Background: Klebsiella pneumoniae is a nosocomial pathogen that causes severe infections in immunocompromised patients. The aim of the study was to conduct a microbiological and clinical analysis of K. pneumoniae infections in children with malignancies or undergoing hematopoietic cell transplantation in Poland. Methods: We conducted a retrospective, multicenter study including children and adolescents under 19 years old treated between 2012 and 2021. We analyzed patients’ characteristics, microbiological data, and the outcomes of antibiotic therapy. Results: A total of 9121 newly diagnosed children were treated for malignancy and 1697 pediatric patients underwent hematopoietic cell transplantation. K. pneumoniae infections were diagnosed in 527 patients. Their overall incidence was 4.86% in pediatric hematology and oncology patients and 4.95% in patients who underwent hematopoietic cell transplantation. The incidence of infection was higher in patients with acute leukemia than with solid tumors (7.8% vs. 4.1%; OR = 2.0; 95% CI = 1.6–2.4; p < 0.0001). The most frequent source of infection was in the urinary tract at 55.2%. More than 57% of K. pneumoniae strains were extended-spectrum β-lactamase-positive and almost 34% were multidrug-resistant. Infections with K. pneumoniae contributed to death in 3.22% of patients. Conclusions: K. pneumoniae is one of the most critical pathogens in children suffering from malignancies or undergoing hematopoietic cell transplantation. The incidence of multidrug-resistant K. pneumoniae strains is increasing and contributing to poor clinical outcome.

Viral infections can be a serious complication of therapy in children with acute lymphoblastic leukemia (ALL). In this study, we focused on the incidence and the profile of viral infection in children with ALL treated in 17 pediatric oncology centers in Poland in the two-year periods of 2018–2019 and 2020–2021. We also compared the frequency of viral infections in 2018–2019 to that in 2020–2021. In 2020–2021, a total of 192 children with ALL had a viral infection during intensive chemotherapy. A total number of 312 episodes of viral infections were diagnosed. The most common infections detected in the samples were: COVID-19 (23%), rhinovirus (18%), and respiratory syncytial virus (14%). COVID-19 and BK virus infections were the reason for the death 1% of all patients. In 2018–2019, a total of 53 ALL patients who had a viral infection were reported and 72 viral events were observed, mainly adenovirus (48.6%), rotavirus (31.9%), and herpes zoster (8.3%). No deaths were reported during this period. The cumulative incidence of viral infections in 2018–2019 was 10.4%, while for 2020–2021, it was 36.7%. In conclusion, a high incidence of COVID-19 infection was observed among pediatric patients with ALL in Poland. The mortality rate in our material was low. The viral profile in ALL children undergoing chemotherapy can be useful for clinicians to improve prophylactic and therapeutic strategies.

Background: Acinetobacter, specifically A. baumannii, are becoming a great threat to hospitalized patients due to increasing antibiotic resistance. The aim of this study was to describe the epidemiology, clinical characteristics, antimicrobial susceptibility pattern and outcome of Acinetobacter infections in pediatric cancer patients and hematopoietic stem cell transplant (HSCT) recipients in Poland. Methods: A total of 125 episodes of Acinetobacter species infections were reported in patients <18 years treated in Polish pediatric hematology and oncology centers over a period from 2012 to 2023. Infections were subdivided into oncohematological disease (OHD) group (n = 106; 84.8%) and HSCT group (n = 19; 15.2%). Each episode represented a separate infection event; therefore, a patient who was infected more than once during the course of treatment was counted for each infection episode. Results: A. baumannii is the most common Acinetobacter species in all groups. The most common diagnoses in OHD group were acute lymphoblastic leukemia (ALL) (n = 32; 30.2%) and acute myeloid leukemia (AML) (n = 13; 12.3%). The most common underlying diseases that were indication for HSCT were hemophagocytic lymphohistiocytosis (n = 3; 15.8%) and neuroblastoma (n = 3; 15.8%). Mortality was significantly higher in the HSCT group compared to the OHD group. In the OHD group, deaths did not correlate with the type of antibiotic, with an exception for gentamicin, which correlated with higher mortality. In the HSCT group, deaths did not correlate with the type of antibiotic, except for levofloxacin that was correlated with a higher mortality rate. Conclusions: Acinetobacter infections are a great danger to immunocompromised patients. More research is needed in order to prevent and treat antibiotic-resistant bacteria.

Background/Objectives: The objective of this study was to analyze the clinical and laboratory features, management, outcomes, and complications of PRES in children with malignancies or following hematopoietic cell transplantation (HCT). Methods: This was a multicenter retrospective analysis of PRES episodes diagnosed between 2014 and 2022 in Polish pediatric hematology and oncology (PHO) centers and HCT units. The study included 438 patients treated for malignancy or post-HCT: 120 with PRES (study group) and 318 without PRES (control group). Results: PRES was diagnosed in children aged 1.7–16.5 years (median = 7.7 years). The most common underlying diagnosis was ALL (76.7%; n = 92). Symptoms of PRES included disturbances of consciousness (84.2%), seizures (80.0%), hypertension (74.2%), apathy (64.2%), abdominal pain (45.0%), visual disturbances (28.3%), and headaches (26.7%). Electrolyte abnormalities were observed in 75.0% of children, most commonly hyponatremia (49.2%) and hypokalemia (37.5%). Children with PRES were more likely to require admission to the intensive care unit (ICU) than controls (50.0% vs. 29.6%, p < 0.001). The most frequent long-term complications of PRES were hypertension (22.5%) and epilepsy (20.8%). Among PHO patients, those with PRES had significantly lower DFS (76.7% vs. 93.7%, p < 0.001) and OS (79.2% vs. 93.4%, p < 0.001). In the HCT group, PRES was also associated with lower DFS (40.0% vs. 83.3%, p = 0.012) and OS (40.0% vs. 77.8%, p = 0.047). Conclusions: PRES is a significant complication of oncological and transplant treatment in children. Its occurrence was associated with worse overall and disease-free survival. We proposed a predictive index for PRES, diagnostic criteria, and a revised name for this syndrome.

Background: Acinetobacter, significantly A.baumannii, are becoming a great threat to hospitalized patients due to increasing antibiotic resistance. The aim of this study was to describe the epidemiology, clinical characteristic, antimicrobial susceptibility pattern and outcome of Acinetobacter infections in pediatric cancer patients and HSCT recipients in Poland. Methods: a total of 125 episodes of Acinetobacter species infections were reported in pa-tients < 18 years treated in Polish pediatric hematology and oncology centers over a pe-riod from 2012 to 2023. Infections were subdivided into oncohematological diseases (OHD) group (n=106; 84,8%) and hematopoietic stem cell transplant (HSCT) group (n=19; 15,2%). Results: A.baumannii is the most common Acinetobacter species in all groups. The most common diagnoses of infected patients in OHD group were: ALL (n=32; 30.2%) and AML (n=13; 12.3%). The most common underlying disease that was indication for HSCT among infected patients were hemophagocytic lymphohistiocytosis (n=3; 15.8%) and neuroblastoma (n=3; 15.8%). In OHD group, deaths did not correlate with the type of antibiotic, with an exception for gentamicin, which correlates with higher mortality. In HSCT group, deaths did not correlate with the type of antibiotic, except for levofloxa-cin that was correlated with higher mortality rate. Mortality was significantly higher in the HSCT group compared to the OHD group. Conclusions: Acinetobacter infections are a great danger to immunocompromised pa-tients. More research is needed in order to prevent and treat antibiotic resistant bacteria.

Objectives: This study evaluates the epidemiological characteristics and survival, functional, and esthetic outcomes of pediatric patients diagnosed with head and neck sarcoma (PHNS) who underwent individualized surgical treatment for local disease control and/or for defect reconstruction. Methods: A cohort of 45 patients aged 0–18 years with histologically confirmed PHNS who underwent surgical resection and/or reconstructive procedures was analyzed. Extracted variables included demographic data, tumor histology and stage, surgical margin status, and systemic therapy modalities. Reconstructive strategies were assessed, considering technique, sequencing, and total duration of treatment. Survival analysis was performed, focusing on both overall survival (OS) and event-free survival (EFS). Results: Rhabdomyosarcoma constituted the predominant diagnosis (19/45), followed by Ewing sarcoma (7/45) and chondrosarcoma (5/45). The maxilla represented the most common primary site (18/45), whereas orbital origin was the least frequent (3/45). Complete surgical excision (R0) was achieved in 80.5% of resected cases. Margin status showed no statistically significant association with final outcome (p = 0.7786). In contrast, nodal metastasis, local recurrence, and distant dissemination were independently and collectively correlated with mortality. Survival analysis demonstrated a 3-year OS of 100% and an EFS of 79.8%, and a 5-year OS of 94.7% with an EFS of 70.7%. Conclusions: Implementation of an individualized surgical and reconstructive protocol was associated with effective local tumor control and favourable reconstructive outcomes. Oncologic prognosis was driven primarily by nodal involvement and recurrent or metastatic disease rather than margin status alone.