The study aimed to describe the epidemiology of multidrug-resistant (MDR) bacteria among solid cancer (SC) patients with bloodstream infections (BSIs), evaluating inappropriate empiric antibiotic treatment (IEAT) use and mortality trends over a 25-year period. All BSI occurrences in adult SC patients at a university hospital were analyzed across five distinct five-year intervals. MDR bacteria were classified as extended-spectrum beta-lactamases (ESBL)-producing and/or Carbapenem-resistant Enterobacterales, non-fermenting Gram-negative bacilli (GNB) resistant to at least three antibiotic classes, methicillin-resistant Staphylococcus aureus (MRSA), and Vancomycin-resistant Enterococci . A multivariate regression model identified the risk factors for MDR BSI. Of 6,117 BSI episodes, Gram-negative bacilli (GNB) constituted 60.4% (3,695/6,117), being the most common are Escherichia coli with 26.8% (1,637/6,117), Klebsiella spp. with 12.4% (760/6,117), and Pseudomonas aeruginosa with 8.6% (525/6,117). MDR-GNB accounted for 644 episodes (84.8% of MDR or 644/759), predominantly ESBL-producing strains (71.1% or 540/759), which escalated significantly over time. IEAT was administered in 24.8% of episodes, mainly in MDR BSI, and was associated with higher mortality (22.9% vs. 14%, P < 0.001). Independent factors for MDR BSI were prior antibiotic use [odds ratio (OR) 2.93, confidence interval (CI) 2.34–3.67], BSI during antibiotic treatment (OR 1.46, CI 1.18–1.81), biliary (OR 1.84, CI 1.34–2.52) or urinary source (OR 1.86, CI 1.43–2.43), admission period (OR) 1.28, CI 1.18–1.38, and community-acquired infection (OR 0.57, CI 0.39–0.82). The study showed an increase in MDR-GNB among SC patients with BSI. A quarter received IEAT, which was linked to increased mortality. Improving risk assessment for MDR infections and the judicious prescription of empiric antibiotics are crucial for better outcomes. IMPORTANCE: Multidrug-resistant (MDR) bacteria pose a global public health threat as they are more challenging to treat, and they are on the rise. Solid cancer patients are often immunocompromised due to their disease and cancer treatments, making them more susceptible to infections. Understanding the changes and trends in bloodstream infections in solid cancer patients is crucial, to help physicians make informed decisions about appropriate antibiotic therapies, manage infections in this vulnerable population, and prevent infection. Solid cancer patients often require intensive and prolonged treatments, including surgery, chemotherapy, and radiation therapy. Infections can complicate these treatments, leading to treatment delays, increased healthcare costs, and poorer patient outcomes. Investigating new strategies to combat MDR infections and researching novel antibiotics in these patients is of paramount importance to avoid these negative impacts.

Bloodstream infection (BSI) caused by P. aeruginosa is related with an elevated morbidity and mortality in neutropenic patients. For this reason, optimal antipseudomonal coverage has been the basis of all historical recommendations in the empirical treatment of febrile neutropenia.

Community‐acquired respiratory viral infections (CARV) significantly impact patients with hematological malignancies (HM), leading to high morbidity and mortality. However, large‐scale, real‐world data on CARV in these patients is limited. This study analyzed data from the EPICOVIDEHA‐EPIFLUEHA registry, focusing on patients with HM diagnosed with CARV during the 2023–2024 autumn–winter season. The study assessed epidemiology, clinical characteristics, risk factors, and outcomes. The study examined 1312 patients with HM diagnosed with CARV during the 2023–2024 autumn–winter season. Of these, 59.5% required hospitalization, with 13.5% needing ICU admission. The overall mortality rate was 10.6%, varying by virus: parainfluenza (21.3%), influenza (8.8%), metapneumovirus (7.1%), RSV (5.9%), or SARS‐CoV‐2 (5.0%). Poor outcomes were significantly associated with smoking history, severe lymphopenia, secondary bacterial infections, and ICU admission. This study highlights the severe risk CARV poses to patients with HM, especially those undergoing active treatment. The high rates of hospitalization and mortality stress the need for better prevention, early diagnosis, and targeted therapies. Given the severe outcomes with certain viruses like parainfluenza, tailored strategies are crucial to improving patient outcomes in future CARV seasons.

Pseudomonas aeruginosa is an opportunistic pathogen capable of causing severe infections in immunocompromised individuals, who often require prolonged antibiotic therapy. The emergence of carbapenemase-producing P. aeruginosa has further complicated the management of nosocomial infections, limiting therapeutic options. Cefiderocol has recently emerged as a promising antipseudomonal agent, using the bacterial iron transport system to gain entry into the cell; however, there have been reports of P. aeruginosa resistant to cefiderocol. We describe the in vivo cefiderocol resistance progression of four consecutive P. aeruginosa isolates from one patient with T-cell acute lymphoblastic leukemia. Analysis of potential genes involved in cefiderocol transport resulted in three genes mutated in two resistant isolates. One isolate presented a S116F substitution in PiuC, and the other presented a deletion of 29 amino acids in the signal peptide of PiuA and a STOP substitution in PirA, resulting in the deletion of a piece of the channel. These mutations increased 24- and 64-folds the cefiderocol minimum inhibitory concentration, respectively. The mutations in the aforementioned genes may directly impact siderophore internalization, thereby contributing to an elevation in the MIC of the antibiotic. IMPORTANCE: Carbapenem-resistant Pseudomonas aeruginosa poses a significant challenge due to its broad antibiotic resistance. Cefiderocol is a novel antibiotic aimed at combating infections caused by such organisms. However, if these pathogens develop resistance to this new drug, it hinders treatment efficacy and options. Therefore, it is crucial to identify and describe mutations in the genes involved in the uptake of cefiderocol to find better treatment strategies for patients infected with multidrug-resistant P. aeruginosa .

Background: Scarce data exist that analyze the outcomes of hematological patients with SARS-CoV-2 infection during the Omicron variant period who received treatment with remdesivir or nirmatrelvir/ritonavir. Methods: This study aims to address this issue by using a retrospective observational registry, created by the Spanish Hematopoietic Stem Cell Transplantation and Cell Therapy Group, spanning from 27 December 2021 to 30 April 2023. Results: This study included 466 patients, 243 (52%) who were treated with remdesivir and 223 (48%) with nirmatrelvir/ritonavir. Nirmatrelvir/ritonavir was primarily used for mild cases, resulting in a lower COVID-19-related mortality rate (1.3%), while remdesivir was preferred for moderate to severe cases (40%), exhibiting a higher mortality rate (9%). A multivariate analysis in the remdesivir cohort showed that male gender (odds ratio (OR) 0.35, p = 0.042) correlated with a lower mortality risk, while corticosteroid use (OR 9.4, p < 0.001) and co-infection (OR 2.8, p = 0.047) were linked to a higher mortality risk. Prolonged virus shedding was common, with 52% of patients shedding the virus for more than 25 days. In patients treated with remdesivir, factors associated with prolonged shedding included B-cell malignancy as well as underlying disease, severe disease, a later onset of and shorter duration of remdesivir treatment and a higher baseline viral load. Nirmatrelvir/ritonavir demonstrated a comparable safety profile to remdesivir, despite a higher risk of drug interactions. Conclusions: Nirmatrelvir/ritonavir proved to be a safe and effective option for treating mild cases in the outpatient setting, while remdesivir was preferred for severe cases, where corticosteroids and co-infection significantly predicted worse outcomes. Despite antiviral therapy, prolonged shedding remains a matter of concern.

Background/Objectives: The rise of multidrug-resistant (MDR) infections demands personalized antibiotic strategies for febrile neutropenia (FN) in hematological malignancies. This study investigates machine learning (ML) for identifying patient profiles with increased susceptibility to bloodstream infections (BSI) during FN onset, aiming to tailor treatment approaches. Methods: From January 2020 to June 2022, we used the unsupervised ML algorithm KAMILA to analyze data from hospitalized hematological malignancy patients. Eleven features categorized clinical phenotypes and determined BSI and multidrug-resistant Gram-negative bacilli (MDR-GNB) prevalences at FN onset. Model performance was evaluated with a validation cohort from July 2022 to March 2023. Results: Among 462 FN episodes analyzed in the development cohort, 116 (25.1%) had BSIs. KAMILA’s stratification identified three risk clusters: Cluster 1 (low risk), Cluster 2 (intermediate risk), and Cluster 3 (high risk). Cluster 2 (28.4% of episodes) and Cluster 3 (43.7%) exhibited higher BSI rates of 26.7% and 37.6% and GNB BSI rates of 13.4% and 19.3%, respectively. Cluster 3 had a higher incidence of MDR-GNB BSIs, accounting for 75% of all MDR-GNB BSIs. Cluster 1 (27.9% of episodes) showed a lower BSI risk (<1%) with no GNB infections. Validation cohort results were similar: Cluster 3 had a BSI rate of 38.1%, including 78% of all MDR-GNB BSIs, while Cluster 1 had no GNB-related BSIs. Conclusions: Unsupervised ML-based risk stratification enhances evidence-driven decision-making for empiric antibiotic therapies at FN onset, crucial in an era of rising multi-drug resistance.