Characteristics of intestinal microbial communities and occurrence of antibiotic resistance genes during degradation of antibiotic mycelial residues by black soldier fly (Hermetia illucens L.) larvae

The disposal of antibiotic mycelial residues (AMR) presents a distinctive challenge as hazardous organic waste, posing a persistent dilemma for pharmaceutical enterprises in the search for safe and effective solutions. Research has focused on treating chlortetracycline mycelial residue (CMR) using black soldier fly larvae (BSFL) with wheat straw. Different CMR/wheat ratios (0:1 CK, 1:20 L, 1:4 M, and 1:2 H) were used as larval biotransformation substrates. Comprehensive investigations were conducted on BSFL biophysiological parameters, CMR conversion, chlortetracycline (CTC) degradation, the microbial community, the prevalence of antibiotic resistance genes (ARGs), and functional microbes in the BSFL gut. The substrate consumption rates ranged from 28.9% to 34.9%, with the harvested BSFL biomass reaching 0.50-1.04 g/10 larvae. Effective degradation of CTC was observed, with a degradation rate ranging from 32.0% to 61.1%. Tetracycline resistance genes (TRGs) predominated among the ARGs. Three TRG classes (tet_rpp, tet_efflux, and tet_mod) were confirmed in the BSFL intestinal microbiota. A total of 341 out of 368 ARG classes presented significant positive correlations with each other, facilitated by plasmids and integrons. Notably, Clostridium, Enterococcus, Leucobacter, and Morganella were identified as hosts of TRGs, whereas Dysgonomonas, Bacteroides, and Massilibacteroides were the key contributors to BSFL biomass. These findings underscore the ability of the BSFL intestinal microbiota to digest and convert CMR, supporting the simultaneous AFR transformation by BSFL with wheat straw addition.