Identification and characterization of Flavobacteriaceae from farmed Oreochromis niloticus and Clarius gariepinus in Uganda

Abstract

Abstract. Racheal A, Kasanga CJ, Byarugaba DK. 2018. Identification and characterization of Flavobacteriaceae from farmed Oreochromis niloticusand Clarius garieoinus. Bonorowo Wetlands 8: 42-50. Bacteria under the family Flavobacteriaceae (also called Flavobacteria) are important pathogens of fish, people, many other animals, and plants in this study. In this study, Flavobacteria from Nile tilapia (Oreochromis niloticus) and African catfish (Clarius gariepinus) were identified and characterized from the selected farms in Uganda. Gill and skin swabs were obtained from 119 fish from 19 farms and were dissected aseptically to sample internal organs. The samples were inoculated onto Shieh media and incubated at 25°C for 48 hours. The suspected isolates were identified by colon characteristics, conventional biochemical tests, and API 20 NE kits. The isolates were grouped into eight based on characteristic colon similarity. One group selected one isolate for 16S rRNA gene sequencing and identified using the EZbiocloud.net ID software. Phylogenetic analysis of selected isolates was performed using the 16S rRNA gene sequences in BioEdit and MEGA 7.0.2 software. Based on extrapolation of sequence analysis of the selected isolates, out of the 86 isolates, Myroides marinus was the most predominant species taking up 4 of the 8 groups (60 isolates) in 13 farms. The rest of the groups comprised; Acinetobacter pitti, one group (6 isolates) in 6 farms, Chryseobacterium gambrini 2 groups (3 isolates) in 3 farms, and one isolate was unidentified in 3 farms. However, a total of 16 isolates did not grow on subculturing. Phylogenetic analysis indicated that M. marinus isolates grouped with other M. marinus isolates from gene bank with significant intra-species diversity, observed with C. gambrini isolates. All the sampled farms had at least one isolate of a Flavobacterium from Tilapia and/or Catfish. Pathogenicity studies should be conducted on the isolates to establish their importance as fish pathogens and transmission dynamics so that an appropriate control measure can be recommended.