We aimed to investigate an outbreak of vancomycin-resistant Enterococcus faecium (VREfm) in paediatric patients from Hospital Pequeno Príncipe. The susceptibility profile was determined, and whole-genome sequencing (WGS) was used to analyse the genetic context of the strains. Five VREfm isolates were recovered from sterile sites and surveillance cultures of two paediatric patients with acute lymphoblastic leukaemia. Species identification was performed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and the minimum inhibitory concentration (MIC) was assessed according to the European Committee for Antimicrobial Susceptibility Testing (EUCAST). WGS was performed to analyse the genetic context of virulence and resistance genes, and in silico multilocus sequence typing was performed to identify the sequence typing of the strains. High-level vancomycin resistance was observed in all isolates (≥256 mg/L). WGS revealed the presence of mobile genetic elements, such as plasmids (rep₂, rep_11a, rep_US15, rep₁₇, and rep_18a), insertion sequences, and phages. Multiple resistance genes (aac(6')-aph(2"), dfrG, ermB, and vanA) and virulence genes (acm and efaAfm) were identified. All the isolates were assigned to ST117 (ST1133 - via a novel MLST), an important epidemic lineage associated with nosocomial infections and outbreaks. Our results show that the ST117 (ST1133) VREfm isolates are circulating in paediatric patients, which raises a great concern. The development of new drugs as well as the implementation of an antimicrobial stewardship program are necessary for their correct management, limiting the spread of resistance in oncohematological patients.

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital- and community-acquired infections (HA-MRSA and CA-MRSA, respectively). Although this microorganism is associated with childhood bacteremia, its epidemiology and predictive factors are not well established. In this study, the susceptibility profiles and molecular characteristics of 46MRSA isolates obtained from blood samples and other sterile fluids of pediatric patients between January 2017 and May 2022 were characterized. The isolates were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry. After that, their antimicrobial susceptibility profiles were assessed trough broth microdilution, and their molecular characteristics was performed by whole genome sequencing. Antibiotic susceptibility tests showed that the isolates were 100% sensitive to vancomycin, linezolid, and sulfamethoxazole-trimethoprim. In terms of SCCmec, types IV and II were the most prevalent, accounting for 47.82% (22/44) and 47.72% (21/44) of the isolates, respectively, whereas type I was identified in just one isolate (2.27%). Thus, 50% of infections were caused by CA-MRSA and HA-MRSA. Sequencing analysis revealed polyclonal spread, with several sequence types (STs) identified. Five STs belonging to the CC5 clonal complex (ST5, ST105, ST1649, ST1176, and ST1307) accounted for most of the isolates (n=38). The detected virulence genes were sak, tst-1, ACME, hlgA, lukF-PV/lukS-PV, and lukD/lukE. The Panton–Valentine Leukocidin (PVL) toxin gene was found in nine isolates, all of which were CA-MRSA and carried SCCmec type IV. Several antimicrobial resistance genes encoding resistance to different antibiotic classes were identified. In conclusion, we conclude that CA-MRSA strains are currently ubiquitous in hospital environments, causing serious infections, with CC5 being predominant over the past five years.

Chemical pollution from industrial, agricultural, and urban activities represents a major threat to freshwater ecosystems and aquatic organisms. This study evaluated hepatic biomarker responses in Oreochromis niloticus (Nile tilapia) maintained under chronic environmental exposure to water from the Iguaçu River, one of the most polluted urban rivers in Brazil. Juvenile fish were kept in cages at three sites along the river, and hepatic biomarkers were assessed after 15 and 22 months of environmental exposure. Fish showed severe histopathological liver lesions, activation of antioxidant defenses, and oxidative stress responses accompanied by increased DNA damage. Immunological responses, particularly melanomacrophage proliferation and granuloma formation, were also observed across the monitored exposure scenarios. Alterations in plasma biochemical parameters, including AST, ALT, LDH, albumin, and globulin, were consistent with changes in hepatic function. Overall, the integrated biomarker responses revealed distinct patterns of biological alteration among the monitored exposure scenarios and were consistent with chronic exposure to complex environmental contaminant mixtures. These findings are consistent with alterations in liver integrity in fish maintained under long-term environmental exposure in the Iguaçu River. The study highlights the sensitivity of Nile tilapia as a bioindicator species for aquatic biomonitoring and provides valuable information to support environmental monitoring, risk assessment, and conservation strategies for the Iguaçu River Basin.

Background/Objectives: Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Understanding its epidemiological characteristics is essential for guiding public health strategies. In this study, we characterized the epidemiological profiles that may contribute to the risk of ALL in children in southern Brazil. Methods: Clinical and epidemiological data from 71 children (1–15 years old) admitted and newly diagnosed with ALL at four hospitals in Curitiba, Paraná, Brazil, were retrieved and analyzed. Results: Among the 71 children with ALL, the majority were male (n = 43, 60.6%), with an age range of 1–3 years (n = 26, 36.6%), self-identified as White (n = 47, 66.2%), and were born in Paraná state (n = 61, 85.9%). Nearly half had a family history of cancer (n = 33, 46.5%), primarily among grandparents (n = 36, 61%). Parental environmental exposures included smoking (n = 30, 42.3%) and occupational exposure to chemicals or radiation (n = 17, 23.9%). At diagnosis, most patients (n = 43, 60.5%) had a bone marrow blast count > 70%, and 27 patients (38%) had a peripheral blood blast count > 70%. B-cell ALL was the predominant subtype (n = 61, 85.9%). In B-cell ALL cases, the most frequent molecular subtype was high hyperdiploidy (n = 17, 23.9%). White blood cell counts differed significantly between the B-cell ALL and T-cell ALL groups (p = 0.029). Conclusions: Our findings provide insights into ALL epidemiology in southern Brazil and highlight regional differences across the country.

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital- and community-acquired infections (HA-MRSA and CA-MRSA, respectively). Although this microorganism is associated with childhood bacteremia, its epidemiology and predictive factors are not well established. In this study, the susceptibility profiles and molecular characteristics of 46MRSA isolates obtained from blood samples and other sterile fluids of pediatric patients between January 2017 and May 2022 were characterized. The isolates were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry. After that, their antimicrobial susceptibility profiles were assessed trough broth microdilution, and their molecular characteristics was performed by whole genome sequencing. Antibiotic susceptibility tests showed that the isolates were 100% sensitive to vancomycin, linezolid, and sulfamethoxazole-trimethoprim. In terms of SCCmec, types IV and II were the most prevalent, accounting for 47.82% (22/44) and 47.72% (21/44) of the isolates, respectively, whereas type I was identified in just one isolate (2.27%). Thus, 50% of infections were caused by CA-MRSA and HA-MRSA. Sequencing analysis revealed polyclonal spread, with several sequence types (STs) identified. Five STs belonging to the CC5 clonal complex (ST5, ST105, ST1649, ST1176, and ST1307) accounted for most of the isolates (n=38). The detected virulence genes were sak, tst-1, ACME, hlgA, lukF-PV/lukS-PV, and lukD/lukE. The Panton–Valentine Leukocidin (PVL) toxin gene was found in nine isolates, all of which were CA-MRSA and carried SCCmec type IV. Several antimicrobial resistance genes encoding resistance to different antibiotic classes were identified. In conclusion, we conclude that CA-MRSA strains are currently ubiquitous in hospital environments, causing serious infections, with CC5 being predominant over the past five years.