Phenotypic, Phylogenetic Characterization and Antimicrobial Susceptibility Determination of Chryseobacterium piscicola Isolates Recovered from Diseased Rainbow Trout

Abstract

Twelve isolates recovered from rainbow trout weighing 1-4 grams showing signs of anorexia, exophthalmos, darkening, and dorsal fin erosion were used in our study. In addition to conventional microbiological tests, comprehensive phenotypic characterization has been performed using the Biolog GEN III microplate. Molecular identification and characterization were performed using the 16S rRNA region. Antimicrobial susceptibilities of the isolates were determined using the disk diffusion method. Our isolates were identified as Chryseobacterium piscicola in molecular identification performed by sequence analysis based on the 16S rRNA region. In a phylogenetic analysis of our isolates, obtained from three different hosts in America, Chile, and Finland, five genogroups were determined with high similarity rate. Isolates from Finland, Chile, the United States, and Turkey (only C-316) were found in the same genogroup. It was determined that the phylogenetic analysis created with the 16S rRNA region could not distinguish the host from which the bacteria was isolated. The phenotypic characterization of six representative isolates selected according to phylogenetic analysis, was determined with the Biolog GENIII microplate. Based on the Biolog GENIII results of the representative isolates, the results of 40 out of 94 tests were found to be variable. With this result, it was found that C. piscicola isolates were not phenotypically homogeneous. Besides, it was found that the zone diameters of our isolates against florfenicol, enrofloxacin, and sulfamethoxazole/trimethoprim were higher than the other isolates, in addition to that C-41 was the most resistant isolate.