Vancomycin-resistant enterococci

Futuristic Non-antibiotic Therapies to Combat Antibiotic Resistance: A Review

The looming problem of resistance to antibiotics in microorganisms is a global health concern. The drug-resistant microorganisms originating from anthropogenic sources and commercial livestock farming have posed serious environmental and health challenges. Antibiotic-resistant genes constituting the environmental "resistome" get transferred to human and veterinary pathogens. Hence, deciphering the origin, mechanism and extreme of transfer of these genetic factors into pathogens is extremely important to develop not only the therapeutic interventions to curtail the infections, but also the strategies to avert the menace of microbial drug-resistance. Clinicians, researchers and policymakers should jointly come up to develop the strategies to prevent superfluous exposure of pathogens to antibiotics in non-clinical settings. This article highlights the present scenario of increasing antimicrobial-resistance in pathogenic bacteria and the clinical importance of unconventional or non-antibiotic therapies to thwart the infectious pathogenic microorganisms.

Mobile genetic elements beyond the VanB-resistance dissemination among hospital-associated enterococci and other Gram-positive bacteria

An increasing resistance to vancomycin among clinically relevant enterococci, such as Enterococcus faecalis and Enterococcus faecium is a cause of a great concern, as it seriously limits treatment options. The vanB operon is one of most common determinants of this type of resistance. Genes constituting the operon are located in conjugative transposons, such as Tn1549-type transposons or, more rarely, in ICEEfaV583-type structures. Such elements show differences in structure and size, and reside in various sites of bacterial chromosome or, in the case of Tn1549-type transposons, are also occasionally associated with plasmids of divergent replicon types. While conjugative transposition contributes to the acquisition of Tn1549-type transposons from anaerobic gut commensals by enterococci, chromosomal recombination and conjugal transfer of plasmids appear to represent main mechanisms responsible for horizontal dissemination of vanB determinants among hospital E. faecalis and E. faecium. This review focuses on diversity of genetic elements harbouring vanB determinants in hospital-associated strains of E. faecium and E. faecalis, the mechanisms beyond vanB spread in populations of these bacteria, and provides an overview of the vanB-MGE distribution among other enterococci and Gram-positive bacteria as potential reservoirs of vanB genes.

Development and validation of a lateral flow immunoassay for rapid detection of VanA-producing enterococci

BACKGROUND

VRE are nosocomial pathogens with an increasing incidence in recent decades. Rapid detection is crucial to reduce their spread and prevent infections and outbreaks.

OBJECTIVES

To evaluate a lateral flow immunoassay (LFIA) (called NG-Test VanA) for the rapid and reliable detection of VanA-producing VRE (VanA-VRE) from colonies and broth.

METHODS

NG-Test VanA was validated on 135 well-characterized enterococcal isolates grown on Mueller-Hinton (MH) agar (including 40 VanA-VRE). Different agar plates and culture broths widely used in routine laboratories for culture of enterococci were tested.

RESULTS

All 40 VanA-VRE clinical isolates were correctly detected in less than 15 min irrespective of the species expressing the VanA ligase and the medium used for bacterial growth. No cross-reaction was observed with any other clinically relevant ligases (VanB, C1, C2, D, E, G, L, M and N). Overall, the sensitivity and specificity of the assay were 100% for VanA-VRE grown on MH agar plates. NG-Test VanA accurately detects VanA-VRE irrespective of the culture medium (agar and broth). Band intensity was increased when using bacteria grown on vancomycin-containing culture media or on MH close to the vancomycin disc as a consequence of VanA induction. The limit of detection of the assay was 6.3 × 106 cfu per test with bacteria grown on MH plates and 4.9 × 105 cfu per test with bacteria grown on ChromID® VRE plates.

CONCLUSIONS

NG-Test VanA is efficient, rapid and easy to implement in the routine workflow of a clinical microbiology laboratory for the confirmation of VanA-VRE.

Resistance in Vancomycin-Resistant Enterococci

Serious infections owing to vancomycin-resistant enterococci have historically proven to be difficult clinical cases, requiring combination therapy and management of treatment-related toxicity. Despite the introduction of new antibiotics with activity against vancomycin-resistant enterococci to the therapeutic armamentarium, significant challenges remain. An understanding of the factors driving the emergence of resistance in vancomycin-resistant enterococci, the dynamics of gastrointestinal colonization and microbiota-mediated colonization resistance, and the mechanisms of resistance to the currently available therapeutics will permit clinicians to be better prepared to tackle these challenging hospital-associated pathogens.

Analysis of Vancomycin-Resistant Enterococci in Hemato-Oncological Patients

Enterococci are important bacterial pathogens, and their significance is even greater in the case of vancomycin-resistant enterococci (VRE). The study analyzed the presence of VRE in the gastrointestinal tract (GIT) of hemato-oncological patients. Active screening using selective agars yielded VRE for phenotypic and genotypic analyses. Isolated strains were identified with MALDI-TOF MS, (Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry) their susceptibility to antibiotics was tested, and resistance genes (vanA, vanB, vanC-1, vanC2-C3) and genes encoding virulence factors (asa1, gelE, cylA, esp, hyl) were detected. Pulsed-field gel electrophoresis was used to assess the relationship of the isolated strains. Over a period of three years, 103 VanA-type VRE were identified in 1405 hemato-oncological patients. The most frequently detected virulence factor was extracellular surface protein (84%), followed by hyaluronidase (40%). Unique restriction profiles were observed in 33% of strains; clonality was detected in 67% of isolates. The study found that 7% of hemato-oncological patients carried VRE in their GIT. In all cases, the species identified was Enterococcus faecium. No clone persisted for the entire 3-year study period. However, genetically different clusters were observed for shorter periods of time, no longer than eight months, with identical VRE spreading among patients.

Thirty years of VRE in Germany - "expect the unexpected": The view from the National Reference Centre for Staphylococci and Enterococci

Enterococci are commensals of the intestinal tract of many animals and humans. Of the various known and still unnamed new enterococcal species, only isolates of Enterococcus faecium and Enterococcus faecalis have received increased medical and public health attention. According to textbook knowledge, the majority of infections are caused by E. faecalis. In recent decades, the number of enterococcal infections has increased, with the increase being exclusively associated with a rising number of nosocomial E. faecium infections. This increase has been accompanied by the dissemination of certain hospital-acquired strain variants and an alarming progress in the development of antibiotic resistance namely vancomycin resistance. With this review we focus on a description of the specific situation of vancomycin resistance among clinical E. faecium isolates in Germany over the past 30 years. The present review describes three VRE episodes in Germany, each of which is framed by the beginning and end of the respective decade. The first episode is specified by the first appearance of VRE in 1990 and a country-wide spread of specific vanA-type VRE strains (ST117/CT24) until the late 1990s. The second decade was initially marked by regional clusters and VRE outbreaks in hospitals in South-Western Germany in 2004 and 2005, mainly caused by vanA-type VRE of ST203. Against the background of a certain "basic level" of VRE prevalence throughout Germany, an early shift from the vanA genotype to the vanB genotype in clinical isolates already occurred at the end of the 2000s without much notice. With the beginning of the third decade in 2010, VRE rates in Germany have permanently increased, first in some federal states and soon after country-wide. Besides an increase in VRE prevalence, this decade was marked by a sharp increase in vanB-type resistance and a dominance of a few, novel strain variants like ST192 and later on ST117 (CT71, CT469) and ST80 (CT1065). The largest VRE outbreak, which involved about 2,900 patients and lasted over three years, was caused by a novel and until that time, unknown strain type of ST80/CT1013 (vanB). Across all periods, VRE outbreaks were mainly oligoclonal and strain types varied over space (hospital wards) and time. The spread of VRE strains obviously respects political borders; for instance, both vancomycin-variable enterococci which were highly prevalent in Denmark and ST796 VRE which successfully disseminated in Australia and Switzerland, were still completely absent among German hospital patients, until to date.

Rational Design of Gram-Specific Antimicrobial Imidazolium Tetramers To Combat MRSA

Antimicrobial resistance poses an increasingly serious global health threat. Hence, new antimicrobials with low propensity toward inducing resistance in bacteria are being developed to combat this threat. In this work, a series of imidazolium tetramers have been synthesized by modulating the linkers between imidazoliums or the length of the end groups within the structures of oligomers in order to optimize the activity, selectivity, and biocompatibility of the compounds. These new materials possess high biocompatibility, Gram selectivity, and high efficacy against the selected bacterium as well as clinically isolated methicillin-resistant Staphylococcus aureus species without inducing drug resistance. Therefore, we believe that these compounds can potentially be used to mitigate resistance as highly effective disinfectants in healthcare products or as antimicrobial therapies specifically for Gram-positive bacterial infections.

New Antimicrobial Bioactivity against Multidrug-Resistant Gram-Positive Bacteria of Kinase Inhibitor IMD0354

Multidrug-resistant pathogens pose a serious threat to human health. For decades, the antibiotic vancomycin has been a potent option when treating Gram-positive multidrug-resistant infections. Nonetheless, in recent decades, we have begun to see an increase in vancomycin-resistant bacteria. Here, we show that the nuclear factor-kappa B (NF-κB) inhibitor N-[3,5-Bis(trifluoromethyl)phenyl]-5-chloro-2-hydroxybenzamide (IMD0354) was identified as a positive hit through a Caenorhabditis elegans–methicillin-resistant Staphylococcus aureus (MRSA) infection screen. IMD0354 was a potent bacteriostatic drug capable of working at a minimal inhibitory concentration (MIC) as low as 0.06 µg/mL against various vancomycin-resistant strains. Interestingly, IMD0354 showed no hemolytic activity at concentrations as high as 16 µg/mL and is minimally toxic to C. elegans in vivo with 90% survival up to 64 µg/mL. In addition, we demonstrated that IMD0354′s mechanism of action at high concentrations is membrane permeabilization. Lastly, we found that IMD0354 is able to inhibit vancomycin-resistant Staphylococcus aureus (VRSA) initial cell attachment and biofilm formation at sub-MIC levels and above. Our work highlights that the NF-κB inhibitor IMD0354 has promising potential as a lead compound and an antimicrobial therapeutic candidate capable of combating multidrug-resistant bacteria.

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

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

Vancomycin-Resistant Enterococci (VRE) in Nigeria: The First Systematic Review and Meta-Analysis

Vancomycin-Resistant Enterococci (VRE) are on the rise worldwide. Here, we report the first prevalence of VRE in Nigeria using systematic review and meta-analysis. International databases MedLib, PubMed, International Scientific Indexing (ISI), Web of Science, Scopus, Google Scholar, and African journals online (AJOL) were searched. Information was extracted by two independent reviewers, and results were reviewed by the third. Two reviewers independently assessed the study quality using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) checklist. OpenMeta analyst was used. The random effect was used, and publication bias was assessed using a funnel plot. Between-study heterogeneity was assessed, and the sources were analysed using the leave-one-out meta-analysis, subgroup analysis, and meta-regression. Nineteen studies met the eligibility criteria and were added to the final meta-analysis, and the study period was from 2009–2018. Of the 2552 isolates tested, 349 were VRE, and E. faecalis was reported the most. The pooled prevalence of VRE in Nigeria was estimated at 25.3% (95% CI; 19.8–30.8%; I² = 96.26%; p < 0.001). Between-study variability was high (t² = 0.011; heterogeneity I² = 96.26% with heterogeneity chi-square (Q) = 480.667, degrees of freedom (df) = 18, and p = 0.001). The funnel plot showed no publication bias, and the leave-one-out forest plot did not affect the pooled prevalence. The South-East region had a moderate heterogeneity though not significant (I² = 51.15%, p = 0.129). Meta-regression showed that all the variables listed contributed to the heterogeneity except for the animal isolate source (p = 0.188) and studies that were done in 2013 (p = 0.219). Adherence to proper and accurate antimicrobial usage, comprehensive testing, and continuous surveillance of VRE are required.

Emergence of pstS-Null Vancomycin-Resistant Enterococcus faecium Clone ST1478, Canada, 2013-2018

Rates of vancomycin-resistant enterococci bloodstream infections have remained relatively low in Canada. We recently observed an increase of 113% in these infections rates, which coincided with emergence of Enterococcus faecium pstS-null sequence type 1478. The proportion of this sequence type increased from 2.7% to 38.7% for all tested isolates from 2013-2018.

Enterococcus faecium: from microbiological insights to practical recommendations for infection control and diagnostics

Early in its evolution, Enterococcus faecium acquired traits that allowed it to become a successful nosocomial pathogen. E. faecium inherent tenacity to build resistance to antibiotics and environmental stressors that allows the species to thrive in hospital environments. The continual wide use of antibiotics in medicine has been an important driver in the evolution of E. faecium becoming a highly proficient hospital pathogen.For successful prevention and reduction of nosocomial infections with vancomycin resistant E. faecium (VREfm), it is essential to focus on reducing VREfm carriage and spread. The aim of this review is to incorporate microbiological insights of E. faecium into practical infection control recommendations, to reduce the spread of hospital-acquired VREfm (carriage and infections). The spread of VREfm can be controlled by intensified cleaning procedures, antibiotic stewardship, rapid screening of VREfm carriage focused on high-risk populations, and identification of transmission routes through accurate detection and typing methods in outbreak situations. Further, for successful management of E. faecium, continual innovation in the fields of diagnostics, treatment, and eradication is necessary.

Visualizing the enzyme mechanism of mevalonate diphosphate decarboxylase

Mevalonate diphosphate decarboxylases (MDDs) catalyze the ATP-dependent-Mg2+-decarboxylation of mevalonate-5-diphosphate (MVAPP) to produce isopentenyl diphosphate (IPP), which is essential in both eukaryotes and prokaryotes for polyisoprenoid synthesis. The substrates, MVAPP and ATP, have been shown to bind sequentially to MDD. Here we report crystals in which the enzyme remains active, allowing the visualization of conformational changes in Enterococcus faecalis MDD that describe sequential steps in an induced fit enzymatic reaction. Initial binding of MVAPP modulates the ATP binding pocket with a large loop movement. Upon ATP binding, a phosphate binding loop bends over the active site to recognize ATP and bring the molecules to their catalytically favored configuration. Positioned substrates then can chelate two Mg2+ ions for the two steps of the reaction. Closure of the active site entrance brings a conserved lysine to trigger dissociative phosphoryl transfer of γ-phosphate from ATP to MVAPP, followed by the production of IPP.

Gómez de Cadiñanos L, Gabant P. In the Age of Synthetic Biology, Will Antimicrobial Peptides be the Next Generation of Antibiotics?

Antibiotics have changed human health and revolutionised medical practice since the Second World War. Today, the use of antibiotics is increasingly limited by the rise of antimicrobial-resistant strains. Additionally, broad-spectrum antibiotic activity is not adapted to maintaining a balanced microbiome essential for human health. Targeted antimicrobials could overcome these two drawbacks. Although the rational design of targeted antimicrobial molecules presents a formidable challenge, in nature, targeted genetically encoded killing molecules are used by microbes in their natural ecosystems. The use of a synthetic biology approach allows the harnessing of these natural functions. In this commentary article we illustrate the potential of applying synthetic biology towards bacteriocins to design a new generation of antimicrobials.

Resistome of Staphylococcus aureus in Response to Human Cathelicidin LL-37 and Its Engineered Antimicrobial Peptides

Staphylococcus aureus is notoriously known for its rapid development of resistance to conventional antibiotics. S. aureus can alter its membrane composition to reduce the killing effect of antibiotics and antimicrobial peptides (AMPs). To obtain a more complete picture, this study identified the resistance genes of S. aureus in response to human cathelicidin LL-37 peptides by screening the Nebraska Transposon Mutant Library. In total, 24 resistant genes were identified. Among them, six mutants, including the one with the known membrane-modifying gene (mprF) disabled, became more membrane permeable to the LL-37 engineered peptide 17BIPHE2 than the wild type. Mass spectrometry analysis detected minimal lysyl-phosphatidylglycerol (lysylPG) from the mprF mutant of S. aureus JE2, confirming loss-of-function of this gene. Moreover, multiple mutants showed reduced surface adhesion and biofilm formation. In addition, four S. aureus mutants were unable to infect wax moth Galleria mellonella. There appears to be a connection between the ability of bacterial attachment/biofilm formation and infection. These results underscore the multiple functional roles of the identified peptide-response genes in bacterial growth, infection, and biofilm formation. Therefore, S. aureus utilizes a set of resistant genes to weave a complex molecular network to handle the danger posed by cationic LL-37. It appears that different genes are involved depending on the nature of antimicrobials. These resistant genes may offer a novel avenue to designing more potent antibiotics that target the Achilles heels of S. aureus USA300, a community-associated pathogen of great threat.

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.

Current Status of Vancomycin Analytical Methods

BACKGROUND

The glycopeptide antibiotics are a class of antimicrobial drugs that are an important alternative for cases of bacterial infections resistant to penicillins, besides being able to be used to treat infections in people allergic to pencilin. They have great activity against Gram-positive microorganisms, including methicillin-resistant Staphylococcus aureus (MRSA), by inhibiting the cell wall synthesis.

OBJECTIVE

There are many analytical methods in the literature for determination of antimicrobial glycopeptide vancomycin in different matrixes that are very effective; however, all of them use toxic solvents, contributing to the generation of waste, causing damage to the environment and to the operator, as well as increased costs of analysis.

RESULTS

The most prevailing method found was high performance liquid chromatography (HPLC), followed by microbiological assays and, in less quantity, spectrometric methods. The chromatographic methods use organic solvents that are toxic, such as acetonitrile and methanol, and buffer solutions, that can damage the equipment and the column. In the microbiological assays the disc diffusion methods are still in the majority. The spectrophotometric methods were based in the UV-Vis region using buffer solutions as a diluent.

CONCLUSIONS

All these methods can become greener, following green analytical chemistry principles, which could bring benefits both to the environment and the operator, and reduce costs.

HIGHLIGHTS

In this paper, a literature review regarding analytical methods for determination of vancomycin was carried out with a suggestion of greener alternatives.

Emergence of vanA-Type Vancomycin-Resistant Enterococcus faecium ST 78 Strain with a rep2-Type Plasmid Carrying a Tn1546-Like Element Isolated from a Urinary Tract Infection in China

Purpose

The emergence of vancomycin-resistant enterococci (VRE) dramatically narrows therapeutic options. Although the prevalence of VRE in China has maintained a low level, VRE outbreaks have been reported in some tertiary hospitals in the developed areas of China. The clonal background of vanA-positive Enterococcus faecium strains has not been well characterized in China. Here, we report the whole-genome sequence of a vanA-type vancomycin-resistant E. faecium belonging to sequence type (ST) 78 isolated from a urinary tract infection in China.

Patients and Methods

A vancomycin-resistant E. faecium was isolated from a 66-year-old male patient diagnosed with brainstem hemorrhage. Antibiotic susceptibility assays were performed according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Complete genome sequencing was performed using both the HiSeq^TM 4000 platform and the MinION platform. Plasmid, genomic and phylogenetic relationship analysis were further performed.

Results

E. faecium VRE1 was resistant to all antimicrobials tested except for tetracyclines and oxazolidinones. The whole genome of E. faecium VRE1 was composed of one chromosomal DNA and four plasmids. Two virulence genes and five antimicrobial resistance genes were identified. In silico multilocus sequence typing (MLST) showed that it belonged to ST78 (clonal complex CC17), a well-known epidemic clone that is widespread in Europe and the United States. Three antimicrobial resistance genes, including aminoglycoside resistance genes ant(6)-Ia and aph(3ʹ)-III; and glycopeptide resistance gene vanA, were located on a rep2-type plasmid carrying a Tn1546-like element that has not been reported. The most closely related strain harboring a similar plasmid backbone was recovered from fodder sample in China that differed by 178 cgMLST loci.

Conclusion

Our study characterizes the genomic feature of a vancomycin-resistant E. faecium ST78 strain harboring a vanA-carrying plasmid in China. The ST78 clonal group possessed the potential to emerge as a successful vanA-carrying epidemic lineage in China.

First Report of the Local Spread of Vancomycin-Resistant Enterococci Ascribed to the Interspecies Transmission of a vanA Gene Cluster-Carrying Linear Plasmid

Increasing multidrug resistance, including vancomycin resistance, in enterococci is a major concern in clinical settings. Horizontal gene transfer, such as via plasmids, has been shown to play a crucial role in the acquisition of vancomycin resistance. Among vancomycin resistance types, the VanA type is one of the most prevalent, and outbreaks caused by VanA-type vancomycin-resistant enterococci (VRE) have occurred worldwide. Here, we describe an enterococcal linear plasmid responsible for multispecies local spread of VanA-type VRE. Such a study is important because although hospital outbreaks caused by mixed enterococcal species have been reported, this particular spread indicates plasmid transfer across species. This is a crucial finding because the high risk for such a spread of antimicrobial resistance calls for regular monitoring and surveillance.

Vancomycin-resistant enterococci pose a threat in the clinical setting and have been linked to hospital outbreaks worldwide. In 2017, a local spread of VanA-type vancomycin-resistant enterococci (VRE) occurred in Japan, and 25 enterococcal isolates, including 14 Enterococcus faecium, 8 E. raffinosus, and 3 E. casseliflavus isolates, were identified from four inpatients. Molecular analysis of the multispecies of VanA-type VRE revealed the involvement of both the dissemination of clonally related VRE strains between patients and the horizontal transfer of plasmids harboring the vanA gene cluster between Enterococcus spp. Pulsed-field gel electrophoresis showed that the plasmid DNAs without S1 nuclease treatment were able to migrate into the gel, suggesting that the topology of the plasmid was linear. Whole-genome sequencing revealed that this plasmid, designated pELF2, was 108,102 bp long and encoded multiple antimicrobial resistance genes, including ermA and ant(9). The amino acid sequences of putative replication- and transfer-related genes were highly conserved between pELF2 and pELF1, the latter of which was the first identified enterococcal conjugative linear plasmid. On comparing the genomic structure, pELF2 showed the presence of a backbone similar to that of pELF1, especially with respect to the nucleotide sequences of both terminal ends, indicating a hybrid-type linear plasmid, possessing two different terminal structures. pELF2 possessed a broad host range and high conjugation frequencies for enterococci. The easy transfer of pELF2 to different Enterococcus spp. in vitro might explain this local spread of multiple species, highlighting the clinical threat from the spread of antimicrobial resistance by an enterococcal linear plasmid.

IMPORTANCE Increasing multidrug resistance, including vancomycin resistance, in enterococci is a major concern in clinical settings. Horizontal gene transfer, such as via plasmids, has been shown to play a crucial role in the acquisition of vancomycin resistance. Among vancomycin resistance types, the VanA type is one of the most prevalent, and outbreaks caused by VanA-type vancomycin-resistant enterococci (VRE) have occurred worldwide. Here, we describe an enterococcal linear plasmid responsible for multispecies local spread of VanA-type VRE. Such a study is important because although hospital outbreaks caused by mixed enterococcal species have been reported, this particular spread indicates plasmid transfer across species. This is a crucial finding because the high risk for such a spread of antimicrobial resistance calls for regular monitoring and surveillance.

Microbiological profile and antibiotic susceptibility pattern of Gram-positive isolates at a tertiary care hospital

OBJECTIVES:

Gram-positive infections such as those by Staphylococcus aureus have contributed to the disease burden by increasing the morbidity and mortality rates in India. This study aims to determine the prevalence and the antibiotic susceptibility pattern of Gram-positive pathogens at a tertiary care hospital, Mumbai, Maharashtra, India.

MATERIALS AND METHODS:

This retrospective cross-sectional study was carried out from January, 2015 to December, 2017, at a tertiary care hospital in Mumbai, India. The clinical isolates were cultured, and identification was done using Vitek 2 culture system. The antibiotic susceptibility testing was done as per the Clinical Laboratory Standard Institute guidelines.

RESULTS:

Out of 2132 (29%) Gram-positive isolates, S. aureus (49%) was the most common encountered pathogen, followed by Enterococcus spp. (24.5%) and coagulase-negative Staphylococcus (16%). Majority of the S. aureus were observed in patients with skin and soft-tissue infections (61.2%) followed by those suffering from respiratory (41%) and bloodstream infections (35%). Among the infections caused by S. aureus, the prevalence of methicillin resistance was 30%. While the MRSA isolates showed lower sensitivity toward co-trimoxazole (39%), clindamycin (30%), erythromycin (23%), and ciprofloxacin (10%), they showed higher susceptibility to linezolid (98%), vancomycin (98%), and teicoplanin (98%). All the isolates were found to be sensitive to daptomycin and tigecycline. While vancomycin-resistant enterococci (VRE) formed 7.5%, the linezolid-resistant enterococcus species was as high as 4.1%.

CONCLUSION:

The study showed a high prevalence of MRSA and VRE, thereby emphasizing the increasing antimicrobial resistance pattern of the Gram-positive pathogens. Therefore, there is an urgent need for novel antimicrobial stewardship to restrict the ongoing resistance rate among the isolates.

Transmission of Vancomycin-Resistant Enterococci in the Hospital Setting: Uncovering the Patient-Environment Interplay

Vancomycin-resistant enterococci (VRE) are relevant nosocomial pathogens with an increasing incidence in the last decades. Their transmission is optimal in the hospital setting, as it offers two potential, large reservoirs that are closely related: susceptible patients and their environment. Here we investigate the role of the hospital environment in the nosocomial transmission of VRE by establishing concrete links between contaminated surfaces and colonized/infected patients in outbreak and non-outbreak settings. Environmental and patient VRE isolates were collected between 2013 and 2019 and analyzed by whole-genome sequencing (WGS), subsequent multilocus sequence typing (MLST), and core genome (cg) MLST. Pairs of isolates differing in <3 alleles were rated as closely related, making a transmission likely. Fifty-three environmental VRE isolates were analyzed. MLST sequence types (ST) ST203 (50.0%), ST192 (21.3%), ST117 (17.3%), ST721 (8.8%), ST80 (2%), and ST1489 (0.7%) were detected, carrying the resistance determinants vanA (72.7%), vanB (24%), or both (3.3%). Of the 53 environmental isolates, 51 were found to form five clusters with genetically related patient isolates (n = 97 isolates). WGS confirms the role of the environment in the transmission dynamics of VRE in both the outbreak and non-outbreak settings, highlighting the importance of prevention and control of VRE spread.

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

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

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.

Multicentre randomised double-blind placebo controlled trial of combination vancomycin and cefazolin surgical antibiotic prophylaxis: the Australian surgical antibiotic prophylaxis (ASAP) trial

INTRODUCTION

Resistant Gram-positive organisms, such as methicillin-resistant staphylococci, account for a significant proportion of infections following joint replacement surgery. Current surgical antimicrobial prophylaxis guidelines recommend the use of first-generation or second-generation cephalosporin antibiotics, such as cefazolin. Cefazolin, however, does not prevent infections due to these resistant organisms; therefore, new prevention strategies need to be examined. One proposed strategy is to combine a glycopeptide antibiotic with cefazolin for prophylaxis. The clinical benefit and cost-effectiveness of this combination therapy compared with usual therapy, however, have not been established.

METHODS AND ANALYSIS

This randomised, double-blind, parallel, superiority, placebo-controlled, phase 4 trial will compare the incidence of all surgical site infections (SSIs) including superficial, deep and organ/space (prosthetic joint) infections, safety and cost-effectiveness of surgical prophylaxis with cefazolin plus vancomycin to that with cefazolin plus placebo. The study will be performed in patients undergoing joint replacement surgery. In the microbiological sub-studies, we will examine the incidence of SSIs in participants with preoperative staphylococci colonisation (Sub-Study 1) and incidence of VRE acquisition (Sub-Study 2). The trial will recruit 4450 participants over a 4-year period across 13 orthopaedic centres in Australia. The primary outcome is the incidence of SSI at 90 days post index surgery. Secondary outcomes include the incidence of SSI according to joint and microorganism and other healthcare associated infections. Safety endpoints include the incidence of acute kidney injury, hypersensitivity reactions and all-cause mortality. The primary and secondary analysis will be a modified intention-to-treat analysis consisting of all randomised participants who undergo eligible surgery. We will also perform a per-protocol analysis.

ETHICS AND DISSEMINATION

The study protocol was reviewed and approved by The Alfred Hospital Human Research Ethics Committee (HREC/18/Alfred/102) on 9 July 2018. Study findings will be disseminated in the printed media, and learnt forums.

TRIAL REGISTRATION NUMBER

ACTRN12618000642280.

Biological, chemical, and biochemical strategies for modifying glycopeptide antibiotics

Since the discovery of vancomycin in the 1950s, the glycopeptide antibiotics (GPAs) have been of great interest to the scientific community. These nonribosomally biosynthesized peptides are highly cross-linked, often glycosylated, and inhibit bacterial cell wall assembly by interfering with peptidoglycan synthesis. Interest in glycopeptide antibiotics covers many scientific disciplines, due to their challenging total syntheses, complex biosynthesis pathways, mechanism of action, and high potency. After intense efforts, early enthusiasm has given way to a recognition of the challenges in chemically synthesizing GPAs and of the effort needed to study and modify GPA-producing strains to prepare new GPAs to address the increasing threat of microbial antibiotic resistance. Although the preparation of GPAs, either by modifying the pendant groups such as saccharides or by functionalizing the N- or C-terminal moieties, is readily achievable, the peptide core of these molecules-the GPA aglycone-remains highly challenging to modify. This review aims to present a summary of the results of GPA modification obtained with the three major approaches developed to date: in vivo strain manipulation, total chemical synthesis, and chemoenzymatic synthesis methods.

Vancomycin resistant Staphylococcus aureus infections: A review of case updating and clinical features

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MRSA infection is a global threat to public health.

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Vancomycin is one of the first-line drugs for the treatment of MRSA infections.

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MRSA with complete resistance to vancomycin have emerged in recent years.

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The total number of VRSA isolates is updated in this paper.

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Resistance mechanisms, characteristics of VRSA infections, as well as clinical treatments are reviewed.

The infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is a global threat to public health. Vancomycin remains one of the first-line drugs for the treatment of MRSA infections. However, S. aureus isolates with complete resistance to vancomycin have emerged in recent years. Vancomycin-resistant S. aureus (VRSA) is mediated by a vanA gene cluster, which is transferred from vancomycin-resistant enterococcus. Since the first VRSA isolate was recovered from Michigan, USA in 2002, 52 VRSA strains have been isolated worldwide. In this paper, we review the latest progresses in VRSA, highlighting its resistance mechanism, characteristics of VRSA infections, as well as clinical treatments.

Risk Factors for Long-Term Vancomycin-Resistant Enterococci Persistence-A Prospective Longitudinal Study

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens that require effective infection control measures, representing a challenge for healthcare systems. This study aimed at identifying risk factors associated with prolonged VRE carriage and determining the rate of clearance that allows the discontinuation of contact precautions. During a 2-year study, screening was performed in patients with a history of VRE or at risk of becoming colonized. After bacterial identification and antibiotic susceptibility testing, glycopeptide resistance was confirmed by PCR. Isolates were compared via whole genome sequence-based typing. Risk factors were recorded, and follow-up screening was performed upon readmission, defining patients as long-term carriers if still colonized ≥10 weeks after first detection. Of 1059 patients positive for VRE, carriage status was assessed upon readmission in 463 patients. VRE was cleared in 56.4% of the cases. Risk factors associated with long-term persistence were hospital stays (frequency, length), hemato-oncological disease, systemic treatment with steroids, and use of antibiotics. No specific genotypic clustering was observed in patients with VRE clearance or persistence. VRE clearance is possibly underestimated. The identification of risk factors favoring long-term carriage may contribute to a targeted implementation of infection control measures upon readmission of patients with history of VRE.

Transferable vancomycin resistance in clade B commensal-type Enterococcus faecium

Objectives

Vancomycin-resistant Enterococcus faecium is a leading cause of MDR hospital infection. Two genetically definable populations of E. faecium have been identified: hospital-adapted MDR isolates (clade A) and vancomycin-susceptible commensal strains (clade B). VanN-type vancomycin resistance was identified in two isolates of E. faecium recovered from blood and faeces of an immunocompromised patient. To understand the genomic context in which VanN occurred in the hospitalized patient, the risk it posed for transmission in the hospital and its origins, it was of interest to determine where these strains placed within the E. faecium population structure.

Methods

We obtained the genome sequence of the VanN isolates and performed comparative and functional genomics of the chromosome and plasmid content.

Results

We show that, in these strains, VanN occurs in a genetic background that clusters with clade B E. faecium, which is highly unusual. We characterized the chromosome and the conjugative plasmid that carries VanN resistance in these strains, pUV24. This plasmid exhibits signatures of in-host selection on the vanN operon regulatory system, which are associated with a constitutive expression of vancomycin resistance. VanN resistance in clade B strains may go undetected by current methods.

Conclusions

We report a case of vancomycin resistance in a commensal lineage of E. faecium responsible for an atypical bacteraemia in an immunocompromised patient. A reservoir of transferable glycopeptide resistance in the community could pose a concern for public health.

Rejuvenated Photodynamic Therapy for Bacterial Infections

The emergence of multidrug resistant bacterial strains has hastened the exploration of advanced microbicides and antibacterial techniques. Photodynamic antibacterial therapy (PDAT), an old-fashioned technique, has been rejuvenated to combat "superbugs" and biofilm-associated infections owing to its excellent characteristics of noninvasiveness and broad antibacterial spectrum. More importantly, bacteria are less likely to produce drug resistance to PDAT because it does not require specific targeting interaction between photosensitizers (PSs) and bacteria. This review mainly focuses on recent developments and future prospects of PDAT. The mechanisms of PDAT against bacteria and biofilms are briefly introduced. In addition to classical macrocyclic PSs, several innovative PSs, including non-self-quenching PSs, conjugated polymer-based PSs, and nano-PSs, are summarized in detail. Numerous multifunctional PDAT systems such as in situ light-activated PDAT, stimuli-responsive PDAT, oxygen self-enriching enhanced PDAT, and PDAT-based multimodal therapy are highlighted to overcome the inherent defects of PDAT in vivo (e.g., limited penetration depth of light and hypoxic environment of infectious sites).

Pathogenicity of Enterococci

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

Cost-Effectiveness of Multifaceted Built Environment Interventions for Reducing Transmission of Pathogenic Bacteria in Healthcare Facilities

OBJECTIVES

The objective of this study is to determine the optimal allocation of budgets for pairs of alterations that reduce pathogenic bacterial transmission. Three alterations of the built environment are examined: handwashing stations (HW), relative humidity control (RH), and negatively pressured treatment rooms (NP). These interventions were evaluated to minimize total cost of healthcare-associated infections (HAIs), including medical and litigation costs.

BACKGROUND

HAIs are largely preventable but are difficult to control because of their multiple mechanisms of transmission. Moreover, the costs of HAIs and resulting mortality are increasing with the latest estimates at US$9.8 billion annually.

METHOD

Using 6 years of longitudinal multidrug-resistant infection data, we simulated the transmission of pathogenic bacteria and the infection control efforts of the three alterations using Chamchod and Ruan's model. We determined the optimal budget allocations among the alterations by representing them under Karush-Kuhn-Tucker conditions for this nonlinear optimization problem.

RESULTS

We examined 24 scenarios using three virulence levels across three facility sizes with varying budget levels. We found that in general, most of the budget is allocated to the NP or RH alterations in each intervention. At lower budgets, however, it was necessary to use the lower cost alterations, HW or RH.

CONCLUSIONS

Mathematical optimization offers healthcare enterprise executives and engineers a tool to assist with the design of safer healthcare facilities within a fiscally constrained environment. Herein, models were developed for the optimal allocation of funds between HW, RH, and negatively pressured treatment rooms (NP) to best reduce HAIs. Specific strategies vary by facility size and virulence.

Enterococcal Genetics

The study of the genetics of enterococci has focused heavily on mobile genetic elements present in these organisms, the complex regulatory circuits used to control their mobility, and the antibiotic resistance genes they frequently carry. Recently, more focus has been placed on the regulation of genes involved in the virulence of the opportunistic pathogenic species Enterococcus faecalis and Enterococcus faecium. Little information is available concerning fundamental aspects of DNA replication, partition, and division; this article begins with a brief overview of what little is known about these issues, primarily by comparison with better-studied model organisms. A variety of transcriptional and posttranscriptional mechanisms of regulation of gene expression are then discussed, including a section on the genetics and regulation of vancomycin resistance in enterococci. The article then provides extensive coverage of the pheromone-responsive conjugation plasmids, including sections on regulation of the pheromone response, the conjugative apparatus, and replication and stable inheritance. The article then focuses on conjugative transposons, now referred to as integrated, conjugative elements, or ICEs, and concludes with several smaller sections covering emerging areas of interest concerning the enterococcal mobilome, including nonpheromone plasmids of particular interest, toxin-antitoxin systems, pathogenicity islands, bacteriophages, and genome defense.

The Enterococcus: a Model of Adaptability to Its Environment

The genus Enterococcus comprises a ubiquitous group of Gram-positive bacteria that are of great relevance to human health for their role as major causative agents of health care-associated infections. The enterococci are resilient and versatile species able to survive under harsh conditions, making them well adapted to the health care environment. Two species cause the majority of enterococcal infections: Enterococcus faecalis and Enterococcus faecium Both species demonstrate intrinsic resistance to common antibiotics, such as virtually all cephalosporins, aminoglycosides, clindamycin, and trimethoprim-sulfamethoxazole. Additionally, a remarkably plastic genome allows these two species to readily acquire resistance to further antibiotics, such as high-level aminoglycoside resistance, high-level ampicillin resistance, and vancomycin resistance, either through mutation or by horizontal transfer of genetic elements conferring resistance determinants.

Molecular characterization and evolution of the first outbreak of vancomycin-resistant Enterococcus faecium in Western Australia

The first outbreak of vancomycin-resistant Enterococcus faecium (VREfm) in Western Australia was recorded in 2001. A state-wide infection control effort that oversaw patient screening and transfers successfully terminated the outbreak within six months; however, the outbreak re-emerged two years later. Over the two outbreaks, the vanB-positive multilocus sequence type (ST) 173 E. faecium strain was isolated from 201 patients. Our objective was to identify differences in genetic traits leading to successful transmission of ST173 VREfm compared with non-ST173 VREfm isolated during the same period. We also aimed to describe the changes observed in the ST173 VREfm genome collected during the two outbreaks. Virulence factors ecbA, fss3, psaA and scm identified in the non-ST173 isolates were largely absent in the ST173 isolates. The esp gene was not identified beyond 45% coverage for any isolate in this study. In terms of resistance genes, tet(U) was identified in 94.7% of ST173 VREfm isolated in the first outbreak but was largely absent in ST173 VREfm isolated in the second outbreak and in non-ST173 VREfm. Seven ST173 VREfm isolates (Clade A) carried dfrG but not tet(M) resistance genes. The average genome size of ST173 VREfm isolated in the first outbreak was significantly larger than the genome size of ST173 VREfm isolated in the second outbreak. The reduced number of virulence factors in ST173 isolates may explain the low infection and high colonization rates observed during the outbreak. In addition, isolates with larger genomes were found to be associated with outbreaks.

Two Strains of Lactobacilli Effectively Decrease the Colonization of VRE in a Mouse Model

Vancomycin-resistant Enterococcus (VRE) infection is a serious challenge for clinical management and there is no effective treatment at present. Fecal microbiota transplantation (FMT) and probiotic intervention have been shown to be promising approaches for reducing the colonization of certain pathogenic bacteria in the gastrointestinal tract, however, no such studies have been done on VRE. In this study, we evaluated the effect of FMT and two Lactobacillus strains (Y74 and HT121) on the colonization of VRE in a VRE-infection mouse model. We found that both Lactobacilli strains reduced VRE colonization rapidly. Fecal microbiota and colon mRNA expression analyses further showed that mice in FMT and the two Lactobacilli treatment groups restored their intestinal microbiota diversity faster than those in the phosphate buffer saline (PBS) treated group. Administration of Lactobacilli restored Firmicutes more quickly to the normal level, compared to FMT or PBS treatment, but restored Bacteroides to their normal level less quickly than FMT did. Furthermore, these treatments also had an impact on the relative abundance of intestinal microbiota composition from phylum to species level. RNA-seq showed that FMT treatment induced the expression of more genes in the colon, compared to the Lactobacilli treatment. Defense-related genes such as defensin α, Apoa1, and RegIII were down-regulated in both FMT and the two Lactobacilli treatment groups. Taken together, our findings indicate that both FMT and Lactobacilli treatments were effective in decreasing the colonization of VRE in the gut.

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.

Dissemination and genetic analysis of the stealthy vanB gene clusters of Enterococcus faecium clinical isolates in Japan

Background

VanB-type vancomycin (VAN) resistance gene clusters confer VAN resistances on Enterococcus spp. over a wide range of MIC levels (MIC = 4–1000 mg/L). However, the epidemiology and the molecular characteristics of the VAN susceptible VanB-type Enterococcus still remain unclear.

Results

We characterized 19 isolates of VanB-type Enterococcus faecium that might colonize in the gut and were not phenotypically resistant to VAN (MIC = 3 mg/L). They were obtained from two hospitals in Japan between 2009 and 2010. These isolates had the identical vanB gene cluster and showed same multilocus sequence typing (MLST) (ST78) and the highly related profiles in pulsed-field gel electrophoresis (PFGE). The vanB gene cluster was located on a plasmid, and was transferable to E. faecium and E. faecalis. Notably, from these VanB-type VREs, VAN resistant (MIC≥16 mg/L) mutants could appear at a frequency of 10^− 6–10^− 7/parent cell in vitro. Most of these revertants acquired mutations in the vanS_B gene, while the remainder of the revertants might have other mutations outside of the vanB gene cluster. All of the revertants we tested showed increases in the VAN-dependent expression of the vanB gene cluster, suggesting that the mutations affected the transcriptional activity and increased the VAN resistance. Targeted mutagenesis revealed that three unique nucleotide substitutions in the vanB gene cluster of these strains attenuated VAN resistance.

Conclusions

In summary, this study indicated that stealthy VanB-type E. faecium strains that have the potential ability to become resistance to VAN could exist in clinical settings.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1342-1) contains supplementary material, which is available to authorized users.

Preliminary investigations into the synthesis and antimicrobial activities of boron-containing capsaicinoids

This preliminary study reports on the synthesis of two new boron-capsaicin derivatives containing either a short or long chain aliphatic tail group using an iridium catalyzed hydroboration reaction with pinacolborane. The boronate ester groups reside on the terminal position of the tail group and are necessary for the bioactivity of these compounds. Indeed, both compounds showed considerable activity against two Gram-positive bacteria, including Vancomycin-resistant Enterococcus. Vancomycin is considered the last resort medication for the treatment of septicemia, and new antibacterial agents that can treat sepsis are of paramount importance. The more lipophilic boron compound with the longer aliphatic chain also showed antifungal activity against Saccharomyces cerevisiae.

Genomic Surveillance of Enterococcus faecium Reveals Limited Sharing of Strains and Resistance Genes between Livestock and Humans in the United Kingdom

The rise in rates of human infection caused by vancomycin-resistant Enterococcus faecium (VREfm) strains between 1988 to the 2000s in Europe was suggested to be associated with acquisition from livestock. As a result, the European Union banned the use of the glycopeptide drug avoparcin as a growth promoter in livestock feed. While some studies reported a decrease in VREfm in livestock, others reported no reduction. Here, we report the first livestock VREfm prevalence survey in the UK since 2003 and the first large-scale study using whole-genome sequencing to investigate the relationship between E. faecium strains in livestock and humans. We found a low prevalence of VREfm in retail meat and limited evidence for recent sharing of strains between livestock and humans with bloodstream infection. There was evidence for limited sharing of genes encoding antibiotic resistance between these reservoirs, a finding which requires further research.

Vancomycin-resistant Enterococcus faecium (VREfm) is a major cause of nosocomial infection and is categorized as high priority by the World Health Organization global priority list of antibiotic-resistant bacteria. In the past, livestock have been proposed as a putative reservoir for drug-resistant E. faecium strains that infect humans, and isolates of the same lineage have been found in both reservoirs. We undertook cross-sectional surveys to isolate E. faecium (including VREfm) from livestock farms, retail meat, and wastewater treatment plants in the United Kingdom. More than 600 isolates from these sources were sequenced, and their relatedness and antibiotic resistance genes were compared with genomes of almost 800 E. faecium isolates from patients with bloodstream infection in the United Kingdom and Ireland. E. faecium was isolated from 28/29 farms; none of these isolates were VREfm, suggesting a decrease in VREfm prevalence since the last UK livestock survey in 2003. However, VREfm was isolated from 1% to 2% of retail meat products and was ubiquitous in wastewater treatment plants. Phylogenetic comparison demonstrated that the majority of human and livestock-related isolates were genetically distinct, although pig isolates from three farms were more genetically related to human isolates from 2001 to 2004 (minimum of 50 single-nucleotide polymorphisms [SNPs]). Analysis of accessory (variable) genes added further evidence for distinct niche adaptation. An analysis of acquired antibiotic resistance genes and their variants revealed limited sharing between humans and livestock. Our findings indicate that the majority of E. faecium strains infecting patients are largely distinct from those from livestock in this setting, with limited sharing of strains and resistance genes.

Rapid and sensitive detection of the vanA resistance gene from clinical Enterococcus faecium and Enterococcus faecalis isolates by loop-mediated isothermal amplification

OBJECTIVES

Vancomycin resistance in Enterococcus spp., mediated mainly by the vanA resistance gene, has become a major health concern as it has spread worldwide. Therefore, a rapid method is urgently required to detect the vanA gene for timely and appropriate antimicrobial control of resistant Enterococcus infections.

METHODS

The loop-mediated isothermal amplification (LAMP) assay was optimised for vanA detection in Enterococcus spp. isolates.

RESULTS

The LAMP primer set designed in this study could reliably recognise seven distinct regions of the vanA gene and amplify the gene within 25min at an isothermal temperature of 65°C with high specificity. The sensitivity of the optimised assay was high, with a detection limit for vanA as low as 100pg/μL, which is 100-fold more sensitive than the PCR assay. A special advantage of this optimised LAMP method is that the vanA gene could be detected directly from clinical specimens.

CONCLUSION

This optimised LAMP assay has great application potential for efficient detection of vanA in clinical diagnosis and epidemiological studies.

[Enterococci and surgical site infections : Causal agent or harmless commensals?]

BACKGROUND

The role of enterococci in the context of peritonitis and surgical site infections (SSI) has not yet been definitively clarified but enterococci are being detected more frequently. Numerous resistances reduce the available antibiotic options.

OBJECTIVE

This article gives an overview of the pathogenic importance of enterococci and of current recommendations for therapy and prophylaxis. On the basis of our own data we discuss the relevance of enterococci for SSI.

MATERIAL AND METHODS

All colorectal resections carried out between January 2008 and September 2016 were retrospectively documented. Revision surgery, SSI and intra-abdominally or subcutaneously detected pathogens were recorded.

RESULTS

A total of 2713 interventions were evaluated with 28.3% having primary peritonitis. In 587 patients (21.6%) SSI followed, and pathogen determination was possible in 431 cases (73.4%). Enterococci were frequently found in re-operations (58.4%) and SSI (46.1%), with E. faecalis and E. faecium in approximately equal proportions. If intra-abdominal enterococci were detectable in patients with primary peritonitis, it was more common to develop SSI and enterococci were more frequently detected subcutaneously. Enterococci in SSI were found to be significantly more frequent in left hemicolectomies as well as in pre-existing renal insufficiency.

CONCLUSION

It can be inferred that enterococci are not adequately covered by commonly used perioperative antibiotic therapy or preoperative prophylaxis, which increases the risk for SSI by enterococci. This could be favored by selection of these pathogens due to the use of antibiotics without enterococcal efficacy (e. g. cephalosporins). The consideration in the choice of perioperative antibiotic prophylaxis by the additional administration of ampicillin or vancomycin could be advantageous.

Vancomycin-resistant Enterococcus faecium at a university hospital in Taiwan, 2002-2015: Fluctuation of genetic populations and emergence of a new structure type of the Tn1546-like element

BACKGROUND/PURPOSES

Vancomycin resistance increased significantly to 31.3% among Enterococcus faecium in 2006 and remained high thereafter at a university hospital in Taiwan. A longitudinal study was retrospectively conducted to characterize these vancomycin-resistant E. faecium (VRE-fm).

METHODS

A total of 378 non-repetitive VRE-fm blood isolates collected during 2002-2015 were studied. Multilocus sequence typing, pulsed-field gel electrophoresis, analysis of van genes and the Tn1546 structure, and conjugation experiments were performed.

RESULTS

The majority (78.0%) of the isolates were associated with hospital-acquired infections. Molecular typing revealed nine major pulsotypes and five predominant sequence types (STs): ST17 (33.9%), ST78 (18.3%), ST414 (14.6%), ST18 (10.6%), and ST203 (7.4%). Fluctuation of these prevailing STs among the study years in association with some major pulsotypes was noted. All isolates carried vanA genes, except that in four isolates vanB genes were found. Among the vanA-carrying Tn1546-like elements, one predominant structure type (Type I, 55.9%) was noted throughout the study years. Since 2009, another predominant structure type (Type II, 40.1%) has emerged firstly in ST414 and gradually spread to other 11 STs in subsequent years. Isolates carrying these Type II Tn1546-like elements have become the most predominant population since 2014, majorly found in ST78 and ST17. Preliminary experiments indicated that plasmids carrying the Type II Tn1546-like elements demonstrated ten-fold higher efficiency than those carrying the Type I Tn1546-like elements.

CONCLUSION

Dissemination of some major STs and horizontal transfer of plasmids carrying two major structure types of Tn1546-like elements may have together contributed to the increase of VRE-fm infection.

Characterization of Clinical Vancomycin-Resistant Enterococcus faecium Isolated in Eastern Hungary

OBJECTIVES

The aim of our study was to characterize and elicit the genetic relatedness of emerging vancomycin-resistant enterococci (VRE) isolated between 2012 and 2015 at a teaching hospital in Debrecen, Hungary.

RESULTS

Altogether 43 nonduplicate vancomycin-resistant Enterococcus faecium (VREfm) clinical isolates were obtained. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used for species identification. Isolates showed 100% resistance to ampicillin and ciprofloxacin while 81.4% were resistant to gentamicin. PCR analysis revealed the presence of VanB in 40 and VanA in 3 isolates. Among ace, agg, and esp virulence genes only esp was found in seven cases. Modified microtiter-plate test showed 13 weak and 4 moderate biofilm producer isolates. Pulsed-field gel electrophoresis revealed nine pulsotypes. According to multilocus sequence typing all of the tested isolates belonged to clonal complex 17 (CC17).

CONCLUSIONS

We report on the alarming emergence of multidrug-resistant VREfm belonging to CC17 at a tertiary hospital in Eastern Hungary. This is the first report of sequence types 412 and 364 from this region. Although outbreak did not occur the increasing prevalence of VREfm is of concern and dissemination must be prevented with proper infection control measures and regular VRE screening.

In vitro activity of salicylamide derivatives against vancomycin-resistant enterococci

A series of 13 salicylamide derivatives was assessed for antibacterial activity against three isolates of vancomycin-resistant Enterococcus faecalis (VRE) and Enterococcus faecalis ATCC 29212 as a quality standard. The minimum inhibitory concentration was determined by the broth microdilution method with subsequent subcultivation of aliquots to assess minimum bactericidal concentration. The growth kinetics was established by the time-kill assay. Ampicillin, ciprofloxacin, tetracycline and vancomycin were used as the reference antibacterial drugs. Three of the investigated compounds showed strong bacteriostatic activity against VRE (0.199-25 µM) comparable to or more potent than ampicillin and ciprofloxacin. In addition, these compounds were tested for synergistic effect with vancomycin, ciprofloxacin and tetracycline, while 5-chloro-2-hydroxy-N-[4-(trifluoromethyl)phenyl]benzamide showed the highest potency as well as synergistic activity with vancomycin against VRE 368. Screening of the cytotoxicity of the most effective compounds was performed using human monocytic leukemia THP-1 cells, and based on LD₅₀ values, it can be stated that the compounds have insignificant toxicity against human cells.