Comparative Analysis of Antimicrobial Resistance, Integrons, and Virulence Genes Among Extended-Spectrum β-Lactamase-Positive Laribacter hongkongensis from Edible Frogs and Freshwater Fish.

Aquatic animals are now recognized to be major hosts of potentially pathogenic Laribacter hongkongensis . A comparative study was carried out among extended-spectrum β-lactamase (ESBL)-producing L. hongkongensis isolated from frogs (47 isolates) and fish (41 isolates) to examine phenotypic and genotypic antimicrobial resistance profiles, integrons, virulence factors, and genetic relatedness. Isolates from frogs showed a higher incidence of antibiotic resistance compared with those from fish for most of the antimicrobials tested, especially trimethoprim-sulfamethoxazole, tetracycline, ciprofloxacin, levofloxacin, and streptomycin. Multidrug-resistant strains were also found more frequently among frog isolates (5.44 traits on average) than among fish isolates (3.29 traits). In frog isolates, class 1 integrons and the resistance genes sul1 , sul2 , tetA , tetR , and aac(6')-Ib-cr showed a clearly higher incidence compared with isolates from fish. In contrast, bla TEM-1 was higher in fish isolates than in frog isolates. Correlation analysis showed that sul1 , sul2 , tetA , and tetR were significantly associated with class 1 integrons in frog isolates. The correlations indicated a potential co-selection risk of bacterial resistance to antibiotics. In addition, the distribution of three virulence-associated determinants for the type IV bundle-forming pili gene ( bfpA ), ferric aerobactin receptor gene ( iucD ), and iron-responsive element gene ( ireA ) was markedly higher in strains isolated from frogs than in those isolated from fish. No obvious genetic relatedness was observed between both populations. The large differences found in the incidence of antibiotic resistance, integrons along with the multiple resistance genes, virulence factors, and genetic fingerprints determined by pulsed-field gel electrophoresis suggest a high degree of antibiotic resistance and pathogenicity potential of ESBL-producing L. hongkongensis from isolates found in frogs.