P1535: assessment of colonization and infection epidemiology in patients undergoing allogeneic stem cell transplantation – a prospective multi-center study of polish adult leukemia group (palg).

Topic: 30. Infections in hematology (incl. supportive care/therapy) Background: Infection-related mortality (IRM) remains a major challenge associated with allogeneic hematopoietic stem cell transplantation (alloHSCT). The emergence of multidrug-resistant (MDR) pathogens has become a global threat connected with life-threatening opportunistic infections causing an increased risk of both early and late IRM. Aims: The aim of the study was to analyze the colonization with pathogenic microorganisms, the incidence of infections up to 100 days after alloHSCT, the effectiveness of the prophylaxis, as well as evaluation of treatment outcomes in patients undergoing alloHSCT. Methods: We present a multicenter prospective study of the Polish Adult Leukemia Group (PALG) assessing the influence of colonization on infection epidemiology in 239 patients (pts)(54% male) with a median age of 47yo (range 19-72yo) who underwent alloHSCT between 01-06.2022 in 7 Hematology Departments in Poland. The most common indication for alloHSCT was AML-45%, followed by ALL-16%, lymphoma-13%, and other-26%. Microbiological cultures of urine and the anal area were performed on each pt in the pre-transplant period to determine colonization. Additionally, colonization of the throat, and the nasal cavity was assessed in 44% pts. Standard antibacterial, antifungal, and antiviral prophylaxis was used. Statistical analysis was performed using multivariate tables and the chi^2 test with Yates’s correction. We used P-values with a significance level of 0.05. Results: Colonization by pathogenic microorganisms was observed in 75% (180/239) pts before alloHSCT, and the most common location was the anal region 46% (188/413), mainly colonized by Escherichia coli ESBL (-) 18% (34/188). MDR pathogens accounted for 29% (118/413) of all positive colonization cultures before alloHSCT. In the post-transplantation period, infections occurred in 81% (194/239) pts. Bacteremia was observed in 37% (89/239) pts, mostly caused by Staphylococcus epidermidis MSCNS. MDR pathogens accounted for 39% (132/340) of all pathogens, mostly - extended-spectrum beta-lactamase (ESBL), observed in 40% (54/132). 25% (45/180) of colonized pts developed a total of 59 infections with the pathogen responsible for their previous colonization (Table 1). Fungal infections were in 20% (48/239) and viral infections in 42% (101/239) of pts. 84% (201/239) of alloHSCT recipients were positive for CMV IgG antibodies, and CMV reactivation occurred in 40% (81/201) of them. Fungal infections were most common in the gastrointestinal tract - 39% (21/53), and the most frequently detected fungal pathogen was Candida albicans-36% (19/53). The initial presence of colonization (p=0.018) and duration of neutropenia <1.0 G/l (p=0.004) significantly increased the risk of infection, while reduced-intensity conditioning (p=0.018) and ciprofloxacin prophylaxis (p=0.02) significantly decreased. Higher age at the time of alloHSCT (HR 1.03 95%CI: 1.01-1.05) and the presence of bacteriemia (HR 2.02 95%CI: 1.03-3.96) were independent predictors of shorter survival. The use of antibacterial prophylaxis was associated with longer survival (HR 0.24 95%CI: 0.08-0.69). Thirteen percent (31/239) of pts died within 100 days after alloHSCT, 52% of them (16/31) due to bacterial septic shock. Summary/Conclusion: Colonization evaluation of the urinary tract, anus area, and throat is an effective tool to identify pts with a high risk of secondary infections, resulting in the implementation of targeted treatment and improved outcomes. Colonization assessment remains strongly recommended in pts undergoing alloHSCT.Keywords: Allo-SCT, Infection, Prophylaxis