Background: Hypervirulent clonal complex (cc) have been associated with higher incidence and case fatality rate of invasive meningococcal disease (IMD). The aim of this study was to describe the clinical manifestations of the hypervirulent cc of meningococcus in children. Methods: Retrospective study in patients hospitalized by IMD microbiologically confirmed at three children’s tertiary health care centers in Santiago, Chile, between 2010 and 2018. Demographic, clinical information and determination of the cc and factor H binding protein (fHbp) alleles were performed. Results: In total 93 cases were evaluated, sequence typing was available for 91 cases, and 87 (95.6%) had a cc assigned; 63.7% were MenW and 31.8% MenB. The median age was 9 months, 67% were male and 18.7% had any comorbidity. A 26.4% presented neurological deficit, 25.3% petechiae and 20% diarrhea. Sixty-seven percent were admitted to the pediatric intensive care unit (PICU) and the case fatality rate was 9.9%. Regarding cc and fHbp alleles, ST11, ST41/44 and allele 22 were the most frequently identified, with 63.7%, 19.8% and 72.5%, respectively. We found statistically significant differences between the cc and presence of petechiae, diagnosis of meningococcemia plus meningitis, admission and days in PICU and advanced support. Allele 22 for fHbp was associated with the absence of petechiae, low suspicion of IMD, less diagnosis of meningitis+meningococcemia, PICU admission, advanced support and adrenal insufficiency. Conclusion: Epidemiological and microbiological surveillance of IMD should integrate clinical and laboratory components, including molecular and genetic characterization, to enrich the dynamic understanding of the clinical evolution of IMD.

Background/Objectives: The objective of this study is to evaluate the efficacy and safety of maintaining antimicrobial (AM) therapy or adjusting AM therapy during episodes of febrile neutropenia (FN) catalogued as a fever of unknown origin (FUO) in children with cancer. Methods: This is a prospective, multicenter, noninferiority, randomized study, approved by ethics committee, in children with episodes of FN in eight hospitals in Chile. Microbiological and molecular samples were drawn at admission. Patients with FUO (negative bacterial and viral study with no clinical focus suggesting infection) and favorable evolution during the first 48–72 h of AM therapy were randomized 1:1 to maintain or adjust treatment, reducing the number and spectrum of AMs. The primary endpoint was the percentage of episodes with an uneventful resolution; the secondary endpoints were the re-adjustment of AM therapy, days of fever/hospitalization/AM therapy, days of vancomycin and meropenem per 1000 days of neutropenia, number of AMs after randomization, pediatric intensive care unit (PICU) admission, sepsis, and death. Results: A total of 266 of 939 FN episodes recruited between March 2021 and January 2024 were catalogued as FUO, of which 231 had a favorable evolution at 48–72 h and were randomized, 111 to maintain and 120 to adjust AM therapy. Both groups presented the same percentage of uneventful resolution, with 106 (96%) in the group that maintain AM therapy and 114 (95%) in the adjusted group (p = 1.00); relative risk 1.01, (95%CI 0.95–1.06); absolute risk difference 0.01, (95%CI −0.05–0.06). Conclusions: The main finding of this study demonstrates that adjusting antimicrobial therapy appears safe in carefully selected FUO cases with a favorable early evolution, during episodes of FN catalogued as FUO in children with cancer. These findings open an opportunity to new AM stewardship strategies in this population, with a possible future impact on AM resistance.