Colonization Rate and Risk Factors of Vancomycin-Resistant Enterococci among Patients Received Hematopoietic Stem Cell Transplantation in Shiraz, Southern Iran

BACKGROUND Infections caused by antimicrobial-resistant bacteria are associated with increased mortality and health care costs. Enterococci have been recognized as a clinically important pathogen in hospitalized patients. Vancomycin-resistant enterococci (VRE) infections cause significant morbidity and mortality among patients undergoing transplantation. OBJECTIVE To identify epidemiology of VRE colonization and related risk factors among patients with hematological malignancies after hematopoietic stem cell transplantation (HSCT). METHODS This cross-sectional study was performed on 42 patients who underwent bone-marrow transplantation between July 2013 and March 2014. A stool sample was taken from each patient 3-5 days after transplantation and cultured on appropriate media. Suspected colonies of enterococci were detected to species level by their culture characteristics, biochemical reactions and molecular features. VRE were confirmed via phenotypic and genotypic methods. RESULTS VRE were detected in 14 (33%) of studied samples. 10 (71%) of the detected VRE isolates were identified as high level vancomycin-resistant E. faecium with minimum inhibitory concentration (MIC) of ≥256 μg/mL of vancomycin; 3 isolates were E. galinarum and 1 was E. casseliflavus with an MIC of 8-16 μg/mL. VanA was dominant phenotype and all VRE isolates with high-level of vancomycin resistance had vanA gene. VRE isolation was mostly observed in patients with acute lymphoblastic leukemia (ALL) than other diseases. Moreover, antibiotic prophylaxis and hospitalization were independent risk factors for acquisition of VRE after transplantation. CONCLUSION We found high level of vancomycin-resistance in E. faecium isolates obtained from HSCT patients. The vancomycin-resistant isolates of E.faecium had vanA and/or simultaneously vanB genes.