Epidemiology and antimicrobial resistance profiles of Aeromonas from pediatric diarrhea in Hangzhou, Zhejiang, China: 2017–2024

This study characterized the epidemiology and antimicrobial resistance of Aeromonas isolates from pediatric patients between 2017 and 2024 to inform improved clinical management and infection control. A retrospective analysis of 439 Aeromonas isolates from 2017 to 2024 included antimicrobial susceptibility testing of 316 isolates by the Kirby–Bauer method and whole-genome sequencing of 217 isolates for species identification, MLST, and resistance gene profiling. The prevalence of Aeromonas spp. in feces was 2.36% (439/18,627) between 2017 and 2024, with significant temporal variation and a pronounced summer peak, while no age or sex differences were observed. Among 316 isolates, resistance was highest to trimethoprim–sulfamethoxazole (45.25%) and lowest to amikacin (0.32%). Resistance to third- and fourth-generation cephalosporins ranged from 5.06% (cefepime) to 9.49%. Carbapenem resistance was higher for imipenem (8.23%) than for meropenem (1.58%). Among the 217 sequenced isolates, Aeromonas caviae predominated (86.18%), followed by A. veronii (5.07%), and most isolates (81.57%) belong to the novel sequence type. Several relatively uncommon species, such as A. trota, A. taiwanensis and A. sanarellii were detected in this study and formed a distinct phylogenetic clade separate from the major species. Additionally, a single A. veronii isolate (strain Q212) was found to branch distantly from other A. veronii strains, raising the possibility of unique genetic features. A. caviae and A. veronii exhibited the broadest resistance profiles, with A. veronii showing higher resistance to several antimicrobials. A total of 779 antimicrobial resistance genes were identified. cphA (5.07%) and imiH (0.92%) were detected in A. veronii , A. dhakensis , and A. hydrophila , whereas bla NDM-14 was detected in one A. caviae isolate. mcr -3 (11.06%) was predominantly detected in A. caviae . Genes such as ampH , ampS , and bla OXA-427 also showed species-associated distribution patterns. Aeromonas , with A. caviae predominating, shows substantial genetic diversity and clinically relevant antimicrobial resistance, with species-specific resistance genes. Furthermore, the detection of rare species should not be overlooked. These findings provide critical evidence for empirical therapy and resistance surveillance.