Relationships between enterococcal virulence and antimicrobial resistance

Molecular Analysis of Enterococcus Faecalis Isolates in a 4-year Period

In the present research, we aimed to determine the characteristics of E. faecalis strains collected from an Iranian Children's Hospital for four years. Sixty-seven E. faecalis isolates with virulence genes detection, variable-number tandem repeat (VNTR), and multiple-locus variable-number tandem repeat analysis (MLVA) typing were investigated. A high frequency of virulence genes belonged to gelatinase (73%) and Enterococcus faecalis (62%). The MLVA of 67 E. faecalis isolates revealed 52 VNTR patterns and 38 MLVA types (MTs). Furthermore, genetic diversities with the majority of the MT1 as a major MT in different Wards of the Children's Hospital were found.

Risk factors of enterococcal bacteriuria in cats: A retrospective study

Objective

To determine if factors associated with urothelial damage and inflammation, including urinary catheterization, urinary obstruction, and urolithiasis are associated with the presence of enterococcal bacteriuria in cats.

Animals

Thirty-one cats with Enterococcus spp. bacteriuria and 31 cats with Escherichia coli bacteriuria.

Procedure

A retrospective case-control study with cases and controls identified by records search for Enterococcus spp. (case) and E. coli (control) bacteriuria from August 1, 2014 to July 31, 2019. Cases and controls were balanced with respect to average age. Binary logistic regression was used to estimate and test whether the odds of having Enterococcus spp. bacteriuria (instead of E. coli) were associated with the presence of any characteristic.

Results

Urinary catheterization, urinary obstruction, and urolithiasis were not observed more often in Enterococcus cases versus E. coli controls (19% versus 25%, P = 0.543; 19% versus 32%, P = 0.244; and 16% versus 16%, P = 1, respectively). Signs of lower urinary tract disease were significantly less common in Enterococcus cases than in E. coli controls (OR: 0.30; 95% CI: 0.10 to 0.83, P = 0.02). Hematuria was significantly less common in cases than controls (P = 0.048).

Conclusion

No association was identified between urinary catheterization, urolithiasis, or any other comorbidities (hyperthyroidism, chronic kidney disease) and enterococcal bacteriuria in cats.

Clinical relevance

Unlike in humans and dogs, urothelial damage and inflammation caused by factors such as urinary catheterization and urolithiasis may not be the mechanism for enterococcal bacteriuria in cats.

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

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

In Vivo Antibacterial Activity of Acetazolamide

Vancomycin-resistant enterococci (VRE) represent a major public health threat that requires the development of new therapeutics. In the present study, acetazolamide (AZM) was evaluated against enterococci. It inhibited different enterococcal strains tested at clinically achievable concentrations. Moreover, AZM outperformed linezolid, the drug of choice for VRE infections, in two in vivo VRE mouse models-murine colonization-reduction and VRE septicemia. Collectively, these results indicate that AZM warrants consideration as a promising treatment option for VRE infections.

Characterization of an Enterococcus faecium strain in a murine mastitis model

AIM

The aim of the study was to characterize phenotypically and genotypically Enterococcus faecium strains collected from bovine mastitis milk and to evaluate one of them for its virulence in a murine mastitis model.

METHODS AND RESULTS

A total of five E. faecium isolates were collected from cows with subclinical mastitis. EF-7A showed resistance to antibiotics tested, it presented alpha haemolysin and did not present gelatinase activity. It yielded cyA, efafm and gelE1 genes and it could be characterized as a moderate biofilm producer. It was able to internalize in MAC-T cells and 1×10⁸ colony forming unit ml^-1 was able to establish an intramammary infection in mice. The strain could be recovered from liver, kidney and blood samples. RAPD profiles showed different bands with respect to the inoculated strain. Histopathology analyses showed different grades of polymorphonuclear neutrophils infiltration in mammary glands.

CONCLUSION

This is the first report that studied E. faecium strain in a lactating mouse model of mastitis and showed that the experimental inoculation was able to stimulate an inflammatory response resulting in mastitis. Results contribute to a better understanding of intramammary infections caused by E. faecium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This investigation shows that mice represent a valuable model for the study of the mastitis pathogenesis caused by E. faecium considering the high costs of using cows for mastitis research.

Enterococci: Between Emerging Pathogens and Potential Probiotics

Enterococci are ubiquitous microorganisms that could be found everywhere; in water, plant, soil, foods, and gastrointestinal tract of humans and animals. They were previously used as starters in food fermentation due to their biotechnological traits (enzymatic and proteolytic activities) or protective cultures in food biopreservation due to their produced antimicrobial bacteriocins called enterocins or as probiotics, live cells with different beneficial characteristics such as stimulation of immunity, anti-inflammatory activity, hypocholesterolemic effect, and prevention/treatment of some diseases. However, in the last years, the use of enterococci in foods or as probiotics caused an important debate because of their opportunistic pathogenicity implicated in several nosocomial infections due to virulence factors and antibiotic resistance, particularly the emergence of vancomycin-resistant enterococci. These virulence traits of some enterococci are associated with genetic transfer mechanisms. Therefore, the development of new enterococcal probiotics needs a strict assessment with regard to safety aspects for selecting the truly harmless enterococcal strains for safe applications. This review tries to give some data of the different points of view about this question.

Probiotic Potential and Safety Evaluation of Enterococcus faecalis OB14 and OB15, Isolated From Traditional Tunisian Testouri Cheese and Rigouta, Using Physiological and Genomic Analysis

Lactic acid bacteria (LAB) strains OB14 and OB15 were isolated from traditional Tunisian fermented dairy products, Testouri cheese and Rigouta, respectively. They were identified as Enterococcus faecalis by the MALDI TOF-MS (matrix assisted laser desorption-ionization time of flight mass spectrometry) biotyper system and molecular assays (species-specific PCR). These new isolates were evaluated for probiotic properties, compared to E. faecalis Symbioflor 1 clone DSM 16431, as reference. The bacteria were found to be tolerant to the harsh conditions of the gastrointestinal tract (acidity and bile salt). They were low to moderate biofilm producers, can adhere to Caco-2/TC7 intestinal cells and strengthen the intestinal barrier through the increase of the transepithelial electrical resistance (TER). Susceptibility to ampicillin, vancomycin, gentamicin and erythromycin has been tested using the broth microdilutions method. The results demonstrated that E. faecalis OB14 and OB15 were sensitive to the clinically important ampicillin (MIC = 1 μg/mL) and vancomycin (MIC = 2 μg/mL) antibiotics. However, Whole Genome Sequencing (WGS) showed the presence of tetracycline resistance and cytolysin genes in E. faecalis OB14, and this led to high mortality of Galleria Mellonella larvae in the virulence test. Hierarchical cluster analysis by MALDI TOF-MS biotyper showed that E. faecalis OB15 was closely related to the E. faecalis Symbioflor 1 probiotic strain than to OB14, and this has been confirmed by WGS using the average nucleotide identity (ANI) and Genome-to-Genome Hybridization similarity methods. According to these results, E. faecalis OB15 seems to be reliable for future development as probiotic, in food or feed industry.

Characterization and anti-salmonella activities of lactic acid bacteria isolated from cattle faeces

Background

Non typhoidal salmonellosis is one of the neglected zoonoses in most African countries. The use of sub-therapeutic doses of antibiotics as animal growth promoter enhances the emergence and dissemination of antimicrobial resistance in bacteria with food animal reservoirs and may also results in antibiotics residue in animal products. One promising alternative to antibiotics in animal feed is Lactic Acid Bacteria (LAB) as probiotics. This study was carried out to determine the anti-salmonella activities and suitability of LAB isolated from cattle faeces in Nigeria as potential probiotics in cattle feed.

Method

The test Salmonella enterica spp strains and LAB were isolated from cattle faeces and identified by MALDI-TOF MS and partial sequencing of 16S rRNA genes respectively. The anti-salmonella activities of the isolated LAB in co-culture, cell-free supernatant, inhibition of growth by viable LAB cells and quantification of organic acids were determined by standard techniques. The ability of the LAB strains to withstand gastric conditions, antibiotic susceptibility and their haemolytic ability on blood agar were also determined.

Results

A total of 88 LAB belonging to 15 species were isolated and identified from cattle faeces. The most abundant species were Streptococcus infantarius (26), Enterococcus hirae (12), Lactobacillus amylovorus (10), Lactobacillus mucosae (10) and Lactobacillus ingluviei (9). Most of the LAB strains showed good anti-salmonella activities against the test Salmonella enterica spp. with 2 Lactobacillus strains; Lactobacillus amylovorus C94 and Lactobacillus salivarius C86 exhibiting remarkable anti-salmonella activities with total inhibition of Salmonella spp after 18 hours of co-incubation. The selected strains were able to survive simultaneous growth at pH 3 and 7% bile concentration and are non hemolytic.

Conclusion

This study reports the vast diversity of culturable LAB in cattle faeces from Nigeria and their putative in-vitro antibacterial activity against Salmonella enterica spp isolated from cattle. Lactobacillus amylovorus C94 and Lactobacillus salivarius C86 demonstrated promising probiotic potentials in-vitro and will be further tested in-vivo in animal field trial.

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.

Spread of Vancomycin-Resistant Enterococcus faecium Isolates Despite Validated Infection Control Measures in an Italian Hospital: Antibiotic Resistance and Genotypic Characterization of the Endemic Strain

An alarming increase of vancomycin-resistant Enterococcus faecium (VREfm) isolates was detected in an Italian referral hospital subjected to policies of infection control validated by the Joint Commission International. Analysis of the population structure of 122 consecutive, nonreplicate VREfm isolates collected over an 18-month period identified a single major clone that spread around the whole hospital, rapidly establishing an endemic state. It belonged to sequence type (ST) 17 and showed a highly multidrug-resistant phenotype, being resistant to all antimicrobial classes for the carriage of several resistance determinants. Furthermore, some strains with decreased susceptibility to daptomycin were detected. Eighteen out of the 122 isolates did not group in the major clone. They showed a low spreading potential inside the hospital wards, even if most of them displayed a multidrug-resistant phenotype and belonged to a hospital-adapted lineage. Causes that led to the VREfm endemic state have not been fully elucidated. However, it is conceivable that the increase in systemic antibiotic consumption and the use of selective digestive tract decontamination, including vancomycin in critically ill patients during the period before 2014, may have played a role in the ST17 clone dissemination, but additional traits conferring high fitness in hospital environment cannot be excluded.

Antimicrobial resistance patterns and virulence factors of enterococci isolates in hospitalized burn patients

OBJECTIVE

The objective of this study was to determine the frequency of the antimicrobial resistance and genes encoding virulence factors of enterococci isolated in hospitalized burn patients in a major burn center in Ahvaz, southwest of Iran. A total of 340 bacterial isolates were collected from the burn center from February 2014 to February 2015. The antimicrobial susceptibility and MIC of vancomycin were determined using the disk diffusion and micro-agar dilution techniques. The genus and species-specific genes, potential virulence genes, and vanA and vanB genes were detected by polymerase chain reaction.

RESULTS

According to our results, out of the 340 bacterial isolates, 16.4% (n = 56) were identified as enterococci. Out of the 56 enterococcal isolates, 35 (62.5%) were Enterococcus faecalis and 21 (37.5%) were Enterococcus faecium. More than 20% (n = 5) of E. faecium demonstrated resistance to vancomycin. The gelE and asa genes were the most prevalent virulence genes in E. faecalis (48.5%) and E. faecium (43%) isolates. The emergence of vancomycin resistant E. faecium strains which have several virulence factors should be considered as a major cause of concern for burn centers. Control and management of infections induced by enterococci should be regarded as highly important in burn patients.

Streptococcus gordonii pheromone s.g.cAM373 may influence the reservoir of antibiotic resistance determinants of Enterococcus faecalis origin in the oral metagenome

Streptococcus gordonii produces a pheromone heptapeptide, s.g.cAM373, which induces a conjugative mating response in Enterococcus faecalis cells carrying the responsive plasmid, pAM373. We investigated the extent of this intergeneric signaling on DNA acquisition by streptococcal species likely to cohabit oral biofilms. E. faecalis/pAM373/pAMS470 cells were incubated with synthetic s.g.cAM373, reverse peptide s.g.cAM373-R, or peptide-free medium and examined for their abilities to transfer plasmid DNA to streptococcal species in the presence of DNase. Preinduction of E. faecalis donors with s.g.cAM373 resulted in transconjugation frequencies in non-pheromone producing strains of Streptococcus mutans, Streptococcus sanguinis, Streptococcus anginosus, and Streptococcus suis that were significantly higher than frequencies when donors were preincubated with s.g.cAM373-R or medium alone. Peptide-mediated communication between commensal streptococci and E. faecalis carrying pheromone-responsive plasmids may facilitate conjugative DNA transfer to bystander species, and influence the reservoir of antibiotic resistance determinants of enterococcal origin in the oral metagenome.

Virulence and Antibiotic Resistance of Enterococci Isolated from Healthy Breastfed Infants

Pathogenic ability has been extensively studied in clinical enterococci, but to a lesser extent in community-derived ones. Most studies to date in enterococci from healthy infants have been focused on Enterococcus faecalis, despite the growing concern about nosocomial infections caused by E. faecium. In this work, we studied the antibiotic resistance and virulence determinants of 26 E. faecalis and 15 E. faecium intestinal isolates from Spanish healthy breastfed infants. Overall, commensal enterococci studied contained antibiotic resistance and virulence genes, although their patterns were not according to those described for antibiotic-resistant hospital-associated enterococci. None of the isolates was resistant to vancomycin, although the majority showed resistance to some antibiotics. E. faecalis isolates harbored considerably more virulence determinants than E. faecium isolates, but some genes linked to colonization were abundant in both species. Hemolysin activity was not detected in any of the isolates; and the gelatinase gene, when present, was silent in E. faecium, whereas gelatinase activity occurred in half of the E. faecalis isolates studied. These results suggest an ambivalent role of some virulence determinants as elements of pathogenesis.

Effect of Vancomycin, Tylosin, and Chlortetracycline on Vancomycin-Resistant Enterococcus faecium Colonization of Broiler Chickens During Grow-Out

Broiler chickens may serve as reservoirs for human colonization by vancomycin-resistant Enterococcus (VRE). We examined the effects of vancomycin and two commonly used antimicrobial feed additives on VRE colonization in broiler chickens during grow-out. Chicks received unsupplemented feed or feed containing vancomycin, chlortetracycline, or tylosin from day of hatch to grow-out at 6 weeks. At 3 days of age, chicks received by crop gavage 10⁷ colony-forming units (CFUs) of a human or poultry VRE isolate. Cecal contents were monitored weekly for VRE, short-chain fatty acids (SCFAs), and bacterial denaturing gradient gel electrophoresis (DGGE) profile methods. Vancomycin promoted persistent and high-level colonization with human- and poultry-derived VRE to grow-out in comparison with controls, while treatment with chlortetracycline and tylosin did not. Colonization by the poultry isolate in control, chlortetracycline, and tylosin groups persisted throughout the grow-out period with low concentrations present at 6 weeks, whereas the human isolate decreased to an undetectable level by week 6. Vancomycin resulted in significant reductions in cecal acetic acid and butyric acid in comparison with controls, but chlortetracycline and tylosin did not. DGGE profiles contained two main clusters with all vancomycin profiles in a smaller cluster and all other profiles in a larger cluster. These results demonstrate that vancomycin, but not chlortetracycline or tylosin, disrupted the indigenous microbiota and SCFA patterns of broiler chickens and promoted colonization by VRE.

Effect of bioactive dental adhesive on periodontal and endodontic pathogens

The objectives of this study were to: (1) develop a new bioactive dental bonding agent with nanoparticles of amorphous calcium phosphate and dimethylaminohexadecyl methacrylate for tooth root caries restorations and endodontic applications, and (2) investigate biofilm inhibition by the bioactive bonding agent against eight species of periodontal and endodontic pathogens for the first time. Bonding agent was formulated with 5 % of dimethylaminohexadecyl methacrylate. Nanoparticles of amorphous calcium phosphate at 30 wt% was mixed into adhesive. Eight species of biofilms were grown on resins: Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Parvimonas micra, Enterococcus faecalis, Enterococcus faecium. Colony-forming units, live/dead assay, biomass, metabolic activity and polysaccharide of biofilms were determined. The results showed that adding dimethylaminohexadecyl methacrylate and nanoparticles of amorphous calcium phosphate into bonding agent did not decrease dentin bond strength (P > 0.1). Adding dimethylaminohexadecyl methacrylate reduced the colony-forming units of all eight species of biofilms by nearly three orders of magnitude. The killing efficacy of dimethylaminohexadecyl methacrylate resin was: P. gingivalis > A. actinomycetemcomitans > P. intermedia > P. nigrescens > F. nucleatum > P. micra > E. faecalis > E. faecium. Dimethylaminohexadecyl methacrylate resin had much less biomass, metabolic activity and polysaccharide of biofilms than those without dimethylaminohexadecyl methacrylate (P < 0.05). In conclusion, a novel dental adhesive was developed for root caries and endodontic applications, showing potent inhibition of biofilms of eight species of periodontal and endodontic pathogens, and reducing colony-forming units by three orders of magnitude. The bioactive adhesive is promising for tooth root restorations to provide subgingival margins with anti-periodontal pathogen capabilities, and for endodontic sealer applications to combat endodontic biofilms.

CRISPR-Cas and Restriction-Modification Act Additively against Conjugative Antibiotic Resistance Plasmid Transfer in Enterococcus faecalis

Enterococcus faecalis is a bacterium that normally inhabits the gastrointestinal tracts of humans and other animals. Although these bacteria are members of our native gut flora, they can cause life-threatening infections in hospitalized patients. Antibiotic resistance genes appear to be readily shared among high-risk E. faecalis strains, and multidrug resistance in these bacteria limits treatment options for infections. Here, we find that CRISPR-Cas and restriction-modification systems, which function as adaptive and innate immune systems in bacteria, significantly impact the spread of antibiotic resistance genes in E. faecalis populations. The loss of these systems in high-risk E. faecalis suggests that they are immunocompromised, a tradeoff that allows them to readily acquire new genes and adapt to new antibiotics.

Enterococcus faecalis is an opportunistic pathogen and a leading cause of nosocomial infections. Conjugative pheromone-responsive plasmids are narrow-host-range mobile genetic elements (MGEs) that are rapid disseminators of antibiotic resistance in the faecalis species. Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas and restriction-modification confer acquired and innate immunity, respectively, against MGE acquisition in bacteria. Most multidrug-resistant E. faecalis isolates lack CRISPR-Cas and possess an orphan locus lacking cas genes, CRISPR2, that is of unknown function. Little is known about restriction-modification defense in E. faecalis. Here, we explore the hypothesis that multidrug-resistant E. faecalis strains are immunocompromised. We assessed MGE acquisition by E. faecalis T11, a strain closely related to the multidrug-resistant hospital isolate V583 but which lacks the ~620 kb of horizontally acquired genome content that characterizes V583. T11 possesses the E. faecalis CRISPR3-cas locus and a predicted restriction-modification system, neither of which occurs in V583. We demonstrate that CRISPR-Cas and restriction-modification together confer a 4-log reduction in acquisition of the pheromone-responsive plasmid pAM714 in biofilm matings. Additionally, we show that the orphan CRISPR2 locus is functional for genome defense against another pheromone-responsive plasmid, pCF10, only in the presence of cas9 derived from the E. faecalis CRISPR1-cas locus, which most multidrug-resistant E. faecalis isolates lack. Overall, our work demonstrated that the loss of only two loci led to a dramatic reduction in genome defense against a clinically relevant MGE, highlighting the critical importance of the E. faecalis accessory genome in modulating horizontal gene transfer. Our results rationalize the development of antimicrobial strategies that capitalize upon the immunocompromised status of multidrug-resistant E. faecalis.

IMPORTANCEEnterococcus faecalis is a bacterium that normally inhabits the gastrointestinal tracts of humans and other animals. Although these bacteria are members of our native gut flora, they can cause life-threatening infections in hospitalized patients. Antibiotic resistance genes appear to be readily shared among high-risk E. faecalis strains, and multidrug resistance in these bacteria limits treatment options for infections. Here, we find that CRISPR-Cas and restriction-modification systems, which function as adaptive and innate immune systems in bacteria, significantly impact the spread of antibiotic resistance genes in E. faecalis populations. The loss of these systems in high-risk E. faecalis suggests that they are immunocompromised, a tradeoff that allows them to readily acquire new genes and adapt to new antibiotics.

Evaluation of technological properties of Enterococcus faecium CECT 8849, a strain isolated from human milk, for the dairy industry

In this work, a variety of biochemical properties of Enterococcus faecium CECT 8849, which had been isolated from breast milk, were analyzed. Its acidifying capacity and proteolytic activity were low but, in contrast, remarkable peptidase and esterase activities were observed. Ethanol and 3-hydroxy-2-butanone were the most abundant volatile compounds found in experimental model cheese manufactured with E. faecium CECT 8849. This strain inhibited the growth of several Listeria monocytogenes and Listeria innocua strains in vitro. Enterocin A and B structural genes were detected in E. faecium CECT 8849. Model fermented milk and cheeses were manufactured from milk inoculated or not with L. innocua CECT 8848 (2.5-3 log10 colony forming units mL(-1)) using E. faecium CECT 8849 or Lactococcus lactis ESI 153 as starter cultures. Although E. faecium CECT 8849 controlled Listeria growth in both dairy models, it led to lower reduction in Listeria counts when compared with L. lactis ESI 153.

Virulence Genes among Enterococcus faecalis and Enterococcus faecium Isolated from Coastal Beaches and Human and Nonhuman Sources in Southern California and Puerto Rico

Most Enterococcus faecalis and E. faecium are harmless to humans; however, strains harboring virulence genes, including esp, gelE, cylA, asa1, and hyl, have been associated with human infections. E. faecalis and E. faecium are present in beach waters worldwide, yet little is known about their virulence potential. Here, multiplex PCR was used to compare the distribution of virulence genes among E. faecalis and E. faecium isolated from beaches in Southern California and Puerto Rico to isolates from potential sources including humans, animals, birds, and plants. All five virulence genes were found in E. faecalis and E. faecium from beach water, mostly among E. faecalis. gelE was the most common among isolates from all source types. There was a lower incidence of asa1, esp, cylA, and hyl genes among isolates from beach water, sewage, septage, urban runoff, sea wrack, and eelgrass as compared to human isolates, indicating that virulent strains of E. faecalis and E. faecium may not be widely disseminated at beaches. A higher frequency of asa1 and esp among E. faecalis from dogs and of asa1 among birds (mostly seagull) suggests that further studies on the distribution and virulence potential of strains carrying these genes may be warranted.

Effect of Tulathromycin on Colonization Resistance, Antimicrobial Resistance, and Virulence of Human Gut Microbiota in Chemostats

To evaluate microbiological safety of tulathromycin on human intestinal bacteria, tulathromycin (0, 0.1, 1, 10, and 100 μg/mL) was added into Chemostats. Before and after drug exposure, we monitored (1) population, SCFA products, antimicrobial resistance, and colonization resistance of gut microbiota, and (2) the antimicrobial resistance genes, transferability, virulent genes, pathogenicity of Enterococus faecalis. Results showed that low level of tulathromycin did not exhibit microbiological hazard on resistance selection and colonization resistance. However, high level of tulathromycin (10 and 100 μg/mL) may disturb colonization resistance of human gut microbiota and select antimicrobial resistant E. faecalis. Most of the selected resistant E. faecalis carried resistant gene of ermB, transferable element of Tn1545 and three virulence genes (esp, cylA, and ace). One of them (E. faecalis 143) was confirmed to have higher horizontal transfer risk and higher pathogenicity. The calculated no observable adverse effect concentration (NOAEC) and microbiological acceptable daily intake (mADI) in our study was 1 μg/mL and 14.66 μg/kg.bw/day, respectively.

Killing of VRE Enterococcus faecalis by commensal strains: Evidence for evolution and accumulation of mobile elements in the absence of competition

Enterococci are members of the gastrointestinal tract of humans and most animals that, over the past 3 decades, have emerged as leading causes of multidrug resistant hospital acquired infection (HAI). In addition to their general hardiness, many traits have entered enterococcal lineages through horizontal gene transfer, which has led to the evolution of pathogenic hospital-associated lineages uniquely adapted for survival and proliferation in the antibiotic perturbed ecology of the gastrointestinal tract. We recently observed that the accretion of mobile genetic elements in the prototype vancomycin resistant E. faecalis, clinical isolate V583, renders it unable to co-exist with native enterococci in healthy human fecal flora. In this addendum, we discuss how these findings inform our understanding of how multidrug resistant enterococci evolve, and the implications for the development of treatments that limit colonization and spread of highly antibiotic refractory microbes of this type.

Incidence of virulence determinants in clinical Enterococcus faecalis and Enterococcus faecium isolates collected in Bulgaria

Objectives

To evaluate the prevalence of some virulence genes among 510 clinical Enterococcus spp. isolates and to assess the association of those genes with the species, infection site, and patient group (inpatients/outpatients).

Methods

Adhesins genes (aggregation substances agg and asa1 of Enterococcus faecalis and Enterococcus faecium, respectively), enterococcal surface protein (esp), endocarditis-specific antigen A (efaA), collagen-binding proteins (ace/acm)); invasins (hyaluronidase (hyl) and gelatinase (gelE)); cytotoxines (activation of cytolysin (cylA) in E. faecalis); and modulators of the host immunity and inflammation (enhanced expression pheromone (eep) in E. faecalis) were detected by polymerase chain reaction.

Results

The overall prevalence was: esp – 44.3%, agg/asa1 – 38.4%, ace/acm – 64.3%, efaA – 85.9%, eep – 69.4%, gelE – 64.3%, hyl – 25.1%, and cylA – 47.1%. E. faecalis isolates had significantly higher frequency of adhesin genes (esp and agg/asa1) and gelatinase in comparison to E. faecium. Multiple virulence genes in E. faecalis were significantly more prevalent than in E. faecium isolates. Domination of E. faecium with or without only one gene compared to the isolates of E. faecalis were found. Enterococcus spp. isolates obtained from outpatients compared to inpatients isolates had significantly higher frequency of agg/asa1, eep, gelE and cylA. Some adhesins genes (esp, agg/asa1 and efaA) had higher prevalence among the non-invasive Enterococcus spp. isolates compared to those causing invasive bacteremia, while ace/acm revealed higher dissemination in isolates causing invasive infections compared to non-invasive isolates.

Conclusion

Most E. faecalis attaches to abiotic surfaces in hospital environment, which correlates with higher prevalence of gene encoding for virulence factors involved in biofilm formation, such as enterococcal surface protein, aggregation substance, and gelatinase. The intestinal tract is an important reservoir for opportunistic enterococcal pathogens and allows them to access infectious sites through different virulence factors, demonstrated in outpatient isolates in this study.

Characteristic and susceptibility to enterocins of enterococci in pheasants possessing virulence factor genes

With an increasing number of pheasants as gamebirds being reared each year, these species are becoming a more prominent part of the workload of many veterinary practices. Only limited information can be found concerning the microflora of common pheasants. A significant part of the obligate microflora consists of lactic acid bacteria, including enterococci. In this study, faeces were sampled from 60 pheasants aged 16-17 weeks. Enterococcal counts reached 5.48±1.9 (log10) CFU/g. Strains (17) were taxonomically classified to the genus Enterococcus using the Maldi-Tof identification system; they were allotted to the species E. hirae (58.8%), E. faecium (23.5%) and E. faecalis (17.7%) by highly probable species identification or by secure genus identification/probable species identication. Species allocation was also confirmed using conventional biochemical tests. Most strains formed β-hemolysis. Gelatinase active phenotype was found in three E. faecalis strains. Enterococci were β-glucuronidase negative, mostly trypsin negative with slight or moderate production of α-chymotrypsin. EH52b and EF42 strains possessed the highest potential for pathogenicity. Average value of lactic acid was 1.78±0.33 mmo/L. Most strains were tetracycline resistant (82.4%). Polyresistant E. faecalis strains with positive gelatinase phenotype and possessing virulence factor genes confirmed using PCR (gelE, efaAfs, ccf cob, cpd) were sensitive to enterocins (activity 1600-25,600 AU/mL).

Draft Genome Sequence of Probiotic Enterococcus faecium Strain L-3

We report here the draft genome sequence of the bacteriocin producer Enterococcus faecium strain L-3, isolated from a probiotic preparation, Laminolact, which is widely used in the Russian Federation. The draft genome sequence is composed of 74 contigs for a total of 2,643,001 bp, with 2,646 coding genes. Five clusters for bacteriocin production were found.

Antimicrobial resistance and virulence factor gene profiles of Enterococcus spp. isolates from wild Arctocephalus australis (South American fur seal) and Arctocephalus tropicalis (Subantarctic fur seal)

Enterococci are natural inhabitants of the gastrointestinal tracts in humans and animals. Epidemiological data suggest that enterococci are important reservoirs of antimicrobial resistant genes that may be transmitted from other bacterial species The aim of this study was to investigate the species composition, antimicrobial resistance and virulence genes in enterococci recovered from fecal samples of wild Arctocephalus australis and A. tropicalis found dead along the South Coast of Brazil. From a total of 43 wild fur seals, eleven were selected for this study. Phenotypic and genotypic characterizations were used to classify Enterococcus species. Strains were tested for susceptibility to 10 antibiotics, presence of ace, gelE, asa, cylA, tet(L), tet(M) and erm(B) genes by PCR, and genetic variability using RAPD-PCR. Among the 50 enterococci isolated, 40% were Enterococcus faecalis, 40% E. hirae, 12% E. casseliflavus and 8 % other enterococcal species. Resistance profiles were observed to erythromycin, nitrofurantoin, tetracycline, norfloxacin and ciprofloxacin. The prevalence of virulence genes was ace (68%), gelE (54%), asa (22%) and cylA (4%). In erythromycin- and tetracycline strains, erm(B) and tet(M) were detected, respectively. The RAPD-PCR demonstrated a close phylogenetic relationship between the enterococci isolated from A. australis and A. tropicalis. In conclusion, different enterococcus species showing antimicrobial resistance and virulence determinates were isolated from fecal samples of fur seals. Antibiotic resistant strains in these animals could be related within food chain and aquatic pollutants or linked to environmental resistome, and demonstrates the potential importance of these animals as reservoirs and disseminators of such determinants in marine environmental.

Prevalence of Virulence Factors and Drug Resistance in Clinical Isolates of Enterococci: A Study from North India

Along with emergence of multidrug resistance, presence of several virulence factors in enterococci is an emerging concept. This study was undertaken to determine the prevalence of various virulence factors phenotypically and genotypically in enterococci and study their association with multidrug resistance. A total of 310 enterococcal isolates were studied, comprising 155 E. faecium and 155 E. faecalis. Antimicrobial susceptibility testing was done by disc diffusion and agar dilution method. Hemolysin, gelatinase, biofilm production, and haemagglutination were detected phenotypically and presence of virulence genes, namely, asa1, gelE, cylA, esp, and hyl, was detected by multiplex PCR. Of the total, 47.41% isolates were high level gentamicin resistant (HLGRE) and 7.09% were vancomycin resistant (VRE). All the virulence traits studied were found in varying proportions, with majority in E. faecalis (p > 0.05). Strong biofilm producers possessed either asa1 or gelE gene. gelE silent gene was detected in 41.37% (12/29). However, increase in resistance was associated with significant decrease in expression or acquisition of virulence genes. Further, acquisition of vancomycin resistance was the significant factor responsible for the loss of virulence traits. Though it is presumed that increased drug resistance correlates with increased virulence, acquisition of vancomycin resistance might be responsible for reduced expression of virulence traits to meet the “biological cost” relating to VRE.

Avaliação da suscetibilidade antimicrobiana de bactérias anaeróbias facultativas isoladas de canais radiculares de dentes com insucesso endodôntico frente aos antibióticos de uso sistêmico

<title>Resumo</title><sec><title>Introdução</title><p>Bactérias associadas ao insucesso do tratamento endodôntico são capazes de adquirir e expressar resistência aos agentes antimicrobianos comumente empregados para tratar infecções, o que torna necessário, em determinadas situações, a realização de testes laboratoriais para detectar a resistência ou a suscetibilidade antimicrobiana desses micro-organismos.</p></sec><sec><title>Objetivo</title><p>avaliar a suscetibilidade antimicrobiana das cepas de <italic>Enterococcus faecalis</italic>, <italic>Enterococcus faecium</italic>, <italic>Actinomyces viscosus</italic> e <italic>Staphylococcus aureus</italic> isoladas de canais radiculares de dentes com insucesso endodôntico.</p></sec><sec><title>Material e método</title><p>Cepas clínicas de <italic>Enterococcus faecalis</italic> (n=3), <italic>Enterococcus faecium</italic> (n=3), <italic>Actinomyces viscosus</italic> (n=3) e <italic>Staphylococcus aureus</italic> (n=3), coletadas in vivo de canais radiculares com insucesso endodôntico, foram testadas quanto à suscetibilidade antimicrobiana por meio do método E-test em duplicata, utilizando os antibióticos: Amoxicilina (AC), Rifampicina (RI), Moxifloxacina (MX), Vancomicina (VA), Tetraciclina (TC), Ciprofloxacina (CI), Cloranfenicol (CL), Benzilpenicilina (PG), Amoxicilina + ácido clavulânico (XL), Doxiciclina (DC), Eritromicina (EM) e Azitromicina (AZ).</p></sec><sec><title>Resultado</title><p>Todas as cepas clínicas testadas foram suscetíveis aos antibióticos AC, XL, PG, DC, MX, TC e VA. Todos os isolados das espécies de <italic>S. aureus</italic> foram suscetíveis aos 12 antibióticos testados. As cepas de <italic>E. faecalis</italic>, <italic>E. faecium</italic> e <italic>A. viscosus</italic> mostraram padrão de suscetibilidade intermediário contra EM. Algumas cepas de <italic>E. faecalis</italic> e <italic>E. faecium</italic> foram resistentes a AZ e RI.</p></sec><sec><title>Conclusão</title><p>As cepas clínicas isoladas dos canais radiculares de dentes com insucesso endodôntico mostraram perfis diferentes de suscetibilidade antimicrobiana e nenhum isolado de <italic>E. faecalis</italic> e <italic>E. faecium</italic>apresentou-se suscetível a AZ e EM.</p></sec>

A novel gene, optrA, that confers transferable resistance to oxazolidinones and phenicols and its presence in Enterococcus faecalis and Enterococcus faecium of human and animal origin

OBJECTIVES

The oxazolidinone-resistant Enterococcus faecalis E349 from a human patient tested negative for the cfr gene and 23S rRNA mutations. Here we report the identification of a novel oxazolidinone resistance gene, optrA, and a first investigation of the extent to which this gene was present in E. faecalis and Enterococcus faecium from humans and food-producing animals.

METHODS

The resistance gene optrA was identified by whole-plasmid sequencing and subsequent cloning and expression in a susceptible Enterococcus host. Transformation and conjugation assays served to investigate the transferability of optrA. All optrA-positive E. faecalis and E. faecium isolates of human and animal origin were analysed for their MICs and their genotype, as well as the location of optrA.

RESULTS

The novel plasmid-borne ABC transporter gene optrA from E. faecalis E349 conferred combined resistance or elevated MICs (when no clinical breakpoints were available) to oxazolidinones (linezolid and tedizolid) and phenicols (chloramphenicol and florfenicol). The corresponding conjugative plasmid pE349, on which optrA was located, had a size of 36 331 bp and also carried the phenicol exporter gene fexA. The optrA gene was functionally expressed in E. faecalis, E. faecium and Staphylococcus aureus. It was detected more frequently in E. faecalis and E. faecium from food-producing animals (20.3% and 5.7%, respectively) than from humans (4.2% and 0.6%, respectively).

CONCLUSIONS

Enterococci with elevated MICs of linezolid and tedizolid should be tested not only for 23S rRNA mutations and the gene cfr, but also for the novel resistance gene optrA.

Antimicrobial resistance, virulence determinants and genetic profiles of clinical and nonclinical Enterococcus cecorum from poultry

Enterococcus cecorum has been implicated as a possible cause of disease in poultry. However, the characteristics that contribute to pathogenesis of Ent. cecorum in poultry have not been defined. In this study, Ent. cecorum from carcass rinsates (n = 75) and diseased broilers and broiler breeders (n = 30) were compared based upon antimicrobial resistance phenotype, the presence of virulence determinants and genetic relatedness using pulsed-field gel electrophoresis (PFGE). Of the 16 antimicrobials tested, Ent. cecorum from carcass rinsates and clinical cases were resistant to ten and six of the antimicrobials, respectively. The majority of Ent. cecorum from carcass rinsates was resistant to lincomycin (54/75; 72%) and tetracycline (46/75; 61.3%) while the highest level of resistance among clinical Ent. cecorum was to tetracycline (22/30; 73.3%) and erythromycin (11/30; 36.7%). Multidrug resistance (resistance to ≥2 antimicrobials) was identified in Ent. cecorum from carcass rinsates (53/75; 70.7%) and diseased poultry (18/30; 60%). Of the virulence determinants tested, efaAfm was present in almost all of the isolates (104/105; 99%). Using PFGE, the majority of clinical isolates clustered together; however, a few clinical isolates grouped with Ent. cecorum from carcass rinsates. These data suggest that distinguishing the two groups of isolates is difficult based upon the characterization criteria used.

Transfer of tetracycline resistance genes with aggregation substance in food-borne Enterococcus faecalis

Enterococcus faecalis has the ability to conjugate with the aid of aggregation substance (AS) and inducible sex pheromones to exchange genetic elements in food matrix. To evaluate the food safety condition and the transferable factor, 250 tetracycline-resistant food-borne E. faecalis were collected in Korea. Among the isolates, a majority of tetracycline-resistant isolates (49.6 %) harbored both the tet(M) and tet(L) genes together, followed by tet(M) (19.6 %), and tet(L) (6.8 %) alone. Also, we found the combination of tet(L)/tet(M)/tet(O) or tet(M)/tet(O). We identified two tet(S) genes including the isolate carrying tet(M) + tet(S) genes. Additionally, most E. faecalis were positive for cpd and ccf (both 96.8 %) followed by cob (57.2 %). Through mating experiments, we confirmed E. faecalis possessing the Int-Tn gene and/or any AS gene successfully transferred tet genes to JH2-2 E. faecalis, whereas neither E. faecalis carrying AS genes nor the Int-Tn gene showed the conjugation. Pulsed-field gel electrophoresis results supported a distinct pattern, implying transfer of genetic information. Our study revealed a high occurrence of tetracycline resistance genes in E. faecalis from various foods. The widespread dissemination of tetracycline resistance genes would be promoted to transfer tetracycline resistance genes by pheromone-mediated conjugation systems.

Enterococcal endocarditis complicated with ruptured infected-intracranial aneurysm: with pharmacokinetic-pharmacodynamic documentation in proof of the successful antimicrobial treatment

A 74-year-old man presented with sudden onset of aphasia and apraxia. Magnetic resonance image (MRI) of the brain disclosed a left frontal hemorrhage. The concomitant low grade fever suggestive of infection was unresponsive to cefazolin 1 g q12h, and refractory to piperacillin (PIPC) 2 g q8h. Blood culture grew enterococci, establishing together with echocardiography the diagnosis of infective endocarditis. The angiography revealed cerebral hemorrhage to have resulted from the rupture of the infected intracranial aneurysm. The antimicrobial therapy was switched to ampicillin (ABPC) 2 g q4h plus gentamicin (GM) 60 mg q8h. The positive blood culture was subsequently identified Enterococcus faecium to which the minimum inhibitory concentration (MIC) of PIPC, and ABPC was 16 mcg/mL, and 4 mcg/mL, respectively. The peak concentration of serum ABPC was 83.1, median 50.8, and trough 25.8 mcg/mL. Thus, the percent time > MIC for ABPC was 100%, and the time > minimum bactericidal concentration (MBC) as well. On the other hand, time > MIC for PIPC, was found nearly 30% in retrospective analysis using population pharmacokinetics. The neurological deficit of the patient was completely restored to the normal status after 4-weeks' antimicrobial therapy with ABPC plus GM, then he underwent cardiac surgery for valvular replacement, where microbiological culture of the resected valve was negative. The constellation of the clinical, pharmacological and microbiological outcome in our case provides scientific evidence that the antibiotic therapy given to our case is the best available strategy as an antimicrobial treatment of severe enterococcal endocarditis complicated by disseminated lesion as infected intracranial aneurysm.

Mutation of environmental mycobacteria to resist silver nanoparticles also confers resistance to a common antibiotic

Non-tuberculous mycobacteria are a threat to human health, gaining entry to the body through contaminated water systems, where they form persistent biofilms despite extensive attempts at disinfection. Silver is a natural antibacterial agent and in nanoparticle form activity is increased by a high surface area. Silver nanoparticles (AgNPs) have been used as alternative disinfectants in circulating water systems, washing machines and even clothing. However, nanoparticles, like any other antibiotic that has a pervasive durable presence, carry the risk of creating a resistant population. In this study Mycobacterium smegmatis strain mc(2)155 was cultured in AgNP enriched agar such that only a small population survived. Surviving cultures were isolated and re-exposed to AgNPs and AgNO3 and resistance to silver was compared to a negative control. After only a single exposure, mutant M. smegmatis populations were resistant to AgNPs and AgNO3. Further, the silver resistant mutants were exposed to antibiotics to determine if general resistance had been conferred. The minimum inhibitory concentration of isoniazid was four times higher for silver resistant mutants than for strain mc(2)155. However, core resistance was not conferred to other toxic metal ions. The mutants had lower resistance to CuSO4 and ZnSO4 than the mc(2)155 strain.

Pyruvate formate-lyase is essential for fumarate-independent anaerobic glycerol utilization in the Enterococcus faecalis strain W11

Although anaerobic glycerol metabolism in Enterococcus faecalis requires exogenous fumarate for NADH oxidation, E. faecalis strain W11 can metabolize glycerol in the absence of oxygen without exogenous fumarate. In this study, metabolic end product analyses and reporter assays probing the expression of enzymes involved in pyruvate metabolism were performed to investigate this fumarate-independent anaerobic metabolism of glycerol in W11. Under aerobic conditions, the metabolic end products of W11 cultured with glycerol were similar to those of W11 cultured with glucose. However, when W11 was cultured anaerobically, most of the glucose was converted to l-lactate, but glycerol was converted to ethanol and formate. During anaerobic culture with glycerol, the expression of the l-lactate dehydrogenase and pyruvate dehydrogenase E1αβ genes in W11 was downregulated, whereas the expression of the pyruvate formate-lyase (Pfl) and aldehyde/alcohol dehydrogenase genes was upregulated. These changes in the expression levels caused the change in the composition of end products. A pflB gene disruptant (Δpfl mutant) of W11 could barely utilize glycerol under anaerobic conditions, but the growth of the Δpfl mutant cultured with either glucose or dihydroxyacetone (DHA) under anaerobic conditions was the same as that of W11. Glucose metabolism and DHA generates one NADH molecule per pyruvate molecule, whereas glycerol metabolism in the dehydrogenation pathway generates two NADH molecules per pyruvate molecule. These findings demonstrate that NADH generated from anaerobic glycerol metabolism in the absence of fumarate is oxidized through the Pfl-ethanol fermentation pathway. Thus, Pfl is essential to avoid the accumulation of excess NADH during fumarate-independent anaerobic glycerol metabolism.

Friend turned foe: evolution of enterococcal virulence and antibiotic resistance

The enterococci are an ancient genus that evolved along with the tree of life. These intrinsically rugged bacteria are highly adapted members of the intestinal consortia of a range of hosts that spans the animal kingdom. Enterococci are also leading opportunistic hospital pathogens, causing infections that are often resistant to treatment with most antibiotics. Despite the importance of enterococci as hospital pathogens, the vast majority live outside of humans, and nearly all of their evolutionary history took place before the appearance of modern humans. Because hospital infections represent evolutionary end points, traits that exacerbate human infection are unlikely to have evolved for that purpose. However, clusters of traits have converged in specific lineages that are well adapted to colonize the antibiotic-perturbed gastrointestinal tracts of patients and that thrive in the hospital environment. Here we discuss these traits in an evolutionary context, as well as how comparative genomics is providing new insights into the evolution of the enterococci.

Prevalence of vancomycin resistant Enterococci and associated risk factors among clients with and without HIV in Northwest Ethiopia: a cross-sectional study

BACKGROUND

Enterococci are the most important multidrug resistant organisms associated with immunocompromised patients. Data are lacking about the epidemiology of vancomycin resistant Enterococci (VRE) in Ethiopia. This study aimed to assess the prevalence of VRE, their susceptibility patterns to different antibiotics and associated risk factors in fecal samples of Human Immunodeficiency Virus (HIV) positive and HIV negative clients.

METHODS

A cross sectional study was carried out in a total of 226 (113 HIV positive and 113 HIV negative) clients, from July 1/2013 to September 30/2013 at the University of Gondar Teaching Hospital. Data on socio-demographic characteristics and risk factors were collected with a short interview guided by pre-tested structured questionnaire. The enterococci were isolated and identified from stool sample using standard bacteriological procedures. Kary Bauer disk diffusion method was used to determine the susceptibility patterns of Enterococci isolates. Data were entered and analyzed using SPSS version 20 statistical package.

RESULTS

The overall colonization of Enterococci was 88.9% (201/226) of which 11 (5.5%) were VRE. The prevalence of VRE among clients with and without HIV infections were 8(7.8%) and 3(3.1%), respectively. Ninety percent of the Enterococci isolates (181/201) were resistant to two or more antibiotics tested. Isolates of Enterococci recovered from stool samples of HIV infected patients were more resistant to amoxicillin and amoxicillin-calvulinic acid than HIV negative clients (P < 0.05). Antibiotic treatment for the last 2 weeks was found to be the risk factor that showed statistically significant association with the presence of high VRE colonization. However, the socio-demographic variables and factors such as malnutrition, leucopenia, thromobocytopenia, anaemia, duration of Highly Active Antiretroviral Therapy, CD4 cell count, stage of WHO and drinking alcohol were not associated with VRE (P > 0.05).

CONCLUSION

The high prevalence of VRE in this study signals the emergence of VRE in the study area. Prior antibiotic treatment was associated with VRE colonization. Therefore, rational use of antibiotics and more detailed study using phenotypic and genotypic methods are needed.

The cell wall architecture of Enterococcus faecium: from resistance to pathogenesis

The cell wall of Gram-positive bacteria functions as a surface organelle that continuously interacts with its environment through a plethora of cell wall-associated molecules. Enterococcus faecium is a normal inhabitant of the GI tract of mammals, but has recently become an important etiological agent of hospital-acquired infections in debilitated patients. Insights into the assembly and function of enterococcal cell wall components and their interactions with the host during colonization and infection are essential to explain the worldwide emergence of E. faecium as an important multiantibiotic-resistant nosocomial pathogen. Understanding the biochemistry of cell wall biogenesis and principles of antibiotic resistance at the molecular level may open up new frontiers in research on enterococci, particularly for the development of novel antimicrobial strategies. In this article, we outline the current knowledge on the most important antimicrobial resistance mechanisms that involve peptidoglycan synthesis and the role of cell wall constituents, including lipoteichoic acid, wall teichoic acid, capsular polysaccharides, LPxTG cell wall-anchored surface proteins, WxL-type surface proteins and pili, in the pathogenesis of E. faecium.

Brain Abscess Caused by Enterococcus avium: A Case Report and Review of the Literature

Brain abscesses can be highly lethal if appropriate treatment is not administered, and reports of such an abscess caused by Enterococcus avium are very rare. Here,we report a case of a 48-year-old man presenting with chronic otitis media. He initially presented with a headache and right otalgia. An otoscopic evaluation performed on the day of admission showed exudation of fresh pus from the right ear. Brain magnetic resonance imaging demonstrated a hypodense area in the right temporoparietal lobe, suggestive of a brain abscess. A culturing of the ear discharge and brain abscess aspirate proved of E. avium infection. Following stereotactic aspiration of the brain abscess and proper antimicrobial treatment, the patient recovered completely. In this report, we also review and discuss the available medical literature on previous cases of E. avium infection associated with brain abscess.

Vancomycin resistance has no influence on outcomes of enterococcal bacteriuria

BACKGROUND

Infections with vancomycin-resistant enterococci (VRE) are a growing concern in hospitals. The impact of vancomycin resistance in enterococcal urinary tract infection is not well-defined.

AIM

To describe the epidemiology of enterococcal bacteriuria in a hospital and compare the clinical picture and patient outcomes depending on vancomycin resistance.

METHODS

This was a 6-month prospective cohort study of hospital patients who were admitted with or who developed enterococcal bacteriuria in a 1250-bed tertiary care hospital. We examined clinical presentation, diagnostic work-up, management, and outcomes.

FINDINGS

We included 254 patients with enterococcal bacteriuria; 160 (63%) were female and median age was 65 years (range: 17-96). A total of 116 (46%) bacteriurias were hospital-acquired and 145 (57%) catheter-associated. Most patients presented with asymptomatic bacteriuria (ASB) (119; 47%) or pyelonephritis (64; 25%); 51 (20%) had unclassifiable bacteriuria and 20 (8%) had cystitis. Secondary bloodstream infection was detected in 8 (3%) patients. Seventy of 119 (59%) with ASB received antibiotics (mostly vancomycin). There were 74 (29%) VRE bacteriurias. VRE and vancomycin-susceptible enterococci (VSE) produced similar rates of pyelonephritis [19 (25%) vs 45 (25%); P = 0.2], cystitis, and ASB. Outcomes such as ICU transfer [10 (14%) VRE vs 17 (9%) VSE; P = 0.3], hospital length of stay (6.8 vs 5.0 days; P = 0.08), and mortality [10 (14%) vs 13 (7%); P = 0.1] did not vary with vancomycin susceptibility.

CONCLUSIONS

Vancomycin resistance did not affect the clinical presentation nor did it impact patient outcomes in this cohort of inpatients with enterococcal bacteriuria. Almost half of our cohort had enterococcal ASB; more than 50% of these asymptomatic patients received unnecessary antibiotics. Antimicrobial stewardship efforts should address overtreatment of enterococcal bacteriurias.

Nonclinical and clinical Enterococcus faecium strains, but not Enterococcus faecalis strains, have distinct structural and functional genomic features

Certain strains of Enterococcus faecium and Enterococcus faecalis contribute beneficially to animal health and food production, while others are associated with nosocomial infections. To determine whether there are structural and functional genomic features that are distinct between nonclinical (NC) and clinical (CL) strains of those species, we analyzed the genomes of 31 E. faecium and 38 E. faecalis strains. Hierarchical clustering of 7,017 orthologs found in the E. faecium pangenome revealed that NC strains clustered into two clades and are distinct from CL strains. NC E. faecium genomes are significantly smaller than CL genomes, and this difference was partly explained by significantly fewer mobile genetic elements (ME), virulence factors (VF), and antibiotic resistance (AR) genes. E. faecium ortholog comparisons identified 68 and 153 genes that are enriched for NC and CL strains, respectively. Proximity analysis showed that CL-enriched loci, and not NC-enriched loci, are more frequently colocalized on the genome with ME. In CL genomes, AR genes are also colocalized with ME, and VF are more frequently associated with CL-enriched loci. Genes in 23 functional groups are also differentially enriched between NC and CL E. faecium genomes. In contrast, differences were not observed between NC and CL E. faecalis genomes despite their having larger genomes than E. faecium. Our findings show that unlike E. faecalis, NC and CL E. faecium strains are equipped with distinct structural and functional genomic features indicative of adaptation to different environments.

High frequency distribution of heterogeneous vancomycin resistant Enterococcous faecium (VREfm) in Iranian hospitals

Background

Enterococcus faecium is a multi-resistant nosocomial pathogen causing infection in debilitated patients. Vancomycin-resistant enterococcus faecium (VREfm) are a major concern and increased dramatically worldwide especially in hospitals environment. The current study focused on determining the high prevalence and distribution patterns of antibiotic resistance and also its genetic linkages among various VREfm strains isolated from indoor hospitalized patients in four major Iranian teaching hospitals of Tehran.

Methods

The clinical samples were obtained from hospitalized patients during September 2010 to June 2011 from different teaching hospitals of Tehran. Antibiotics Resistance patterns, minimum inhibition concentration (MIC) value for vancomycin, ampicillin, gentamicin and presence of genetic linkage among the isolates were determined by pulsed-field gel electrophoresis (PFGE).

Results

Overall, total of 92 (41.4%) isolates were identified as E. faecium, 45 (49%) were resistant to vancomycin with an MIC₅₀ of ≥128 mg/L. The results showed that simultaneous resistance to teicoplanin, ampicillin, gentamicin, ciprofloxacine, tetracycline and erythromycin were observed the most frequent pattern. All the vancomycin resistant E. faecium isolates carried the vanA gene. intensive care units (ICUs) and Kidney transplantation, are most probably the wards with highest risk of infection by VRE. 17 pulsotypes were also detected by PFGE, most of the related pulsotypes belongs to the same hospitals.

Conclusions

This study shows the high alarming prevalence of Enterococcus faecium infection and similar clones of VREfm strains in Iranian hospitals with threatening resistance phenotypes.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1270863903102282

Increase in bloodstream infection due to vancomycin-susceptible Enterococcus faecium in cancer patients: risk factors, molecular epidemiology and outcomes

We conducted a prospective study to assess the risk factors, molecular epidemiology and outcome of bloodstream infection (BSI) due to Enterococcus faecium in hospitalized cancer patients. Between 2006 and 2012, a significant increase in vancomycin-susceptible E. faecium BSI was observed among cancer patients. Comparison of 54 episodes of BSI due to E. faecium with 38 episodes of BSI due to E. faecalis showed that previous use of carbapenems was the only independent risk factor for E. faecium acquisition (OR 10.24; 95% CI, 1.35-77.66). All E. faecium isolates were susceptible to glycopeptides, whereas 97% showed high-level resistance to ampicillin and ciprofloxacin. All 30 isolates available for genotyping belonged to the hospital-associated E. faecium lineages 17, 18 and 78. After 2009, most of the isolates belonged to ST117 (lineage 78). Patients with E. faecium BSI were more likely to receive inadequate initial empirical antibiotic therapy than patients with E. faecalis BSI, and time to adequate empirical antibiotic therapy was also longer in the former group. No significant differences were found between the two groups regarding early and overall case-fatality rates. Independent risk factors for overall case-fatality were current corticosteroids (OR 4.18; 95% CI, 1.34-13.01) and intensive care unit admission (OR 9.97; 95% CI, 1.96-50.63). The emergence of E. faecium among cancer patients is a concern since there are limited treatment options and it may presage the emergence of vancomycin-resistant enterococci. A rationale approach that combines infection control with antimicrobial stewardship.