Vancomycin-Resistant Enterococci: A Review of Antimicrobial Resistance Mechanisms and Perspectives of Human and Animal Health

Antibiotic Resistance by Enzymatic Modification of Antibiotic Targets

Antibiotic resistance remains a significant threat to modern medicine. Modification of the antibiotic target is a resistance strategy that is increasingly prevalent among pathogens. Examples include resistance to glycopeptide and polymyxin antibiotics that occurs via chemical modification of their molecular targets in the cell envelope. Similarly, many ribosome-targeting antibiotics are impaired by methylation of the rRNA. In these cases, the antibiotic target is subjected to enzymatic modification rather than genetic mutation, and in many instances the resistance enzymes are readily mobilized among pathogens. Understanding the enzymes responsible for these modifications is crucial to combat resistance. Here, we review our current understanding of enzymatic modification of antibiotic targets as well as discuss efforts to combat these resistance mechanisms.

Evaluation of the Effect of Contezolid (MRX-I) on the Corrected QT Interval in a Randomized, Double-Blind, Placebo- and Positive-Controlled Crossover Study in Healthy Chinese Volunteers

Contezolid (MRX-I), a new oxazolidinone, is an antibiotic in development for treating complicated skin and soft tissue infections caused by resistant Gram-positive bacteria. This was a thorough QT study conducted in 52 healthy subjects who were administered oral contezolid at a therapeutic (800 mg) dose, a supratherapeutic (1,600 mg) dose, placebo, and oral moxifloxacin at 400 mg in four separate treatment periods. The pharmacokinetic profile of contezolid was also evaluated. Time point analysis indicated that the upper bounds of the two-sided 90% confidence interval (CI) for placebo-corrected change-from-baseline QTc (ΔΔQTc) were <10 ms for the contezolid therapeutic dose at each time point. The upper bound of the 90% CI for ΔΔQTc was slightly more than 10 ms with the contezolid supratherapeutic dose at 3 and 4 h postdose, and the prolongation effect on the QT/QTc interval was less than that of the positive control, moxifloxacin, at 400 mg. At 3 and 4 h after the moxifloxacin dose, the moxifloxacin group met the assay sensitivity criteria outlined in ICH Guidance E14 by having a lower confidence bound of ≥5 ms. The results of a linear exposure-response model which were similar to that of a time point analysis demonstrated a slightly positive relationship between contezolid plasma levels and ΔQTcF interval with a slope of 0.227 ms per mg/liter (90% CI, 0.188 to 0.266). In summary, contezolid did not prolong the QT interval at a therapeutic dose and may have a slight effect on QT interval prolongation at a supratherapeutic dose.

Characterization of clinical enterococci isolates, focusing on the vancomycin-resistant enterococci in a tertiary hospital in China: based on the data from 2013 to 2018

Background

Vancomycin-resistant Enterococcus spp. (VRE) have spread all over the world. The present study aims to investigate the species distribution, specimen type and susceptibilities of Enterococcal species collected from Nanjing Drum Tower Hospital from 2013 to 2018. Additionally, distribution of VRE and prevalence of van gene among VRE isolates were also analyzed.

Methods

The susceptibilities of 3913 Enterococcus isolates were retrospectively investigated. Among these strains, 60 VRE strains were further anazlyed in this study. The minimum inhibitory concentrations (MICs) of the VRE strains towards vancomycin, teicoplanin and linezolid were determined by E-test. Polymerase chain reaction (PCR) and DNA sequencing were used to investigate the prevalence of van genes among VRE. Furthermore, the sequence types (STs) of VRE strains were explored by multi-locus sequence typing (MLST).

Results

Among the 3913 enterococci isolates, Enterococcus faecalis (n = 1870, 47.8%) and Enterococcus faecium (1738, 44.4%) were the main isolates. These Enterococcus strains were mainly isolated from urine (n = 1673, 42.8%), followed by secretions (n = 583, 14.9%) and ascites (n = 554, 14.2%). VRE displayed a decreasing trend year by year. Molecular analysis revealed that 49 out of 60 VRE isolates carried vanA gene, 10 carried vanM, and 1 carried both vanA and vanM genes. Sixteen distinct STs were identified among the 58 VREM, with ST78 (n = 16), ST192 (n = 8) and ST570 (n = 7) being the most dominant ones.

Conclusions

E. faecalis and E. faecium were the major enterococci strains which are the main pathogens of urinary traction infections; vanA and vanM were the main determinants conferring resistance to vancomycin; ST78, ST192 and ST570 were the leading STs of VREM which displayed a decreasing trend of prevalence year by year.

Vancomycin-Nonsusceptible Enterococci Mediated by vanC at a Large Children's Hospital: Prevalence, Susceptibility, and Impact on Care of Enterococcal Bacteremia

Enterococcus gallinarum and casseliflavus have inherent vancomycin resistance and, though known as pathogens, have not been well characterized in pediatric patients. We identified a significant prevalence of these enterococcal species among immunocompromised patients at a large pediatric institution and describe the impact on patient care, antibiotic stewardship, and infection control.

Exploring the resistome, virulome and microbiome of drinking water in environmental and clinical settings

Aquatic ecosystems harbor a vast pool of antibiotic resistance genes (ARGs), which can suffer mutation, recombination and selection events. Here, we explored the diversity of ARGs, virulence factors and the bacterial community composition in water samples before (surface raw water, RW) and after (disinfected water, DW) drinking water conventional treatment, as well as in tap water (TW) and ultrafiltration membranes (UM, recovered from hemodialysis equipment) through metagenomics. A total of 852 different ARGs were identified, 21.8% of them only in RW, which might reflect the impact of human activities on the river at the sampling point. Although a similar resistance profile has been observed between the samples, significant differences in the frequency of clinically relevant antibiotic classes (penam and peptide) were identified. Resistance determinants to last resort antibiotics, including sequences related to mcr, optrA and poxtA and clinically relevant beta-lactamase genes (i.e. bla_KPC, bla_GES, bla_IMP, bla_VIM, bla_SPM and bla_NDM) were detected. 830 coding sequences (CDSs - related to 217 different ARGs) were embedded in contigs associated with mobile genetic elements, specially plasmids, of which 68% in RW, DW and TW, suggesting the importance of water environments in resistance dissemination. Shifts in bacterial pathogens genera were observed, such as a significant increase in Mycobacterium after treatment and distribution. In UM, the potentially pathogenic genus Halomonas predominated. Its draft genome was closely related to H. stevensii, hosting mainly multidrug efflux pumps. These results broaden our understanding of the global ARGs diversity and stress the importance of tracking the ever-expanding environmental resistome.

Next-Generation Sequencing and MALDI Mass Spectrometry in the Study of Multiresistant Processed Meat Vancomycin-Resistant Enterococci (VRE)

Vancomycin-resistant enterococci (VRE), due to their intrinsic resistance to various commonly used antibiotics and their malleable genome, make the treatment of infections caused by these bacteria less effective. The aims of this work were to characterize isolates of Enterococcus spp. that originated from processed meat, through phenotypic and genotypic techniques, as well as to detect putative antibiotic resistance biomarkers. The 19 VRE identified had high resistance to teicoplanin (89%), tetracycline (94%), and erythromycin (84%) and a low resistance to kanamycin (11%), gentamicin (11%), and streptomycin (5%). Based on a Next-Generation Sequencing NGS technique, most isolates were vanA-positive. The most prevalent resistance genes detected were erm(B) and aac(6')-Ii, conferring resistance to the classes of macrolides and aminoglycosides, respectively. MALDI-TOF mass spectrometry (MS) analysis detected an exclusive peak of the Enterococcus genus at m/z (mass-to-charge-ratio) 4428 ± 3, and a peak at m/z 6048 ± 1 allowed us to distinguish Enterococcus faecium from the other species. Several statistically significant protein masses associated with resistance were detected, such as peaks at m/z 6358.27 and m/z 13237.3 in ciprofloxacin resistance isolates. These results reinforce the relevance of the combined and complementary NGS and MALDI-TOF MS techniques for bacterial characterization.

Antibacterial and ATP Synthesis Modulating Compounds from Salvia tingitana

A surface extract of the aerial parts of Salvia tingitana afforded a nor-sesterterpenoid (1) and eight new sesterterpenoids (2-̵9), along with five known sesterterpenoids, five labdane and one abietane diterpenoid, one sesquiterpenoid, and four flavonoids. The structures of the new compounds were established by 1D and 2D NMR spectroscopy, HRESIMS, and VCD data and Mosher's esters analysis. The antimicrobial activity of compounds was evaluated against 30 human pathogens including 27 clinical strains and three isolates of marine origin for their possible implications on human health. The methyl ester of salvileucolide (10), salvileucolide-6,23-lactone (11), sclareol (15), and manool (17) were the most active against Gram-positive bacteria. The compounds were also tested for the inhibition of ATP production in purified mammalian rod outer segments. Terpenoids 10, 11, 15, and 17 inhibited ATP production, while only 17 inhibited also ATP hydrolysis. Molecular modeling studies confirmed the capacity of 17 to interact with mammalian ATP synthase. A significant reduction of ATP production in the presence of 17 was observed in Enterococcus faecalis and E. faecium isolates.

Interregional spread in Spain of linezolid-resistant Enterococcus spp. isolates carrying the optrA and poxtA genes

The emergence of linezolid-resistant Enterococcus spp. (LRE) due to transferable resistance determinants is a matter of concern. To understand the contribution of the plasmid-encoded optrA and poxtA genes to the emergence of LRE, clinical isolates from different Spanish hospitals submitted to the Spanish Reference Laboratory from 2015-2018 were analysed. Linezolid resistance mechanisms were screened in all isolates by PCR and sequencing. Genetic relatedness of Enterococcus spp. carrying optrA and poxtA was studied by PFGE and MLST. Antimicrobial susceptibility was tested by broth microdilution using EUCAST standards. A total of 97 LRE isolates were studied, in 94 (96.9%) of which at least one resistance determinant was detected; 84/97 isolates (86.6%) presented a single resistance mechanism as follows: 45/84 (53.6%) carried the optrA gene, 38/84 (45.2%) carried the G2576T mutation and 1/84 (1.2%) carried the poxtA gene. In addition, 5/97 isolates (5.2%) carried both optrA and the G2576T mutation and 5/97 (5.2%) carried both optrA and poxtA. The optrA gene was more frequent in Enterococcus faecalis (83.6%) than Enterococcus faecium (11.1%) and was mainly associated with community-acquired urinary tract infections. Carriage of the poxtA gene was more frequent in E. faecium (13.9%) than E. faecalis (1.6%). Among the optrA-positive E. faecalis isolates, two main clusters were detected by PFGE. These two clusters belonged to ST585 and ST480 and were distributed throughout 11 and 6 Spanish provinces, respectively. This is the first description of LRE carrying the poxtA gene in Spain, including the co-existence of optrA and poxtA in five isolates.

Antibiogram of Urinary Enterococcus Isolates from a Tertiary Care Hospital

PURPOSE

Urinary tract infection (UTI) is one of the serious infections caused by the bacteria Enterococci. Vancomycin-Resistant Enterococci (VRE) is a persevering clinical problem globally. This study aims to detect high-level aminoglycoside and vancomycin resistance in uropathogenic Enterococcus spp.

METHODOLOGY

A total of 75 clinically relevant Enterococcus spp. grown from urine samples, were collected following convenience non-random sampling method. Identified by standard biochemical tests and susceptibility to antibiotics was studied by Kirby Bauer's disc diffusion method. The MIC of vancomycin was detected by agar dilution test. Van A, and Van B genes in VREs were detected by PCR.

RESULTS

Among 75 Enterococcal isolates, 43 (57.3%) were E. faecalis, 12 (16%) were E. faecium, 6 (8%) of each were E. pseudoavium and E. casseliflavus, 5(6.66%) were E. dispar and 3 (4%) were E. durans. E. faecalis (n=19) and E. faecium (n=3) were resistant to High Level Streptomycin (HLS). E. faecalis (n=21) and E. faecium (n=6) were resistant to High Level Gentamicin (HLG). 4 (9.3%) E. faecalis were vancomycin-resistant, out of which 3 were of Van A, and one was both Van A and Van B genotype.

CONCLUSION

Isolation of high level aminoglycoside resistant (HLAR) Enterococci is a challenge for the treating physician because aminoglycoside cannot be used in combination with glycopeptide or ampicillin for such isolates. The occurrence of HLAR, Van A, and Van B VRE genotypes is a cause of concern as they may transfer drug resistance genes to other bacterial isolates, thus leading to limited therapeutic options.

Whole Genome Sequence Analysis of the First Vancomycin-Resistant Enterococcus faecium Isolates from a Libyan Hospital in Tripoli

The purpose of the study was to investigate the molecular characteristics and genetic relatedness of the first reported cases of vancomycin-resistant enterococci (VRE) from the Tripoli Medical Center, Libya. In total, 43 VRE isolates were obtained from various clinical sites throughout the years 2013-2014, including 40 vanA-type and 2 vanB-type vancomycin-resistant Enterococcus faecium isolates and 1 vanC1-type Enterococcus gallinarum. Of the 42 E. faecium, 19 isolates were subjected to whole genome sequencing. Core genome multilocus sequence typing (cgMLST) analysis revealed three sequence clusters (SCs) of clonally related isolates, which were linked to different hospital wards. The first two VRE isolates, isolated early 2013 from patients in the medical intensive care unit, were grouped in SC1 (MLST [ST] 78, vanB) and differed in only 3 of 1423 cgMLST alleles. The SC2 (n = 16, special care baby unit, neonatal intensive care unit, pediatric surgery ward, and oncology ward) and SC3 (n = 1, antenatal ward) were all ST80 vanA-VRE, but the single SC3 isolate differed in 233 alleles compared with SC2. Within SC2, isolates differed in 1-23 alleles. Comparison with a larger database of E. faecium strains indicated that all isolates clustered within the previously defined hospital clade A1. A combination of Resfinder and mlplasmid analysis identified the presence of resistance genes on different plasmid predicted genetic elements among different SCs. In conclusion, this study documents the first isolates causing outbreaks with VRE in the Libyan health care system. Further surveillance efforts using molecular typing methods to monitor spread of multidrug-resistant bacteria in the Libyan health care system are urgently needed.

Synthesis and Biological Evaluation of Novel Carbazole Hybrids as Promising Antimicrobial Agents

Two series of carbazole analogs of 8-methoxy-N-substituted-9H-carbazole-3-carboxamides (series 1) and carbazolyl substituted rhodanines (series 2) were synthesized through facile synthetic routes. All the final compounds from these two series were evaluated for their preliminary in vitro antifungal and antibacterial activity against four fungal (Candida albicans, Cryptococcus neoformans, Cryptococcus tropicalis and Aspergillus niger) and four bacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) strains, respectively. Among the tested compounds, three compounds of series 1 displayed promising antifungal and antibacterial activity, especially against C. neoformans and S. aureus. In addition, one compound of series 1 displayed notable antimicrobial activity (MIC: 6.25 μg/mL) against clinical isolates of C. albicans and C. neoformans (MIC: 12.5 μg/mL). From the second series, four compounds exhibited significant antifungal and antibacterial activity, especially against C. neoformans and S. aureus. The most active compound of series 2 displayed a prominent antimicrobial activity against C. neoformans (MIC: 3.125 μg/mL) and S. aureus (MIC: 1.56 μg/mL), respectively.

Dietary Supplementation With Bacillus subtilis Direct-Fed Microbials Alters Chicken Intestinal Metabolite Levels

Direct-fed microbials (DFMs) are dietary supplements containing live microorganisms which confer a performance and health benefit to the host, but the mechanisms are unclear. Here, a metabolomics approach was used to identify changes in intestinal metabolite levels in chickens fed an unsupplemented diet or a diet supplemented with B. subtilis strain 1781 or strain 747. Body weight gains of chickens fed the B. subtilis-supplemented diets were increased up to 5.6% in the B. subtilis 1781 group and 7.6% in the B. subtilis 747 group compared with chickens fed the unsupplemented diet. Compared with unsupplemented controls, the levels of 83 metabolites were altered (p < 0.05) (25 increased, 58 decreased) in chickens given the B. subtilis 1781-supplemented diet, while 50 were altered (p < 0.05) (12 increased, 38 decreased) with the B. subtilis 747-supplemented diet. Twenty-two metabolites were altered (p < 0.05) (18 increased, 4 decreased) in the B. subtilis 1781 vs. B. subtilis 747 groups. A random forest analysis of the B. subtilis 1781 vs. control groups gave a predictive accuracy of 87.5%, while that of the B. subtilis 747 vs. control groups was 62.5%. A random forest analysis of the B. subtilis 1781 vs. B. subtilis 747 groups gave a predictive accuracy of 75.0%. Changes in the levels of these intestinal biochemicals provided a distinctive biochemical signature unique to each B. subtilis-supplemented group, and were characterized by alterations in the levels of dipeptides (alanylleucine, glutaminylleucine, phenylalanylalanine, valylglutamine), nucleosides (N1-methyladenosine, N6-methyladenosine, guanine, 2-deoxyguanosine), fatty acids (sebacate, valerylglycine, linoleoylcholine), and carbohydrates (fructose). These results provide the foundation for future studies to identify biochemicals that might be used to improve poultry growth performance in the absence of antibiotic growth promoters.

Phenotypic and Genotypic Traits of Vancomycin-Resistant Enterococci from Healthy Food-Producing Animals

Food-producing animals may be a reservoir of vancomycin-resistant enterococci (VRE), potentially posing a threat to animal and public health. The aims of this study were to estimate the faecal carriage of VRE among healthy cattle (n = 362), pigs (n = 350), sheep (n = 218), and poultry (n = 102 flocks) in Switzerland, and to characterise phenotypic and genotypic traits of the isolates. VRE were isolated from caecum content of six bovine, and 12 porcine samples respectively, and from pooled faecal matter collected from 16 poultry flock samples. All isolates harboured vanA. Three different types of Tn1546-like elements carrying the vanA operon were identified. Conjugal transfer of vanA to human Enterococcus faecalis strain JH2-2 was observed for porcine isolates only. Resistance to tetracycline and erythromycin was frequent among the isolates. Our data show that VRE harbouring vanA are present in healthy food-producing animals. The vanA gene from porcine isolates was transferable to other enterococci and these isolates might play a role in the dissemination of VRE in the food production chain.

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

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

Phenotype and genomic background of Arcobacter butzleri strains and taxogenomic assessment of the species

In this study the phenotypic and genomic characterization of two Arcobacter butzleri (Ab) strains (Ab 34_O and Ab 39_O) isolated from pre-cut ready-to-eat vegetables were performed. Results provided useful data about their taxonomy and their overall virulence potential with particular reference to the antibiotic and heavy metal susceptibility. These features were moreover compared with those of two Ab strains isolated from shellfish and a genotaxonomic assessment of the Ab species was performed. The two Ab isolated from vegetables were confirmed to belong to the Aliarcobacter butzleri species by 16S rRNA gene sequence analysis, MLST and genomic analyses. The genome-based taxonomic assessment of the Ab species brought to the light the possibility to define different subspecies reflecting the source of isolation, even though further genomes from different sources should be available to support this hypothesis. The strains isolated from vegetables in the same geographic area shared the same distribution of COGs with a prevalence of the cluster "inorganic ion transport and metabolism", consistent with the lithotrophic nature of Arcobacter spp. None of the Ab strains (from shellfish and from vegetables) metabolized carbohydrates but utilized organic acids and amino acids as carbon sources. The metabolic fingerprinting of Ab resulted less discriminatory than the genome-based approach. The Ab strains isolated from vegetables and those isolated from shellfish endowed multiple resistance to several antibiotics and heavy metals.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

In vitro Antibacterial Activity of Isopropoxy Benzene Guanidine Against Multidrug-Resistant Enterococci

Background

Bacterial infections cause a serious public health crisis due to the emergence of resistance towards multiple conventional antibacterial drugs. In particular, multidrug-resistant (MDR) Enterococcus faecium which belongs to "ESKAPE" organisms is causing significant problems worldwide. Hence, there is an urgent need to find alternative therapies. Recently, substituted benzene guanidine compounds have been used as lead structures to discover new promising drugs in both synthetic and medicinal chemistry.

Purpose

Here we investigated the antimicrobial activity of a new substituted benzene guanidine analog, isopropoxy benzene guanidine, against Enterococci.

Material and methods

The isopropoxy benzene guanidine was synthesized by Guangzhou Insighter Biotechnology Co., Ltd and tested on both reference bacterial strain and 32 clinical MDR Enterococci strains. The in vitro antibacterial activity was evaluated by microdilution method and kill kinetic assays. The potential antibacterial mechanism was measured by fluorescence spectrometry using fluorescent membrane potential probe 3, 3-diethyloxacarbocyanine iodide (DiOC₂ (3)).

Results

Isopropoxy benzene guanidine exhibited potent bactericidal activity against both reference strain and MDR Enterococci isolates. The minimum inhibitory concentration (MIC) range for isopropoxy benzene guanidine was 1-4 μg/mL. Minimum bactericidal concentration (MBC) was about 2-8-fold of its MIC values. Time-kill studies showed that isopropoxy benzene guanidine provided superior bactericidal effect against reference and MDR strains within 12 hrs at 2×MIC. Furthermore, isopropoxy benzene guanidine could cause a large reduction in the magnitude of the generated membrane potential compared to that of the untreated cells.

Conclusion

The present study highlights the potent bactericidal activity of isopropoxy benzene guanidine on Enterococci by disrupting the cell membrane potential. These findings demonstrate that isopropoxy benzene guanidine may be a good chemical lead for further medicinal chemistry and pharmaceutical development and could be used as a therapeutic agent for infectious diseases caused by MDR Enterococci.

Automated Incubation and Digital Image Analysis of Chromogenic Media Using Copan WASPLab Enables Rapid Detection of Vancomycin-Resistant Enterococcus

Objective: The aim of the present study was to assess whether the WASPLab automation enables faster detection of vancomycin-resistant Enterococcus (VRE) on chromogenic VRE-specific plates by shortening the incubation time.

Methods: Ninety different VRE culture negative rectal ESwab specimens were spiked with various concentrations (ranging from 3 × 10² to 3 × 10⁷ CFU/ml) of 10 Enterococcus faecium strains (vancomycin MICs ranging from 32 to >256 mg/l), 3 E. faecium VanB strains (vancomycin MICs: 4, 8, and 16 mg/l), and 2 E. faecium VanB strains displaying vancomycin heteroresistance (vancomycin MICs: 64 and 96 mg/l).

Results: Besides the two strains exhibiting vancomycin heteroresistance, all the other 13 VRE strains included in this study were detected as early as 24 h on the WASPLab even if the inoculum was low (3 × 10³ CFU/ml). When the vancomycin MICs were high, all strains were detected as early as at 18 h. However, 30 h was a conservative time point for finalizing the analysis of chromogenic cultures.

Conclusion: These results suggested that the WASPLab automated incubation could allow decreasing the initial incubation time to 18 h, followed by an intermediate time at 24 h and a final incubation period of 30 h for VRE culture screening, to deliver rapid results without affecting the analytical sensitivity.

Novel Small-molecule Antibacterials against Gram-positive Pathogens of Staphylococcus and Enterococcus Species

Defeat of the antibiotic resistance of pathogenic bacteria is one great challenge today and for the future. In the last century many classes of effective antibacterials have been developed, so that upcoming resistances could be met with novel drugs of various compound classes. Meanwhile, there is a certain lack of research of the pharmaceutical companies, and thus there are missing developments of novel antibiotics. Gram-positive bacteria are the most important cause of clinical infections. The number of novel antibacterials in clinical trials is strongly restricted. There is an urgent need to find novel antibacterials. We used synthetic chemistry to build completely novel hybrid molecules of substituted indoles and benzothiophene. In a simple one-pot reaction, two novel types of thienocarbazoles were yielded. Both indole substituted compound classes have been evaluated as completely novel antibacterials against the Staphylococcus and Enterococcus species. The evaluated partly promising activities depend on the indole substituent type. First lead compounds have been evaluated within in vivo studies. They confirmed the in vitro results for the new classes of small-molecule antibacterials.

Reshaped as polyester-based nanoparticles, gallic acid inhibits platelet aggregation, reactive oxygen species production and multi-resistant Gram-positive bacteria with an efficiency never obtained

Natural polyphenols such as Gallic Acid (GA) form an important class of bioactive chemical entities that, having innumerable biological properties, could represent a safer alternative to common drugs against several disorders, including platelet aggregation, radical oxygen species (ROS) hyperproduction, oxidative stress (OS) and bacterial infections. Unfortunately, their clinical uses are limited by pharmacokinetics drawbacks and high sensitivity to environmental factors. In order to overcome these problems and to exploit the GA curative potentials, it has been linked to a biodegradable nanospherical dendrimer matrix, capable of protecting it, thus obtaining a GA-enriched nanosized dendrimer (GAD) endowed with a strong antioxidant capacity. GAD activity as an inhibitor of platelet aggregation and ROS accumulation and its antibacterial efficiency are evaluated here and compared to those of free GA, obtaining outcomes never achieved. Regarding platelet aggregation induced by thrombin and collagen, the GAD proved to be stronger by 7.1 and 7.3 times, respectively. Furthermore, the GAD showed a ROS inhibitory activity higher than that of GA by 8.1 (thrombin) and 6.9 (collagen) times. Concerning the antibacterial activities, evaluated on eleven multi-resistant Gram-positive strains of clinical relevance, the GAD is far more potent than GA, by exerting a growth inhibitory activity at MIC (μM) concentrations lower by factors in the range 12-50.

Comparison of Antibiotic Resistance Mechanisms in Antibiotic-Producing and Pathogenic Bacteria

Antibiotic resistance poses a tremendous threat to human health. To overcome this problem, it is essential to know the mechanism of antibiotic resistance in antibiotic-producing and pathogenic bacteria. This paper deals with this problem from four points of view. First, the antibiotic resistance genes in producers are discussed related to their biosynthesis. Most resistance genes are present within the biosynthetic gene clusters, but some genes such as paromomycin acetyltransferases are located far outside the gene cluster. Second, when the antibiotic resistance genes in pathogens are compared with those in the producers, resistance mechanisms have dependency on antibiotic classes, and, in addition, new types of resistance mechanisms such as Eis aminoglycoside acetyltransferase and self-sacrifice proteins in enediyne antibiotics emerge in pathogens. Third, the relationships of the resistance genes between producers and pathogens are reevaluated at their amino acid sequence as well as nucleotide sequence levels. Pathogenic bacteria possess other resistance mechanisms than those in antibiotic producers. In addition, resistance mechanisms are little different between early stage of antibiotic use and the present time, e.g., β-lactam resistance in Staphylococcus aureus. Lastly, guanine + cytosine (GC) barrier in gene transfer to pathogenic bacteria is considered. Now, the resistance genes constitute resistome composed of complicated mixture from divergent environments.

Applications of sequencing technology in clinical microbial infection

Infectious diseases are a type of disease caused by pathogenic microorganisms. Although the discovery of antibiotics changed the treatment of infectious diseases and reduced the mortality of bacterial infections, resistant bacterial strains have emerged. Anti‐infective therapy based on aetiological evidence is the gold standard for clinical treatment, but the time lag and low positive culture rate of traditional methods of pathogen diagnosis leads to relative difficulty in obtaining the evidence of pathogens. Compared with traditional methods of pathogenic diagnosis, next‐generation and third‐generation sequencing technologies have many advantages in the detection of pathogenic microorganisms. In this review, we mainly introduce recent progress in research on pathogenic diagnostic technology and the applications of sequencing technology in the diagnosis of pathogenic microorganisms. This review provides new insights into the application of sequencing technology in the clinical diagnosis of microorganisms.

Genomics of vancomycin-resistant Enterococcus faecium

Vancomycin-resistant Enterococcus faecium (VREfm) is a globally significant public health threat and was listed on the World Health Organization's 2017 list of high-priority pathogens for which new treatments are urgently needed. Treatment options for invasive VREfm infections are very limited, and outcomes are often poor. Whole-genome sequencing is providing important new insights into VREfm evolution, drug resistance and hospital adaptation, and is increasingly being used to track VREfm transmission within hospitals to detect outbreaks and inform infection control practices. This mini-review provides an overview of recent data on the use of genomics to understand and respond to the global problem of VREfm.

Whole Slide Imaging for High-Throughput Sensing Antibiotic Resistance at Single-Bacterium Level and Its Application to Rapid Antibiotic Susceptibility Testing

Since conventional culture-based antibiotic susceptibility testing (AST) methods are too time-consuming (typically 24–72 h), rapid AST is urgently needed for preventing the increasing emergence and spread of antibiotic resistant infections. Although several phenotypic antibiotic resistance sensing modalities are able to reduce the AST time to a few hours or less, concerning the biological heterogeneity, their accuracy or limit of detection are limited by low throughput. Here, we present a rapid AST method based on whole slide imaging (WSI)-enabled high-throughput sensing antibiotic resistance at single-bacterium level. The time for determining the minimum inhibitory concentration (MIC) was theoretically shortest, which ensures that the growth of each individual cell present in a large population is inhibited. As a demonstration, our technique was able to sense the growth of at least several thousand bacteria at single-cell level. Reliable MIC of Enterobacter cloacae against gentamicin was obtained within 1 h, while the gold standard broth dilution method required at least 16 h for the same result. In addition, the application of our method prevails over other imaging-based AST approaches in allowing rapid and accurate determination of antibiotic susceptibility for phenotypically heterogeneous samples, in which the number of antibiotic resistant cells was negligible compared to that of the susceptible cells. Hence, our method shows great promise for both rapid AST determination and point-of-care testing of complex clinical bacteria isolates.

Agricultural Origins of a Highly Persistent Lineage of Vancomycin-Resistant Enterococcus faecalis in New Zealand

Historical antimicrobial use in NZ agriculture has driven the evolution of ST108, a VRE lineage carrying a range of clinically relevant antimicrobial resistances. The persistence of this lineage in NZ for over a decade indicates that coselection may be an important stabilizing mechanism for its persistence.

Enterococcus faecalis and Enterococcus faecium are human and animal gut commensals. Vancomycin-resistant enterococci (VRE) are important opportunistic pathogens with limited treatment options. Historically, the glycopeptide antibiotics vancomycin and avoparcin selected for the emergence of vancomycin resistance in human and animal isolates, respectively, resulting in global cessation of avoparcin use between 1997 and 2000. To better understand human- and animal-associated VRE strains in the postavoparcin era, we sequenced the genomes of 231 VRE isolates from New Zealand (NZ; 75 human clinical, 156 poultry) cultured between 1998 and 2009. E. faecium lineages and their antibiotic resistance carriage patterns strictly delineated between agricultural and human reservoirs, with bacitracin resistance ubiquitous in poultry but absent in clinical E. faecium strains. In contrast, one E. faecalis lineage (ST108) predominated in both poultry and human isolates in the 3 years following avoparcin discontinuation. Both phylogenetic and antimicrobial susceptibility (i.e., ubiquitous bacitracin resistance in both poultry and clinical ST108 isolates) analyses suggest an agricultural origin for the ST108 lineage. VRE isolate resistomes were carried on multiple, heterogeneous plasmids. In some isolate genomes, bacitracin, erythromycin, and vancomycin resistance elements were colocalized, indicating multiple potentially linked selection mechanisms.

IMPORTANCE Historical antimicrobial use in NZ agriculture has driven the evolution of ST108, a VRE lineage carrying a range of clinically relevant antimicrobial resistances. The persistence of this lineage in NZ for over a decade indicates that coselection may be an important stabilizing mechanism for its persistence.

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.

VanA-type vancomycin-resistant Enterococcus faecium ST1336 isolated from mussels in an anthropogenically impacted ecosystem

We report the occurrence and genomic features of multidrug-resistant vancomycin-resistant Enterococcus faecium vanA belonging to a novel sequence type (designated ST1336), carrying a Tn1546-like element, in marine brown mussels (Perna perna) from anthropogenically affected coastal waters of the Atlantic coast of Brazil, highlighting a potential source of dissemination for related ecosystems, with additional consequences for seafood safety and quality.

Genomic Characterization of Arcobacter butzleri Isolated From Shellfish: Novel Insight Into Antibiotic Resistance and Virulence Determinants

Arcobacter (A.) butzleri is an emerging pathogenic microorganism, whose taxonomy has been recently suggested to be emended to the Aliarcobacter (Al.) butzleri comb. nov. Despite extensive taxonomic analysis, only few fragmented studies have investigated the occurrence and the prevalence of virulence and antibiotic resistance determinants of this species in strains isolated from shellfish. Herein we report for the first time the whole genome sequencing and genomic characterization of two A. butzleri strains isolated from shellfish, with particular reference to the antibiotic, heavy metals and virulence determinants. This study supported the taxonomic assignment of these strains to the Al. butzleri species, and allowed us to identify antibiotic and metal resistance along with virulence determinants, also additional to those previously reported for the only two A. butzleri strains from different environments genomically characterized. Moreover, both strains showed resistance to β-lactams, vanocomycin, tetracycline and erythromycin and susceptibility to aminoglycosides and ciprofloxacin. Beside enlarging the availability of genomic data to perform comparative studies aimed at correlating phenotypic differences associated with ecological niche and geographic distribution with the genetic diversity of A. butzleri spp., this study reports the endowment of antibiotic and heavy metal resistance and virulence determinants of these shellfish-isolated strains. This leads to hypothesize a relatively high virulence of A. butzleri isolated from shellfish and prompt the need for a wider genomic analysis and for in vitro and in vivo studies of more strains isolated from this and other ecological niches, to unravel the mechanism of pathogenicity of this species, and the potential risk associated to their consumption.

Continuing occurrence of vancomycin resistance determinants in Danish pig farms 20 years after removing exposure to avoparcin

Vancomycin-resistant Enterococcus spp. is a major health problem worldwide and livestock have been implicated in constituting a reservoir for the transmission of vancomycin resistance to zoonotic pathogens. Vancomycin resistance determinants can be situated on mobile genetic elements and transferred between bacterial species The livestock reservoir must therefore be included in a risk assessment of the vancomycin resistance burden. Avoparcin, a vancomycin analogue, has not been used in Danish pig production for over 20 years and vancomycin has never been used. The objective of this study was to screen faecal samples from Danish pig farms for nine selected vancomycin resistance determinants. We found at least four different vancomycin resistance determinants in all screened Danish pig farms (665 finisher farms and 78 sow farms). The vancomycin resistance determinants present in vanB or vanG clusters were found at significantly different levels in sow and finisher farms. However, vanA was not detected in any of the farms. In conclusion, vancomycin resistance determinants are still present in Danish pig production 25 years after the ban on avoparcin use.

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.

Factors Associated with Vancomycin-Resistant Enterococcus Colonization in Patients Transferred to Emergency Departments in Korea

BACKGROUND

Vancomycin-resistant enterococci (VRE) infections have become a major healthcare-associated pathogen problem worldwide. Nosocomial VRE infections could be effectively controlled by screening patients at high risk of harboring VRE and thereby lowering the influx of VRE into healthcare centers. In this study, we evaluated factors associated with VRE colonization in patients transferred to emergency departments, to detect patients at risk for VRE carriage.

METHODS

This study was conducted in the emergency department of a medical college-affiliated hospital in Korea. Every patient transferred to the emergency department and admitted to the hospital from January to December 2016 was screened for VRE using rectal cultures. In this cross-sectional study, the dependent variable was VRE colonization and the independent variables were demographic and clinical factors of the patients and factors related to the transferring hospital. Patients were divided into two groups, VRE and non-VRE, and previously collected patient data were analyzed. Then we performed logistic regression analyses of characteristics that differed significantly between groups.

RESULTS

Out of 650 patients, 106 (16.3%) had positive VRE culture results. Significant variables in the logistic analysis were transfer from geriatric long-term care hospital (adjusted odds ration [aOR]: 8.017; 95% confidence interval [CI]: 1.378-46.651), hospital days (4-7 days; aOR: 7.246; 95% CI: 3.229-16.261), duration of antimicrobial exposure (1-3 days; aOR: 1.976; 95% CI: 1.137-3.436), and age (aOR: 1.025; 95% CI: 1.007-1.043).

CONCLUSION

VRE colonization in patients transferred to the emergency department is associated primarily with factors related to the transferred hospitals rather than demographic and clinical characteristics.

Design and Synthesis of Pyrophosphate-Targeting Vancomycin Derivatives for Combating Vancomycin-Resistant Enterococci

As the last resort for intractable Gram-positive bacterial infections, vancomycin is losing efficacy with the emergence of vancomycin-resistant bacteria, especially vancomycin-resistant Enterococci (VRE). To combat this threat, we rationally designed and synthesized 39 novel vancomycin derivatives by respective or combined modifications using metal-chelating, lipophilic, and galactose-attachment strategies for extensive structure-activity relationship (SAR) analysis. In a proposed mechanism, the conjugation of dipicolylamine on the seventh amino acid resorcinol position or C-terminus endowed the vancomycin backbone with binding capacity for the pyrophosphate moiety in lipid II while maintaining the intrinsic binding affinity for the dipeptide terminus of the bacterial cell wall peptidoglycan precursor. The in vitro antibacterial activities were evaluated, and the optimal compounds indicated 16- to 1024-fold higher activity against VRE than that of vancomycin. Compound 11 b (3',5'-bis(dipicolylaminomethyl)tyrosine [1,2,3]triazolylmethoxylethyoxyl ethylaminomethyl-N-decylvancomycin) was found to have particularly potent activity against VRE through synergistic effects brought about by combining two peripheral modifications.

Antimicrobial Resistance in Enterococcus spp. of animal origin

Enterococci are natural inhabitants of the intestinal tract in humans and many animals, including food-producing and companion animals. They can easily contaminate the food and the environment, entering the food chain. Moreover, Enterococcus is an important opportunistic pathogen, especially the species E. faecalis and E. faecium, causing a wide variety of infections. This microorganism not only contains intrinsic resistance mechanisms to several antimicrobial agents, but also has the capacity to acquire new mechanisms of antimicrobial resistance. In this review we analyze the diversity of enterococcal species and their distribution in the intestinal tract of animals. Moreover, resistance mechanisms for different classes of antimicrobials of clinical relevance are reviewed, as well as the epidemiology of multidrug-resistant enterococci of animal origin, with special attention given to beta-lactams, glycopeptides, and linezolid. The emergence of new antimicrobial resistance genes in enterococci of animal origin, such as optrA and cfr, is highlighted. The molecular epidemiology and the population structure of E. faecalis and E. faecium isolates in farm and companion animals is presented. Moreover, the types of plasmids that carry the antimicrobial resistance genes in enterococci of animal origin are reviewed.

OG716: Designing a fit-for-purpose lantibiotic for the treatment of Clostridium difficile infections

Lantibiotics continue to offer an untapped pipeline for the development of novel antibiotics. We report here the discovery of a novel lantibiotic for the treatment of C. difficile infection (CDI). The leads were selected from a library of over 300 multiple substitution variants of the lantibiotic Mutacin 1140 (MU1140). Top performers were selected based on testing for superior potency, solubility, manufacturability, and physicochemical and/or metabolic stability in biologically-relevant systems. The best performers in vitro were further evaluated orally in the Golden Syrian hamster model of CDAD. In vivo testing ultimately identified OG716 as the lead compound, which conferred 100% survival and no relapse at 3 weeks post infection. MU1140-derived variants are particularly attractive for further clinical development considering their novel mechanism of action.

Developments in Glycopeptide Antibiotics

Glycopeptide antibiotics (GPAs) are a key weapon in the fight against drug resistant bacteria, with vancomycin still a mainstream therapy against serious Gram-positive infections more than 50 years after it was first introduced. New, more potent semisynthetic derivatives that have entered the clinic, such as dalbavancin and oritavancin, have superior pharmacokinetic and target engagement profiles that enable successful treatment of vancomycin-resistant infections. In the face of resistance development, with multidrug resistant (MDR) S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) together causing 20-fold more infections than all MDR Gram-negative infections combined, further improvements are desirable to ensure the Gram-positive armamentarium is adequately maintained for future generations. A range of modified glycopeptides has been generated in the past decade via total syntheses, semisynthetic modifications of natural products, or biological engineering. Several of these have undergone extensive characterization with demonstrated in vivo efficacy, good PK/PD profiles, and no reported preclinical toxicity; some may be suitable for formal preclinical development. The natural product monobactam, cephalosporin, and β-lactam antibiotics all spawned multiple generations of commercially and clinically successful semisynthetic derivatives. Similarly, next-generation glycopeptides are now technically well positioned to advance to the clinic, if sufficient funding and market support returns to antibiotic development.

Mutacin 1140 Lantibiotic Variants Are Efficacious Against Clostridium difficile Infection

Lantibiotics offer an untapped pipeline for the development of novel antibiotics to treat serious Gram-positive (+) infections including Clostridium difficile. Mutacin 1140 (MU1140) is a lantibiotic produced by Streptococcus mutans and acts via a novel mechanism of action, which may limit the development of resistance. This study sought to identify a lead compound for the treatment of C. difficile associated diarrhea (CDAD). Compounds were selected from a saturation mutagenesis library of 418 single amino acid variants of MU1140. Compounds were produced by small scale fermentation, purified, characterized and then subjected to a panel of assays aimed at identifying the best performers. The screening assays included: in vitro susceptibility testing [MIC against Micrococcus luteus, Clostridium difficile, vancomycin-resistant enterococci (VRE), Staphylococcus aureus, Streptococcus pneumonia, Mycobacterium phlei, and Pseudomonas aeruginosa; cytotoxicity screening on HepG2 hepatocytes; in vitro pharmacological profiling with the Safety Screen 44^TM, metabolic and chemical stability in biologically relevant fluids (FaSSGF, FaSSIF and serum); and efficacy in vivo]. Several lantibiotic compounds had better MIC against C. difficile, compared to vancomycin, but not against other bacterial species tested. The Safety Screen 44^TMin vitro pharmacological profiling assay suggested that this class of compounds has relatively low overall toxicity and that compound OG253 (MU1140, Phe1Ile) is not likely to present inadvertent off-target effects, as evidenced by a low promiscuity score. The in vitro cytotoxicity assay also indicated that this class of compounds was characterized by low toxicity; the EC₅₀ of OG253 was 636 mg/mL on HepG2 cells. The half-life in simulated gastric fluid was >240 min. for all compound tested. The stability in simulated intestinal fluid ranged between a half-life of 5 min to >240 min, and paralleled the half-life in serum. OG253 ultimately emerged as the lead compound based on superior in vivo efficacy along with an apparent lack of relapse in a hamster model of infection. The lessons learned from this report are applicable to therapeutic lanthipeptides in general and may assist in the design of novel molecules with improved pharmacological, therapeutic and physicochemical profiles. The data presented also support the continued clinical development of OG253 as a novel antibiotic against CDAD that could prevent recurrence of the infection.

Antimicrobial susceptibility of enterococci recovered from healthy cattle, pigs and chickens in nine EU countries (EASSA Study) to critically important antibiotics

The European Antimicrobial Susceptibility Surveillance in Animals (EASSA) program collects zoonotic and commensal bacteria from food-producing animals at slaughter and tracks their susceptibility to medically important antibiotics. Results of commensal enterococci species (2013-2014) are presented here. Intestinal content from cattle, pigs and chickens were randomly sampled (5-6 countries/host; ≥4 abattoirs/country; 1 sample/animal/farm) for isolation of enterococci, MICs of 9 antibiotics were assessed by CLSI agar dilution in a central laboratory. Clinical breakpoints (CLSI) and epidemiological cut-off values (EUCAST) were applied for data interpretation. In total 960 Enterococcus faecium and 779 Enterococcus faecalis strains were recovered. Seven porcine E. faecium/faecalis strains of Spanish origin were resistant to linezolid. One avian E. faecalis and one porcine E. faecium strain were non-wild type (MICs 8 mg/L) to daptomycin. Clinical vancomycin resistance was absent; 2 poultry E. faecium and 1 bovine E. faecalis strains were non-wild type, all with MICs of 8 mg/L. None of the strains tested were clinically resistant to tigecycline. Little clinical resistance to ampicillin or gentamicin was observed. Clinical resistance of E. faecium to quinupristin/dalfopristin was slightly higher (2.2-12.0%) but 61.9-83.2% of the strains were classified as non-wild type. Very high percentages resistance to tetracycline (67.4-78.3%) and to erythromycin (27.1-57.0%) were noted for both E. faecium and E. faecalis in pigs and chickens compared to cattle (5.2-30.4 and 9.0-10.4%, respectively). Similar non-wild type results were observed for E. hirae (n = 557), E. durans (n = 218) and E. casseliflavus (n = 55) including percentage non-wild type for daptomycin, linezolid, tigecycline being absent and for vancomycin low. For these species percentage non-wild type to erythromycin was lower as compared to E. faecalis/faecium. This pan-EU survey shows high variability in antibiotic susceptibility of commensal enterococci from healthy food animals. Clinical resistance to critically important antibiotics for human medicine was absent or low, except for erythromycin.