Vancomycin-resistant Enterococcus faecium in hospitalized children

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.

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.

Effectiveness of a Lytic Phage SRG1 against Vancomycin-Resistant Enterococcus faecalis in Compost and Soil

Nosocomial infections caused by vancomycin-resistant Enterococcus have become a major problem. Bacteriophage therapy is proposed as a potential alternative therapy. Bacteriophages are viruses that infect bacteria and are ubiquitous in nature. Lytic bacteriophage was isolated from sewage water that infects VREF, the causative agent of endocarditis, bacteraemia, and urinary tract infections (UTIs). The phage produced clear plaques with unique clear morphology and well-defined boundaries. TEM results of phage revealed it to be 108 ± 0.2 nm long and 90 ± 0.5 nm wide. The characterization of bacteriophage revealed that infection process of phage was calcium and magnesium dependent and phage titers were highest under optimum conditions for VREF, with an optimal temperature range of 37–50°C. The maximum growth was observed at 37°C, hence having 100% viability. The latent period for phage was small with a burst size of 512 viral particles per bacterial cell. The phage was tested against various clinical strains and results proved it to be host specific. It can be used as a potential therapeutic agent for VREF infections. The phage efficiently eradicated VREF inoculated in cattle compost, poultry compost, and a soil sample which makes it a potential agent for clearing compost and soil sample.

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.

Metagenomic evidence for taxonomic dysbiosis and functional imbalance in the gastrointestinal tracts of children with cystic fibrosis

Cystic fibrosis (CF) results in inflammation, malabsorption of fats and other nutrients, and obstruction in the gastrointestinal (GI) tract, yet the mechanisms linking these disease manifestations to microbiome composition remain largely unexplored. Here we used metagenomic analysis to systematically characterize fecal microbiomes of children with and without CF, demonstrating marked CF-associated taxonomic dysbiosis and functional imbalance. We further showed that these taxonomic and functional shifts were especially pronounced in young children with CF and diminished with age. Importantly, the resulting dysbiotic microbiomes had significantly altered capacities for lipid metabolism, including decreased capacity for overall fatty acid biosynthesis and increased capacity for degrading anti-inflammatory short-chain fatty acids. Notably, these functional differences correlated with fecal measures of fat malabsorption and inflammation. Combined, these results suggest that enteric fat abundance selects for pro-inflammatory GI microbiota in young children with CF, offering novel strategies for improving the health of children with CF-associated fat malabsorption.

Increased risk of vancomycin-resistant enterococcus (VRE) infection among patients hospitalized for inflammatory bowel disease in the United States

BACKGROUND

Vancomycin-resistant Enterococcus (VRE) infection has become an increasingly common hospital-acquired infection in U.S. hospitals. Patients with inflammatory bowel disease (IBD) frequently require hospitalization and therefore may be at increased risk of nosocomial infections.

METHODS

We used the Nationwide Inpatient Sample (NIS) to identify admissions for IBD (n = 116,842) between 1998 and 2004. We compared the prevalence of VRE in this group to that of non-IBD gastrointestinal (GI) inpatients and general inpatients and assessed for associations between VRE and hospital mortality, length of stay, and total charges.

RESULTS

The crude VRE prevalence was 2.1/10,000 in hospitalized IBD patients, 1.3/10,000 in non-IBD GI patients, and 0.9/10,000 in general inpatients. After adjustment for confounders, IBD inpatients were at increased risk of VRE compared to the non-IBD GI (adjusted odds ratio [aOR] 1.65; 95% confidence interval [CI]: 1.03-2.64) and general inpatient (aOR 2.37; 95% CI: 1.31-4.27) groups. Among IBD patients, there was a higher prevalence of VRE infection in those who had surgery (4.4/10,000 versus 1.7/10,000; P < 0.04) and total parenteral nutrition (6.9/10,000 versus 1.8/10,000; P < 0.003). VRE infection was not associated with an increase in mortality (0% versus 0.7%, P = 0.8); however, it was associated with 3-fold higher total hospital charges ($63,517 versus $21,918 USD; P < 0.0001) and increased average length of stay in hospital (16.1 versus 6.1 days; P < 0.0001).

CONCLUSIONS

Hospitalized IBD patients have increased susceptibility to VRE that is associated with increased economic burden. This study reinforces the importance of measures to prevent nosocomial infection, particularly in the vulnerable IBD population.

Accuracy and potential usefulness of triplex real-time PCR for improving antibiotic treatment of patients with blood cultures showing clustered gram-positive cocci on direct smears

Bacterial identification and antibiotic susceptibility testing currently require 48 h when a first blood culture (BC) is positive for clustered gram-positive cocci on direct smear examination (DSE). Meanwhile, antibiotic treatment is often inadequate, reducing the chances of effective treatment or creating unnecessary selective pressure. A new real-time PCR (RT-PCR) technique that differentiates Staphylococcus aureus from coagulase-negative staphylococci (CoNS) and detects methicillin resistance in 90 min in BC bottles could help solve these problems. BC bottles from 410 patients with gram-positive cocci on DSE were processed by current methods, and patients' treatments were prospectively recorded. The RT-PCR assay was performed on aliquots of these BCs, which had been kept frozen. For the 121 patients who had true bacteremia, we established whether the faster availability of RT-PCR results could have led to the initiation of treatments different from those actually given. RT-PCR sensitivity and specificity were 100% for differentiating between S. aureus and CoNS and detecting methicillin resistance with two manufacturers' BC bottles. For 31/86 (36%) of the S. aureus-infected patients and for 8/35 (23%) of the CoNS-infected patients who either had suboptimal or nonoptimal treatment or were untreated 48 h after positivity was detected, the early availability of RT-PCR results could have allowed more effective treatment. Unnecessary glycopeptide treatments could have been avoided for 28 additional patients. The use of RT-PCR would increase treatment effectiveness in patients with staphylococcal bacteremia and reduce the selective pressure created by glycopeptides.

Vancomycin-resistant Staphylococcus aureus in the United States, 2002-2006

BACKGROUND

This report compares the clinical characteristics, epidemiologic investigations, infection-control evaluations, and microbiologic findings of all 7 of the cases of vancomycin-resistant Staphylococcus aureus (VRSA) infection in the United States during the period 2002-2006.

METHODS

Epidemiologic, clinical, and infection-control information was collected. VRSA isolates underwent confirmatory identification, antimicrobial susceptibility testing, pulsed-field gel electrophoresis, and typing of the resistance genes. To assess VRSA transmission, case patients and their contacts were screened for VRSA carriage.

RESULTS

Seven cases were identified from 2002 through 2006; 5 were reported from Michigan, 1 was reported from Pennsylvania, and 1 was reported from New York. All VRSA isolates were vanA positive and had a median vancomycin minimum inhibitory concentration of 512 microg/mL. All case patients had a history of prior methicillin-resistant S. aureus and enterococcal infection or colonization; all had several underlying conditions, including chronic skin ulcers; and most had received vancomycin therapy prior to their VRSA infection. Person-to-person transmission of VRSA was not identified beyond any of the case patients. Infection-control precautions were evaluated and were consistent with established guidelines.

CONCLUSIONS

Seven patients with vanA-positive VRSA have been identified in the United States. Prompt detection by microbiology laboratories and adherence to recommended infection control measures for multidrug-resistant organisms appear to have prevented transmission to other patients.

Does vancomycin prescribing intervention affect vancomycin-resistant enterococcus infection and colonization in hospitals? A systematic review

Background

Vancomycin resistant enterococcus (VRE) is a major cause of nosocomial infections in the United States and may be associated with greater morbidity, mortality, and healthcare costs than vancomycin-susceptible enterococcus. Current guidelines for the control of VRE include prudent use of vancomycin. While vancomycin exposure appears to be a risk factor for VRE acquisition in individual patients, the effect of vancomycin usage at the population level is not known. We conducted a systematic review to determine the impact of reducing vancomycin use through prescribing interventions on the prevalence and incidence of VRE colonization and infection in hospitals within the United States.

Methods

To identify relevant studies, we searched three electronic databases, and hand searched selected journals. Thirteen studies from 12 articles met our inclusion criteria. Data were extracted and summarized for study setting, design, patient characteristics, types of intervention(s), and outcome measures. The relative risk, 95% confidence interval, and p-value associated with change in VRE acquisition pre- and post-vancomycin prescription interventions were calculated and compared. Heterogeneity in study results was formally explored by stratified analysis.

Results

No randomized clinical trials on this topic were found. Each of the 13 included studies used a quasi-experimental design of low hierarchy. Seven of the 13 studies reported statistically significant reductions in VRE acquisition following interventions, three studies reported no significant change, and three studies reported increases in VRE acquisition, one of which reported statistical significance. Results ranged from a reduction of 82.5% to an increase of 475%. Studies of specific wards, which included sicker patients, were more likely to report positive results than studies of an entire hospital including general inpatients (Fisher's exact test 0.029). The type of intervention, endemicity status, type of study design, and the duration of intervention were not found to significantly modify the results. Among the six studies that implemented vancomycin reduction strategies as the sole intervention, two of six (33%) found a significant reduction in VRE colonization and/or infection. In contrast, among studies implementing additional VRE control measures, five of seven (71%) reported a significant reduction.

Conclusion

It was not possible to conclusively determine a potential role for vancomycin usage reductions in controlling VRE colonization and infection in hospitals in the United States. The effectiveness of such interventions and their sustainability remains poorly defined because of the heterogeneity and quality of studies. Future research using high-quality study designs and implementing vancomycin as the sole intervention are needed to answer this question.

Enterococcal Infection in Children

From relative obscurity, enterococci have become a leading cause of nosocomial infection. This has been attributed, in part, to the growth in susceptible host populations, increased use of intravascular devices, prolonged hospital stay, and widespread antibiotics use. Furthermore, the facility with which enterococci acquire resistance characteristics coupled with their capacity to survive in the environment renders them uniquely suited as nosocomial opportunists and have resulted in global dissemination of resistant strains. Debate continues as to whether most serious infections arise from a person's indigenous flora or dissemination of virulent clones. Enterococci are normal inhabitants of the human gastrointestinal tract. Classically associated with endocarditis and wound and urinary tract infections, increasingly they are a cause of nosocomial bacteremia. The rise in incidence of serious enterococcal infection has been particularly evident in neonatal, paediatric intensive care, and haematology/oncology units. Spread of resistant phenotypes has posed a difficult therapeutic challenge. We have been rescued, albeit perhaps only temporarily, by the addition of newer agents, such as linezolid, to the therapeutic armamentarium. However, there is no room for complacency. Linezolid resistance already has been reported. Efforts must continue to focus on prevention of the emergence and dissemination of resistance through policies of rational antibiotic use, infection control and education.

Guidelines for the control of glycopeptide-resistant enterococci in hospitals

The increase since the mid 1980s in glycopeptide resistant enterococci (GRE) raised concerns about the limited options for antimicrobial therapy, the implications for ever-increasing numbers of immunocompromised hospitalised patients, and fuelled fears, now realised, for the transfer of glycopeptide resistance to more pathogenic bacteria, such as Staphylococcus aureus. These issues underlined the need for guidelines for the emergence and control of GRE in the hospital setting. This Hospital Infection Society (HIS) and Infection Control Nurses Association (ICNA) working party report reviews the literature relating to GRE prevention and control. It provides guidance on microbiological investigation, treatment and management, including antimicrobial prescribing and infection control measures. Evidence identified to support recommendations has been categorized. A risk assessment approach is recommended and areas for research and development identified.

Barrier precautions, isolation protocols, and personal hygiene in veterinary hospitals

Because nosocomial and zoonotic diseases are inherent and ever-present risks in veterinary hospitals, proactive policies should be in place to reduce the risk of sporadic cases and outbreaks. Policies should ideally be put in place before disease issues arise, and policies should be effectively conveyed to all relevant personnel. Written policies are required for practical and liability reasons and should be reviewed regularly. Although no infection control program can eliminate disease concerns, proper implementation of barrier precautions and isolation can reduce the exposure of hospitalized animals and hospital personnel to infectious agents. Appropriate personal hygiene, particularly hand hygiene, can assist in the prevention of disease transmission when pathogens bypass barriers and are able to contact personnel. Veterinary hospitals have moral, professional, and legal requirements to provide a safe workplace and to reduce the risks to hospitalized patients. Based on experience in the human medical field and on the continual emergence of new infectious diseases, infection control challenges can only be expected to increase in the future. Regular reassessment of protocols based on ongoing research and clinical experiences is required.

Association between antecedent intravenous antimicrobial exposure and isolation of vancomycin-resistant enterococci

Vancomycin-resistant enterococci (VRE) have become important causes of nosocomial infections. This study evaluated the association between a variety of intravenous antimicrobial exposures and the isolation of VRE using two control groups: (1) a vancomycin-susceptible enterococci (VSE) group, to assess factors associated with development of VRE, and (2) a nonenterococci control group, to assess factors associated with positive cultures for enterococci without regard to vancomycin resistance. After adjusting for the effect of other antimicrobials, time at risk, and patient morbidity, compared to vancomycin-susceptible enterococci controls, exposures to imipenem (OR = 4.9, 95% CI = 1.6-14.1) and ceftazidime (OR = 2.6, 95% CI = 1.1-6.1) were significant predictors of VRE. When compared to nonenterococci controls, exposures to ampicillin (OR = 20.1, 95% CI = 1.5-263.1) and imipenem (OR = 5.1, 95% CI = 1.5-17.1) were significantly associated with VRE. Neither piperacillin nor vancomycin was associated with VRE compared to either control group. This study offers further evidence that the replacement of broad-spectrum cephalosporins by extended-spectrum penicillins, specifically piperacillin, may be effective in reducing VRE.

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Clostridium difficile infection and concurrent vancomycin-resistant Enterococcus stool colonization in a health care worker: case report and review of the literature

Clostridium Difficile diarrhea was noted in a previously healthy health care worker from the study institution after receiving oral clindamycin therapy; the worker also had vancomycin-resistant Enterococcus stool colonization. Health care workers should be aware that antibiotic therapy may place them at increased risk for colonization and infection with nosocomial pathogens such as Clostridium difficile and vancomycin-resistant Enterococcus.

Safety and efficacy of quinupristin/dalfopristin for treatment of invasive Gram-positive infections in pediatric patients

BACKGROUND

Antibiotic-resistant Gram-positive pathogens are an increasingly common cause of serious pediatric infections. Although quinupristin/dalfopristin demonstrates favorable activity against resistant Gram-positive pathogens (including many vancomycin-resistant and methicillin-resistant staphylococci), published experience in the pediatric patient population is limited.

METHODS

We retrospectively analyzed data from the global quinupristin/dalfopristin Emergency-Use Program, which enrolled patients with serious Gram-positive infections who had no further therapy options because of resistance to, failure on or intolerance to standard antibiotic treatments. Our subset included safety and efficacy data from pediatric patients (age <18 years). There were no restrictions on underlying diseases, severity of illness or prior/concomitant antimicrobial use.

RESULTS

Between May 1995 and October 1999, 127 pediatric patients with 131 infections were enrolled. Microbiologic confirmation of etiology was available in 124 patients. All patients had 1 or more concomitant conditions, including malignancy and solid organ or bone marrow transplantation. The most frequent causative pathogens were vancomycin-resistant (80%), spp. (7%), methicillin-resistant (6%) and (4%). All but 21 patients received intravenous quinupristin/dalfopristin 7.5 mg/kg every 8 h. The favorable clinical response rate of quinupristin/dalfopristin was 86 of 124 (69%); the favorable microbiologic response rate was 97 of 124 (78%). Eleven patients (8%) had nonvenous adverse events classified as possibly or probably related to quinupristin/dalfopristin.

CONCLUSIONS

Quinupristin/dalfopristin demonstrated favorable response rates and was reasonably well-tolerated in pediatric patients with serious Gram-positive infections unable to receive alternative therapy. In our opinion quinupristin/dalfopristin is a therapeutic option for the management of such infections.

Antecedent treatment with different antibiotic agents as a risk factor for vancomycin-resistant Enterococcus

We conducted a matched case-control study to compare the effect of antecedent treatment with various antibiotics on subsequent isolation of vancomycin-resistant Enterococcus (VRE); 880 in-patients; 233 VRE cases, and 647 matched controls were included. After being matched for hospital location, calendar time, and duration of hospitalization, the following variables predicted VRE positivity: main admitting diagnosis; a coexisting condition (e.g., diabetes mellitus, organ transplant, or hepatobiliary disease); and infection or colonization with methicillin-resistant Staphylococcus aureus or Clostridium difficile within the past year (independent of vancomycin treatment). After controlling for these variables, we examined the effect of various antibiotics. Intravenous treatment with third-generation cephalosporins, metronidazole, and fluoroquinolones was positively associated with VRE. In our institution, when we adjusted the data for temporo-spatial factors, patient characteristics, and hospital events, treatment with third-generation cephalosporins, metronidazole, and fluoroquinolones was identified as a risk factor for VRE. Vancomycin was not a risk factor for isolation of VRE.

[Risk factors and prevention of the acquisition and transmission of glycopeptide resistant enterococci]

We reviewed the literature concerning the role of antibiotic use as a risk factor for glycopeptide-resistant enterococci (VRE) infection/colonisation, to enable us to develop measures for preventing the acquisition and transmission of VRE. We found that the length of stay, the number of stays in hospital and the transfer of patients between hospitals and units were all risk factors for acquiring VRE infection. However, analysis of group and individual data showed that there was also a clear link between vancomycin and third-generation cephalosporin use and the prevalence of VRE colonisation/infection. Evidence for this link was provided by the consistent association and dose-effect relationship observed, and from the frequently consistent variations observed over time. However, it is difficult to give precise recommendations because very few studies have investigated both intrinsic bacterial factors making specific strains more epidemic and the precise characteristics of the conditions determining antibiotic selection pressure. In the absence of this information, and maintaining the prevention measures against cross-contamination which remain a priority, these results suggest that programs aimed at improving the prescription of antibiotics should be initiated in hospitals.

Effects of adjunctive treatment with combined cytokines in a neutropenic mouse model of multidrug-resistant Enterococcus faecalis septicemia

STUDY OBJECTIVE

To examine whether the antienterococcal efficacy of a regimen of gentamicin plus vancomycin combined with granulocyte colony-stimulating factor (G-CSF) is enhanced by concurrent therapy with interferon-gamma (IFN-gamma).

SETTING

Hospital laboratory.

INTERVENTION

Mice rendered neutropenic by cyclophosphamide were intraperitoneally inoculated with a gentamicin- and vancomycin-resistant Enterococcus faecalis isolate.

MEASUREMENTS AND MAIN RESULTS

Infected animals were randomized into treatment groups that received G-CSF alone or in combination with various dosages of IFN-gamma. Additional groups of animals received vancomycin; G-CSF, G-CSF plus vancomycin, IFN-gamma, and G-CSF; or vancomycin with both cytokines. Addition of IFN-gamma to G-CSF regimen resulted in no significant change (p>0.05) in survival, compared with treatment with G-CSF alone. Also, the antienterococcal efficacy of antibiotic plus G-CSF was not modified by coadministration of IFN-gamma.

CONCLUSION

This study suggests that adjunctive application of combined cytokines may not be more beneficial than only G-CSF in combination with an antibiotic to treat multidrug-resistant enterococcal infection.

Relationships between enterococcal virulence and antimicrobial resistance

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Antienterococcal antibiotics

The treatment of severe enterococcal infections based on the currently available antibacterial agents is difficult. The help of the microbiology laboratory for determining MICs, MBCs, and most effective synergistic combinations is crucial. There is a need for good prospective multicenter clinical trials to improve the prognosis of such infections by defining therapeutic strategies better. Such a requirement is highly suitable for the treatment of infections caused by enterococci exhibiting acquired resistance mechanisms to the available agents. The current clinical development of new compounds looks promising in these persistently life-threatening infections mostly occurring in deficient hosts.

Relationships between enterococcal virulence and antimicrobial resistance

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Role of transposon Tn5482 in the epidemiology of vancomycin-resistant Enterococcus faecium in the pediatric oncology unit of a New York City Hospital

During a 36-month period between 1993 and 1995 in the Pediatric Oncology Unit of Memorial Sloan Kettering Cancer Center, 74 patients experienced episodes of infection or colonization caused by vancomycin-resistant enterococci (VRE). Characterization of the 74 bacterial isolates by microbiological and molecular techniques (pulsed-field gel electrophoresis and hybridization with DNA probes specific for the vanA and vanB genes and for IS1251) identified 73 Enterococcusfaecium and one Enterococcusfaecalis (vanB) among the primary VRE isolates. Most (69/73) of the E. faecium isolates carried vanA and four isolates, the vanB gene complex. The overwhelming majority (67/69) of the vanA -positive isolates also gave hybridization signal for IS1251, indicating the presence of the newly described conjugative transposon Tn5482. No hybridization with IS1251 was obtained with the four vanB-carrying isolates. About 30% of the vanA-positive strains (23/69) were represented by PFGE subtype variants of a single clone, most isolates of which were recovered during a 4-month period between April to June of 1994. The larger portion of the vanA-carrying VRE represented by close to 70% of the isolates (46/69) belonged to as many as 37 different clonal types, indicating tremendous genetic diversity. Among 67 of the 69 vanA-carrying isolates, the localization of the Tn5482-associated vanA gene complex could be unequivocally identified either on the chromosome (40/69) or in plasmids (27/69). Transconjugants recovered from filter mating experiments using either a chromosomally located or plasmid-borne vanA donor strain and a single vancomycin-susceptible strain of either E. faecium or E. faecalis were analyzed by molecular typing techniques. Seven out of 10 independent transconjugants recovered from the same cross showed extensive differences in PFGE pattern and also in the localization of the vanA hybridizing DNA fragment transferred from the common VRE donor with chromosomally located vanA. The observations suggest that the extensive genetic diversity observed among the clinical isolates of VRE may be generated during conjugation between vancomycin-resistant and -susceptible enterococcal isolates. The observations also suggest that the epidemic spread of VRE in the United States may be linked to the frequent presence of Tn5482 among the American isolates.

A nationwide, multicenter, case-control study comparing risk factors, treatment, and outcome for vancomycin-resistant and -susceptible enterococcal bacteremia

National Nosocomial Resistance Surveillance Group participants from 22 hospitals across the United States reviewed medical records for hospitalized patients with vancomycin-resistant enterococcal (VRE) or vancomycin-susceptible enterococcal (VSE) bacteremia to identify risk factors associated with the acquisition of VRE bacteremia, describe genetic traits of VRE strains, and identify factors predictive of clinical outcome. VRE cases were matched to VSE controls within each institution. Multiple logistic regression (LR) and classification and regression tree (CART) analysis were used to probe for factors associated with VRE bacteremia and clinical outcome. A total of 150 matched-pairs of VRE cases and VSE controls were collected from 1995 to 1997. Using LR, the following were found to be highly associated with VRE bacteremia: history of AIDS, positive HIV status, or drug abuse (OR 9.58); prior exposure with parenteral vancomycin (OR 8.37); and liver transplant history (OR 6. 75). CART analysis revealed that isolation of Enterococcus faecium, prior vancomycin exposure, and serum creatinine values > or = 1.1 mg/dl were predictors of VRE bacteremia. Greater proportions of clinical failure (60% versus 40%, P < 0.001) and all-cause mortality (52% versus 27%, P < 0.001) were seen in patients with VRE versus VSE bacteremia. Results from both LR and CART indicated that patients with persisting enterococcal bacteremia, intubation at baseline, higher APACHE II scores, and VRE bacteremia were at greater risk for poor outcome.

Molecular epidemiology of vancomycin-resistant Enterococcus faecium in a large urban hospital over a 5-year period

To investigate the dissemination of vancomycin-resistant Enterococcus faecium (VREF) in a 728-bed tertiary-care hospital, all clinical VREF isolates recovered from June 1992 to June 1997 were typed by pulsed-field gel electrophoresis, and the transfer histories of the patients were documented. A total of 413 VREF isolates from urine (52%), wounds (16%), blood (11%), catheter tips (6%), and other sites (15%) were studied. VREF specimens mostly came from patients on wards (66%) but 34% came from patients in an intensive care unit. The number of VREF isolates progressively increased over time, with higher rates of isolation during the winter months and lower rates in the late summer months. Four distinct banding patterns were detected by pulsed-field gel electrophoresis among 316 samples (76%). Strain A (122 samples; 30%) appeared in June 1992 as the first VREF strain and was found until December 1994 throughout the entire hospital. Type B (92 samples; 22%) was initially detected in January 1994 and disappeared in November 1996. Strain C (10 samples; 2%) was limited to late 1996 and early 1997. Strain D (92 samples; 22%) showed two major peaks during March 1996 to August 1996 and January 1997 to February 1997. Unrelated strains (97 samples; 24%) appeared 1 year after the appearance of the first VREF isolate, and the numbers increased slightly over the years. Nosocomial acquisition (i.e., no known detection prior to admission and first isolation from cultures performed with samples retrieved >/=2 days after hospitalization) was found for 316 (91%) of 347 patients. Despite the implementation of Centers for Disease Control and Prevention guidelines, the proportion of related strains and high number of nosocomial cases of infection indicate a high transmission rate inside the hospital. The results imply an urgent need for stringent enforcement of more effective infection control measures.

Vancomycin use in pediatric neurosurgery patients

OBJECTIVE

The objective of this article is to describe a pediatric neurosurgery patient population receiving vancomycin and examine the indications for and appropriateness of vancomycin use.

METHODS

A cross-sectional study was performed on the pediatric neurosurgery patients at Egleston Children's Hospital who received vancomycin from January 1 through December 31, 1996. Vancomycin use was compared with the Centers for Disease Control and Prevention Hospital Infection Control Practices Advisory Committee recommendations for vancomycin use.

RESULTS

Thirty patients received 115 doses of vancomycin. The median patient age was 8.0 years, and 17 (56.7%) were male. Vancomycin was used for prophylaxis in 28 (93.3%) patients and empiric therapy in 3 (10.0%) patients; one patient received vancomycin for surgical prophylaxis followed by empiric therapy for suspected meningitis. Vancomycin prophylaxis was initiated after the incision in 6 (21.4%) patients and was continued as prophylaxis for more than one dose in 26 (92.9%) patients.

CONCLUSIONS

Vancomycin was used primarily as surgical prophylaxis in pediatric neurosurgery patients, and use was not consistent with the Hospital Infection Control Practices Advisory Committee recommendations. These data suggest that for certain subpopulations, such as pediatric neurosurgery patients, there is a need for more specialized recommendations. Furthermore, prudent vancomycin use is warranted to successfully decrease the risk of further emergence of vancomycin resistance. Because vancomycin use may be prevalent in this population, assessment of vancomycin use in pediatric neurosurgery patients followed by establishment of vancomycin clinical guidelines may help improve the appropriateness of vancomycin use in this population.

Influence of adjunctive interferon-gamma on treatment of gentamicin- and vancomycin-resistant Enterococcus faecalis infection in mice

Increasing antibiotic resistance and the development of multidrug-resistance in the enterococci has complicated the treatment of serious enterococcal infections. It has been demonstrated in vitro that interferon-gamma (IFN-gamma) significantly augments the activities of gentamicin and vancomycin against Enterococcus faecalis resistant to these antibiotics. The present study was aimed at determining whether this beneficial effect of IFN-gamma on antienterococcal antibiotic activity can be validated in vivo. Following intraperitoneal inoculation in mice with a gentamicin- and vancomycin-resistant E. faecalis clinical isolate, the animals received IFN-gamma, antibiotic or a combination of both agents, subcutaneously, at determined dosing regimens. Treatment with IFN-gamma alone significantly improved survival of infected animals in a dose-dependent manner. High dose IFN-gamma was not beneficial and the level of enterococcal infectious burden influenced the effectiveness of the cytokine. The addition of IFN-gamma to therapy with gentamicin or vancomycin, or a combination of both antibiotics was associated with a marked increase in survival of infected non-neutropenic mice compared to treatments with the agents alone. However, the same treatments made in infected neutropenic mice did not show an enhancement effect by IFN-gamma after a combination therapy with antibiotics. In a study to examine pharmacokinetic interactions, concurrent administration with IFN-gamma significantly modified the disposition of gentamicin but not that of vancomycin. The results of this study suggest that the use of IFN-gamma in combination with vancomycin or gentamicin is a new treatment option that might improve the outcome of therapy of multidrug-resistant E. faecalis infections.

Vancomycin-resistant enterococci: recent advances in genetics, epidemiology and therapeutic options

Vancomycin-resistant enterococci (VRE) have gained much attention in the last decade. Currently, there are five known types of vancomycin resistance based on genes encoding ligase enzymes that the organisms use to produce their cell wall precursors, namely, VanA, VanB, VanC, VanD and VanE. An additional unclassified type was discovered in Australia. The basis of resistance among these phenotypes appears to be similar in that the resistant organisms produce peptidoglycan precursors that end in moieties other than D-alanyl-D-alanine, the usual target of vancomycin. The other dipeptide-like termini identified to date include D-alanyl-D-lactate and D-alanyl-D-serine, which have low affinity for glycopeptides. Recent evidence suggests that glycopeptide-producing organisms might be the remote origin of the vancomycin resistance genes. In European countries, avoparcin, a glycopeptide used in farm animals as a growth promoter, has been linked to the occurrence of VRE and occasional common strains have been identified in food products, farm animals, healthy subjects and hospitalized patients. There have been no such reports in the USA where heavy use of vancomycin and use of broad spectrum antibiotics such as cephalosporins have been identified as important risk factors for acquisition of VRE. Transmission within the same or between hospitals has been reported in many countries. Infection control measures and efforts to use antibiotics, particularly vancomycin, more appropriately have been implemented in a number of healthcare facilities with varying degrees of success. Many antibiotics, as a single agent or a combination of drugs, as well as various new antibiotics have been tested in vitro, in animal models, or used in anecdotal cases but clinical data from large comparative trials are not available to date. Because of the limited susceptibility of many VRE to other agents, efforts to control these organisms are particularly important. Copyright 1999 Harcourt Publishers LtdCopyright 1999 Harcourt Publishers Ltd.

Epidemiology and control of vancomycin-resistant enterococci in a regional neonatal intensive care unit

BACKGROUND

After the occurrence of two cases of bloodstream infection with vancomycin-resistant enterococci (VRE) in our regional neonatal intensive care unit, we studied the epidemiology of VRE and applied extensive infection control measures to the unit to control VRE transmission.

METHODS

Infection control measures applied to the unit included weekly surveillance for VRE colonization; education; cohorting of VRE-positive, VRE-negative and VRE-exposed babies with separate personnel and equipment for each group; use of gowns and gloves on room entry; and hand washing before and after each patient contact. Risk factors for VRE colonization were determined with a stepwise logistic regression model.

RESULTS

Thirty-three (40.2%) babies became colonized with VRE. The VRE colonization rate was reduced from 67% to 7% after implementation of infection control measures. Prolonged antimicrobial treatment and low birth weight were significantly associated with an increased risk of VRE colonization.

CONCLUSION

VRE can spread rapidly among newborns in a regional neonatal intensive care unit. Strict infection control measures can reduce the rate of VRE colonization among neonates.

Improving the appropriateness of vancomycin use by sequential interventions

BACKGROUND

Vancomycin usage is directly associated with the incidence of vancomycin-resistant enterococci. Optimal methods to reduce inappropriate use have not been delineated. We determined the appropriateness of vancomycin prescribing at our hospital on the basis of national guidelines and assessed the effect of sequential administrative and educational interventions.

METHODS

In this prospective 3-phase study conducted in a Veterans Affairs Medical Center, we monitored vancomycin prescribing at baseline and in 2 follow-up periods. Administrative interventions included discussions with service chiefs and revising routine perioperative antibiotic prophylaxis orders. Educational interventions included in-services about vancomycin-resistant enterococci and appropriate vancomycin prescribing. In each monitoring period, 50 consecutive new vancomycin orders that could be evaluated were classified for appropriateness and categorized by indication.

RESULTS

At baseline, 70% of vancomycin use was inappropriate. Surgical services accounted for 84% of orders. Interventions targeted services with high or frequently inappropriate vancomycin use. After administrative interventions, inappropriate vancomycin use dropped to 40% of orders (P =.003). Improvements were noted in targeted services. Educational interventions further decreased inappropriate vancomycin use, but the effect appeared transient.

CONCLUSIONS

The simple, nonrestrictive administrative interventions used resulted in a statistically significant (30%) reduction in inappropriate vancomycin prescribing. However, educational interventions provided only transient benefit on institutional prescribing patterns.

Vancomycin-resistant enterococci: the clinical effect of a common nosocomial pathogen

Enterococcus spp. is now the third most common pathogen among hospitalized patients, accounting for nearly 12% of nosocomial infections. Enterococcus faecalis is the most prevalent enterococcal species (85%-89%), whereas Enterococcus faecium accounts for 10%-15% of enterococcal isolates. Only 5% of E. faecalis isolates are resistant to glycopeptides. E. faecium has also been shown to be resistant to nonglycopeptide compounds, such as penicillins (97%), high-level gentamicin (52.1%), and high-level streptomycin (58.3%). Numerous risk factors for vancomycin-resistant enterococci (VRE) have been identified, including as length of hospital- or ICU-stay, proximity to a hospitalized, colonized VRE, patient severity of illness, renal failure, recent surgery, immunosuppression, and organ recipient status. An important risk factor is prior exposure to antibiotics such as vancomycin, ceftazidime, ciprofloxacin, and metronidazole, as well as the number and duration of recent antibiotics. Interventions to reduce nosocomial VRE cross-transmission have also been studied. Using gowns in addition to gloves diminished the incidence of VRE in one study, but had a negligible effect in a second study. Studies have shown that in many cases (> 60%) vancomycin usage is inappropriate. While controlling the use of vancomycin alone has only variably diminished VRE colonization, other efforts such as narrowing the spectrum of antibiotics, antiseptics, and reducing immunosuppression may be salutary. Attempts to eradicate VRE intestinal carriage with enteral agents (bacitracin, tetracycline + rifampin, novobiocin) have been reported but seem to have only a transient effect. Non-antimicrobial interventions such as removal of intravenous or bladder catheters and/or surgical or percutaneous drainage may be beneficial. In addition, the development of new antimicrobial agents such as streptogramins, glycopeptides, everninomicins, and oxazalididones will hopefully play an important role in reducing morbidity from these pathogens.

Survival of vancomycin-resistant and vancomycin-susceptible enterococci on dry surfaces

We compared the abilities of Enterococcus faecium strains (three vancomycin-resistant enterococci [VRE] and five vancomycin-susceptible enterococci [VSE]) and Enterococcus faecalis strains (one VRE and 10 VSE) to survive under dry conditions. Bacterial suspensions of the strains were inoculated onto polyvinyl chloride and stored under defined conditions for up to 16 weeks. All strains survived for at least 1 week, and two strains survived for 4 months. A statistical model was used to distribute the 19 resulting survival curves between two types of survival curves. The type of survival curve was not associated with the species (E. faecalis versus E. faecium), the source of isolation (patient versus environment), or the susceptibility to vancomycin (VRE versus VSE). Resistance to dry conditions may promote the transmissibility of a strain, but VRE have no advantages over VSE with respect to their ability to survive under dry conditions.

Detection of vancomycin-resistant enterococci colonization in a children's hospital

BACKGROUND

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens in many hospitals. The true prevalence of VRE in pediatric hospitals is not known.

METHODS

A surveillance study was performed at a pediatric tertiary care medical center by using vancomycin-containing screening media.

RESULTS

Six children (of 112 screened) were found to be colonized with VRE. Colonized patients had a history of receiving broad-spectrum antimicrobial agents.

CONCLUSION

In the absence of VRE infections, surveillance studies can help determine the extent of VRE colonization and support infection control measures.

Clonal dissemination of vancomycin-resistant Enterococci and comparison of susceptibility testing methods

One hundred fifty clinical isolates of Enterococcus faecalis (88 isolates) and Enterococcus faecium (62 isolates) were tested in vitro for their susceptibility to vancomycin and high-level aminoglycosides (HLA). Remel's Synergy Quad Plates (RSQ) were used as the reference method and compared to Kirby-Bauer disc diffusion test, Vitek GPS-TA card, MicroScan Panel (GP-6), and Etest. Streptomycin susceptibility results for MicroScan GP-6 and RSQ were recorded at 24 and 48 h and all other methods and antibiotics were read at 24 h or less. When compared with the agar screen method, all of the methods demonstrated > 99% agreement. One isolate was falsely sensitive to gentamicin at 24 h, but resistant at 48 h, when tested on both MicroScan and RSQ agar screen. Thirty-nine isolates showed resistance to vancomycin with all methods. These isolates were from three different local hospitals and were identified as E. faecium. Pulse-field gel electrophoresis demonstrated that all of the vancomycin-resistant isolates were derived from the same clone. Of interest is the observation that high-level resistance to aminoglycosides varied between the clonally related isolates.

Epidemiology of a dominant clonal strain of vancomycin-resistant Enterococcus faecium at separate hospitals in Boston, Massachusetts

In 1996, the dominant (43%) strain of vancomycin-resistant enterococci (VRE; type A) at Massachusetts General Hospital was identified at Brigham and Women's Hospital (BWH). To characterize the epidemiology of infection with type A isolates of VRE at BWH, we collected demographic and clinical data for all patients from whom VRE were isolated from a clinical specimen through September 1996. The first clinical isolates from all BWH patients from whom VRE were isolated were typed by pulsed-field gel electrophoresis of SmaI digests of chromosomal DNA. Among patients hospitalized after the first patient at BWH infected with a type A isolate of VRE was identified, exposures were compared between patients who acquired type A isolates of VRE and those who acquired other types of VRE. Isolates from 99 patients identified to have acquired VRE were most commonly from blood (n = 27), urine (n = 19), or wounds (n = 19). Three months after the index patient arrived at BWH and at a time when > or =12 types of strains of VRE were present, type A isolates of VRE became dominant; 39 of 75 (52%) of the study cohort had acquired type A isolates of VRE. We found no association between the acquisition of type A isolates of VRE and transfer from another institution or temporal overlap by service, ward, or floor with patients known to have acquired type A isolates of VRE. By multivariate analysis, only residence in the medical intensive care unit (adjusted odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4 to 107) and the receipt of two or more antibiotics per patient-day (adjusted OR, 12.2; 95% CI, 1.2 to 9.0) were associated with the acquisition of strain A. This strain of VRE, dominant at two Boston hospitals, was associated with intensity of antibiotic exposures (i.e., two or more antibiotics per patient-day). We hypothesize that this strain may have unidentified properties providing a mechanism favoring its spread and dominance over other extant isolates, and further studies are needed to define these properties.

Epidemiology and control of vancomycin-resistant enterococci in an adult and children's hospital

BACKGROUND

The incidence of vancomycin-resistant enterococci (VRE) has reached endemic proportions in many medical centers. To initiate an effective infection control program, an understanding of the epidemiologic attributes of the genus in medical facilities is imperative.

METHODS

We studied 138 consecutive cases of VRE from April through December 1995. We created a database to analyze the risk factors for patients in both an adult hospital and a children's hospital and screened all specimens, submitted for routine microbiologic analysis, for VRE.

RESULTS

One hundred twenty-three cases (89%) occurred in the adult acute care hospital, and 15 (11%) occurred in the children's hospital. Eighty patients (58%) were colonized with VRE, and 58 (42%) had an infection with VRE. Eighty-three percent of all the cases of VRE were nosocomially acquired. The majority of cases occurred in the medical service. Urine was the most important clinical specimen infected or colonized. Prior use of an antibiotic, other than vancomycin, was the most important risk factor for all nosocomial cases, followed by prior vancomycin use for surgical patients and residence in a unit with other patients infected with VRE for the medical service. Direct admission from another hospital was the most important risk factor for community-acquired cases. Special microbiologic screening of cultures yielded 48% of all VRE identified. Enterococcus faecium was the predominant resistant isolate recovered.

CONCLUSIONS

The control of VRE in the hospital setting is difficult for several reasons. Almost half of all patients carrying VRE would not have been identified without special microbiologic screening efforts, as would patients, admitted from the community, who are already colonized with VRE. Controlling antibiotic use both in the hospital and the community is basic for controlling these organisms. Continuous education of all staff about VRE and other nosocomially significant organisms is the key to controlling the spread of these bacteria.