Isolation and Characterization of Ichtyopathogenic Bacteria from a Northwestern Algerian Dam

Freshwater ecosystems have a significant fauna diversity. Among the latter, fishes play an important role in the trophic chain and are subject to multiple attacks from anthropogenic or natural origins. Natural attacks are mostly caused by pathogenic or opportunistic bacteria responsible of a broad range of severe infections. The aim of this work was to study the diversity of ichtyopathogenic bacteria in the dam of Sekkak (northwest of Algeria). In order to determine the water quality, physico-chemical analysis of the dam water was carried out in situ (temperature, pH, salinity, conductivity, dissolved oxygen) and elsewhere in the laboratory (NO₃, NO₂, NH₄, RS, PO₄, DBO, DCO, MO). The identification of the selected bacterial isolates was carried out by API galleries and confirmed by molecular techniques (PCR and sequencing of the 16S r RNA gene). Besides, an antibiogram test of the studied strains was realized. The physico-chemical analysis allowed us to classify the dam water as moderately polluted to polluted whereas the results of the microbiological study showed an important diversity of ichtyopathogenic species such as Aeromonas hydrophila, Providencia rettgeri, Pseudomonas aeruginosa, Yersinia enterocolitica were retrieved. The antibiogram test revealed notable resistance. The antibiotic family for which most resistances were found was the β-lactam family followed by aminoglycosides and macrolides. These results indicate that aquatic environments can shelter multidrug-resistant pathogenic bacteria representing a threat for the endemic fauna. Therefore, it is important to closely monitor these waters in order to improve the fish living environment and ensure healthier production.