Genomic characterization of a clinical Enterocloster aldenensis strain: First report in Thailand

This study presents the first comprehensive genome analysis of Enterocloster aldenensis in Thailand, an organism typically found in the gut but occasionally acting as an opportunistic pathogen. A scrotal tissue sample from a patient with suspected Fournier's gangrene was initially collected for Bacteroides surveillance in Southern Thailand, E. aldenensis PSUA25 was identified to Bacteroides thetaiotaomicron by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and later reclassified as E. aldenensis following whole-genome sequencing. Species confirmation via Average Nucleotide Identity analysis showed 97 % identity with the representative strain. Phylogenetic analysis using all available E. aldenensis genomes revealed that strain PSU25A is closely related to AM40-2 AC-an isolate from human feces in China (NCBI BioSample: SAMN11413088) selected for comparative analysis based on high genomic similarity. Comparative analysis revealed shared antimicrobial resistance genes, including poxtA, vanYG, vanWI, and vanTG. Unique to PSU25A were two mobile genetic elements: a conjugative transposon (Tn6009 with tetM) and a phage-associated region, suggesting horizontal gene transfer. This study emphasizes the need for accurate microbial identification, as misidentification can impact treatment decisions. Understanding the genomic traits of E. aldenensis from specific regions provides valuable insights into its pathogenic potential.