[Molecular epidemiological study of 72 human-derived aeromonas in Guangdong Province, 2019-2024]

Objective: To investigate the drug resistance profiles and molecular epidemiological characteristics of Aeromonas species isolated from human clinical samples. Methods: A total of 72 Aeromonas isolates were collected and identified to the species level using biochemical tests, mass spectrometry, and average nucleotide identity based on whole-genome sequencing. Antimicrobial susceptibility testing was performed by the broth microdilution method. The phylogenetic relationships among isolates were reconstructed based on core single-nucleotide polymorphisms. Whole-genome sequencing data were used to determine multilocus sequence types and identify the virulence genes. The correlation between identified resistance genes and the corresponding resistant phenotypes was assessed. Results: Conventional biochemical and mass spectrometry methods yielded inconsistent species identification results for some Aeromonas strains compared with whole-genome sequencing. The predominant strains of human Aeromonas infections were Aeromonas veronii (48/72, 66.66%). The prevalent sequence types were ST425 (5/72, 6.94%). Antibiotic susceptibility testing revealed that human-derived Aeromonas species were sensitive to most antimicrobial agents, with slightly higher resistance rates to tetracycline (18.06%) and compound sulfamethoxazole (13.89%). A high concordance rate was observed between the antimicrobial resistance genotypes and phenotypes of Aeromonas. The number of toxin gene-positive strains is large, and the number of toxin gene-positive strains of different species of Aeromonas is different. Conclusions: Aeromonas veronii was the predominant species among human-derived Aeromonas isolates, and the sequence types showed high diversity. The overall antimicrobial resistance rate was low, with most resistance phenotypes mediated by resistance genes, and the number of positive strains of Aeromonas toxin genes is different among different species.