The detection of multi-resistant bacterial pathogens, particularly those to carbapenemases, in leukemic and stem cell transplant patients forces the use of old or non-conventional agents as the only remaining treatment options. These include colistin/polymyxin B, tigecycline, fosfomycin and various anti-gram-positive agents. Data on the use of these agents in leukemic patients are scanty, with only linezolid subjected to formal trials. The Expert Group of the 4^th European Conference on Infections in Leukemia has developed guidelines for their use in these patient populations. Targeted therapy should be based on (i) in vitro susceptibility data, (ii) knowledge of the best treatment option against the particular species or phenotype of bacteria, (iii) pharmacokinetic/pharmacodynamic data, and (iv) careful assessment of the risk-benefit balance. For infections due to resistant Gram-negative bacteria, these agents should be preferably used in combination with other agents that remain active in vitro, because of suboptimal efficacy (e.g., tigecycline) and the risk of emergent resistance (e.g., fosfomycin). The paucity of new antibacterial drugs in the near future should lead us to limit the use of these drugs to situations where no alternative exists.

Nocardiosis is rare after hematopoietic cell transplantation (HCT). Little is known regarding its presentation, management, and outcome in this population. In this retrospective international study, we reviewed nocardiosis episodes in HCT recipients (01.01.2000-31.12.2018; 135 transplant centers; 33 countries) and described their clinical, microbiological, radiological, and outcome characteristics. We identified 81 nocardiosis episodes in 74 allo- and 7 auto-HCT recipients. Nocardiosis occurred at a median of 8 (IQR 4–18) months post-HCT. The most frequently involved organs were lungs (70/81; 86%) and brain (30/81; 37%); 29 (36%) patients were afebrile; 46/81 (57%) had disseminated infections. The most common lung imaging findings were consolidations (33/68; 49%) or nodules (32/68; 47%); and brain imaging findings were multiple brain abscesses (19/30; 63%). 10/30 (33%) patients with brain involvement lacked neurological symptoms. 14/48 (29%) patients were bacteremic. N. farcinica was the most common among molecularly identified species (27%, 12/44). Highest susceptibility rates were reported to linezolid 45/45 (100%), amikacin 56/57 (98%), trimethoprim-sulfamethoxazole 57/63 (90%), and imipenem 49/57 (86%). One-year and last follow-up (IQR: 4-42.5 months) all-cause mortality were 40% (32/81) and 52% (42/81), respectively. In the multivariable analysis, underlying disease not in complete remission (HR 2.81, 95%CI 1.32-5.95), and prior bacterial infection (HR 3.42, 95%CI 1.62-7.22) were associated with higher one-year all-cause mortality. Nocardiosis is a late post-HCT infection usually manifesting as a pulmonary disease with frequent dissemination, brain infection and bacteremia. Brain imaging should be performed in HCT recipients with nocardiosis regardless of neurological symptoms. Overall mortality is high.

Patients with hematological malignancies (HM) or undergoing hematopoietic cell transplantation (HCT) face high risk of bloodstream infections (BSI) during febrile neutropenia. Rising antimicrobial resistance (AMR), especially among Gram-negative (GN) bacteria, challenges effective empirical antibiotic therapy (EAT) selection. This ECIL-10 systematic review updates European resistance epidemiology since the 2011 ECIL-4 guidelines publication to inform clinical recommendations. We conducted a systematic review (ID: CRD42025638003) of bacterial epidemiology and resistance in HM/HCT patients across Europe, from June 2011 to September 2024 using PubMed, Embase, and Web of Science according to PRISMA guidelines. We included studies reporting BSI or colonization rates and resistance patterns, including extended-spectrum beta-lactamase-producing/third-generation cephalosporin-resistant (ESBL/3GCR), fluoroquinolone-resistant (FQ-R) carbapenem-resistant (CR), and multidrug-resistant (MDR) for GN bacteria; methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) for Gram-positive (GP) bacteria. Two reviewers independently extracted data with ECDC/EARS-Net surveillance 2011 and 2022 data providing supporting analysis. We examined fluoroquinolone prophylaxis (FQ-P) impact on BSI rate and resistance. Analysis included 40 studies (33,387 patients/febrile episodes from observational studies and 21,402 patients from one meta-analysis) across 12 European countries. BSI prevalence averaged 30% (range, 15-59%), with 42% GN and 51% GP distribution. Median resistance rates among GN BSI were: 55% for FQ-R, 30% for ESBL/3GCR, 13% for both CR and MDR. CR reached 26% in P. aeruginosa (PsA) and 38% in K. pneumoniae (KPn). Among GP BSI resistance was 3% for MRSA and 1% for VRE. Colonization studies demonstrated 20% ESBL/3GCR and 5% CR rates. We identified a southeastern European resistance gradient and significant temporal increase in ESBL/3GCR, CR KPn, and MDR PsA, confirmed in ECDC/EAR-Net analysis. FQ-P reduced overall and GN BSI incidence but increased FQ-R and ESBL/3GCR GN infections in adults. In children, FQ-P reduced BSI in leukemia but not in HCT and data on resistance were inconclusive. ECIL-10 proposed resistance reporting aligned with ESCMID/IDSA guidelines. AMR presents an escalating challenge in febrile neutropenic HM/HCT patients with geographical variability and increasing resistance trends. These findings strongly support the need for updated guidelines, antimicrobial stewardship programs, rapid diagnostics implementation, and prospective studies to optimize effective empirical therapy strategies.

Background: Urinary tract infection (UTI) is the most frequent severe bacterial infection in infants. Up to 31% of infants with UTI have bacteremia. Methods: We retrospectively identified all infants aged 0–2 months who were managed in our hospital with UTI during a 1-year period. Those with bacteremia were compared with those without bacteremia, according to the following variables: ethnicity, age, gender, white blood cell and polymorphonuclear counts, C-reactive protein, urinalysis and blood creatinine values as related to age-appropriate norms, imaging and outcome. Results: We identified 81 infants with 82 episodes of UTI. Most occurred in males (72.8%) and 35 (42.7%) were in infants of non-Jewish origin. In 14/81 (17.3%) of episodes, Escherichia coli was cultured from blood. In multivariate analysis, increased blood creatinine levels (P = 0.004) and non-Jewish origin (P = 0.006) were associated with bacteremia. Time to defervescence was significantly longer in bacteremic versus nonbacteremic children (P = 0.018). Duration of hospitalization was longer in bacteremic infants—10 (7–17) days in bacteremic versus 7 (1–14) days in nonbacteremic children (P < 0.001). Conclusions: In infants aged 0–2 months with UTI, increased blood creatinine value at admission was associated with bacteremia. This value provides an additional clue on admission, independent of personal judgment, to help identify infants at higher risk for bacteremia, prolonged hospitalization and possible complications.