Quantification of antibiotic resistance genes in Siberian sturgeons (Acipenser baerii) fed Hermetia illucens-based diet

Siberian sturgeon (Acipenser baerii) represents a high-value fish farmed for obtaining high-priced food. In this study, the occurrence of antibiotic resistance (AR) genes encoding for resistance to antimicrobial administered in clinical practice, as aminoglycosides, -lactams, macrolide-lincosamide-streptogramin B, tetracyclines, and vancomycin, were studied in the gut of sturgeons fed a diet containing 50% Hermetia illucens larvae by qPCR assays. Erm(A), erm(B), erm(C), tet(K), tet(M), tet(S), and tet(W) were detected in all samples. Feed and guts of sturgeons at beginning of rearing were negative for tet(O), vanA, vanB, mecA, and aac-aph. BlaZ was exclusively detected in control diet. The highest copy numbers were observed for tet(M), tet(K) and tet(S) in control diet. The copy numbers of most of the genes were higher in control diet than in diet containing 50% insect. Despite the differences in the gene copy numbers in control or insect-based diet, the results for AR genes contained in the guts of fish highlighted that, at medium levels of substitution (50%), no effect of the insect-based diet on the AR genes seems to occur in the experimental sturgeons at the end of rearing.