Real-time PCR detection and quantification of selected transferable antibiotic resistance genes in fresh edible insects from Belgium and the Netherlands

The occurrence of antibiotic resistance genes in foodstuffs involves a human health risk. Fresh edible insects present an emerging source of human food but they were not yet assessed in a quantitative way for antibiotic resistances as a matter of food safety. In this study, a real-time quantitative PCR assessment was optimised to detect and quantify relevant transferable antibiotic resistance genes [tet(O, K, M, S) and erm(B)] in edible insects. Subsequently, the technology was applied on 30 fresh insect samples, including two mealworm species and two cricket species from different production batches and rearing companies in Belgium and the Netherlands. The sampling periods and the post-harvest treatments applied were also taken into account. Results showed that mealworms contained, on average, higher numbers of tet(K), tet(M), and tet(S) genes than crickets, but tet(O) was almost uniquely present in crickets. The erm(B) gene was only detected in one mealworm sample and the tet(K) gene showed higher abundances in samples originating from the Netherlands than in samples from Belgium. A large difference in antibiotic resistance profile was revealed between mealworms and crickets, but not between different mealworm species or cricket species. Species-specific microbiomes and insect feed may have contributed to this distinction. Interestingly, important correlations between the presence of some tet genes and the microbiota previously encountered in the investigated edible insects were uncovered. While a geographical distribution was observed for the tet(K) gene, post-harvest treatments and sampling period were not shown to have a significant influence on the occurrence of the antibiotic resistance genes considered. In conclusion, insects may carry considerable amounts of antibiotic resistance genes, but the health risk in terms of antibiotic resistances is comparable to other food matrices.