Risk factors and outcomes associated with vancomycin-resistant Enterococcus infections with reduced susceptibilities to linezolid

Clonal distribution of vancomycin-resistant Enterococcus faecium in Turkey and the new singleton ST733

Background

The aim of this study was to provide information about the spread and characteristics of the vancomycin‐resistant Enterococcus faecium isolates (VREfm) in Turkey.

Methods

Seventy‐one nonduplicate consecutive isolates of VREfm were obtained from various clinical specimens of inpatients treated at university or training hospitals in seven regions of Turkey. Further characteristics included antibiotic susceptibility testing, pulsed‐field gel electrophoresis (PFGE) of SmaI‐digested genomic DNA, and multilocus sequence typing (MLST) of selected isolates. The presence of vancomycin resistance and virulence genes (esp and hyl) was investigated by polymerase chain reaction (PCR).

Results

All VREfm isolates had MICs to vancomycin of ≥32 mg/L and contained the vanA gene. The presence of esp gene was identified in 64 and hyl in eight VREfm isolates. All VREfm showed the multiresistance phenotype, including ampicillin (99%), penicillin (99%), imipenem (99%), ciprofloxacin (87%), moxifloxacin (87%), erythromycin (97%), streptomycin (86%), gentamicin (82%), tetracycline (70%), and teicoplanin (99%). All were susceptible to tigecycline while quinupristin‐dalfopristin (97%) and linezolid (93%) were the most active other agents. Analysis of the PFGE profiles showed that 53 (74.6%) VREfm isolates shared a similar electrophoretic profile, designed as type 1, and were closely related (>85%). The sequence type was identified by MLST in 44 VRE isolates with unrelated or closely related PFGE patterns. MLST revealed that nosocomial spread of VREfm resulted from dissemination of lineage C1 E faecium clones. Sequence types ST78, ST203, and ST117 were the most frequently isolated. This is the first report of ST733 around the world.

Conclusions

Lineage C1 clones are disseminated among clinical VREfm isolates in seven different regions in Turkey. Regarding VREfm isolates, the worldwide epidemic strains are in circulation in Turkey.

Perfil microbiológico dos pacientes submetidos à cultura de vigilância ativa em um hospital universitário da Região Sudeste de Minas Gerais

Objetivo: Identificar o perfil microbiológico dos pacientes submetidos à cultura de vigilância ativa. Material e métodos: Estudo de prevalência realizado em um hospital universitário da Região Sudeste de Minas Gerais no período de março a dezembro de 2018, com os pacientes elegíveis pelos critérios pré-estabelecidos pelo Serviço de Controle de Infecção Hospitalar da referida unidade, submetidos à cultura de vigilância por meio de swab retal e nasal. Os critérios definidos foram: pacientes transferidos de outra instituição com permanência maior que 96 horas; pacientes transferidos de outra instituição com internação mínima de 48 horas e submetidos a algum dispositivo invasivo; realização de terapia renal substitutiva; passagem por Unidade de Terapia Intensiva (nos últimos 90 dias com permanência mínima de 72h;internação prévia nos últimos 90 dias com permanência mínima de 30 dias. O banco de dados foi estruturado e analisado por meio do Excel e as análises estatísticas pelo MedCalc. Resultados: Foram identificados 591 pacientes que atendiam aos critérios para a realização da cultura de vigilância, destes 25,4% foram positivos. Os critérios mais frequentes para realização de cultura foram: pacientes transferidos de outra instituição com permanência maior que 96 horas e pacientes com passagem por unidade de terapia intensiva nos últimos 90 dias com permanência mínima de 72h. Os Principais microrganismos identificados foram: Staphylococcus aureus resistente à o meticilina, Klebsiellapneumoniae e Acinetobacter baumannii resistentes à carbapenêmicos com 38,3%, 31,2% e 25,3%, respectivamente. Conclusão: A cultura de vigilância ativa contribuiu para a detecção precoce de microrganismos resistentes, permitindo a prevenção precoce, favorecendo a redução da disseminação cruzada. O banco de dados com resultados das culturas de vigilância é uma estratégia importante, pois caso ocorra reinternações desses pacientes, as equipes de controle de infecção e assistencial podem identificar aqueles já infectados/colonizados e instaurar as medidas de controle na admissão dos mesmos.

Risk Factors and Outcomes Associated With Acquisition of Daptomycin and Linezolid-Nonsusceptible Vancomycin-Resistant Enterococcus

Background

Vancomycin-resistant enterococcus (VRE) causes substantial health care–associated infection with increasing reports of resistance to daptomycin or linezolid. We conducted a case–control study reporting 81 cases of daptomycin and linezolid–nonsusceptible VRE (DLVRE), a resistance pattern not previously reported.

Methods

We reviewed VRE isolates from June 2010 through June 2015 for nonsusceptibility to both daptomycin (minimum inhibitory concentration [MIC] > 4) and linezolid (MIC ≥ 4). We matched cases by year to control patients with VRE susceptible to both daptomycin and linezolid and performed retrospective chart review to gather risk factor and outcome data.

Results

We identified 81 DLVRE cases. Resistance to both daptomycin and linezolid was more common than resistance to either agent individually. Compared with susceptible VRE, DLVRE was more likely to present as bacteremia without focus (P < 0.01), with DLVRE patients more likely to be immune suppressed (P = .04), to be neutropenic (P = .03), or to have had an invasive procedure in the prior 30 days (P = .04). Any antibiotic exposure over the prior 30 days conferred a 4-fold increased risk for DLVRE (odds ratio [OR], 4.25; 95% confidence interval [CI], 1.43−12.63; P = .01); multivariate analysis implicated daptomycin days of therapy (DOT) over the past year as a specific risk factor (OR, 1.10; 95% CI, 1.01−1.19; P = .03). DLVRE cases had longer hospitalizations (P = .04) but no increased risk for in-hospital death.

Conclusions

DLVRE is an emerging multidrug-resistant pathogen associated with immune suppression, neutropenia, and recent invasive procedure. Prior antibiotic exposure, specifically daptomycin exposure, confers risk for acquisition of DLVRE.

Prediction of Bloodstream Infection Due to Vancomycin-Resistant Enterococcus in Patients Undergoing Leukemia Induction or Hematopoietic Stem-Cell Transplantation

Background.

Bloodstream infection (BSI) to due vancomycin-resistant Enterococcus (VRE) is an important complication of hematologic malignancy. Determining when to use empiric anti-VRE antibiotic therapy in this population remains a clinical challenge.

Methods.

A single-center cohort representing 664 admissions for induction or hematopoietic stem-cell transplant (HSCT) from 2006 to 2014 was selected. We derived a prediction score using risk factors for VRE BSI and evaluated the model's predictive performance by calculating it for each of 16232 BSI at-risk inpatient days.

Results.

VRE BSI incidence was 6.5% of admissions (2.7 VRE BSI per 1000 BSI at-risk days). Adjusted 1-year mortality and length of stay were significantly higher in patients with VRE BSI. VRE colonization (adjusted odds ratio [aOR] = 8.4; 95% confidence interval [CI] = 3.4-20.6; P < .0001), renal insufficiency (aOR = 2.4; 95% CI = 1.0-5.8; P = .046), aminoglycoside use (aOR = 4.7; 95% CI = 2.2-9.8; P < .0001), and antianaerobic antibiotic use (aOR = 2.8; 95% CI = 1.3-5.8; P = .007) correlated most closely with VRE BSI. A prediction model with optimal performance included these factors plus gastrointestinal disturbance, severe neutropenia, and prior beta-lactam antibiotic use. The score effectively risk-stratified patients (area under the receiver operating curve = 0.84; 95% CI = 0.79-0.89). At a threshold of ≥5 points, per day probability of VRE BSI was increased nearly 4-fold.

Conclusions.

This novel predictive score is based on risk factors reflecting a plausible pathophysiological model for VRE BSI in patients with hematological malignancy. Integrating VRE colonization status with risk factors for developing BSI is a promising method of guiding rational use of empiric anti-VRE antimicrobial therapy in patients with hematological malignancy. Validation of this novel predictive score is needed to confirm clinical utility.

Prolonged linezolid use is associated with the development of linezolid-resistant Enterococcus faecium

We assessed risk factors for and outcomes of linezolid-resistant vancomycin-resistant Enterococcus faecium (LRVREF) bacteremia over 7 years. Thirty-four LRVREF cases were matched to 68 linezolid-susceptible VREF controls. The odds of bacteremia with LRVREF increased by 7% for each additional day of prior linezolid exposure.

Resistance mechanisms and clinical characteristics of linezolid-resistant Enterococcus faecium isolates: A single-centre study in South Korea

OBJECTIVES

This study aimed to determine the prevalence of linezolid-resistant (LR) vancomycin-resistant enterococci and to investigate the mechanisms of linezolid resistance with clinical and microbiological characterisation.

METHODS

All vancomycin-resistant Enterococcus faecium (VREF) isolated from blood and rectal swab cultures during 2012-2015 were tested for linezolid resistance. LR-VREF isolates were tested for antimicrobial susceptibility, glycopeptide resistance genes and virulence genes. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed. Isolates were tested for known mechanisms of linezolid resistance.

RESULTS

Among 389 VREF isolates, 7 (1.8%) were found to be resistant to linezolid. All LR-VREF isolates carried the vanA gene. Five isolates had both hyl and esp genes. The isolates were susceptible to tigecycline, daptomycin and quinupristin/dalfopristin, except for one isolate with daptomycin resistance. Two LR-VREF isolates recovered from patients with previous linezolid exposure contained the G2576T mutation in 23S rRNA and exhibited high-level resistance to linezolid (MIC>64mg/L). The other five isolates recovered from linezolid-naïve patients revealed no known linezolid resistance mechanism and exhibited low-level resistance to linezolid (MICs=8-16mg/L). Plasmid-mediated genes encoding cfr or optrA were not detected. LR-VREF isolates were represented by six different sequence types, belonging to hospital lineages, and were assigned to seven PFGE types.

CONCLUSIONS

The prevalence of LR-VREF in this centre was low. Both linezolid exposure and horizontal transmission appear to be responsible for acquisition of LR-VREF in hospitalised patients. Prudent use of linezolid and improved infection control strategies are needed to limit the spread of LR-VREF.

Retrospective analysis of hospital-acquired linezolid-nonsusceptible enterococci infection in Chongqing, China, 2011-2014

BACKGROUND

Linezolid-nonsusceptible enterococci (LNSE) is an increasingly emerging multidrug-resistant pathogen, and the caused nosocomial infections are difficult to manage. However, data on the host-related risk factors and clinical outcomes for LNSE infection are poorly characterized.

METHODS

A retrospective case-case-control study of risk factors and clinical outcomes of hospitalized patients with LNSE infection during the period 2011-2014 was conducted in a teaching hospital in Chongqing, China. Case patients with LNSE and those with linezolid-susceptible enterococci (LSE) and controls with no enterococcal infection were compared at a ratio of 1:1:4. Two parallel multivariate logistic regression models were used to evaluate independent predictors for acquiring LNSE and LSE, respectively.

RESULTS

Forty-four LNSE cases, 44 LSE cases, and 176 uninfected controls were analyzed. Multivariable analysis indicated that transferring from another hospital (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.58-8.09), peripheral vascular disease (OR, 4.36; 95% CI, 1.64-11.60), and exposure to cephalosporins (OR, 4.24; 95% CI, 1.85-9.71) were unique independent predictors for acquiring LNSE. Gallbladder disease (OR, 3.64; 95% CI, 1.36-9.74) was independently associated with LSE acquisition. Polymicrobial infection was the only factor identified in both LNSE and LSE groups compared with controls; however, no statistical significance was observed in in-hospital mortality.

CONCLUSION

Timely control efforts and appropriate antibiotic stewardship programs are necessary to effectively reduce the burden of LNSE infections among high-risk patients.

Antibacterial Discovery and Development: From Gene to Product and Back

Concern over the reports of antibiotic-resistant bacterial infections in hospitals and in the community has been publicized in the media, accompanied by comments on the risk that we may soon run out of antibiotics as a way to control infectious disease. Infections caused by Enterococcus faecium, Staphylococcus aureus, Klebsiella species, Clostridium difficile, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, and other Enterobacteriaceae species represent a major public health burden. Despite the pharmaceutical sector's lack of interest in the topic in the last decade, microbial natural products continue to represent one of the most interesting sources for discovering and developing novel antibacterials. Research in microbial natural product screening and development is currently benefiting from progress that has been made in other related fields (microbial ecology, analytical chemistry, genomics, molecular biology, and synthetic biology). In this paper, we review how novel and classical approaches can be integrated in the current processes for microbial product screening, fermentation, and strain improvement.

Enterococcal endocarditis revisited

The Enterococcus species is the third main cause of infective endocarditis (IE) worldwide, and it is gaining relevance, especially among healthcare-associated cases. Patients with enterococcal IE are older and have more comorbidities than other types of IE. Classical treatment options are limited due to the emergence of high-level aminoglycosides resistance (HLAR), vancomycin resistance and multidrug resistance in some cases. Besides, few new antimicrobial alternatives have shown real efficacy, despite some of them being recommended by major guidelines (including linezolid and daptomycin). Ampicillin plus ceftriaxone 2 g iv./12 h is a good option for Enterococcus faecalis IE caused by HLAR strains, but randomized clinical trials are essential to demonstrate its efficacy for non-HLAR EFIE and to compare it with ampicillin plus short-course gentamicin. The main mechanisms of resistance and treatment options are also reviewed for other enterococcal species.

Multidrug-resistant bacteria in organ transplantation: an emerging threat with limited therapeutic options

Multidrug-resistant organisms (MDROs) are an emerging threat in solid organ transplantation (SOT). The changing epidemiology of these MDROs is reviewed along with the growing evidence regarding risk factors and outcomes associated with both colonization and infection in SOT. The management of these infections is complicated by the lack of antimicrobial agents available to treat these infections, and only a handful of new agents, especially for the treatment of MDR GNR infections, are being evaluated in clinical trials. Due to the increased prevalence of MDROs and limited treatment options, as well as organ shortages, transplant candidacy and use of organs from donors with evidence of MDRO colonization and/or infection remain controversial. Increasing collaboration between transplant programs, individual practitioners, infection control programs, and researchers in antimicrobial development will be needed to face this challenge.

Current and prospective treatments for multidrug-resistant gram-positive infections

INTRODUCTION

Staphylococcus aureus and Enterococcus spp. are two of the most common organisms causing nosocomial infections today; and are consistently associated with high mortality rates (approximately 20 and 44%, respectively). Resistance among these pathogens to first line agents such as methicillin and vancomycin continues to rise while isolates with reduced susceptibility to newer agents including linezolid and daptomycin continue to emerge, representing a serious concern for clinicians.

AREAS COVERED

Mechanisms of action and resistance as well as in vitro and clinical experience in the treatment of resistant staphylococci and enterococci with currently available agents are discussed. Additionally, novel combination regimens showing enhanced efficacy and available data pertaining to prospective therapies including solithromycin, tedizolid, dalbavancin and oritavancin will be covered.

EXPERT OPINION

With an increase in organisms displaying reduced susceptibility to vancomycin and the associated treatment failures, the significance of alternative therapies such as daptomycin, linezolid, ceftaroline, and prospective anti-gram-positive agents is on the rise. As our understanding of antimicrobial pharmacokinetic-pharmacodynamics principles continues to evolve, the selection of highly effective agents and optimization of dosages may lead to improved patient outcomes and delay the development of resistance.