PATHOGENICITY OF Oligoflexus tunisiensis BACTERIUM ON FRESHWATER FISHES
Oligoflexus tunisiensis is the first culture isolate and the only bacteria strain in the newly described class Oligoflexia, as of the time of the experiment. This bacteria was isolated from a 0.2µm filtrate of a sand gravel suspension collected from the Eastern margin of the Sahara desert. However genome sequence of the bacteria shows that it encodes the gene for the ABC transporter of the amino acid ̶ RND- type efflux pump system - which is widely known among gram-negative bacteria to promote multidrug resistance in pathogenic bacteria. Also the genome sequence of the bacteria showed a higher similarity (67% identity and 99% coverage) to the fish pathogenic bacteria Pseudomonas aeruginosa -a well-known antibiotic resistant bacteria in some freshwater aquaculture fishes, and the causative agent of some important freshwater fish diseases. The aim of this present study was to ascertain the pathogenicity of the bacteria, Oligoflexus tunisiensis on freshwater fishes.
Using the infection challenge trial, three freshwater fishes (Heterotilapia buttikoferi, Nimbochromis venustus and Epalzeorhynchos bicolor) of average weight 3±0.5g were challenged intraperitoneally with 108 cfu/fish bacterial cells of O. tunisiensis, and observed for their response to the infection.
48 ̶ 72 hours after post inoculation, Oligoflexus tunisiensis infected samples showed some strong pathological and clinical symptoms such as haemorrhagic septicemia, tail rot, degradation of some internal organs and mortality. In order to justify that these clinical signs observed were elicited by O. tunisiensis, we used the traditional culture-independent technique to retrieve the bacteria from the liver, spleen and kidney of the affected samples.
Our results indicated that O. tunisiensis significantly influenced the observed symptoms post-infection.
