Effects of antibiotics on the development and intestinal bacterial diversity of black soldier fly larvae

Abstract

The effects of four antibiotics (metronidazole (M) levofloxacin (L), sodium ampicillin (A), and streptomycin sulphate (S)) and their pair-wise combinations at three doses on the development and intestinal bacterial diversity of the black soldier fly (BSF; Hermetia illucens) larvae were studied. At a low dose M and L were able to inhibit larval growth. At a high dose, all antibiotics were shown to inhibit larval growth. However, the pair-wise combinational use of the antibiotics did not effectively enhance the inhibitory effect. The gut bacterial diversity of the normal control (NC) was significantly higher than the antibiotic-treated groups with 737 operational taxonomic units (OTUs) from the larval guts of NC, compared to 305 and 227 from ML and AS. The number of anaerobic bacteria in ML was significantly lower than in NC and AS, with the relative abundance of OTUs from larval guts of ML being only about 0.01, compared to 0.4 for NC and 0.15 for AS. These results indicated that antibiotics at the experimental concentration did not affect the palatability of food for insects, but they would affect the diversity of food and intestinal microorganisms of BSF larvae, and the inhibitory effect of antibiotics on growth and development of BSF larvae displayed in this study was a complex effect.