The characterization of <i>Herbaspirillum huttiense</i> isolated from a uremic patient: virulence and antimicrobial efficacy in the <i>Galleria mellonella</i> model

Herbaspirillum species are typically isolated from plants and are known for their role in crop nitrogen fixation. Recently, they have been found to colonize humans and cause infections. This study aimed to identify and characterize two Herbaspirillum huttiense strains (CLJ01 and CLJ02) isolated from the blood of a uremic patient, with a focus on evaluating their pathogenicity and antibiotic efficacy. The strains were identified using the VITEK2 system, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry , and 16S rRNA gene sequencing, confirming their identity as H. huttiense. High-throughput sequencing further revealed the presence of the resistance gene arnA, which confers resistance to polymyxin. For the first time, the pathogenicity of H. huttiense was assessed using a Galleria mellonella infection model. The results demonstrated a concentration-dependent virulence, with CLJ01 exhibiting slightly higher pathogenicity. Additionally, meropenem showed significant antimicrobial efficacy in the G. mellonella infection model, particularly under conditions of high bacterial load, indicating strong therapeutic potential. In conclusion, this study provides experimental evidence supporting the correct diagnosis and treatment of H. huttiense infections. Furthermore, the findings underscore the importance of accurately identifying rare pathogens in clinical settings for effective treatment.