Identification and characterization of integron-associated antibiotic resistant Laribacter hongkongensis isolated from aquatic products in China

Laribacter hongkongensis is a recently discovered bacterium associated with gastroenteritis. In this study, a total of 199 isolates of this species obtained from aquatic products (n = 462) in Guangzhou City, China, were examined for their susceptibility to 19 antimicrobial agents and the presence of antimicrobial resistance integrons. The genetic relatedness of the isolates with integrons was also evaluated. A PCR-based method was used to screen integrons and found that 13 (6.5%) of the isolates harbored class 1 integrons. The antimicrobial resistance rates of integron-positive isolates were significantly higher than integron-negative ones for cefepime, ciprofloxacin, gentamicin, tetracycline, trimethoprim-sulfamethoxazole and rifampicin. Genetic sequence analysis revealed that these integrons contained various antimicrobial-resistance genes (dfrA1, dfrA14, dfrA17, dfrA32, aadA1, aadA2, aadA5, cmlA5, arr2, ereA and orfC) organized into different gene cassettes arrangements including a novel array of dfrA14-arr2-cmlA5. Pulsed-field gel electrophoresis (PFGE) yielded 13 different patterns among 13 integron-positive isolates, which could be grouped into four clusters. These indicate the dispersal of multi-resistant integrons among different molecular types. To the best of our knowledge, this is the first report showing distribution and characterization of class 1 integrons among L. hongkongensis isolates.