P1538: multidrug resistant bacterial colonization and related bloodstream infections in febrile haematologic patients: epidemiology and outcome

Topic: 30. Infections in hematology (incl. supportive care/therapy) Background: Infections due to multidrug resistant (MDR) bacteria are considered a major problem worldwide, particularly in immunosuppressed patients. Epidemiologic surveillance of MDR bacterial colonization and bloodstream infections (BSI) in patients (pts) affected by haematological malignancies (HM) may allow a better selection of empiric antibiotic treatment in febrile pts. Aims: With the aim of evaluating the epidemiology and impact on prognosis of MDR bacterial colonization and related BSI (MDR relBSI) in febrile HM pts, we analyzed all febrile episodes occurred at our Institution during a 2-year period of observation. Methods: To detect MDR colonization, rectal swabs are routinely performed at our Institution; data concerning MDR colonization during the period between 2021 and 2022 were evaluated in all febrile HM inpatients, and stratified according to type and phase of HM, previous fluoroquinolone (Fq) treatment (within 1 year), type of MDR bacteria and of BSI. We defined a MDR relBSI when the same pathogen was isolated from blood at any time after documented MDR colonization. Results: Overall, 538 febrile episodes occurred in 341 HM patients. Median age was 62y (range 18-86), and M/F ratio 213/128. A diagnosis of acute leukaemia (AL), lymphoma (Ly) and multiple myeloma (MM) was observed in 107 (31.4%), 127 (37.2%) and 79 (23.2%) pts, respectively; HM phase was diagnosis (Dx) in 109 (32%) pts, complete or partial remission (CR/PR) in 176 (51.6%) and relapse/refractory (R/R) in 56 (16.2%). Seventy-seven MDR colonizations during the same HM status were observed in 76/341 febrile pts (22.3%). Multiple colonization was observed in 11 pts. Extended spectrum beta-lactamases producers (ESBLp) E. coli was observed in 46 febrile pts, ESBLp K. pneumoniae in 5, carbapenem resistant (CR) K. pneumoniae in 2, CR Citrobacter spp in 1 and vancomycin resistant Enterococci (VRE) in 28. Table 1 summarizes the clinical characteristics of febrile pts with MDR bacteria colonization. Overall, MDR bacterial colonization was more frequent in AL febrile pts (33/107, 30.8%) vs Ly and MM pts (40/208, 19.2%) (p=0.034) and in RR pts (18/56, 32.1%) vs Dx and CR/PR pts (59/285, 20.7%) (p=0.079). Frequency of ESBLp E. coli colonization was similar in AL (14/107, 13.1%), Ly (19/127, 15%) and MM (10/79, 12.7%), whereas VRE was more frequently observed in AL pts (21/107, 19.6%) as compared to Ly and MM pts (11/208, 5.3%) (p=0.0001). In particular, no cases of VRE colonization were observed in MM pts. VRE colonization was rarely observed for the first time in CR/PR pts (9/176, 5.1%) vs Dx and R/R pts (23/165, 13.9%) (p=0.008). In 62 (80.5%) cases, a Fq treatment has been delivered in the previous year, with no differences for type of MDR bacterial colonization. In 34 cases, a BSI was documented, and in 18/77 (23.4%) it was a MDR relBSI. Colonization with MDR enterobacteria was more frequently associated with MDR relBSI than VRE (15/54, 27.8% vs 3/35, 8.6%) (p=0.032). Thirty-day mortality was 5/18 (27.8%) in pts with MDR relBSI vs 2/59 (3.4%) in those without (p=0.0066). At multivariable analysis, MDR relBSI was the only independent factor associated to 30-day mortality (OR 9.949, CI 1.355-73.055). Summary/Conclusion: MDR colonization was more frequent in AL febrile pts, particularly VRE, which was also associated to active HM phase, probably due to increased antibiotic pressure. Frequency of MDR relBSI was high, particularly in pts with MDR enterobacterial colonization. As development of a MDR relBSI was the only independent risk factor for 30-day mortality, MDR bacterial colonization screening should be routinely performed in HM pts, in order to choose the most appropriate empiric antibiotic treatment.Keywords: Epidemiology, Outcome, Infection