Abstract

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This study was designed to isolate and characterize pathogenic bacteria from fish samples from Niger, Otuocha and Amansea rivers using polymerase chain reaction (PCR) and sequencing approaches. Thirty-two fishes (16 tilapia and 16 catfish) were sampled from the three rivers. The intestines (one gram each) of all the fish samples were screened for the presence of pathogenic microbes of green colonies using Aeromonas agar base (Sigma) enriched with Ampicillin for selectivity. The extraction and sequencing of 16s rRNA of the pure isolates was done in GeneWiz laboratory USA. Polymerase chain reaction was used to assay for haemolysin gene and microscope for their morphological characteristics respectively. Basic local ailment tool (BLAST) compared the 16s rRNA sequences with the ones in the National Centre for Biotechnology Information (NCBI) Database. Results showed that 99% of the catfish samples grew with green colouration and were resistant to ampicillin, while none of the tilapia samples showed any form of growth on the selective media. BLAST analysis of the 16s rRNA sequences showed pathogenic Enterobacteriaceae spp. (Citrobacter freundi, Enterobacter cloacae and Serratia rubidaea) and Ochrobactrum anthropi bacteria in the catfish samples which were 99% identical with 16s rRNA sequences. They were haemolysin negative and microscopic result showed the isolates to be rod shaped and motile. The study showed that 99% of the catfish samples contained more than one pathogenic microorganism. These findings serve for awareness creation to fish consumers, handlers and processor in order to guide against such infectious microbes.

Keywords: Fish Pathogens, Molecular Characterization, Sequencing, River Niger