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Background Febrile neutropenia (FN) is a common complication in patients with solid tumors and hematologic malignancies. Identification of the causative microorganisms would contribute to optimization of antimicrobial treatment and thus improve the outcome of FN. However, causative microorganisms are detected in only 10% to 20% of FN patients. Next-generation sequencing (NGS) allows us to comprehensively analyze all microorganisms present in a clinical sample. In this study, we aimed to utilize NGS for the detection of microbial pathogens in infectious diseases and elucidate the infection source in FN. Methods FN is defined by two characteristics: (1) neutrophils count < 500/µL, and (2) fever ≥38.0°C. From 2016 to 2018, 112 plasma/serum samples of pediatric FN patients (11 positive blood cultures) were analyzed. Serum samples from 10 neutropenic patients without fever were also analyzed as controls. Shotgun sequencing method was applied for these samples. The metagenomic analyses were performed through the pipeline PATHDET, which has been newly established in our laboratory. Diagnosis based on NGS results was made based on the following criteria: (1) number of reads from all pathogens per million reads (PR) >650, (2) a specific pathogen's reads per million reads (RPM) >200, and (3) diversity index >3.0. The NGS results were compared with those from blood culture. Results Sequencing reads of bacteria isolated through blood culture were identified by NGS in all 11 plasma/serum samples leading to the diagnosis of FN. The causative pathogens were diagnosed by NGS using the above criteria in 11 patients. However, the results were consistent with those of blood culture in only 4 samples. Of 101 cases with negative blood culture results, the causative pathogens were detected in 17 cases: Acinetobacter soli (2 cases), Burkholderia cepacian (1 case), Klebsiella variicola (1 case), and Roseomonas sp. (1 case) were identified at the species level. In addition, 7 cases (e.g. Acinetobacter) were identified at the genus level, and 5 cases (e.g. Enterobacteriaceae) were identified at the family level. Conclusion Metagenomic NGS technique has great potential for detecting causative pathogens with greater efficiency than the conventional methods. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background In the field of infectious diseases, identification of etiologic pathogen is essential for definitive diagnosis and decisions regarding appropriate management. Bronchoalveolar lavage fluid (BALF) is considered a sterile type of specimen that is suitable for detecting pathogens of respiratory infections. Recently, next-generation sequencing (NGS) has been applied in the field of infectious diseases and has enabled us to identify pathogenic microorganisms comprehensively. The aim of this study was to comprehensively identify pathogens using NGS in BALF samples from immunocompetent pediatric patients with respiratory failure. Methods Ten patients hospitalized in the pediatric intensive care unit with respiratory failure were included. BALF samples obtained in the acute phase were used to prepare DNA- and RNA-sequencing libraries. The libraries were sequenced on MiSeq, and the sequence data were analyzed using metagenome analysis tools. Results A mean of 2,041,216 total reads were sequenced for each library. A significant number of four types of bacterial reads was detected in three BALF samples with DNA-sequencing, whereas pathogenic respiratory viruses were detected in seven of 10 patients with RNA-sequencing.Candidate pathogens were detected in three patients in whom etiologic agents were not identified by conventional methods. A summary of the detected pathogens is listed in Table 1. Sequence coverage and depth of each reference bacterial and viral genome are shown in Figures 1 and 2, respectively. The complete genome of enterovirus D68 was identified in two patients without underlying diseases, and phylogenetic analysis suggested that both strains belong to subclade B3, which is an epidemic strain that has spread worldwide in recent years. Conclusion We demonstrated the utility of the NGS-based approach for detection of candidate pathogens in BALF from pediatric patients with severe respiratory failure. Our results suggest that NGS can be applied for comprehensive molecular diagnostics as well as surveillance of pathogens in the field of infectious diseases. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]