (54.04%), streptomycin (82.11%), tetracycline (45.26%), amoxicillin (64.91%), penicillin (92.28%), and vancomycin (0.35%). The resistant strains also possessed varying complements of resistance genes including tem (77.89%), tetM (33.68%), gyrA (37.54%), parC (34.74%), aph(3′)-III (22.46%), aac(6′)/aph2″ (10.88%), and ant(6′)-I (8.42%). Genes for vancomycin resistance (vanB and vanC) and erythromycin resistance (mefA) were not detected. These results indicate high levels of antibiotic resistance among the isolates, although no positive correlation was observed between resistance genes and antibiotic resistance spectrum.

Advances and Prospects in Vaccine Development against Enterococci

Enterococci are the second most common Gram-positive pathogen responsible for nosocomial infections. Due to the limited number of new antibiotics that reach the medical practice and the resistance of enterococci to the current antibiotic options, passive and active immunotherapies have emerged as a potential prevention and/or treatment strategy against this opportunistic pathogen. In this review, we explore the pathogenicity of these bacteria and their interaction with the host immune response. We provide an overview of the capsular polysaccharides and surface-associated proteins that have been described as potential antigens in anti-enterococcal vaccine formulations. In addition, we describe the current status in vaccine development against enterococci and address the importance and the current advances toward the development of well-defined vaccines with broad coverage against enterococci.

Upregulation of efrAB efflux pump among Enterococcus faecalis ST480, ST847 in Iran

Antibiotic resistance and especially multiresistance in Enterococci, is a serious public health issue especially in infections of immunocompromised patients. EfrAB is a heterodimeric multidrug ATP-binding cassette (ABC) transporter that causes endogenous resistance to antimicrobials including fluoroquinolones in Enterococcus spp. The aim of this study was to seek the gene expression rate and role of efrAB efflux pump in ciprofloxacin resistant Enterococcus faecalis and Multilocus Sequence Typing (MLST) of multiresistant isolates. Phenotypic and genotyping identification of 80 E. faecalis isolates were performed. Minimum inhibitory concentrations (MICs) to ciprofloxacin (CIP) were measured with and without carbonylcyanide 3-chlorophenylhydrazone (CCCP) by broth microdilution. After DNA extraction and sequencing for detection of efrA and efrB genes, the efrAB efflux positive isolates that were resistant to ciprofloxacin and showed decrease of ciprofloxacin MIC range were identified. Isolates that exhibited decrease in ciprofloxacin MIC range from two to ten folds were assessed for biofilm formation and finally, the expression levels of efrB, efrA genes were measured by quantitative Real-Time PCR (qRT-PCR). High rates of resistance to tetracycline and minocycline and low rates of resistance to the most antibiotics used in this study were detected. The results in this study indicated that the incidence of Multiple drug resistance (MDR) was 23.7% and all isolates that were resistant to ciprofloxacin revealed several degrees of overexpression in efrA and efrB genes. Our study found two ST480 and one ST847 in E. faecalis isolates. In conclusion, despite of low frequency of resistance to the most antibiotics and MDRs in our region, we found one ST480 isolate with resistance to eight antibiotics that also exists in other parts of the world.

Genome-Wide Mutagenesis Identifies Factors Involved in Enterococcus faecalis Vaginal Adherence and Persistence

Enterococcus faecalis is a Gram-positive commensal bacterium native to the gastrointestinal tract and an opportunistic pathogen of increasing clinical concern. E. faecalis also colonizes the female reproductive tract, and reports suggest vaginal colonization increases following antibiotic treatment or in patients with aerobic vaginitis. Currently, little is known about specific factors that promote E. faecalis vaginal colonization and subsequent infection. We modified an established mouse vaginal colonization model to explore E. faecalis vaginal carriage and demonstrate that both vancomycin-resistant and -sensitive strains colonize the murine vaginal tract. Following vaginal colonization, we observed E. faecalis in vaginal, cervical, and uterine tissue. A mutant lacking endocarditis- and biofilm-associated pili (Ebp) exhibited a decreased ability to associate with human vaginal and cervical cells in vitro but did not contribute to colonization in vivo Thus, we screened a low-complexity transposon (Tn) mutant library to identify novel genes important for E. faecalis colonization and persistence in the vaginal tract. This screen revealed 383 mutants that were underrepresented during vaginal colonization at 1, 5, and 8 days postinoculation compared to growth in culture medium. We confirmed that mutants deficient in ethanolamine catabolism or in the type VII secretion system were attenuated in persisting during vaginal colonization. These results reveal the complex nature of vaginal colonization and suggest that multiple factors contribute to E. faecalis persistence in the reproductive tract.

Identification of Enterococcus faecalis in a patient with urinary-tract infection based on metagenomic next-generation sequencing: a case report

Background

Urinary tract infection (UTI) caused by various pathogenic microorganisms is ubiquitous in the parts of the urinary system such as kidney, ureter, bladder, and urethra. Currently, clinical detection of UTI is mainly focused on urine culture; however, the diagnostic value of urine culture remains limited due to the time-consuming procedure and low detection rate, especially in patients who have used antibiotics. Generally, treatment for UTI relies on empirical medication rather than pathogen diagnosis, which leads to the inappropriate use of antimicrobial agents and a significant increase in resistant strains. Comparatively, metagenomic next-generation sequencing (mNGS) is capable of overcoming the disadvantages of clinical culture, and identifying pathogens for further treatment.

Case presentation

A 33-year-old male patient was admitted to hospital with a high fever and chills. None of his autoimmune disease or thyroid function related indicators were positive, and he had no risk of endocarditis. His white blood cell count, C-reactive protein, procalcitonin, interleukin 6, and neutrophil proportion were markedly elevated. He was initially diagnosed as having an infection of unknown etiology. Since empirical treatment of Sulperazon and Metronidazole did not relieve his symptoms, both the blood and urine specimens were examined using traditional culture, serological testing, and mNGS assay. Traditional culture and serological testing produced negative results, while the mNGS assay revealed the presence of a potential pathogen, Enterococcus faecalis, in the urine specimen, which was further confirmed by both Sanger sequencing and qPCR analysis. A CT scan of the patient’s whole abdomen showed stones in the right kidney. Once targeted antibiotic therapy was administered, the patient recovered quickly.

Conclusions

Our case illustrated that mNGS, as a novel culture-independent approach, demonstrated the capability of rapid, sensitive, and accurate pathogen identification. Furthermore, this technology provides strong support for guiding clinicians to determine appropriate treatment.

Structural determinants of macrocyclization in substrate-controlled lanthipeptide biosynthetic pathways

Lanthipeptides are characterized by thioether crosslinks formed by post-translational modifications. The cyclization process that favors a single ring pattern over many other possible ring patterns has been the topic of much speculation. Recent studies suggest that for some systems the cyclization pattern and stereochemistry is determined not by the enzyme, but by the sequence of the precursor peptide. However, the factors that govern the outcome of the cyclization process are not understood. This study presents the three-dimensional structures of seven lanthipeptides determined by nuclear magnetic resonance spectroscopy, including five prochlorosins and the two peptides that make up cytolysin, a virulence factor produced by Enterococcus faecalis that is directly linked to human disease. These peptides were chosen because their substrate sequence determines either the ring pattern (prochlorosins) or the stereochemistry of cyclization (cytolysins). We present the structures of prochlorosins 1.1, 2.1, 2.8, 2.10 and 2.11, the first three-dimensional structures of prochlorosins. Our findings provide insights into the molecular determinants of cyclization as well as why some prochlorosins may be better starting points for library generation than others. The structures of the large and small subunits of the enterococcal cytolysin show that these peptides have long helical stretches, a rare observation for lanthipeptides characterized to date. These helices may explain their pore forming activity and suggest that the small subunit may recognize a molecular target followed by recruitment of the large subunit to span the membrane.

Surveillance of bloodstream infections in intensive care units in England, May 2016-April 2017: epidemiology and ecology

BACKGROUND

Bloodstream infections (BSIs) in patients in intensive care units (ICUs) are associated with increased morbidity, mortality and economic costs. Many BSIs are associated with central venous catheters (CVCs). The Infection in Critical Care Quality Improvement Programme (ICCQIP) was established to initiate surveillance of BSIs in English ICUs.

METHODS

A web-based data capture system was launched on 1^st May 2016 to collect all positive blood cultures (PBCs), patient-days and CVC-days. National Health Service (NHS) trusts in England were invited to participate in the surveillance programme. Data were linked to the antimicrobial resistance dataset maintained by Public Health England and to mortality data.

FINDINGS

Between 1^st May 2016 and 30^th April 2017, 84 ICUs (72 adult ICUs, seven paediatric ICUs and five neonatal ICUs) based in 57 of 147 NHS trusts provided data. In total, 1474 PBCs were reported, with coagulase-negative staphylococci, Escherichia coli, Staphylococcus aureus and Enterococcus faecium being the most commonly reported organisms. The rates of BSI and ICU-associated CVC-BSI were 5.7, 1.5 and 1.3 per 1000 bed-days and 2.3, 1.0 and 1.5 per 1000 ICU-CVC-days in adult, paediatric and neonatal ICUs, respectively. There was wide variation in BSI and CVC-BSI rates within ICU types, particularly in adult ICUs (0-44.0 per 1000 bed-days and 0-18.3 per 1000 ICU-CVC-days).

CONCLUSIONS

While the overall rates of ICU-associated CVC-BSIs were lower than 2.5 per 1000 ICU-CVC-days across all age ranges, large differences were observed between ICUs, highlighting the importance of a national standardized surveillance system to identify opportunities for improvement. Data linkage provided clinically important information on resistance patterns and patient outcomes at no extra cost to participating trusts.

Probiotic Enterococcus faecalis Symbioflor 1 ameliorates pathobiont-induced miscarriage through bacterial antagonism and Th1-Th2 modulation in pregnant mice

The bacterium-bacterium interaction between pathogenic and probiotic Enterococcus as well as the bacterium-host interaction between Enterococcus and intestinal epithelium has drawn increasing attentions, but the influence of those interactions on host pregnancy remains largely unexplored. In the present study, we evaluated the effects of probiotic E. faecalis Symbioflor 1 or/and pathogenic E. faecalis OG1RF on the miscarriage of pregnant mice. Using in vitro assays of competition and exclusion and displacement, antagonistic property of E. faecalis Symbioflor 1 against E. faecalis OG1RF was observed, and the former inhibited the translocation of the later in vivo. The rate of miscarriage induced by E. faecalis OG1RF challenge was significantly reduced by 28% with E. faecalis Symbioflor 1 intervention; and the tissue integrity of ileum, colon, uterus, and placenta and placental blood cell density in pregnant mice were drastically improved by such probiotic intervention. Compared with the controls, probiotic intervention significantly upregulated the level of IL-10 and TGF-β, downregulated levels of IFN-γ, and increased progesterone level that reversed the trend of being Th1 predominance state reported for adverse pregnancy outcome at early pregnancy stage. In conclusion, E. faecalis Symbioflor 1 decreased the translocation of E. faecalis OG1RF, prevented pathogen-induced tissue damage, and changed Th1-Th2 homeostasis toward Th2 predominance during early pregnancy resulting in decreased miscarriage. KEY POINTS: •The mechanism of how probiotic E. faecalis Symbioflor 1 improves pregnancy of mice • Influence of interactions of pathogenic and probiotic Enterococcus on host pregnancy • E. faecalis Symbioflor 1 change Th1-Th2 homeostasis toward Th2 predominance.

Delayed antibiotic exposure induces population collapse in enterococcal communities with drug-resistant subpopulations

The molecular underpinnings of antibiotic resistance are increasingly understood, but less is known about how these molecular events influence microbial dynamics on the population scale. Here, we show that the dynamics of E. faecalis communities exposed to antibiotics can be surprisingly rich, revealing scenarios where increasing population size or delaying drug exposure can promote population collapse. Specifically, we demonstrate how density-dependent feedback loops couple population growth and antibiotic efficacy when communities include drug-resistant subpopulations, leading to a wide range of behavior, including population survival, collapse, or one of two qualitatively distinct bistable behaviors where survival is favored in either small or large populations. These dynamics reflect competing density-dependent effects of different subpopulations, with growth of drug-sensitive cells increasing but growth of drug-resistant cells decreasing effective drug inhibition. Finally, we demonstrate how populations receiving immediate drug influx may sometimes thrive, while identical populations exposed to delayed drug influx collapse.

Antibiotic interactions shape short-term evolution of resistance in E. faecalis

Antibiotic combinations are increasingly used to combat bacterial infections. Multidrug therapies are a particularly important treatment option for E. faecalis, an opportunistic pathogen that contributes to high-inoculum infections such as infective endocarditis. While numerous synergistic drug combinations for E. faecalis have been identified, much less is known about how different combinations impact the rate of resistance evolution. In this work, we use high-throughput laboratory evolution experiments to quantify adaptation in growth rate and drug resistance of E. faecalis exposed to drug combinations exhibiting different classes of interactions, ranging from synergistic to suppressive. We identify a wide range of evolutionary behavior, including both increased and decreased rates of growth adaptation, depending on the specific interplay between drug interaction and drug resistance profiles. For example, selection in a dual β-lactam combination leads to accelerated growth adaptation compared to selection with the individual drugs, even though the resulting resistance profiles are nearly identical. On the other hand, populations evolved in an aminoglycoside and β-lactam combination exhibit decreased growth adaptation and resistant profiles that depend on the specific drug concentrations. We show that the main qualitative features of these evolutionary trajectories can be explained by simple rescaling arguments that correspond to geometric transformations of the two-drug growth response surfaces measured in ancestral cells. The analysis also reveals multiple examples where resistance profiles selected by drug combinations are nearly growth-optimized along a contour connecting profiles selected by the component drugs. Our results highlight trade-offs between drug interactions and resistance profiles during the evolution of multi-drug resistance and emphasize evolutionary benefits and disadvantages of particular drug pairs targeting enterococci.

Scrubs contamination, domestic laundry effect and workwear habits of clinical staff at a referral hospital

OBJECTIVE

To determine contamination rates of scrub suits worn by veterinary surgeons and nurses following a single shift.

MATERIALS AND METHODS

Cross-sectional preliminary study at a UK small animal referral centre. Sterilised scrub suits were distributed to veterinary surgeons (n = 9) and nurses (n = 9) at the beginning of their clinical shift and worn for at least 8 hours. They were then analysed for bacterial contamination before and after home laundry at 30°C. A questionnaire was distributed to hospital clinical staff regarding workwear habits.

RESULTS

Median bacterial counts were 47 (interquartile range: 14 to 162) and 7 (interquartile range: 0 to 27) colony forming units per cm² before and after laundering scrub suits. Bacteria identified included Staphylococcus sp., Enterococcus sp., Escherichia coli , Bacillus sp., Pseudomonas aeruginosa , Micrococcus sp., β-haemolytic Streptococci and a Group G Streptococcus. From 101 staff surveyed, 64.0% reported wearing fresh, clean scrub tops and 58.4% fresh, clean trousers each day, while 64.4% left the workplace wearing the same clothing in which they undertook clinical work.

CLINICAL SIGNIFICANCE

Workwear contamination risks spread of pathogens into the community and personnel compliance with workplace guidelines warrants further attention. Home laundry at 30°C significantly decreases, but does not eliminate, the bacterial burden after a single shift.

Macrolide-susceptible probiotic Enterococcus faecium ST296 exhibits faecal-environmental-oral microbial community cycling among beef cattle in feedlots

Enterococci are included in the United States National Antimicrobial Resistance Monitoring System to track antibiotic resistance among commensal Gram-positive enteric bacteria, largely due to their high abundance in food animals and in retail meat. In the U.S. cattle industry, macrolides are used to prevent and control liver abscesses, which cause significant economic losses. Previous studies have suggested that feeding tylosin and the intensity of the pen environment, both expand and sustain respectively the prevalence of multidrug resistance among enterococci in feedlot cattle. This has led to research into alternative feed supplements and improved stewardship practices. In a randomized controlled trial, we measured the impact of a probiotic and an altered pen environment on antimicrobial resistance among faecal Enterococcus spp. in cattle fed tylosin. Supplementing cattle with an Enterococcus faecium and Saccharomyces cerevisiae-based probiotic yielded the isolation of E. faecium of the probiotic sequence type (ST296) from faecal and environmental samples in treatment groups, as well as from cattle and the manure pack in nearby pens. Of importance, the probiotic strain also was found in a desiccated and milled manure pack sample taken 120 days after the initial trial ended. Phylogenetic and SNP analyses revealed clonal survival and spread compatible with faecal-environmental-oral recycling of the probiotic strain within and among cattle and pens. The increase in prevalence of the ST296 strain occurred concomitant with a decrease in ST240, the dominant sequence type associated with ermB and tet(M) resistance genes in this trial. SIGNIFICANCE AND IMPACT OF THE STUDY: We demonstrate that a macrolide-susceptible probiotic Enterococcus faecium ST296 strain fed to beef cattle becomes fully embedded in the microbial community cycling of bacteria via faecal-environmental-oral transmission within and among feedlot pens. An initial investment in feeding the probiotic is thereby leveraged into expanding numbers of susceptible bacteria in cattle and their environment, even among those cattle fed tylosin.

Development of the Bacterial Spectrum and Antimicrobial Resistance in Surgical Site Infections of Trauma Patients

Background: While ubiquitously multi-resistant bacteria are on the rise, peri-operative antimicrobial prophylaxis in trauma and near-to-bone surgical procedures has only been changed slightly during the last 25 years. Recent clinical studies concerning the bacterial spectrum and efficacy of antimicrobial treatment in infected trauma surgical patients are rare. The aim of the study was analysis of the contemporary bacterial spectrum and its antimicrobial resistance including the assessment of the appropriateness of peri-operative antimicrobial prophylaxis with cefuroxime. Methods: Patients of a level-I academic trauma center who underwent open or arthroscopic surgery because of a recent trauma necessitating the use of bone-near metal implants were included in the study. All patients in whom a surgical site infection (SSI) had developed during six weeks post-operatively necessitating surgical debridement and had positive microbiologic culture results from an intra-operative surgical site swab were analyzed, retrospectively. In particular, age, gender, date and duration of surgical interventions, and patient's related risk factors were collected, and infecting agents and their minimum inhibitory concentration values for 34 selected antimicrobial agents were evaluated. An SSI occurring later than 6 weeks post-operatively and patients with chronic and septic wounds were excluded. Statistical analysis was performed with SPSS^® (IBM, Armonk, NY). Results: There were 438 pathogens cultured in specimens from 303 enrolled patients (female = 140, male = 163). The most frequent pathogens were Staphylococcus aureus (27.1%), S. epidermidis (20.6%), Enterococcus faecalis (13.6%), Escherichia coli (5.1%), and Pseudomonas aeruginosa (3.7%) accounting for 303 isolates. Of those, 89 (29.4%) were multi-resistant. Of the S. epidermidis isolates, 79.8% (n = 71) were resistant against Oxacillin and thus against most beta-lactam antibiotic agents. Altogether, only 44.1% of the infecting organisms were susceptible to cefuroxime, the antimicrobial agent most often being used for prophylactic purposes. Conclusion: Standardized antimicrobial prophylaxis with cephalosporins has to be reconsidered critically. Multi-resistant species such as S. epidermidis are an increasing challenge in trauma operations.

Enterococci used as complementary indicator of fecal contamination to assess water quality from public schools in the city of Curitiba, Paraná, Brazil

Abstract The study evaluated the drinking water quality from 45 public schools in the city of Curitiba, Brazil. Water samples were harvested from two different points at each school: the first one, drinking fountain used by students (n=45) and the second, kitchen faucet (n=45), comprising 90 samples. The samples were submitted to analysis according to current legislation, such as: dosage of free chlorine; colony counts of heterotrophic bacteria; presence of total coliform bacteria and Escherichia coli. In addition, an enterococci analysis was also included as a complementary microbiological indicator of fecal contamination. The isolated strains of enterococci were identified and submitted to an antibiotic susceptibility test. In relation to the legal parameters, 35.5% (n=16) of the 45 schools evaluated did not meet the quality water standards set by the Brazilian legislation. Although none of the 90 samples exhibited the presence Escherichia coli, 6.6% (n=6) of the analyzed samples presented enterococci contamination. Regarding the antibiotic susceptibility test, the isolated strains demonstrated a similar behavior, became resistant to six antibiotics and had intermediate sensitivity to one (Streptomycin) of the nine antibiotics tested. The drinking water destined for human consumption in the public schools may pose health risks for students since the fecal contamination by enterococci was confirmed, and it could be observed that the water may be a source of genes from bacteria resistant to antimicrobials. This study reinforces the importance of monitoring complementary microbiological indicators to assure water quality, seeing that fecal contamination was detected only when alternative parameters were inserted, emphasizing the relevance of including microbiological indicators beyond what the legislation requires to evaluate the drinking water more effectively and to safeguard public health.

Renaissance of vancomycin: approaches for breaking antibiotic resistance in multidrug-resistant bacteria

The emergence of multidrug-resistant bacteria demands innovations in the development of new antibiotics. For decades, the glycopeptide antibiotic vancomycin has been considered as the “last resort” treatment of severe infections caused by Gram-positive bacteria. Since the discovery of the first vancomycin-resistant enterococci strains in the late 1980s, the number of resistances has been steadily rising, with often life-threatening consequences. As an alternative to the generation of completely new substances, novel approaches focus on structural modifications of established antibiotics such as vancomycin to overcome these resistances. Here, we provide an overview of several promising modifications of vancomycin to restore its efficacy against vancomycin-resistant enterococci.

Susceptibility of Nitrofurantoin and Fosfomycin Against Outpatient Urinary Isolates of Multidrug-Resistant Enterococci over a Period of 10 Years from India

With the increasing emergence of drug resistance in enterococci, there have been very limited data on the efficacy of orally available nitrofurantoin and fosfomycin on enterococci causing urinary tract infections (UTIs), particularly for multidrug-resistant (MDR) strains. This study aimed to determine the in vitro effectiveness of these two drugs against the MDR enterococci. A total of 514 phenotypically and genotypically confirmed isolates of enterococci (239, 46.5% Enterococcus faecalis and 275, 53.5% Enterococcus faecium) showed E. faecalis as significantly more resistant (p < 0.05) to ciprofloxacin and high strength gentamicin. Vancomycin resistance was seen in 37 (7.2%) isolates. Of these, 114 (22.18%) isolates (51, 44.73% E. faecalis and 63, 55.26% E. faecium) were MDR. Nitrofurantoin minimum inhibitory concentrations (MICs) for the MDR enterococci varied from 1 to 128 μg/mL (MIC₅₀ 8 μg/mL, MIC₉₀ 64 μg/mL for E. faecalis), while fosfomycin MICs for the MDR E. faecalis, including vancomycin resistant enterococci (VRE) were in susceptible range (≤64 μg/mL, MIC₅₀ 8 μg/mL, MIC₉₀ 16 μg/mL). An efficacy ratio of ≥8 for nitrofurantoin was observed in the 39 (76.5%) MDR E. faecalis and 44 (69.8%) MDR E. faecium isolates as against the 50 (98%) E. faecalis isolates for fosfomycin. Although nitrofurantoin has been widely prescribed for the treatment of UTIs for the past several years, it was still found to be active in vitro against the urinary isolates of MDR enterococci, including VRE. As for fosfomycin, it holds robust potential to be used against the urinary MDR enterococci and VRE (E. faecalis).

Maternal-neonatal transmission of Enterococcus strains during delivery

Background

Cesarean delivery (c-section) is on the rise globally. C-section is generally preferred if complications prevail in a vaginal delivery. Some private institutions conduct it unnecessarily for economic gains. This has led to a severe risk to a child’s health. The neonate’s gut microbiota has been observed to be influenced by the mode of delivery. Lactobacilli and other bacteria are very vital for developing healthy gut flora. An attempt has been made to investigate the passage of lactic acid bacteria to the infant via delivery. The vaginal swabs of the mothers and fresh meconium samples of the newborns post-delivery were examined for the presence of lactobacilli through culture techniques.

Results

The present investigation revealed that c-section-delivered infants lacked these bacteria in comparison with vaginally delivered infants. Biochemical tests and 16S rRNA sequencing showed similarity with groups 1, 2, 3, and 5 of Enterococcus genus. Phylogenetic analysis revealed more than 98% similarity with several Enterococcus species. E. canintestini, E.rivorum, and E. dispar were transferred frequently from mother to infants born via vaginal delivery. The strains were submitted to the NCBI GenBank database under accession numbers KX830968–KX830982.

Conclusion

The study supports the hypothesis of maternal-neonatal transmission of bacteria during delivery and also possibilities of isolating newer strains for probiotic use.

Assessing the intestinal carriage rates of vancomycin-resistant enterococci (VRE) at a tertiary care hospital in Hungary

Excessive use of antibiotics contributes to the selection of resistant bacteria and intestinal colonization with multiresistant pathogens poses a risk factor for subsequent infections. The present study assessed vancomycin-resistant enterococci (VRE) carriage rates in patients admitted to our tertiary care hospital. Stool samples sent for routine culturing were screened with vancomycin containing solid or broth enrichment media. VRE isolates were identified with matrix-assisted laser desorption/ionization-time of flight mass spectrometry and antibiotic susceptibilities were tested by E-test. Vancomycin resistance genes were detected by polymerase chain reaction. Medical records of carriers were examined for suspected risk factors for colonization. Altogether 3025 stool specimens were analyzed. Solid media identified a VRE carriage rate of 2.2% while broth enrichment detected 5.8%. Seventy percent of the isolates were Enterococcus faecium. VanB genotype was detected in 38.2%, VanA in 37.3%, VanC1 in 22.6%, and VanC2 in 1.9%. All VRE were sensitive to linezolid, daptomycin, and tigecycline. Collective risk factors for carriage were diabetes, normal flora absence, Clostridioides difficile positivity, longer hospital stay, and advanced age. 78.5% of the carriers received antibiotic therapy which was metronidazole in most cases (47.3%). We recommend regular screening of risk groups such as patients with diabetes, history of recent hospitalization, or former C. difficile infection as an imperative step for preventing VRE dissemination.

Peritonitis from Anaerobic Gram-positive Cocci Likely Due to Translocation of Bacteria from Gut in a Patient Undergoing Peritoneal Dialysis

Peritonitis is a severe complication encountered in patients undergoing peritoneal dialysis, often causing high morbidity and mortality. High vigilance is required from healthcare providers involved in the management of these patients to prevent this complication. There has been recognition of peritonitis caused by unusual organisms because of improved microbiological detection techniques. Gram-positive organisms are the frequent cause of peritonitis compared to Gram-negative organisms. We report a rare case of peritonitis caused by Enterococcus avium. A 60-year-old male on peritoneal dialysis presented with palpitations, abdominal pain, diarrhea, and cloudy effluent. The peritoneal fluid analysis was consistent with peritonitis, and peritoneal fluid culture grew E. avium. The patient was treated with linezolid after failing to respond to vancomycin. The peritoneal dialysis catheter was removed, and the dialysis modality has been switched to hemodialysis because of refractory peritonitis.

Novel linezolid resistance plasmids in Enterococcus from food animals in the USA

Objectives

To sequence the genomes and determine the genetic mechanisms for linezolid resistance identified in three strains of Enterococcus isolated from cattle and swine caecal contents as part of the US National Antimicrobial Resistance Monitoring System (NARMS) surveillance programme.

Methods

Broth microdilution was used for in vitro antimicrobial susceptibility testing to assess linezolid resistance. Resistance mechanisms and plasmid types were identified from data generated by WGS on Illumina® and PacBio® platforms. Conjugation experiments were performed to determine whether identified mechanisms were transmissible.

Results

Linezolid resistance plasmids containing optrA were identified in two Enterococcus faecalis isolates and one Enterococcus faecium. The E. faecium isolate also carried the linezolid resistance gene cfr on the same plasmid as optrA. The linezolid resistance plasmids had various combinations of additional resistance genes conferring resistance to phenicols (fexA), aminoglycosides [spc and aph(3')-III] and macrolides [erm(A) and erm(B)]. One of the plasmids was confirmed to be transmissible by conjugation, resulting in linezolid resistance in the transconjugant.

Conclusions

To the best of our knowledge, this is the first identification of linezolid resistance in the USA in bacteria isolated from food animals. The oxazolidinone class of antibiotics is not used in food animals in the USA, but the genes responsible for resistance were identified on plasmids with other resistance markers, indicating that there may be co-selection for these plasmids due to the use of different antimicrobials. The transmissibility of one of the plasmids demonstrated the potential for linezolid resistance to spread horizontally. Additional surveillance is necessary to determine whether similar plasmids are present in human strains of Enterococcus.

Pervasive and diverse collateral sensitivity profiles inform optimal strategies to limit antibiotic resistance

Evolved resistance to one antibiotic may be associated with "collateral" sensitivity to other drugs. Here, we provide an extensive quantitative characterization of collateral effects in Enterococcus faecalis, a gram-positive opportunistic pathogen. By combining parallel experimental evolution with high-throughput dose-response measurements, we measure phenotypic profiles of collateral sensitivity and resistance for a total of 900 mutant-drug combinations. We find that collateral effects are pervasive but difficult to predict because independent populations selected by the same drug can exhibit qualitatively different profiles of collateral sensitivity as well as markedly different fitness costs. Using whole-genome sequencing of evolved populations, we identified mutations in a number of known resistance determinants, including mutations in several genes previously linked with collateral sensitivity in other species. Although phenotypic drug sensitivity profiles show significant diversity, they cluster into statistically similar groups characterized by selecting drugs with similar mechanisms. To exploit the statistical structure in these resistance profiles, we develop a simple mathematical model based on a stochastic control process and use it to design optimal drug policies that assign a unique drug to every possible resistance profile. Stochastic simulations reveal that these optimal drug policies outperform intuitive cycling protocols by maintaining long-term sensitivity at the expense of short-term periods of high resistance. The approach reveals a new conceptual strategy for mitigating resistance by balancing short-term inhibition of pathogen growth with infrequent use of drugs intended to steer pathogen populations to a more vulnerable future state. Experiments in laboratory populations confirm that model-inspired sequences of four drugs reduce growth and slow adaptation relative to naive protocols involving the drugs alone, in pairwise cycles, or in a four-drug uniform cycle.

Global prevalence of antibiotic resistance in blood-isolated Enterococcus faecalis and Enterococcus faecium: a systematic review and meta-analysis

INTRODUCTION

One of the global concerns is the increasing trend toward antimicrobial resistance and the consequent lack of efficient antimicrobials. Nosocomial infections present a big threat for patients all over the world and treatment with broad-spectrum antibiotics leads to outgrowth of hospital-associated resistant Enterococci clones that are very important in bloodstream infections. We surveyed the frequency and time trend of antibiotic resistance in Enterococci blood isolates from hospitalized patients in different regions of the world.

METHODS

Literature from January 1, 2000 to May 20, 2018 was searched systematically using Medline (via PubMed), Embase, and Cochrane Library and all original publications on the antibiotic resistance prevalence in blood-isolated Enterococci strains with standard laboratory tests were included. Quality of the included studies was assessed with the modified Critical Appraisal Checklist recommended by the Joanna Briggs Institute. Depending on the heterogeneity test, we used either random or fixed effect models to assess the appropriateness of the pooled prevalence of drug resistance.

RESULTS

A total of 291 studies were enrolled in the meta-analysis. Between all antibiotics, based on the WHO original offices, American countries showed the lowest prevalence of resistance for linezolid in Enterococcus faecalis. Regarding the prevalence of vancomycin resistance, Western Pacific, European, and American countries had the lowest level of resistance and South-East Asia and Eastern Mediterranean countries showed the highest level of resistance. Moreover, our findings for Enterococcus faecium indicated that America and South-East Asia had the lowest and the highest levels of resistance for linezolid, respectively.

CONCLUSION

Based on our findings, the prevalence of vancomycin-resistant E. faecium in bloodstream infections is significantly high, especially in Eastern Mediterranean countries, which is a massive warning signal for resistance to this broad-spectrum antibiotic. Therefore, the establishment of appropriate antibiotic usage guidelines should be essential in these countries.

A novel synthesis of trans-unsaturated fatty acids by the Gram-positive commensal bacterium Enterococcus faecalis FA2-2

A key mechanism of Pseudomonas spp. adaptation to environmental stressors is their ability to convert the cis-unsaturated fatty acids of the membrane lipids to their trans-isomers to rigidify the membrane and thereby resist stresses. Although this Cti-catalyzed enzymatic isomerization has been well investigated in the P. putida paradigm, several bacterial species have been found to produce trans-unsaturated fatty acids. Although cti orthologs have only been reported in Gram-negative bacteria, we report that E. faecalis FA2-2 cultures synthesize trans-unsaturated fatty acids during growth by a mechanism similar of P. putida. Although the role of trans-unsaturated fatty acids (trans-UFAs) in E. faecalis remains obscure, our results indicate that organic solvents, as well as the membrane altering antibiotic, daptomycin, had no effect on trans-UFA formation in E. faecalis FA2-2. Moreover trans-UFA production in E. faecalis FA2-2 membranes was constant in oxidative stress conditions or when metal chelator EDTA was added, raising the question about the role of heme domain in cis-trans isomerization in E. faecalis FA2-2. Although growth temperature and growth phase had significant effects on cis-trans isomerization, the bulk physical properties of the membranes seems unlikely to be altered by the low levels of trans-UFA. Hence, any effects seems likely to be on membrane proteins and membrane enzyme activities. We also report investigations of cti gene distribution in bacteria was and suggest the distribution to be triggered by habitat population associations. Three major Cti clusters were defined, corresponding to Pseudomonas, Pseudoalteromonas and Vibrio Cti proteins.

In search of novel protein drug targets for treatment of Enterococcus faecalis infections

Enterococcus faecalis (Ef) is one of the major pathogens involved in hospital-acquired infections. It can cause nosocomial bacteremia, surgical wound infection, and urinary tract infection. It is important to mention here that Ef is developing resistance against many commonly occurring antibiotics. The occurrence of multidrug resistance (MDR) and extensive-drug resistance (XDR) is now posing a major challenge to the medical community. In this regard, to combat the infections caused by Ef, we have to look for an alternative. Rational structure-based drug design exploits the three-dimensional structure of the target protein, which can be unraveled by various techniques such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. In this review, we have discussed the complete picture of Ef infections, the possible treatment available at present, and the alternative treatment options to be explored. This study will help in better understanding of novel biological targets against Ef and the compounds, which are likely to bind with these targets. Using these detailed structural informations, rational structure-based drug design is achievable and tight inhibitors against Ef can be prepared.

Pathogenicity of Enterococci

Enterococci are unusually well adapted for survival and persistence in a variety of adverse environments, including on inanimate surfaces in the hospital environment and at sites of infection. This intrinsic ruggedness undoubtedly played a role in providing opportunities for enterococci to interact with other overtly drug-resistant microbes and acquire additional resistances on mobile elements. The rapid rise of antimicrobial resistance among hospital-adapted enterococci has rendered hospital-acquired infections a leading therapeutic challenge. With about a quarter of a genome of additional DNA conveyed by mobile elements, there are undoubtedly many more properties that have been acquired that help enterococci persist and spread in the hospital setting and cause diseases that have yet to be defined. Much remains to be learned about these ancient and rugged microbes, particularly in the area of pathogenic mechanisms involved with human diseases.

N-Methylation of Amino Acids in Gelatinase Biosynthesis-Activating Pheromone Identifies Key Site for Stability Enhancement with Retention of the Enterococcus faecalis fsr Quorum Sensing Circuit Response

The growing prevalence of multiantibiotic-resistant bacteria necessitates looking at potential alternative approaches for attenuating infections by bacteria while reducing the rate of antibiotic resistance development. Enterococcus faecalis is responsible for a large percentage of clinical enterococci infections, and its pathogenicity has been demonstrated to be influenced by quorum sensing (QS). In this study, we report the systematic study of the relationship between backbone hydrogens and the ability to activate the FsrC receptor. We demonstrate that N-methylation was particularly well-tolerated at one site (Phe7) and granted stability against protease digestion, increasing the peptide half-life relative to the native signal by more than 6-fold. The inclusion of the N-Me-Phe7 modification may be useful for improving the pharmacological properties of E. faecalis QS inhibitors as part of the development of future therapeutic candidates.

Reciprocal Regulation of PASTA Kinase Signaling by Differential Modification

Transmembrane Ser/Thr kinases containing extracellular PASTA (penicillin-binding protein [PBP] and Ser/Thr-associated) domains are ubiquitous among Actinobacteria and Firmicutes species. Such PASTA kinases regulate critical bacterial processes, including antibiotic resistance, cell division, cell envelope homeostasis, and virulence, and are sometimes essential for viability. Previous studies of purified PASTA kinase fragments revealed they are capable of autophosphorylation in vitro, typically at multiple sites on the kinase domain. Autophosphorylation of a specific structural element of the kinase known as the activation loop is thought to enhance kinase activity in response to stimuli. However, the role of kinase phosphorylation at other sites is largely unknown. Moreover, the mechanisms by which PASTA kinases are deactivated once their stimulus has diminished are poorly understood. Enterococcus faecalis is a Gram-positive intestinal bacterium and a major antibiotic-resistant opportunistic pathogen. In E. faecalis, the PASTA kinase IreK drives intrinsic resistance to cell wall-active antimicrobials, and such antimicrobials trigger enhanced phosphorylation of IreK in vivo Here we identify multiple sites of phosphorylation on IreK and evaluate their function in vivo and in vitro While phosphorylation of the IreK activation loop is required for kinase activity, we found that phosphorylation at a site distinct from the activation loop reciprocally modulates IreK activity in vivo, leading to diminished activity (and diminished antimicrobial resistance). Moreover, this site is important for deactivation of IreK in vivo upon removal of an activating stimulus. Our results are consistent with a model in which phosphorylation of IreK at distinct sites reciprocally regulates IreK activity in vivo to promote adaptation to cell wall stresses.IMPORTANCE Transmembrane Ser/Thr kinases containing extracellular PASTA domains are ubiquitous among Actinobacteria and Firmicutes species and regulate critical processes, including antibiotic resistance, cell division, and cell envelope homeostasis. Previous studies of PASTA kinase fragments revealed autophosphorylation at multiple sites. However, the functional role of autophosphorylation and the relative impacts of phosphorylation at distinct sites are poorly understood. The PASTA kinase of Enterococcus faecalis, IreK, regulates intrinsic resistance to antimicrobials. Here we identify multiple sites of phosphorylation on IreK and show that modification of IreK at distinct sites reciprocally regulates IreK activity and antimicrobial resistance in vivo Thus, these results provide new insights into the mechanisms by which PASTA kinases can regulate critical physiological processes in a wide variety of bacterial species.

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.

Bloodstream infections with vancomycin-resistant enterococci are associated with a decreased survival in patients with hematological diseases

Enterococcus species are commensals of the human gastrointestinal tract with the ability to cause invasive infections. For patients with hematological diseases, enterococcal bloodstream infections (BSI) constitute a serious clinical complication which may even be aggravated if the pathogen is vancomycin-resistant. Therefore, we analyzed the course of BSI due to vancomycin-susceptible enterococci (VSE) in comparison to vancomycin-resistant enterococci (VRE) on patient survival. In this retrospective single-center study, BSI were caused by VRE in 47 patients and by VSE in 43 patients. Baseline patient characteristics were similar in both groups. Concerning infection-related characteristics, an increased CRP value and an increased rate of prior colonization with multidrug-resistant organisms were detected in the VRE BSI group. More enterococcal invasive infections were found in the VSE group. The primary endpoint, overall survival (OS) at 30 days after BSI, was significantly lower in patients with VRE BSI compared to patients with VSE BSI (74.5% vs. 90.7%, p = 0.039). In a multivariate regression analysis, VRE BSI and a Charlson comorbidity index higher than 4 were independent factors associated with 30-day mortality. Moreover, we found that VRE with an additional teicoplanin resistance showed a trend towards an even lower OS.

Ceftriaxone Administration Disrupts Intestinal Homeostasis, Mediating Noninflammatory Proliferation and Dissemination of Commensal Enterococci

Enterococci are Gram-positive commensals of the mammalian intestinal tract and harbor intrinsic resistance to broad-spectrum cephalosporins. Disruption of colonization resistance in humans by antibiotics allows enterococci to proliferate in the gut and cause disseminated infections. In this study, we used Enterococcus faecalis (EF)-colonized mice to study the dynamics of enterococci, commensal microbiota, and the host in response to systemic ceftriaxone administration. We found that the mouse model recapitulates intestinal proliferation and dissemination of enterococci seen in humans. Employing a ceftriaxone-sensitive strain of enterococci (E. faecalis JL308), we showed that increased intestinal abundance is critical for the systemic dissemination of enterococci. Investigation of the impact of ceftriaxone on the mucosal barrier defenses and integrity suggested that translocation of enterococci across the intestinal mucosa was not associated with intestinal pathology or increased permeability. Ceftriaxone-induced alteration of intestinal microbial composition was associated with transient increase in the abundance of multiple bacterial operational taxonomic units (OTUs) in addition to enterococci, for example, lactobacilli, which also disseminated to the extraintestinal organs. Collectively, these results emphasize that ceftriaxone-induced disruption of colonization resistance and alteration of mucosal homeostasis facilitate increased intestinal abundance of a limited number of commensals along with enterococci, allowing their translocation and systemic dissemination in a healthy host.

Rational Design of Potent Activators and Inhibitors of the Enterococcus faecalis Fsr Quorum Sensing Circuit

The increasing rate of resistance development to conventional antibiotics by bacteria necessitates the identification of alternative treatment possibilities that can reduce the ability of bacteria to adapt. Enterococcus faecalis remains the leading cause of clinical enterococci infections and has exhibited quorum sensing (QS)-dependent pathogenicity. Here, we report the development of macrocyclic peptide-based activators and inhibitors of the E. faecalis Fsr QS circuitry. To this end, we developed, optimized, and compared three synthetic routes for lactone-containing macrocyclic peptide scaffolds. We then utilized previous and current structure-activity relationship (SAR) insights of the native QS signaling peptide to rationally design the most potent activators and inhibitors of the Fsr QS circuitry identified to date. The application of these peptides could provide a means to attenuate the pathogenicity of E. faecalis without introducing significant selective pressure on the bacteria to develop resistance.

Exploring bioactive peptides from bacterial secretomes using PepSAVI-MS: identification and characterization of Bac-21 from Enterococcus faecalis pPD1

As current methods for antibiotic drug discovery are being outpaced by the rise of antimicrobial resistance, new methods and innovative technologies are necessary to replenish our dwindling arsenal of antimicrobial agents. To this end, we developed the PepSAVI-MS pipeline to expedite the search for natural product bioactive peptides. Herein we demonstrate expansion of PepSAVI-MS for the discovery of bacterial-sourced bioactive peptides through identification of the bacteriocin Bac-21 from Enterococcus faecalis pPD1. Minor pipeline modifications including implementation of bacteria-infused agar diffusion assays and optional digestion of peptide libraries highlight the versatility and wide adaptability of the PepSAVI-MS pipeline. Additionally, we have experimentally validated the primary protein sequence of the active, mature Bac-21 peptide for the first time and have confirmed its identity with respect to primary sequence and post-translational processing. Successful application of PepSAVI-MS to bacterial secretomes as demonstrated herein establishes proof-of-principle for use in novel microbial bioactive peptide discovery.

Synergistic Effect of Newly Introduced Root Canal Medicaments; Ozonated Olive Oil and Chitosan Nanoparticles, Against Persistent Endodontic Pathogens

This study was conducted to investigate the antimicrobial-biofilm activity of chitosan (Ch-NPs), silver nanoparticles (Ag-NPs), ozonated olive oil (O3-oil) either separately or combined together against endodontic pathogens. While testing the antimicrobial activity, Ch-NPs showed the least minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values exerting eightfold higher bactericidal activity than O3-oil against both Enterococcus faecalis and Streptococcus mutans as well as fourfold higher fungicidal activity against Candida albicans. Antimicrobial synergy test revealed synergism between O3-oil and Ch-NPs against the test pathogens (FIC index ≤ 0.5). Ch-NPs was superior at inhibiting immature single and mixed-species biofilm formations by 97 and 94%, respectively. Both of O3-oil and Ch-NPs had a complete anti-fibroblast adherent effect. The safety pattern results showed that O3-oil was the safest compound, followed by Ch-NPs. The double combination of Ch-NPs and O3-oil reduced the mature viable biofilm on premolars ex vivo model by 6-log reductions, with a fast kill rate, indicating potential use in treating root canals. Therefore, the double combination has the potential to eradicate mature mixed-species biofilms and hence it is potent, novel and safe.

Antibacterial gold nanoparticle-based photothermal killing of vancomycin-resistant bacteria

Aim: The extensive use of vancomycin has given rise to vancomycin-resistant bacterial strains, such as vancomycin-resistant Enterococci (VRE). We aim to explore potent medical treatments that can inhibit the growth of VRE. Materials & methods: Vancomycin-immobilized gold nanoparticles (Au@Van NPs) with polygonal shapes from one-pot reactions were generated within approximately 7 min. Results & discussion: The as-prepared Au NPs exhibit not only antibacterial capability but also photothermal competence. The temperature of the sample solution containing the as-prepared Au@Van NPs can be raised by approximately 15°C under irradiation by a near-infrared laser (λ = 808 nm) within 5 min. Conclusion: The required amount of vancomycin on the as-prepared Au@Van NPs combined with near-infrared irradiation for inhibiting VRE is approximately 16-fold lower than that of free-form vancomycin.

Identification and characterization of an endolysin - Like from Bacillus subtilis

Drug-resistant Gram-positive pathogens have been a rising risk in hospitals and food industries from the last decades. Here in, the potential of endolysin production in Dasht Desert Bacterial Culture Collection (DDBCC), against indicator bacteria, was investigated. DDBCC was screened against autoclaved-indicator bacteria; Streptococcus faecalis, Streptococcus pyogenes, Bacillus sp, Bacillus subtilis and Staphylococcus aureus as the substrates for the endolysin enzymes. The endolysins were produced in BHI medium followed by ammonium sulfate purification. Peptidoglycan hydrolytic activity was tested by zymogram method. Lysogenic bacteria were induced by 0.1 μg/ml mitomycin C for bacteriophages extraction. The lysogenic bacteria inhibited S. pyogenes, S. faecalis, Bacillus sp. and B. subtilis. The strain DDBCC10 was selected for further experiments on its higher and specific activity against the cell wall of S. faecalis. The highest activity for the endolysin was obtained at 50-60% ammonium sulfate saturation as 8 U/ml. Lys10, a 22 kDa enzyme, digested the cell wall of S. faecalis in 15 min while the whole phage from DDBCC10 could form plaque on S. faecalis and S. pyogenes. In a Transmission Electron Microscopy assay (TEM), the phage was distinguished as a member of Siphoviridae. Here; Lys10 is introduced as a new biocontrol agent against S. faecalis for therapeutics, disinfection, and food preservatives purposes at a much lower expense than recombinant endolysins.

Khan A, M. Alamshany Z, Gull M, S. Azam E, A. Kosa S, Tahir Soomro M. Synthesis, Electrochemical and Antimicrobial Activity of Colloidal Copper Nanoparticles

ABSTRACT: The colloidal dispersion of copper nanoparticles (CuNPs), prepared by reducing Cu2+ ions using ascorbic acid, was characterized and used for electrochemical and antimicrobial activity investigations. By depositing CuNPs onto the glassy carbon electrode (GCE) surface the CuNPs/GCE was constructed, which was used to study electrochemical behavior of CuNPs and to carry out direct electrochemical detection of trichloroacetic acid (TCA) and 2-chlorophenol (2-CP) in neutral medium. Excellent electrocatalytic ability of CuNPs, assessed by cyclic voltammetry (CV), for the reduction of TCA and 2-CP was detected. The electrochemical impedance analysis (EIS) of the GCE and CuNPs modified GCE evidenced higher charge transfer activity across the modified electrode surface. The antibacterial activity tests of as-synthesized CuNPs on the selected pathogenic strains of pathogenic strains of Salmonella group B (7.9±0.912), Klebsiella pneumonia (8.33±1.561), Escherichia Coli (15.65±1.612), Enterococcus faecalis (5.4±0.612), Staphylococcus aureus (12.6±1.531) and yeast Candida albicans (11.4.3±1.512), respectively, were performed. The results indicated that the use of CuNPs can be pursued as an alternative strategy (to antibiotics) for averting infections by controlling bacterial adhesion and bacterial bio-film formation against microbial infections.

Enterococci and Their Interactions with the Intestinal Microbiome

The Enterococcus genus comprises over 50 species that live as commensal bacteria in the gastrointestinal (GI) tracts of insects, birds, reptiles, and mammals. Named "entero" to emphasize their intestinal habitat, Enterococcus faecalis and Enterococcus faecium were first isolated in the early 1900s and are the most abundant species of this genus found in the human fecal microbiota. In the past 3 decades, enterococci have developed increased resistance to several classes of antibiotics and emerged as a prevalent causative agent of health care-related infections. In U.S. hospitals, antibiotic use has increased the transmission of multidrug-resistant enterococci. Antibiotic treatment depletes broad communities of commensal microbes from the GI tract, allowing resistant enterococci to densely colonize the gut. The reestablishment of a diverse intestinal microbiota is an emerging approach to combat infections caused by antibiotic-resistant bacteria in the GI tract. Because enterococci exist as commensals, modifying the intestinal microbiome to eliminate enterococcal clinical pathogens poses a challenge. To better understand how enterococci exist as both commensals and pathogens, in this article we discuss their clinical importance, antibiotic resistance, diversity in genomic composition and habitats, and interaction with the intestinal microbiome that may be used to prevent clinical infection.

A Novel Biomimetic Nanosponge Protects the Retina from the Enterococcus faecalis Cytolysin

Endophthalmitis is a serious, potentially blinding infection that can result in vision loss, leaving a patient with only the ability to count fingers, or it may require enucleation of the globe. The incidence of postoperative endophthalmitis has markedly increased over the past 2 decades, paralleling the rise in ocular surgeries and intravitreal therapies. E. faecalis is a leading cause of infection following ocular procedures, and such infections are increasingly difficult to treat due to multidrug resistance. Cytolysin is the primary virulence factor responsible for retinal tissue damage in E. faecalis eye infections. Treatment of these infections with antibiotics alone does not impede ocular damage and loss of visual function. Pore-forming toxins (PFTs) have been established as major virulence factors in endophthalmitis caused by several bacterial species. These facts establish a critical need for a novel therapy to neutralize bacterial PFTs such as cytolysin. Here, we demonstrate that biomimetic nanosponges neutralize cytolysin, protect the retina, preserve vision, and may provide an adjunct detoxification therapy for bacterial infections.

Intraocular infections are a potentially blinding complication of common ocular surgeries and traumatic eye injuries. Bacterial toxins synthesized in the eye can damage intraocular tissue, often resulting in poor visual outcomes. Enteroccocus faecalis causes blinding infections and is responsible for 8 to 17% of postoperative endophthalmitis cases. These infections are increasingly difficult to treat due to the emergence of multidrug-resistant strains. Virulent E. faecalis isolates secrete a pore-forming bicomponent cytolysin that contributes to retinal tissue damage during endophthalmitis. We hypothesized that a biomimetic nanosponge, which mimics erythrocytes, might adsorb subunits of the cytolysin and reduce retinal damage, protecting vision. To test the efficacy of nanosponges in neutralizing the cytolysin in vitro, hemoglobin release assays were performed on culture supernatants from cytolysin-producing E. faecalis with and without preincubation with nanosponges. Treatment with nanosponges for 30 min reduced hemolytic activity by ~70%. To determine whether nanosponges could neutralize the cytolysin in vivo, electroretinography was performed on mice 24 h after intravitreal injection with cytolysin-containing supernatants treated with nanosponges. Pretreatment of cytolysin-containing supernatants with nanosponges increased the A-wave retention from 12.2% to 65.5% and increased the B-wave retention from 21.0% to 77.0%. Histology revealed that in nanosponge-treated eyes, retinas remained intact and attached, with little to no damage. Rabbit nanosponges were also nontoxic and noninflammatory when injected into mouse eyes. In an experimental murine model of E. faecalis endophthalmitis, injection of nanosponges into the vitreous 6 h after infection with a wild-type cytolysin-producing strain increased A-wave retention from 5.9% to 31% and increased B-wave retention from 12.6% to 27.8%. Together, these results demonstrated that biomimetic nanosponges neutralized cytolysin activity and protected the retinas from damage. These results suggest that this novel strategy might also protect eyes from the activities of pore-forming toxins of other virulent ocular bacterial pathogens.

IMPORTANCE Endophthalmitis is a serious, potentially blinding infection that can result in vision loss, leaving a patient with only the ability to count fingers, or it may require enucleation of the globe. The incidence of postoperative endophthalmitis has markedly increased over the past 2 decades, paralleling the rise in ocular surgeries and intravitreal therapies. E. faecalis is a leading cause of infection following ocular procedures, and such infections are increasingly difficult to treat due to multidrug resistance. Cytolysin is the primary virulence factor responsible for retinal tissue damage in E. faecalis eye infections. Treatment of these infections with antibiotics alone does not impede ocular damage and loss of visual function. Pore-forming toxins (PFTs) have been established as major virulence factors in endophthalmitis caused by several bacterial species. These facts establish a critical need for a novel therapy to neutralize bacterial PFTs such as cytolysin. Here, we demonstrate that biomimetic nanosponges neutralize cytolysin, protect the retina, preserve vision, and may provide an adjunct detoxification therapy for bacterial infections.

Draft Genome Sequences of Eight Streptogramin-Resistant Enterococcus Species Isolated from Animal and Environmental Sources in the United States

Here, we present the draft genome sequences of eight streptogramin-resistant Enterococcus species isolated from animals and an environmental source in the United States from 2001 to 2004. Antimicrobial resistance genes were identified conferring resistance to the macrolide-lincosamide-streptogramins, aminoglycosides, tetracyclines, beta-lactams, and glycopeptides.

Gram-Positive Uropathogens, Polymicrobial Urinary Tract Infection, and the Emerging Microbiota of the Urinary Tract

Gram-positive bacteria are a common cause of urinary-tract infection (UTI), particularly among individuals who are elderly, pregnant, or who have other risk factors for UTI. Here we review the epidemiology, virulence mechanisms, and host response to the most frequently isolated Gram-positive uropathogens: Staphylococcus saprophyticus, Enterococcus faecalis, and Streptococcus agalactiae. We also review several emerging, rare, misclassified, and otherwise underreported Gram-positive pathogens of the urinary tract including Aerococcus, Corynebacterium, Actinobaculum, and Gardnerella. The literature strongly suggests that urologic diseases involving Gram-positive bacteria may be easily overlooked due to limited culture-based assays typically utilized for urine in hospital microbiology laboratories. Some UTIs are polymicrobial in nature, often involving one or more Gram-positive bacteria. We herein review the risk factors and recent evidence for mechanisms of bacterial synergy in experimental models of polymicrobial UTI. Recent experimental data has demonstrated that, despite being cleared quickly from the bladder, some Gram-positive bacteria can impact pathogenic outcomes of co-infecting organisms. When taken together, the available evidence argues that Gram-positive bacteria are important uropathogens in their own right, but that some can be easily overlooked because they are missed by routine diagnostic methods. Finally, a growing body of evidence demonstrates that a surprising variety of fastidious Gram-positive bacteria may either reside in or be regularly exposed to the urinary tract and further suggests that their presence is widespread among women, as well as men. Experimental studies in this area are needed; however, there is a growing appreciation that the composition of bacteria found in the bladder could be a potentially important determinant in urologic disease, including susceptibility to UTI.

An Entirely Solid Phase Peptide Synthesis-Based Strategy for Synthesis of Gelatinase Biosynthesis-Activating Pheromone (GBAP) Analogue Libraries: Investigating the Structure-Activity Relationships of the Enterococcus faecalis Quorum Sensing Signal

The development of an entirely solid-phase peptide synthesis (SPPS)-based synthesis of the quorum sensing signal gelatinase biosynthesis-activating pheromone (GBAP) from Enterococcus faecalis is reported. The method was used to prepare three libraries of analogues to investigate the structure-activity relationships (SARs) of the GBAP signal. The SAR studies revealed new characteristics of the GBAP signal and uncovered the most potent quorum sensing activator in E. faecalis known to date.