ORIGINAL ARTICLE Bacteremias in children receiving hemopoietic SCT E Castagnola 1 ,MFaraci 2 ,CMoroni 1 , R Bandettini 3 ,SCaruso 4 , F Bagnasco 4 , I Caviglia 1 , AR Natalizia 1 ,VdeFazio 2 , G Morreale 2 ,ELanino 2 ,GDini 2 and R Haupt 4 1 Infectious Diseases Unit, Department of Hematology and Oncology, G Gaslini Children’s Hospital, Genoa, Italy; 2 Bone Marrow Transplant Unit, Department of Hematology and Oncology, G Gaslini Children’s Hospital, Genoa, Italy; 3 Laboratory of Microbiology, G Gaslini Children’s Hospital, Genoa, Italy and 4 Epidemiology and Biostatistics Section, Scientific Directorate, G Gaslini Children’s Hospital, Genoa, Italy The incidence of bacteremia following hemopoietic SCT (HSCT) changes over time from the procedure. The first 30 days have the highest incidence, both in autologous and allogeneic HSCT recipients. In the following periods, bacteremia is a frequent complication in allogeneic HSCT, especially from alternative donors. Gram-positive cocci represent the most frequent cause of single-agent bacteremia. Knowledge of epidemiology (incidence and etiology) of bacteremias following HSCT is pivotal for planning management strategies (prevention, diagnosis and therapy) that must be distinct in the different post- transplant period. Bone Marrow Transplantation (2008) 41, S104–S106; doi:10.1038/bmt.2008.66 Keywords: epidemiology; bacteremia; HSCT Introduction Bacteremia represents a frequent and severe complication after hemopoietic SCT (HSCT) in children. 1–3 The risk of developing bacteremia varies in the different phases following transplantation, pre-engraftment (day 0–30), early post-engraftment (day 31–100) and late post- engraftment (after day 100). Incidence of bacteremia and risk factors after HSCT In the pre-engraftment period, neutropenia and mucositis probably represent the most important risk factors 4–6 both in autologous and allogeneic HSCT recipients. A retro- spective analysis of the incidence of bacteremia following autologous HSCT in children with high-risk neuroblasto- ma 7 showed that 34% of the procedures were complicated by bacteremia with a rate of 0.43 episodes/100 days of follow-up, but the incidence decreased in the different protocols,probablybecauseofchangesintheconditioning regimens. In another retrospective study on the incidence and timing of bacteremia in children undergoing auto- logous or allogeneic HSCT, this complication was diag- nosedin24%oftheautologousHSCTwitharateof0.11 episodes/100 patient-day at risk. 2 The majority of the episodes (90%) were observed in the presence of neutro- penia, especially in the first 30 days after the procedure (when 96% of bacteremias diagnosed in neutropenic patientswereobserved).InallogeneicHSCT,theproportion of bacteremic episodes (32%) and the rate (0.17 episodes/ 100patient-daysatrisk)werehigherthanafterautologous HSCT.However,only45%oftheepisodeswerediagnosed inthepresenceofneutropenia,evenifthemajorityofthem (76%) were still observed during the pre-engraftment period. However, in a prospective 3-year study on the incidence of fever during neutropenic episodes, performed at Gaslini Children’s Hospital, Genoa, Italy, we observed that the proportion of febrile episodes and bacteremias observedinthefirst30daysaftertheprocedurewassimilar in the two types of transplants (Table 1), underlying the role of neutropenia and mucositis as the most important risk factors, independent of the HSCT source. The type of donor (familiar or non-familiar) or the degree of HLA matching (fully or partially) may represent other risk factors for the development of bacteremia after allogeneic HSCT. 3,8–11 In a retrospective study on the epidemiology of bacteremias in 267 allogeneic HSCTs performed at Gaslini Children’s Hospital that compared the incidence of bacteremias stratifying patients according to the type of donor(matchedrelateddonor(MRD)oranytypeofalter- native donor (AD)), children receiving transplant from AD had a fourfold higher risk (95% CI 2.7–6.2) of deve- loping bacteremia, compared with recipients of MRD- HSCT. The incidence was higher during the first 30 days afterHSCTandespeciallyduringthefirst20days,whenall episodesoccurredinthepresenceofneutropenia(Figure1), withasignificantdifferencebetweenAD-andMRD-HSCT recipients. In the post-engraftment period, bacteremia represents a major problem mainly for allogeneic HSCT recipients, 2 because of the presence of many other risk factors. The presence and severity of GvHD and its management (including the use of MoAbs), neutropenia due to poor Correspondence:ECastagnola,InfectiousDiseasesUnit,Departmentof Hematology and Oncology, G Gaslini Children’s Hospital, L go G Gaslini, 5, Genoa 16147, Italy. E-mail: eliocastagnola@ospedale-gaslini.ge.it Bone Marrow Transplantation (2008) 41, S104–S106 & 2008 Nature Publishing Group All rights reserved 0268-3369/08 $30.00 www.nature.com/bmt