Genome exploration and predicted antimicrobial resistance profiles of Bartonella spp. in Thailand

Background: Bartonellosis, caused by Bartonella species, is a group of zoonotic infectious diseases affecting both humans and animals. Rodents serve as important reservoirs, particularly in Southeast Asia, where pathogen diversity remains underexplored. Objectives: This study aimed to characterize the genomic features and antimicrobial resistance profiles of Bartonella isolates obtained from rodent and deer hosts in Thailand. Materials and methods: Six Bartonella isolates recovered from rodent and deer blood samples in Thailand were confirmed by gltA and rpoB PCR and subjected to whole-genome sequencing using the Illumina MiSeq platform. Genome quality and annotation were assessed using QUAST and Prokka, respectively. Taxonomic assignment and prediction of antimicrobial resistance-associated determinants were performed using CZ ID, while orthologous gene clusters were compared using OrthoVenn3. Results: Whole-genome sequencing and metagenomic analyses were performed on six Bartonella isolates. Sequence identity analysis revealed that all isolates were closely related to Bartonella vinsonii, suggesting potential zoonotic transmission. Additional species identified included B. schoenbuchensis, B. kosoyi, and B. tribocorum, which are primarily associated with animal infections, as well as B. grahamii, a species with known zoonotic potential. Draft genome sizes ranged from 1.52 to 2.57 Mb, with predicted gene counts between 1,258 and 2,115. The largest genome was observed in isolate RT1 (B. grahamii). Analysis of predicted antimicrobial resistance-associated genes revealed a diverse distribution of putative resistance determinants across the isolates. Most of the identified determinants were annotated as protein homologs and associated with antibiotic inactivation mechanisms. Conclusion: The genomic data generated in this study provide valuable resources for developing molecular markers for Bartonella detection and surveillance. These genomic findings provide preliminary information on putative antimicrobial resistance-associated determinants in Bartonella spp.; however, phenotypic antimicrobial susceptibility testing is required to confirm their functional relevance.