sequences of bacteria
Materials and MethodsStrain Selection Clinical data and blood samples from A. baumannii BSI patients were prospectively collected from 2018 to 2024 at Shanghai Children's Medical Center and the Second Affiliated Hospital of Nanjing Medical University. The cohort included 42 pediatric (1 month to 13 years) and 35 adult patients (mainly elderly with comorbidities). Only one A. baumannii strain per patient was included.Strain IdentificationIsolates were subcultured on blood and chocolate agar plates at 37C under 5% CO. Species identification was performed using MALDI-TOF MS.Antimicrobial Susceptibility TestingMICs of 22 antibiotics were determined using the agar dilution method, following CLSI-M100 guidelines.Whole-Genome Sequencing Genomic DNA was extracted using bacterial DNA kits, quantified, and libraries were prepared for next-generation sequencing. Multilocus Sequence Typing (MLST) Sequence types (STs) were determined using the Pasteur MLST scheme with seven housekeeping genes (gltA, gyrB, gdhB, recA, cpn60, gpi, rpoD). Core Genome SNP Phylogenetic Tree The core genome SNP phylogenetic tree was constructed using Parsnp (v1.2) and visualized with iTOL.Drug Resistance Gene Analysis Antimicrobial resistance genes (ARGs) were identified using CARD and RGI. Virulence Gene Profiling Virulence factors were identified using DIAMOND BLASTp against the Virulence Factor Database (VFDB). COG Functional Classification COG enrichment analysis was performed to examine gene distribution in different functional categories.Statistical Analysis Statistical analyses were performed using IBM SPSS Statistics 27. Categorical variables were compared with chi-square or Fisher's exact test, and continuous variables with Mann-Whitney U test. P < 0.62 was considered significant.