Vancomycin-resistant enterococcal bacteremia in a hematology unit: molecular epidemiology and analysis of clinical course

Comparison of morbidity and mortality after bloodstream infection with vancomycin-resistant versus -susceptible Enterococcus faecium: a nationwide cohort study in Denmark, 2010-2019

The emergence of bloodstream infections (BSI) caused by vancomycin-resistant Enterococci (VRE) has caused concern. Nonetheless, it remains unclear whether these types are associated with an excess risk of severe outcomes when compared with infections caused by vancomycin-susceptible Enterococci (VSE). This cohort study included hospitalized patients in Denmark with Enterococcus faecium-positive blood cultures collected between 2010 and 2019 identified in the Danish Microbiology Database. We estimated 30-day hazard ratio (HR) of death or discharge among VRE compared to VSE patients adjusted for age, sex, and comorbidity. The cohort included 6071 patients with E. faecium BSI (335 VRE, 5736 VSE) among whom VRE increased (2010-13, 2.6%; 2014-16, 6.3%; 2017-19; 9.4%). Mortality (HR 1.08, 95%CI 0.90-1.29; 126 VRE, 37.6%; 2223 VSE, 37.0%) or discharge (HR 0.89, 95%CI 0.75-1.06; 126 VRE, 37.6%; 2386 VSE, 41.6%) was not different between VRE and VSE except in 2014 (HR 1.87, 95% CI 1.18-2.96). There was no interaction between time from admission to BSI (1-2, 3-14, and >14 days) and HR of death (P = 0.14) or discharge (P = 0.45) after VRE compared to VSE, despite longer time for VRE patients (17 vs. 10 days for VSE, P < 0.0001). In conclusion, VRE BSI was not associated with excess morbidity and mortality. The excess mortality in 2014 only may be attributed to improved diagnostic- and patient-management practices after 2014, reducing time to appropriate antibiotic therapy. The high level of mortality after E. faecium BSI warrants further study.

Does vancomycin resistance increase mortality in Enterococcus faecium bacteraemia after orthotopic liver transplantation? A retrospective study

BACKGROUND

The relevance of vancomycin resistance in enterococcal blood stream infections (BSI) is still controversial. Aim of this study was to outline the effect of vancomycin resistance of Enterococcus faecium on the outcome of patients with BSI after orthotopic liver transplantation (OLT).

METHODS

The outcome of OLT recipients developing BSI with vancomycin-resistant (VRE) versus vancomycin-susceptible Enterococcus faecium (VSE) was compared based on data extraction from medical records. Multivariate regression analyses identified risk factors for mortality and unfavourable outcomes (defined as death or prolonged intensive care stay) after 30 and 90 days.

RESULTS

Mortality was similar between VRE- (n = 39) and VSE- (n = 138) group after 30 (p = 0.44) or 90 days (p = 0.39). Comparable results occurred regarding unfavourable outcomes. Mean SOFA_Non-GCS score during the 7-day-period before BSI onset was the independent predictor for mortality at both timepoints (HR 1.32; CI 1.14-1.53; and HR 1.18; CI 1.08-1.28). Timely appropriate antibiotic therapy, recent ICU stay and vancomycin resistance did not affect outcome after adjusting for confounders.

CONCLUSION

Vancomycin resistance did not influence outcome among patients with Enterococcus faecium bacteraemia after OLT. Only underlying severity of disease predicted poor outcome among this homogenous patient population.

TRIAL REGISTRATION

This study was registered at the German clinical trials register (DRKS-ID: DRKS00013285).

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.

Outbreaks caused by vancomycin-resistant Enterococcus faecium in hematology and oncology departments: A systematic review

Background

Vancomycin-resistance in Enterococcus faecium (VRE) poses a major threat in health care settings. It is well known that patients in hematology and oncology departments are especially at risk of nosocomial VRE acquisition. This systematic review of the literature provides data on the main sources, transmission modes and potential risk factors for VRE acquisition as well as appropriate infection control measures in order to terminate such nosocomial outbreaks.

Methods

Data on nosocomial VRE outbreaks on hematology and oncology wards was retrieved from the Outbreak Database and PubMed.

Results

A total of 35 VRE outbreaks describing 757 affected patients and 77 deaths were included in this review. The most frequent site of pathogen detection were stool samples or rectal swabs (57% of all isolation sites), followed by blood cultures (30%). The most common outbreak source was an index patient. The main modes of transmission were 1) hands of health care workers, 2) contact to a contaminated environment and 3) patient-to-patient contact. The most common risk factor for VRE positivity was prior antibiotic treatment. The most common infection control measures performed were screening and isolating or cohorting of patients.

Conclusion

A rational use of antibiotics in hematology and oncology units is recommended in order to reduce selection pressure on resistant pathogens such as VRE. In addition the importance of hand hygiene should be stressed to all staff whenever possible.

Where is the difference between an epidemic and a high endemic level with respect to nosocomial infection control measures? An analysis based on the example of vancomycin-resistant Enterococcus faecium in hematology and oncology departments

Some infection control recommendations distinguish epidemic and endemic levels for infection control. However, it is often difficult to separate long lasting outbreaks from high endemic levels and it remains open, if this distinction is really useful. Aim: To compare infection control measures in endemic and epidemic outbreaks. Methods: The example of vancomycin-resistant Enterococcus faecium outbreaks in haematology or oncology departments was used to analyse differences in infection control measures between outbreaks and high endemic levels. The outbreak database and PubMed, including long lasting outbreaks, were used for this analysis. Two time limits were used for separation: 6 and 12 months. In addition, monoclonal and polyclonal outbreaks were distinguished. Findings: A total of 36 outbreaks were included. 13 outbreaks lasted 6 months or less, 9 outbreaks more than 6 months but at maximum 12 months and 9 more than 12 months. For the remaining outbreaks, no information about their duration was available. Altogether, 11 outbreaks were monoclonal and 20 polyclonal. Considering infection control measures, there were almost no differences between the different groups compared. Patient screening was given up in 37.5% of long lasting outbreaks (>12 months) and hand hygiene not reported in the majority of polyclonal outbreaks (77.8%). Conclusion: Despite many institutions trying to add further infection control measures in case of an outbreak, evidence based infection control measures should be implemented in endemic and epidemic situations. The crucial aspect is probably the degree of implementation and its control in both situations.

Colonization With Vancomycin-Resistant Enterococci and Risk for Bloodstream Infection Among Patients With Malignancy: A Systematic Review and Meta-Analysis

Background

Vancomycin-resistant enterococci (VRE) cause severe infections among patients with malignancy, and these infections are usually preceded by gastrointestinal colonization.

Methods

We searched the PubMed and EMBASE databases (up to May 26, 2016) to identify studies that reported data on VRE gastrointestinal colonization among patients with solid or hematologic malignancy.

Results

Thirty-four studies, reporting data on 8391 patients with malignancy, were included in our analysis. The pooled prevalence of VRE colonization in this population was 20% (95% confidence interval [CI], 14%–26%). Among patients with hematologic malignancy, 24% (95% CI, 16%–34%) were colonized with VRE, whereas no studies reported data solely on patients with solid malignancy. Patients with acute leukemia were at higher risk for VRE colonization (risk ratio [RR] = 1.95; 95% CI, 1.17–3.26). Vancomycin use or hospitalization within 3 months were associated with increased colonization risk (RR = 1.92, 95% CI = 1.06–3.45 and RR = 4.68, 95% CI = 1.66–13.21, respectively). Among the different geographic regions, VRE colonization rate was 21% in North America (95% CI, 13%–31%), 20% in Europe (95% CI, 9%–34%), 23% in Asia (95% CI, 13%–38%), and 4% in Oceania (95% CI, 2%–6%). More importantly, colonized patients were 24.15 (95% CI, 10.27–56.79) times more likely to develop a bloodstream infection due to VRE than noncolonized patients.

Conclusions

A substantial VRE colonization burden exists among patients with malignancy, and colonization greatly increases the risk for subsequent VRE bloodstream infection. Adherence to antimicrobial stewardship is needed, and a re-evaluation of the use of vancomycin as empiric therapy in this patient population may be warranted.

VRE and VSE Bacteremia Outcomes in the Era of Effective VRE Therapy: A Systematic Review and Meta-analysis

BACKGROUND

Prior data suggest that vancomycin-resistant Enterococcus (VRE) bacteremia is associated with worse outcomes than vancomycin-sensitive Enterococcus (VSE) bacteremia. However, many studies evaluating such outcomes were conducted prior to the availability of effective VRE therapies.

OBJECTIVE

To systematically review VRE and VSE bacteremia outcomes among hospital patients in the era of effective VRE therapy.

METHODS

Electronic databases and grey literature published between January 1997 and December 2014 were searched to identify all primary research studies comparing outcomes of VRE and VSE bacteremias among hospital patients, following the availability of effective VRE therapies. The primary outcome was all-cause, in-hospital mortality, while total hospital length of stay (LOS) was a secondary outcome. All meta-analyses were conducted in Review Manager 5.3 using random-effects, inverse variance modeling.

RESULTS

Among all the studies reviewed, 12 cohort studies and 1 case control study met inclusion criteria. Similar study designs were combined in meta-analyses for mortality and LOS. VRE bacteremia was associated with increased mortality compared with VSE bacteremia among cohort studies (odds ratio [OR], 1.80; 95% confidence interval [CI], 1.38–2.35; I²=0%; n=11); the case-control study estimate was similar, but not significant (OR, 1.93; 95% CI, 0.97–3.82). LOS was greater for VRE bacteremia patients than for VSE bacteremia patients (mean difference, 5.01 days; 95% CI, 0.58–9.44]; I²=0%; n=5).

CONCLUSIONS

Despite the availability of effective VRE therapy, VRE bacteremia remains associated with an increased risk of in-hospital mortality and LOS when compared to VSE bacteremia.

Infect. Control Hosp. Epidemiol. 2015;37(1):26–35

Risk factors for vancomycin-resistant enterococcus bacteremia and its influence on survival after allogeneic hematopoietic cell transplantation

Vancomycin-resistant enterococcus (VRE) is a well-known infectious complication among immunocompromised patients. We performed a retrospective analysis to identify risk factors for the development of VRE bacteremia (VRE-B) within 15 months after allogeneic hematopoietic cell transplantation (alloHCT) and to determine its prognostic importance for other post-transplant outcomes. Eight hundred consecutive adult patients who underwent alloHCT for hematologic diseases from 1997 to 2011 were included. Seventy-six (10%) developed VRE-B at a median of 46 days post transplant. Year of transplant, higher HCT comorbidity score, a diagnosis of ALL, unrelated donor and umbilical cord blood donor were all significant risk factors on multivariable analysis for the development of VRE-B. Sixty-seven (88%) died within a median of 1.1 months after VRE-B, but only four (6%) of these deaths were attributable to VRE. VRE-B was significantly associated with worse OS (hazard ratio 4.28, 95% confidence interval 3.23-5.66, P<0.001) in multivariable analysis. We conclude that the incidence of VRE-B after alloHCT has increased over time and is highly associated with mortality, although not usually attributable to VRE infection. Rather than being the cause, this may be a marker for a complicated post-transplant course. Strategies to further enhance immune reconstitution post transplant and strict adherence to infection prevention measures are warranted.

Impact of vancomycin resistance on mortality in neutropenic patients with enterococcal bloodstream infection: a retrospective study

BACKGROUND

Vancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI) is generally associated with the delayed administration of adequate antibiotics. The identification of risk factors and outcomes of VRE BSI is necessary for establishing strategies for managing neutropenic fever in patients with hematological malignancies.

METHODS

We retrospectively analysed consecutive cases of enterococcal BSI in patients with neutropenia after chemotherapy or stem cell transplantation between July 2009 and December 2011 at a single center.

RESULTS

During the 30-month period, among 1,587 neutropenic patients, the incidence rate of enterococcal BSI was 1.76 cases per 1,000 person-days. Of the 91 enterococcal BSIs, there were 24 cases of VRE. VRE BSI was associated with E. faecium infection (P < .001), prolonged hospitalization (P = .025) and delayed administration (≥ 48 hours after the febrile episode) of adequate antibiotics (P = .002). The attributable mortality was 17% and 9% for VRE and vancomycin-susceptible Enterococcus (VSE), respectively (P = .447). The 30-day crude mortality was 27% and 23% for VRE and VSE, respectively (OR 1.38, 95% CI 0.53-3.59; P = .059). Only SAPS-II was an independent predictive factor for death (adjusted OR 1.12, 95% CI 1.08-1.17; P < .001).

CONCLUSIONS

In conclusion, vancomycin resistance showed some trend towards increasing 30-day mortality, but is not statistically significant despite the delayed use of adequate antibiotics (≥48 hours). Only underlying severity of medical condition predicts poor outcome in a relatively homogeneous group of neutropenic patients.

Molecular epidemiology of vancomycin-resistant Enterococcus faecium bloodstream infections among patients with neutropenia over a 6-year period in South Korea

Over a 6-year period (March 2000-February 2006), there were 60 vancomycin-resistant Enterococcus faecium (VREF) bloodstream infections (BSIs) in a hematology unit, accounting for 83.3% of all VREF BSIs in the hospital. We investigated 49 VREF isolates causing BSIs in patients with neutropenia to understand the molecular epidemiology at this unit. All isolates had the vanA genotype. Pulsed-field gel electrophoresis typing revealed high clonal diversity (23 types with nine clusters comprising 35 isolates) and 1 predominant type, type A (14/49, 28.6%), persisted at this unit throughout the study period, suggesting the clonal spread of this endemic strain by cross-contamination. Tn1546 types were less heterogeneous, with five main Tn1546 types, two of which (types I and IV) accounted for 67.4% of isolates. This indicates that in addition to clonal spread, the horizontal transfer of Tn1546 played a major role in the nosocomial dissemination of vancomycin resistance. The genetic diversity of VREF increased over time, implying an increasing influx of new strains into the unit and genetic changes, possibly attributable to the horizontal transfer of diverse Tn1546 types. Despite such diversity, all the isolates belonged to clonal complex 17, which is the epidemic clone worldwide, enriched with the esp (35/49, 71.4%) and hyl (24/49, 48.9%) virulence genes. This hospital-adapted clone has become endemic and is well suited to causing BSIs in patients with neutropenia in this unit.

Vancomycin-resistant enterococcal colonization appears associated with increased mortality among allogeneic hematopoietic stem cell transplant recipients

There are no cohort studies describing outcomes of patients colonized with vancomycin-resistant enterococci (VRE) undergoing allogeneic hematopoietic stem cell transplantation (AHSCT). We therefore conducted a retrospective cohort study of 217 consecutive adults undergoing AHSCT at the Mayo Clinic (Rochester, MN, USA) from 1998 to 2004. We analyzed the association between VRE colonization prior to transplant and 100-day post transplant mortality and morbidity. We identified 22 pretransplant VRE colonized patients and 195 non-colonized patients. Both groups had similar baseline characteristics with the following six exceptions. Colonized patients were more likely to have had pretransplant Clostridium difficile-associated diarrhea, pretransplant acute renal failure, AML, Cy/TBI conditioning, decreased platelet count at time of transplantation and myeloablative conditioning regimens. Overall, patients colonized with VRE were twice as likely to die by day 100 post transplant compared to non-colonized patients (hazard ratio: 2.1, P=0.028). This association persisted even after adjusting for differences in baseline characteristics. Increased mortality in the colonized group correlated with the presence of VRE bacteremia. Overall, pretransplant VRE colonization appears to be an independent risk factor for increased mortality post-AHSCT.

Intensified strategies to control vancomycin-resistant enterococci in immunocompromised patients

Increasing colonization and infection with vancomycin-resistant enterococci (VRE) in immunocompromised patients are associated with increased mortality. Despite contact precautions for VRE control, rapid limitation of its spread is often impossible. We report on a VRE outbreak in a hematologic/oncologic unit including 33 patients. Although 28 of the patients had only VRE colonization, VRE-related infection was probable in 4 patients, and VRE infection of the bloodstream occurred in 1 case. Two patients were identified by VRE screening on admission, 20 were identified by weekly routine VRE screening, and 6 were identified from specimens taken to clarify infections (eg, urine, bronchoalveolar lavage). Five individuals acquired VRE colonization as inpatients (contact patients). Multiple-locus variable-number tandem repeat analysis (MLVA) proved that the outbreak was caused by VanA gene-positive Enterococcus faecium belonging to MLVA genogroup C1(MLVA types 1, 7, 12). The outbreak strains exhibited the potential virulence factor esp(enterococcus surface protein). The outbreak was terminated within 2 months by intensified infection-control measures, including quarantine and the cohorting of patients who tested positive for VRE; however, VRE spread recurred after the measures were discontinued but was again limited by resuming the measures. We conclude that intensive infection-control strategies enable the timely termination of VRE outbreaks, even those involving VRE strains with high epidemic potential on "high-risk wards" (eg, hematologic/oncologic units). Premature discontinuation of infection-control measures may cause recurrence of the VRE spread.

Vancomycin-resistant Enterococcus faecium infection in patients with hematologic malignancy: patients with acute myeloid leukemia are at high-risk

BACKGROUND

Vancomycin-resistant enterococci (VRE) are significant nosocomial pathogens in patients with hematologic malignancy. Identification of risk factors for infection is necessary for targeted prevention and surveillance.

OBJECTIVES AND METHODS

An outbreak of VRE infection occurred at a tertiary cancer hospital between 1 August 2003 and 30 June 2005. Infection control measures recommended by the Society for Healthcare Epidemiology of America were used throughout the outbreak period. A matched case-control study was performed to identify risk factors for VRE infection.

RESULTS

Fourteen VRE infections (13 episodes of bacteremia, one urinary tract infection) occurred a median of 10.5 d following hospital admission. All were due to Enterococcus faecium vanB. Univariate analysis identified the following variables to be significantly associated with VRE infection: presence of neutropenia, neutropenia >or=7 d, underlying diagnosis of acute myeloid leukemia (AML), and receipt of vancomycin, metronidazole or carbapenem antibiotic therapy in the 30 d prior to infection. On multivariate analysis, an underlying diagnosis of AML [odds ratio (OR), 15.00; P = 0.017] and vancomycin therapy during the previous 30 d (OR, 17.96; P = 0.036) were retained as independent risk factors for infection.

CONCLUSIONS

Risk stratification for development of VRE infection is possible for patients with hematologic malignancy. Patients with AML represent a high-risk population, and targeted prevention strategies must include improved antibiotic stewardship, particularly judicious use of vancomycin therapy.

High-level gentamicin-resistant Enterococcus faecium strains isolated from bone marrow transplant patients: accumulation of antibiotic resistance genes, large plasmids and clonal strain dissemination

Twenty-six high-level gentamicin-resistant (HLGR) Enterococcus faecium strains colonising neutropenic bone marrow transplant patients were studied. Polymerase chain reaction analysis showed that high-level gentamicin resistance was mediated by the aac(6')-Ia-aph(2'')-Ie gene; the aph(2'')-Id gene responsible for gentamicin resistance was also detected in 16 strains. Multiple antibiotic resistance was related to the presence of aph(3')-IIIa, ant(6)-Ia, erm(B), erm (A) and tet(M) genes. Strains clustered into 18 groups according to their plasmid content as well as 16 pulsed-field gel electrophoresis (PFGE) patterns. Although the majority of PFGE patterns were single isolates, three microclones were identified. Hybridisation showed that in the majority of the strains the aac(6')-aph(2'') gene resided on a large plasmid of ca. 96kb detected only on PFGE gels. Based on these findings, colonisation by HLGR E. faecium strains was a result of either possibly related plasmid spread or strain dissemination.