Microbiological and clinical characteristics of vancomycin-resistant Enterococcus faecium bacteraemia in Taiwan: implication of sequence type for prognosis

Vancomycin-resistant Enterococcus faecium in Japan, 2007-2015: a molecular epidemiology analysis focused on examining strain characteristics over time

IMPORTANCE

Our study emphasizes the efficacy of whole-genome sequencing (WGS) in addressing outbreaks of vancomycin-resistant enterococci. WGS enables the identification and tracking of resistant bacterial strains, early detection and management of novel infectious disease outbreaks, and the appropriate selection and use of antibiotics. Furthermore, our approach deepens our understanding of how resistant bacteria transfer genes and adapt to their environments or hosts. For modern medicine, these insights have significant implications for controlling infections and effectively managing antibiotic use in the current era, where antibiotic resistance is progressing.

Molecular Rapid Diagnostics Improve Time to Effective Therapy and Survival in Patients with Vancomycin-Resistant Enterococcus Bloodstream Infections

Delays in appropriate antibiotic therapy are a key determinant for deleterious outcomes among patients with vancomycin-resistant Enterococcus (VRE) bloodstream infections (BSIs). This was a multi-center pre/post-implementation study, assessing the impact of a molecular rapid diagnostic test (Verigene® GP-BC, Luminex Corporation, Northbrook, IL, USA) on outcomes of adult patients with VRE BSIs. The primary outcome was time to optimal therapy (TOT). Multivariable logistic and Cox proportional hazard regression models were used to determine the independent associations of post-implementation, TOT, early vs. delayed therapy, and mortality. A total of 104 patients with VRE BSIs were included: 50 and 54 in the pre- and post-implementation periods, respectively. The post- vs. pre-implementation group was associated with a 1.8-fold faster rate to optimized therapy (adjusted risk ratio, 1.841 [95% CI 1.234-2.746]), 6-fold higher likelihood to receive early effective therapy (<24 h, adjusted odds ratio, 6.031 [2.526-14.401]), and a 67% lower hazards for 30-day in-hospital mortality (adjusted hazard ratio, 0.322 [0.124-1.831]), after adjusting for age, sex, and severity scores. Inversely, delayed therapy was associated with a 10-fold higher risk of in-hospital mortality (aOR 10.488, [2.497-44.050]). Reduced TOT and in-hospital mortality were also observed in subgroups of immunosuppressed patients in post-implementation. These findings demonstrate that the addition of molecular rapid diagnostic tests (mRDT) to clinical microbiology and antimicrobial stewardship practices are associated with a clinically significant reduction in TOT, which is associated with lower mortality for patients with VRE BSIs, underscoring the importance of mRDTs in the management of VRE infections.

Recommendations and guidelines for the treatment of infections due to multidrug resistant organisms

Antimicrobial drug resistance is one of the major threats to global health. It has made common infections increasingly difficult or impossible to treat, and leads to higher medical costs, prolonged hospital stays and increased mortality. Infection rates due to multidrug-resistant organisms (MDRO) are increasing globally. Active agents against MDRO are limited despite an increased in the availability of novel antibiotics in recent years. This guideline aims to assist clinicians in the management of infections due to MDRO. The 2019 Guidelines Recommendations for Evidence-based Antimicrobial agents use in Taiwan (GREAT) working group, comprising of infectious disease specialists from 14 medical centers in Taiwan, reviewed current evidences and drafted recommendations for the treatment of infections due to MDRO. A nationwide expert panel reviewed the recommendations during a consensus meeting in Aug 2020, and the guideline was endorsed by the Infectious Diseases Society of Taiwan (IDST). This guideline includes recommendations for selecting antimicrobial therapy for infections caused by carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and vancomycin-resistant Enterococcus. The guideline takes into consideration the local epidemiology, and includes antimicrobial agents that may not yet be available in Taiwan. It is intended to serve as a clinical guide and not to supersede the clinical judgment of physicians in the management of individual patients.

Emergence of aac(6')-Ie-aph(2'')-Ia-positive enterococci with non-high-level gentamicin resistance mediated by IS1216V: adaptation to decreased aminoglycoside usage in Taiwan

OBJECTIVES

To explore the mechanisms mediating the different levels of gentamicin resistance in enterococci.

METHODS

Susceptibility testing with gentamicin and PCR of resistance determinants were performed in 149 enterococcal isolates. Genetic relatedness was characterized by MLST and PFGE analysis. Sequences of the aac(6')-Ie-aph(2'')-Ia gene and its surrounding environment were determined by Illumina sequencing. Stability assays of gentamicin resistance were carried out to evaluate the probability of loss of the high-level gentamicin resistance (HLGR) phenotype.

RESULTS

A total of 17 (11.4%) aac(6')-Ie-aph(2'')-Ia-positive enterococcal isolates (2 Enterococcus faecalis and 15 Enterococcus faecium) with non-HLGR phenotype were found. MLST analysis revealed that the 2 E. faecalis belonged to ST116 and ST618, while all the 15 E. faecium belonged to clonal complex 17. Sequence analysis demonstrated that IS1216V was inserted into the 5'-end of aac(6')-Ie-aph(2'')-Ia, leading to loss of HLGR phenotype. Three IS1216V insertion types were found, and type II and III were frequently found in E. faecium. Interestingly, a total of 38 aac(6')-Ie-aph(2'')-Ia-positive E. faecium with HLGR phenotype also had type II or type III IS1216V insertion. Sequencing of the aac(6')-Ie-aph(2'')-Ia-positive HLGR E. faecium E37 revealed that an intact aac(6')-Ie-aph(2'')-Ia was located adjacent to IS1216V-disrupted aac(6')-Ie-aph(2'')-Ia. In a non-antibiotic environment, E37 tended to lose HLGR phenotype with a probability of 1.57 × 10-4, which was largely attributed to homologous recombination between the intact and disrupted aac(6')-Ie-aph(2'')-Ia.

CONCLUSIONS

This is first study to elucidate that the E. faecium is capable of changing its HLGR phenotype, which may contribute to adaptation to hospital environments with decreased usage of gentamicin.

First characterization of Tn1546-like structures of vancomycin-resistant Enterococcus faecium Thai isolates

INTRODUCTION

Vancomycin-resistant Enterococcus faecium (VREfm) carrying vanA was first isolated from patient at Siriraj Hospital, Thailand in 2004. Since then, VREfm isolates have been detected increasingly in this 2500-bed university hospital. To understand the epidemiology of vanA VREfm in this setting, the isolates collected during 2004-2013 were characterized.

METHODS

A total of 49 vanA VREfm isolates previously confirmed by multiplex PCR were characterized by determining resistance phenotypes to vancomycin, teicoplanin, ampicillin and ciprofloxacin by broth microdilution method. Multilocus sequence typing (MLST) and virulence genes of those isolates were investigated. The Tn1546 structure diversity was studied by long-range overlapping PCR and primer walking sequencing.

RESULTS

Of all isolates studied, 9 sequence types (ST17, ST80, ST78, ST730, ST203, ST18, ST280, ST64, ST323) in clonal complex 17 and a novel ST1051 were revealed. The esp-positive isolates were 73.5%. Of all vanA operons characterized, at least 9 types of Tn1546-like structures were detected. All of vanA determinants contained 5'-end different from the Tn1546 prototype. Approximately 47% of them also carried the insertion sequence IS1251 at the intergenic region between vanS and vanH. Interestingly, another IS (ISEfa4) was found to be inside the sequence of IS1251 in ST17 isolate.

CONCLUSION

Heterogeneity of vanA VREfm was observed. Nearly all of isolates studied belonged to CC17. One novel ST1051 strain was detected. Isolates in the initial period carried vanA operon similar to the prototype. The diversity of vanA determinants has been increased in the recent isolates. A novel vanA operon structure was detected.

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.

Predictors for vancomycin resistant Enterococcus faecium transforming from colonization to infection: a case control study

Background

Little is known about risk factors for subsequent infections among vancomycin resistant Enterococcus faecium (VREfm) colonizers, especially characterized by concordant pulsotypes (CP) of paired colonization and infection-related isolates.

Methods

This case-control study was conducted at a teaching hospital between 2011 and 2014. Targeted patients received active surveillance culture for VREfm by anal swabs at admission. Cases were those who developed VREfm infection within 180 days after colonization of VREfm. Controls were those colonized with VREfm without subsequent VREfm infection. CP were defined by similarities ≥86.7% using pulsed-field gel electrophoresis between paired colonization and infection-related isolates.

Results

Ninety-seven cases and 194 controls were enrolled. By conditional multivariable logistic regression analysis, the risk factors for subsequent infection among VREfm colonizers were intensive care unit (ICU) admission (adjusted odds ratio [aOR], 9.32; 95% CI, 3.61–24.02), receipt of central venous catheters (CVC) (aOR, 3.38; 95% CI, 1.30–8.82), and utilization of third- and fourth-generation cephalosporins (aOR, 4.06; 95% CI, 1.79–9.20, and aOR, 5.32; 95% CI, 1.85– 10.29, respectively) (all P ≤ 0.01). Fifty-six (57.7%) of case patients belonged to the CP group, which were associated with ICU admission (aOR, 3.74; 95% CI, 1.38–10.13), and infection developing within 30 days after colonization (aOR, 3.34; 95% CI, 1.25–8.91).

Conclusions

Among VREfm colonizers, being admitted to ICU and receiving CVC or broad spectrum cephalosporins, were the risk factors for subsequent infections. These findings highlight the importance of conducting more strict infection control measures on specific groups of VREfm colonizers.

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.

Antimicrobial-resistant CC17 Enterococcus faecium: The past, the present and the future

Enterococcus faecium is a robust opportunistic pathogen that is most commonly found as a commensal of the human and animal gut but can also survive in the environment. Since the introduction and use of antimicrobials, E. faecium has been found to rapidly acquire resistance genes that, when expressed, can effectively circumvent the effects of most antimicrobials. The rapid acquisition of multiple antimicrobial resistances has led to the adaptation of specific E. faecium clones in the hospital environment, collectively known as clonal complex 17 (CC17). CC17 E. faecium are responsible for a significant proportion of hospital-associated infections, which can cause severe morbidity and mortality. Here we review the history of E. faecium from commensal to a significant hospital-associated pathogen, its robust phenotypic characteristics, commonly used laboratory typing schemes, and antimicrobial resistances with a focus on vancomycin and its associated mechanism of resistance. Finally, we review the global epidemiology of vancomycin-resistant E. faecium and potential solutions to problems faced in public health.

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.

Clinical and microbiological characteristics of vancomycin-resistant Enterococcus faecium bloodstream infection in Central Taiwan

Bloodstream infections (BSIs) due to vancomycin-resistant Enterococcus faecium (VREfae) remain a therapeutic challenge. This study aimed to evaluate mortality from BSIs due to VREfae in Central Taiwan.We retrospectively analyzed patients with significant VREfae BSIs in the Changhua Christian Hospital System between January 1, 2010 and December 31, 2014.Of the 152 patients with Enterococcal BSI, 56 patients (36.8%) were admitted to intensive care units (ICUs) at the onset of BSI and 20 (13.2%) patients were associated with polymicrobial bacteremia. VREfae BSI was observed in 36 (23.7%) patients. Van A (100%) is the prevalence genotype, and ST 17 (41.7%) is the predominant ST type among 36 VREfae isolates during the study period. The 30-day mortality rate was 13.2% (20/152). The multivariate logistic regression analysis showed that the onset of VREfae BSI in the ICU (odds ratio [OR] = 4.2, 95% confidence interval [CI] = 1.7-10.0, P = .002) was a significant risk factor for 30-day mortality, whereas an appropriate antimicrobial therapy was a protective factor for 30-day mortality (OR = 0.33, 95% CI = 0.14-0.79, P = .013).Our results underscore the need to assist patients who are admitted to ICUs with VREfae BSIs. We emphasize the use of an appropriate antimicrobial therapy for VREfae BSI with the aim to treat more patients with these infections.

On the Role of Enterococci in the Bloodstream: Results of a Single-Center, Retrospective, Observational Study at a German University Hospital

This study assesses the clinical relevance of vancomycin-susceptible enterococci in bacteremic patients and compares it with bacteremia due to Staphylococcus aureus and Escherichia coli. During a 5-year-study interval, clinical and diagnostic features of patients with enterococcal bacteremia were compared to those of patients with E. coli or S. aureus bacteremia. Each patient was only counted once per hospital stay. During the 5-year study interval, data from 267 patients with enterococcal bacteremia and from 661 patients with bacteremia due to E. coli or S. aureus were evaluated. In spite of a comparable risk of death, patients with enterococci more frequently needed catecholamines and invasive ventilation. Furthermore, enterococci were more frequently associated with a mixed bacterial flora in bloodstream infections. While fatal sepsis due to E. coli and S. aureus was associated with typical shock symptoms, this association was not confirmed for enterococci. Although enterococcal bacteremia is associated with a risk of dying comparable to that with bacteremia due to E. coli and S. aureus, a lower pathogenic potential of enterococci in bloodstream has to be acknowledged. Enterococci in the bloodstream are more likely to be an epiphenomenon of impending death than its major cause.

Changed epidemiology during intra and interhospital spread of high-risk clones of vanA-containing Enterococcus in Brazilian hospitals

We report changes in the molecular epidemiology of vanA-containing Enterococcus during the intra and interhospital spread of high-risk clones, in Southeastern Brazil. While VRE faecalis predominated during 1998 to 2006, a reversal has been observed in the last years, where VRE faecium belonging to ST114, ST203, ST412, ST478 and ST858 have become endemic.

Comparison of clinical outcomes and risk factors in polymicrobial versus monomicrobial enterococcal bloodstream infections

BACKGROUND

Enterococcal bloodstream infections (EBSIs) are frequently polymicrobial but scant data describe the outcomes and risk factors of polymicrobial EBSI. This study describes the outcomes and risk factors of polymicrobial versus monomicrobial EBSI.

METHODS

In this single-center, retrospective, matched cohort study, patients with polymicrobial EBSI were matched 1:1 to patients with monomicrobial EBSI by age ± 10 years, EBSI source, Pitt bacteremia score, and enterococcal species. Conditional logistic regression was performed to determine independent predictors of 30-day mortality and polymicrobial EBSI.

RESULTS

In 142 matched pairs, 30-day mortality was 18.3% versus 21.1% (P = .551) in monomicrobial and polymicrobial EBSI, respectively. In multivariable analysis, recent chemotherapy/radiation (adjusted odds ratio [OR], 4.799; 95% confidence interval [CI], 1.814-12.696), chronic renal disease (aOR, 2.310; 95% CI, 1.176-4.539), and Pitt bacteremia score (aOR, 1.399; 95% CI, 1.147-1.706) were associated with 30-day mortality. Recent chemotherapy/radiation (aOR, 2.770; 95% CI, 1.016-7.551), and recent antibiotic exposure (aOR, 1.892; 95% CI, 1.157-3.092) were positively associated with polymicrobial EBSI, whereas chronic hemodialysis was negatively associated (aOR, 0.496; 95% CI, 0.29-81).

CONCLUSIONS

Overall, polymicrobial EBSI were not independently associated with mortality. Risk factors for, and the clinical implications of, polymicrobial EBSI should be further studied to inform clinical management and improve outcomes.

Daptomycin versus linezolid for the treatment of vancomycin-resistant enterococcal bacteraemia: implications of daptomycin dose

Treatment options for vancomycin-resistant enterococci (VRE) bloodstream infection are limited. Studies comparing daptomycin or linezolid in treating VRE bloodstream infection have conflicting results and suggest daptomycin underdosing. The responses to different daptomycin doses have not been studied. We conducted a multicentre prospective cohort study to compare linezolid and daptomycin (≥6 mg/kg) for the treatment of VRE bloodstream infection. The primary outcome was 14-day mortality. We used multivariate logistic regression analysis for outcome analysis and a generalized additive model for dose-dependent response estimation. Two hundred twelve patients were included (daptomycin, n = 141; linezolid, n = 71). All-cause 14-day mortality was higher in the daptomycin group (36.9% vs. 21.1%; p 0.03). After adjusting for confounders in logistic regression, mortality was lower in the linezolid group (adjusted odds ratio (aOR), 0.45; 95% confidence interval (CI), 0.21-0.96; p 0.04). The generalized additive model showed that higher-dose daptomycin (≥9 mg/kg) was associated with better survival than lower-dose daptomycin (6-9 mg/kg). Logistic regression showed that linezolid (aOR, 0.36; 95% CI, 0.17-0.79; p 0.01) and higher-dose daptomycin (aOR, 0.26; 95% CI, 0.09-0.74; p 0.01) independently predicted lower mortality compared to lower-dose daptomycin. Linezolid was not superior to higher-dose daptomycin in terms of mortality (aOR, 1.40; 95% CI, 0.45-4.37; p 0.57). Higher-dose daptomycin had lower mortality than lower-dose daptomycin. Despite higher mortality for lower-dose daptomycin than linezolid, linezolid conferred no survival benefit compared to higher-dose daptomycin. Our findings suggest that the recommended daptomycin dose is suboptimal for treating VRE bacteraemia.

Time Is of the Essence: The Impact of Delayed Antibiotic Therapy on Patient Outcomes in Hospital-Onset Enterococcal Bloodstream Infections

BACKGROUND

With increasing prevalence of vancomycin-resistant enterococci (VRE), appropriate antibiotic therapy for enterococcal bloodstream infections (EBSI) can be delayed. Data regarding the impact of delayed therapy on EBSI outcomes are conflicting, and the time delay most strongly associated with poor outcomes has not been defined.

METHODS

This was a single-center, retrospective cohort study of adult, nonneutropenic patients with hospital-onset EBSI from 2010 to 2014. Classification and regression tree (CART) analysis was used to determine the delay in appropriate therapy most predictive of 30-day mortality. Appropriate therapy was defined as antibiotic therapy to which the enterococci and copathogen, where applicable, were susceptible. Outcomes and clinical characteristics were compared between patients receiving early or delayed therapy, defined by CART timepoint. Poisson regression was employed to determine the independent association of delayed therapy on 30-day mortality and predictors of delayed therapy.

RESULTS

Overall, 190 patients were included. A breakpoint in time to appropriate therapy was identified at 48.1 hours, where 30-day mortality was substantially increased (14.6% vs 45.3%; P < .001). Patients receiving appropriate therapy after 48.1 hours also experienced higher in-hospital mortality and longer EBSI duration. After adjustment for severity of illness and comorbidity, delayed therapy ≥48.1 hours was associated with a 3-fold increase in 30-day mortality (risk ratio, 3.16 [95% confidence interval, 1.96-5.09]). Vancomycin resistance was the only independent predictor of delayed therapy.

CONCLUSIONS

In patients with hospital-onset EBSI, receipt of appropriate therapy within the first 48 hours was associated with reduced mortality, underscoring the potential role of rapid diagnostic testing for early identification of VRE.

Identification of subclinical transmission of vancomycin-resistant enterococcus within an intensive care unit in Taiwan

BACKGROUND/PURPOSE

Colonization, infection, and clonal dissemination of vancomycin-resistant enterococcus (VRE) have been reported in the literature. We aimed to investigate the incidence rate of VRE acquisition and route of transmission of VRE within the medical intensive care unit (ICU) to prove whether subclinical transmission occurs in medical ICUs.

METHODS

Between March 1, 2012 and September 30, 2013, rectal cultures were obtained from all inpatients on admission and after admission to medical ICU. Strain types of VRE were determined by both multilocus sequence typing and pulsed-field gel electrophoresis.

RESULTS

A total of 66 of the 405 rectal swab surveillance cultures obtained from 46 inpatients were positive for VRE, among which 27 inpatients were culture-positive for VRE on admission to medical ICU, and 19 inpatients were initially culture-negative but converted to culture-positive after admission. All isolates carried vanA gene consisting of 51 Enterococcus gallinarum, 13 Enterococcus faecium, and two Eenterococcus casseliflavus. Of the 51 E. gallinarum isolates, 40 were type ST 341, seven were ST 252, two were ST 78, and two were ST 64. The Enterococcus spp., MLST and PFGE subtypes were almost similar among these two groups of inpatients. Linezolid and tigecycline were most active against VRE in vitro.

CONCLUSION

Subclinical VRE cross transmission may occur in ICU. Active surveillance and maximal barrier precautions of VRE are required at ICU with high colonization rate of VRE and shall be beneficial.

Epidemiology of vancomycin-resistant enterococci in Canadian hospitals (CANWARD study, 2007 to 2013)

Of 1,927 Enterococcus species isolates collected across Canada from 2007 to 2013, 80 (4.2%) were identified as vancomycin-resistant enterococci (VRE). VRE infections during this time tripled in Canadian hospitals, from 1.8% to 6.0% (P = 0.03). All VRE were Enterococcus faecium, with 90% possessing vanA. The prevalence of vanB decreased from 37.5% in 2007 to 0% in 2013 (P < 0.05). The VRE were multidrug resistant, but 70.6%, 86.3%, and 100% were susceptible to doxycycline, linezolid, and daptomycin, respectively.

National surveillance on vancomycin-resistant Enterococcus faecium in Taiwan: emergence and widespread of ST414 and a Tn1546-like element with simultaneous insertion of IS1251-like and IS1678

Cases of bacteremia caused by vancomycin-resistant E. faecium (VRE-fm) increased significantly in Taiwan. The present multicenter surveillance study was performed to reveal the associated epidemiological characteristics. In 2012, 134 non-repetitive VRE-fm isolates were prospectively collected from 12 hospitals in Taiwan. Antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and analysis of van genes and Tn1546 structures were investigated. Two isolates carried vanB genes, while all the remaining isolates carried vanA genes. Three isolates demonstrated a specific vanA genotype - vanB phenotype. Nine (6.7%) isolates demonstrated tigecycline resistance, and all were susceptible to daptomycin and linezolid. Molecular typing revealed 58 pulsotypes and 13 sequence types (STs), all belonged to three major lineages 17, 18, and 78. The most frequent STs were ST17 (n = 48, 35.8%), ST414 (n = 22, 16.4%), and ST78 (n = 16, 11.9%). Among the vanA harboring isolates, eight structure types of the Tn1546-like element were demonstrated. Type I (a partial deletion in the orf1 and insertion of IS1251-like between the vanS - vanH genes) and Type II (Type I with an additional insertion of IS1678 between orf2 - vanS genes) were the most predominant, consisted of 60 (45.5%) and 62 (47.0%) isolates, respectively. The increase of VRE-fm bacteremia in Taiwan may be associated with the inter- and intra-hospital spread of some major STs and horizontal transfer of vanA genes mostly carried on two efficient Tn1546-like elements. The prevailing ST414 and widespread of the Type II Tn1546-like elements are an emerging problem that requires continuous monitoring.

Daptomycin versus linezolid for treatment of vancomycin-resistant enterococcal bacteremia: systematic review and meta-analysis

Background

Linezolid, which has bacteriostatic activity, is approved for the treatment of vancomycin-resistant enterococci (VRE) infections. Meanwhile, daptomycin exerts bactericidal activity against VRE, but is not approved for the treatment of VRE bacteremia. Only a few studies with small sample sizes have compared the effectiveness of these drugs for treatment of VRE bacteremia.

Methods

PubMed, EMBASE, and the Cochrane Library were searched for studies of VRE bacteremia treatment published before January 1, 2014. All studies reporting daptomycin and linezolid treatment outcomes simultaneously were included. The endpoints were mortality and microbiological cure. The adjusted odds ratios (aORs) of mortality in daptomycin- and linezolid-treated patients were extracted if available. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for all outcomes using a random-effects model.

Results

Thirteen studies (532 patients receiving daptomycin, 656 patients receiving linezolid) met the selection criteria. All studies had retrospective cohort designs and relatively small sample sizes. Eight studies compared the aORs of mortality in daptomycin- and linezolid-treated patients. Four studies were published as conference papers and there was significant heterogeneity among these studies (I² = 63%, p = 0.04). Daptomycin use was not associated with better microbiological cure (daptomycin vs. linezolid, OR: 0.67, 95% CI: 0.42–1.06, p = 0.09). However, mortality was higher in patients receiving daptomycin (OR: 1.43, 95% CI: 1.09–1.86, p = 0.009). Subgroup analysis of studies that reported aORs indicated that daptomycin was associated with higher mortality (OR: 1.59, 95% CI: 1.02–2.50, p = 0.04). There was no evidence of publication bias, but all enrolled studies were retrospective, had small sample sizes, and had substantial limitations.

Conclusions

Although limited data is available, the current meta-analysis shows that linezolid treatment for VRE bacteremia was associated with a lower mortality than daptomycin treatment. However, the results should be interpreted cautiously because of limitations inherent to retrospective studies and the high heterogeneity among studies. A large randomized trial is needed to confirm the present results.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0687-9) contains supplementary material, which is available to authorized users.

Systematic review and meta-analysis of linezolid and daptomycin for treatment of vancomycin-resistant enterococcal bloodstream infections

Bloodstream infections due to vancomycin-resistant enterococci (VRE-BSI) result in substantial patient mortality and cost. Daptomycin and linezolid are commonly prescribed for VRE-BSI, but there are no clinical trials to determine optimal antibiotic selection. We conducted a systematic review for investigations that compared daptomycin and linezolid for VRE-BSI. We searched Medline from 1966 through 2012 for comparisons of linezolid and daptomycin for VRE-BSI. We included searches of EMBASE, clinicaltrials.gov, and national meetings. Data were extracted using a standardized instrument. Pooled odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using a fixed-effects model. Our search yielded 4,243 publications, of which 482 contained data on VRE treatment. Most studies (452/482) did not present data on BSI or did not provide information on linezolid or daptomycin. Among the remaining 30 studies, 9 offered comparative data between the two agents. None were randomized clinical trials. There was no difference in microbiologic (n = 5 studies, 517 patients; OR, 1.0; 95% CI, 0.4 to 1.7; P = 0.95) and clinical (n = 3 studies, 357 patients; OR, 1.2; 95% CI, 0.7 to 2.0; P = 0.7) cures between the two antibiotics. There was a trend toward increased survival with linezolid compared to daptomycin treatment (n = 9 studies, 1,074 patients; OR, 1.3; 95% CI, 1.1 to 1.8; I(2) = 0 [where I(2) is a measure of inconsistency]), but this did not reach statistical significance (P = 0.054). There are limited data to inform clinicians on optimal antibiotic selection for VRE-BSI. Available studies are limited by small sample size, lack of patient-level data, and inconsistent outcome definitions. Additional research, including randomized clinical trials, is needed before conclusions can be drawn about treatment options for VRE therapy.

Identification of vancomycin-resistant enterococci clones and inter-hospital spread during an outbreak in Taiwan

BACKGROUND

In 2003, nosocomial infections caused by vancomycin-resistant enterococci (VRE) occurred rarely in Taiwan. Between 2003 and 2010, however, the average prevalence of vancomycin resistance among enterococci spp. increased from 2% to 16% in community hospitals and from 3% to 21% in medical centers of Taiwan. We used molecular methods to investigate the epidemiology of VRE in a tertiary teaching hospital in Taiwan.

METHODS

Between February 2009 and February 2011, rectal samples and infection site specimens were collected from all inpatients in the nephrology ward after patient consent was obtained. VRE strain types were determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

RESULTS

A total of 59 vanA gene-containing VRE isolates (1 per patient) were obtained; 24 originated from rectal sample surveillance of patients who exhibited no symptoms (22 Enterococcus faecium and 2 Enterococcus faecalis), and 35 had developed infections over 3 days after admission (32 E. faecium, 2 E. faecalis, and 1 Enterococcus durans). The 59 VRE isolates demonstrated vancomycin minimum inhibitory concentrations (MICs) of ≥256 μg/m. The MIC range for linezolid, tigecycline, and daptomycin was 0.25-1.5 μg/mL, 0.032-0.25 and 1-4 μg/mL, respectively. For 56 isolates, the MIC for teicoplanin was >8 μg/mL. The predominant types in the nephrology ward were MLST types 414, 78, and18 as well as PFGE types A, C, and D.

CONCLUSION

VREs are endemic in nephrology wards. MLST 414 is the most predominant strain. The increase VRE prevalence is due to cross-transmission of VRE clones ST 414,78,18 by undetected VRE carriers. Because similar VRE STs had been reported in a different hospital of Taiwan, this finding may indicate inter-hospital VRE spread in Taiwan. Active surveillance and effective infection control policies are important controlling the spread of VRE in high risk hospital zones. All endemic VRE strains are resistant to teicoplanin but are sensitive to daptomycin, linezolid, and tigecycline.

Antimicrobial resistance in Asia: current epidemiology and clinical implications

Antimicrobial resistance has become one of the most serious public health concerns worldwide. Although circumstances may vary by region or country, it is clear that some Asian countries are epicenters of resistance, having seen rapid increases in the prevalence of antimicrobial resistance of major bacterial pathogens. In these locations, however, the public health infrastructure to combat this problem is very poor. The prevalence rates of methicillin-resistant Staphylococcus aureus (MRSA), macrolide-resistant Streptococcus pneumoniae, and multidrug-resistant enteric pathogens are very high due to the recent emergence of extremely drug-resistant gram-negative bacilli in Asia. Because antimicrobial options for these pathogens are extremely limited, infections caused by antimicrobial-resistant bacteria are often associated with inappropriate antimicrobial therapy and poor clinical outcomes. Physicians should be aware of the current epidemiological status of resistance and understand the appropriate use of antimicrobial agents in clinical practice. This review focuses on describing the epidemiology and clinical implications of antimicrobial-resistant bacterial infections in Asian countries.