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

BMC Infectious Diseases Impact of vancomycin resistance on mortality in neutropenic patients with enterococcal bloodstream infection: a retrospective study Sung-Yeon Cho 1 Dong-Gun Lee 0 1 Su-Mi Choi 1 Jae-Cheol Kwon Si-Hyun Kim Jae-Ki Choi 1 Sun Hee Park 1 Yeon-Joon Park Jung-Hyun Choi 1 Jin-Hong Yoo 1 0 The Catholic Blood and Marrow Transplantation Center , Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea , Seoul , Republic of Korea 1 Division of Infectious Diseases, Department of Internal Medicine, Vaccine Bio Research Institute, College of Medicine, The Catholic University of Korea , Seoul , Republic of Korea 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. Bacteremia; Enterococcus; Mortality; Neutropenia; Risk factors; Vancomycin resistance - Background Enterococcal bloodstream infections (BSI) have been increasing in hospitalized patients since the 1990s [1,2]. Enterococci are normal intestinal flora of humans, but usually cause infections when immunity of the host is compromised [3]. At our Blood and Marrow Transplantation Center, Enterococcus has emerged as the third most common pathogen, constituting 14.0% of all BSIs, and vancomycin resistant Enterococcus (VRE) was responsible for 20.6% of proven enterococcal BSIs [4]. There are several studies on outcomes after administration of newer antimicrobial agents such as linezolid, daptomycin, quinupristin-dalfopristin or tigecycline [5,6]. But VRE BSI is still a major concern, because of the limited therapeutic options available and higher mortality subsequent to infection [7,8]. It has been demonstrated that vancomycin resistance increases mortality in patients with enterococcal BSI [1,9-14]; however, controversy remains [5,15-19]. Conflicting results on the clinical implications of vancomycin resistance may have been due to the varied severity of the underlying illness in patients with VRE BSI. Previous meta-analysis concluded that vancomycin resistance is independently associated with increased mortality in enterococcal BSI [1]. However, only a subset of the studies involved in the meta-analysis examined immunocompromised individuals [13,14]. Whether vancomycin resistance increases mortality in patients with enterococcal BSI could be one of the important considerations in determining empirical therapeutic approach, especially in the setting of chemotherapyinduced reversible neutropenia. This study examined the risk factors and outcomes of VRE BSI as compared with vancomycin-susceptible Enterococcus (VSE) BSI, and the factors associated with mortality in a relatively homogeneous group of patients with neutropenia after chemotherapy or stem cell transplantation (SCT) for underlying hematologic diseases. Methods Study design and clinical setting We retrospectively reviewed all consecutive episodes of enterococcal BSIs in adult patients with neutropenic fever from July 2009 to December 2011 at the Catholic Blood and Marrow Transplantation Center, Seoul St. Marys Hospital. Our hospital is a 1,200-bed, universityaffiliated, tertiary-care center in Seoul, South Korea. The Catholic Blood and Marrow Transplantation Center performs over 350 SCTs annually. Eligible patients included those with hematological malignancies, who experienced neutropenic fever during chemotherapy or SCT, who were older than 18 years of age, and were documented to be blood culture positive for Enterococcus species. Enterococcal BSI cases were obtained from a computerized microbiology database. We collected data targeted to positive blood culture results from chemotherapy ward and SCT ward. In cases with persistent BSI, we analysed the first episode. If cases met the definition of separate BSI, each infection was considered individually. Concomitant VRE and VSE BSI were excluded. Even in cases with neutropenic fever and documented enterococcal BSI, patients who had not previously received treatment for hematological malignancies, such as anti-cancer chemotherapy or SCT, were excluded. The data obtained for each patient included age, sex, underlying diseases, absolute neutrophil count (ANC) at the onset of fever, severity and duration of neutropenia, severity of illness (Simplified Acute Physiology Score, SAPS II) and Charlsons comorbidity index at the onset of BSI, length of hospital stay, stay in intensive care unit (ICU) before the onset of BSI, septic shock, the presence of previously documented rectal VRE colonization, organisms isolated from blood and antimicrobial susceptibility, antibiotics administered, and survival 7 and 30 days after the onset of BSI. Blood for cultures was sampled using sterile techniques, with one set from peripheral vein puncture and another set simultaneously from a central venous catheter. Each 10~15 mL of blood was inoculated into aerobic and anaerobic bottles (BD BACTEC Plus Aerobic/F, Lytic/10 Anaerobic/F Culture Vials, Becton Dickinson, Sparks, MD, USA), which were immediately transported to the clinical laboratory. Antibiotic susceptibility testing was performed with an automatic system (Vitek-2, bioMrieux, Hazelwood, MO, USA). E. faecalis clinical isolates are almost always susceptible to ampicillin; hence, ampicillin sensitivity of E. faecalis was not tested in our study. Polymerase chain reaction (PCR) test to look for van A, B, C genes was not performed routinely. At our center, during the chemotherapy or SCT, oral cipr (...truncated)