Aeromonas isolates from fish and patients in Tainan City, Taiwan: genotypic and phenotypic characteristics

The present study aimed to isolate Aeromonas from fish sold in the markets as well as in sushi and seafood shops and compare their virulence factors and antimicrobial characteristics with those of clinical isolates. Among the 128 fish isolates and 47 clinical isolates, Aeromonas caviae, A. dhakensis, and A. veronii were the principal species. A. dhakensis isolates carried at least 5 virulence genes, more than other Aeromonas species. The predominant genotype of virulence genes was hlyA lip alt col ela in both A. dhakensis and A. hydrophila isolates, alt col ela in A. caviae isolates, and act in A. veronii isolates. A. dhakensis, A. hydrophila, and A. veronii isolates more often exhibited hemolytic and proteolytic activity and showed greater virulence than A. caviae isolates in Caenorhabditis elegans and the C2C12 cell line. However, the link between the genotypes and phenotypes of the studied virulence genes in Aeromonas species was not evident. Among the four major clinical Aeromonas species, nearly all (99.0%) A. dhakensis, A. hydrophila, and A. veronii isolates harbored bla_CphA, which encodes a carbapenemase, but only a minority (6.7%, 7/104) were nonsusceptible to carbapenem. Regarding AmpC β-lactamase genes, bla_AQU-1 was exclusively found in A. dhakensis isolates, and bla_MOX3 was found only in A. caviae isolates, but only 7.6% (n = 6) of the 79 Aeromonas isolates carrying blaAQU-1 or bla_MOX3 exhibited a cefotaxime resistance phenotype. In conclusion, fish Aeromonas isolates carry a variety of combinations of virulence β =-lactamase resistance genes and exhibit virulence phenotypes and antimicrobial resistance profiles similar to those of clinical isolates.