Dual resistance to heavy metals and antibiotics of Aeromonas hydrophila isolated from Carassius carassius (Linnaeus, 1758) in Lake Tonga, Algeria

Abstract

Aeromonas hydrophila, a bacterium with significant virulence potential, is the predominant pathogenic bacteria naturally infecting fish. This study aims to identify the antibiogram and heavy metal resistance pattern of Aeromonas hydrophila obtained from both Carassius carassius fish and their surrounding water environment in Lake Tonga, Algeria. A total of 59 strains of Aeromonas hydrophila were isolated from 168 Carassius carassius samples and 144 waters samples of Lake Tonga. All the strains were tested for resistance to 13 antibiotics and three types of heavy metals (Cobalt, copper and cadmium) using disk diffusion and two-fold agar dilution method, respectively. Clinical macroscopic examination of the fish was also carried out. More than 14% of the examined fishes showed the characteristic clinical signs. Drug screening showed high levels of resistance to β-lactam antibiotics, 100% of the strains were resistant to ampicillin followed by cefalotin (91.53%) and ticarcillin (88.14%). More than 40% of the strains exhibited resistance against gentamicin, amikacin and chloramphenicol. The multiple antibiotic resistance (MAR) indexing of A. hydrophila strains showed that all of them originated from high-risk sources. Among tested heavy metals, bacterial isolates exhibited resistant pattern of Co>Cu >Cd. A positive correlation was observed between antimicrobial resistance and metal tolerance (Odds Ratio>0.1). These resistant profiles could be useful information to avoid unnecessary use of chemical and antimicrobial products in the aquatic environment and to provide a novel approach to manage bacterial infection in fish.