β-lactamase x PBP1b x PBP3

The study proposes a planned, double-blind, non-inferiority clinical trial involving patients with febrile neutropenia and risk of extended-spectrum beta-lactamase (ESBL) infection. The goal is:
- Analyze the efficacy and tolerability of Ceftolozane/tazobactam (CEF/TAZ) compared to the current standard of care (meropenem) in patients with febrile neutropenia and risk of ESBL infection.
Patients will be randomly assigned to receive CEF/TAZ or meropenem, with assessment of clinical response, toxicity and microbiological evolution. Stool samples will be collected before, during and after treatment for intestinal microbiota analysis and intestinal microbiome analysis to evaluate possible effects on GVHD. Analysis of the results will include the taxonomic classification of the organisms present. Data will be analyzed to assess non-inferiority in clinical response, incidence of GVHD, antimicrobial resistance and other outcomes.

Patients with hematological malignancies receive highly myelotoxic chemotherapy regimens that cause periods of severe myelosuppression, which places them at high risk of developing bacteremia.
At a global level, a very significant increase in multidrug-resistant (MDR) Gram-negative microorganisms, particularly Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBL) and MDR P.aeruginosa, have been described during the last decade. Among the strategies to reduce bacterial resistance, ceftolozane/tazobactam (C/T) as a "carbapenem-sparing" antibiotic has been proposed.
C/T has broad-spectrum activity since it has action against ESBL-producing Enterobacteriaceae and MDR P. aeruginosa. Studies carried out in the real world using this antibiotic in patients with hematological malignancies have demonstrated clinical success in reports and case series, considered a therapeutic option in patients with Enterobacteriaceae and P. aeruginosa infections, particularly in MDR pathogens.
At the National Cancer Institute (in Spanish, Instituto Nacional de Cancerologia), Gram-negative bacilli have been identified for more than 20 years as the pathogens most frequently associated with bacteremia. Escherichia coli occupies the first place in 25% (41% ESBL), followed by Klebsiella spp. in 5.6% (11.2% ESBL) and P. aeruginosa in 5.6% (11.2% MDR). The protocol for approaching and treating hematological malignancy patients with severe neutropenia and fever is to initiate an antimicrobial regimen with piperacillin/tazobactam (P/T). In patients who persist with fever after 48 to 72 hours of starting antibiotics, who present with clinical deterioration, or in whom P/T-resistant bacteria are identified, this is escalated to carbapenem.
Therefore, it is proposed to compare the clinical and microbiological response in patients with hematological malignancies who present with severe neutropenia and fever and who present clinical data of bacteremia, with empirical treatment with C/T vs. P/T, trying to reduce the use of carbapenems in this group of patients.