Early bacteremia following allogeneic hematopoietic stem cell transplantation without antibiotic prophylaxis: epidemiology and antimicrobial resistance.

Objective: Bacteremia is a serious complication in patients undergoing allogeneic hematopoietic stem cell transplantation. The aim of this study was to determine the frequency, epidemiological profile, and risk factors of bacteremia early after allogeneic hematopoietic stem cell transplantation.

Methods: An observational descriptive retrospective study was conducted in patients who received transplants between January 2016 and December 2021. Early bacteremia was defined as blood stream infection occurring between Day 0 and Day 100 after transplantation.

Results: Forty episodes of early bacteremia occurred in 36/245 transplanted patients. Fifteen episodes (37.5%) were due to gram-positive bacteria and 25 (62.5%) to gram-negative bacteria. The most frequent species isolated were coagulase negative staphylococci (CoNS) in gram-positive bacteremia (n = 8/15), and Klebsiella species (8/25) and Pseudomonas species (8/25) in gram-negative bacteremia. Twenty-nine episodes of bacteremia (72.5%) occurred during the first 30 days after transplantation with a median time of nine days (range: 0-90 days). Coagulase negative staphylococci were methicillin-resistant in 75% of cases, the only Staphylococcus aureus isolated was methicillin-resistant. All gram-positive bacilli were penicillin-resistant. Gram-negative bacilli were multidrug resistant in 61.5% of cases. In multivariate analysis, bone marrow as source of graft (p-value = 0.02) and cytomegalovirus reactivation (p-value = 0.02) were significantly associated with an increased risk of bacteremia. Mortality attributable to bacteremia was 2.8%. The one-year overall survival was not significantly different between those with and without bacteremia.

Conclusions: Bacteremia was more frequent within the first 30 days after transplantation indicating the crucial role of neutropenia. An increase in multidrug resistant gram-negative bacteremia was noted.