Vancomycin-resistant Enterococcus faecalis in a bone-marrow transplant recipient

Early vancomycin-resistant enterococcus (VRE) bacteremia after allogeneic bone marrow transplantation is associated with a rapidly deteriorating clinical course

Vancomycin-resistant enterococcal (VRE) infection is a growing threat. We studied the incidence, risk factors, and clinical course of early-onset VRE bacteremia in allogeneic hematopoietic stem cell transplant recipients. We carried out a chart review of 281 allogeneic hematopoietic stem cell transplant recipients from 1997-2003, including preparative regimen, diagnosis, status of disease, graft-versus-host disease prophylaxis, antimicrobial therapy, and survival. VRE bacteremia developed in 12/281 (4.3%) recipients; 10 (3.6%) were within 21 days of transplant. Diagnoses were acute leukemia (7), NHL (2), and MDS (1). In all, 70% had refractory/relapsed disease; 30% were in remission. In total, 50% had circulating blasts. Nine of 10 had matched unrelated donors (7/9 with CD8+ T-cell depletion). The average time to positive VRE cultures was 15 days; average WBC was 0.05, and 80% had concomitant infections. Despite treatment, all patients died within 73 days of VRE bacteremia. Intra-abdominal complications were common. Causes of death included bacterial or fungal infection, multiorgan failure, VOD, ARDS, and relapse. A total of 60% of patients engrafted neutrophils, but none engrafted platelets. Early VRE bacteremia after allogeneic bone marrow transplant is associated with a rapidly deteriorating clinical course, although not always directly due to VRE. Early VRE may be a marker for the critical condition of these high-risk patients at the time of transplant.

Incidence and clinical complications of vancomycin-resistant enterococcus in pediatric stem cell transplant patients

Vancomycin-resistant enterococcus (VRE) are increasingly important pathogens in stem cell transplant (SCT). In all, 61 pediatric SCT patients had surveillance stool cultures for VRE between July 1999 and November 2002. When VRE was identified, the patients were placed on strict contact isolation. VRE was detected in 15 patients (24.6%). The median age was 3.6 years (range 0.6-18.5 years). Of the 15, 13 (87%) received an allogeneic transplant (six unrelated and seven related). Five of the 15 (33%) colonized patients developed VRE bacteremia. The bacteremia resolved in all five patients after therapy with quinupristin/dalfopristin; three patients required central line removal. Four patients died (38-153 days) post-SCT due to relapse or transplant complication not related to VRE. Of the 11 surviving patients, seven cleared the colonization at a median of 144 days (range 61-198 days) postcolonization. Four patients remain colonized at 68-702 days after the first positive culture. Intestinal colonization with VRE occurred commonly in pediatric SCT patients. Although the morbidity from VRE was not substantial, transplant patients were colonized for prolonged periods. Our results indicate that surveillance for VRE is an effective way to identify colonized patients and may lead to a decrease in transmission to other patients.

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 closer look at vancomycin, teicoplanin, and antimicrobial resistance

The worldwide increase in the incidence of resistant Gram-positive infections has renewed interest in the glycopeptide class of antimicrobial agents. Two glycopeptides are available in many parts of the world--vancomycin and teicoplanin. These two agents appear to differ in several respects, including: potential for selecting microbial resistance, dosing convenience, safety, and efficacy in severe infection. Teicoplanin appears to have lower toxicity and greater convenience; however, its widespread acceptance has been plagued by concerns over antimicrobial resistance, efficacy, and appropriate dosing. A review of available studies suggests that teicoplanin, when dosed at 6 mg/kg/day, is better tolerated than vancomycin 15 mg/kg/q12h; however, at these doses, it appears to be somewhat less effective than vancomycin in serious Staphylococcus aureus infection, such as endocarditis. Although higher doses of teicoplanin, 12 mg/kg/day to 30 mg/kg/day, have been associated with efficacy comparable to that of vancomycin in serious S. aureus infections, such doses may eliminate some of the safety advantages conferred by lower teicoplanin doses. Teicoplanin has been associated with resistance among coagulase-negative staphylococci and the selection of resistance in S. aureus. There is some evidence that widespread use of teicoplanin might accelerate the development of S. aureus resistance to both teicoplanin and vancomycin. The selection of an appropriate glycopeptide in an individual patient should be based not only on convenience, but also on a determination of optimal efficacy, safety at an efficacious dose, and the potential for resistance.

Vancomycin-resistant Enterococcus faecium on a pediatric oncology ward: duration of stool shedding and incidence of clinical infection

OBJECTIVE

To determine the duration of stool shedding and incidence of clinical infection among pediatric oncology patients colonized with vancomycin-resistant Enterococcus faecium (VRE) in our institution.

METHODS

Stool cultures were obtained from all patients admitted from May 15 to August 2, 1994. Patients were followed for evidence of clinical VRE infection and surveillance stool results through August 15, 1995. Genetic relatedness of stool-clinical isolate pairs and serial stool samples was evaluated using pulsed field gel electrophoresis.

RESULTS

Twenty-three (32%) of 73 screened patients were colonized with VRE. Eight (35%) of the colonized patients cleared VRE from stool; 10 (43%) were persistent carriers, excreting organisms for 19 to 331 days (median, 112 days); and 5 patients had an insufficient number of stools to determine length of carriage. Persistent carriers had a median of 6 hospital readmissions; 8 of 10 were positive at first or second readmission Clinical VRE infection developed in 6 of 73 patients (annual incidence, 8.2%). Clinical cases had more days of neutropenia between colonization and infection than colonized patients during a comparable follow-up (49 vs. 16 days, P = 0.04). Five of 6 stool-clinical isolate pairs were identical by pulsed field gel electrophoresis. Serial stools from 6 of 7 patients (collected 20 to 343 days apart) were identical by pulsed field gel electrophoresis.

CONCLUSION

Persistent gastrointestinal colonization with VRE is common among pediatric oncology patients. Carriage of the same VRE clone for up to 1 year was demonstrated. In the majority of cases invasive and colonizing isolates were identical by DNA fingerprinting techniques, suggesting that the colonizing VRE was the source of infection. Intermittent excretion of organisms in stool makes vigilant tracking and immediate isolation of such patients crucial to control efforts. Prolonged neutropenia may increase the risk of developing clinical infection among VRE-colonized patients.

Vancomycin-resistant enterococci

OBJECTIVE

To review vancomycin resistance in enterococci (Enterococcus faecalis and Enterococcus faecium) with respect to history, epidemiology, mechanism of resistance, and management.

DATA SOURCES

A MEDLINE, IDIS, and current journal search of English-language articles on vancomycin-resistant enterococci (VRE) published between 1982 and 1994 was conducted.

STUDY SELECTION

Studies and reports pertaining to vancomycin-resistant E. faecalis and E. faecium were evaluated. Case reports, cohort, epidemiologic, in vitro and in vivo studies were evaluated.

DATA EXTRACTION

Reports in which vancomycin minimum inhibitory concentrations were 32 micrograms/mL or more were evaluated.

DATA SYNTHESIS

Large outbreaks of VRE infection have occurred as a result of nosocomial spread. Such outbreaks have required intensive infection control procedures to limit the spread of VRE. Vancomycin resistance in E. faecalis and E. faecium has been subdivided into phenotypes, VanA and VanB. The mechanism of vancomycin resistance is caused by the production of depsipeptide D-Ala-D-Lac, which replaces D-Ala-D-Ala in the peptidoglycan pathway, thereby preventing the binding of vancomycin to D-Ala-D-Ala in the peptidoglycan cell wall. The vanA gene is associated with a transpositional element (Tn1546) that can be transferred via conjugation while most data suggest that vanB has an endogenous origin. Education, aggressive infection control practices. surveillance programs, and appropriate use of vancomycin are necessary to respond to the VRE problem.

CONCLUSIONS

The prevalence of VRE has increased significantly in recent years and has become a worldwide problem. Several factors, such as prior exposure to vancomycin and antibotics (e.g., cephalosporins, antianaerobic agents), physical location in the hospital, immunosuppression, prolonged hospital stay, and VRE gastrointestinal colonization are associated with VRE infection and colonization. Antibiotic treatment of serious VRE infection depends on the phenotype. Optimal treatment of the VanA phenotype is unknown; the VanB phenotype may be treated with teicoplanin and an aminoglycoside.

Current perspectives on glycopeptide resistance

In the last 5 years, clinical isolates of gram-positive bacteria with intrinsic or acquired resistance to glycopeptide antibiotics have been encountered increasingly. In many of these isolates, resistance arises from an alteration of the antibiotic target site, with the terminal D-alanyl-D-alanine moiety of peptidoglycan precursors being replaced by groups that do not bind glycopeptides. Although the criteria for defining resistance have been revised frequently, the reliable detection of low-level glycopeptide resistance remains problematic and is influenced by the method chosen. Glycopeptide-resistant enterococci have emerged as a particular problem in hospitals, where in addition to sporadic cases, clusters of infections with evidence of interpatient spread have occurred. Studies using molecular typing methods have implicated colonization of patients, staff carriage, and environmental contamination in the dissemination of these bacteria. Choice of antimicrobial therapy for infections caused by glycopeptide-resistant bacteria may be complicated by resistance to other antibiotics. Severe therapeutic difficulties are being encountered among patients infected with enterococci, with some infections being untreatable with currently available antibiotics.

Randomized trial of the addition of gram-positive prophylaxis to standard antimicrobial prophylaxis for patients undergoing autologous bone marrow transplantation

The purpose of the study reported here was to investigate the impact of prophylaxis against gram-positive infections in patients undergoing high-dose chemotherapy and autologous bone marrow transplantation in a randomized trial. Forty-three patients undergoing high-dose chemotherapy with autologous bone marrow transplant were enrolled in a nonblinded randomized trial to receive or not to receive prophylaxis for gram-positive infections with 10(6) U of penicillin intravenously (i.v.) every 6 h (q6h) (if penicillin allergic, 750 mg of vancomycin i.v. q12h) in addition to standard antimicrobial prophylaxis with 400 mg of norfloxacin orally three times a day, 200 mg of fluconazole orally once a day, and 5 mg of acyclovir per kg of body weight i.v. q12h. The patients were being treated for germ cell cancer (n = 15), breast cancer (n = 16), Hodgkin's disease (n = 3), non-Hodgkin's lymphoma (n = 4), acute myeloid leukemia (n = 1), acute lymphoblastic leukemia (n = 1), and ovarian cancer (n = 3). The trial was stopped because of excess morbidity in the form of streptococcal septic shock in the group not receiving gram-positive prophylaxis. There were significantly fewer overall infections (10 versus 3; P = 0.016) and streptococcal infections (9 versus 1; P = 0.0078) in the group receiving gram-positive prophylaxis. There were no significant differences in the numbers of deaths, duration of broad-spectrum antibiotics, or incidence of neutropenic fever between the two groups. Prophylaxis for gram-positive infections with penicillin or vancomycin is effective in reducing the incidence of streptococcal infections in patients undergoing high-dose chemotherapy and autologous bone marrow transplant. However, this approach may carry a risk of fostering resistance among streptococci to penicillin or vancomycin.