Tetracycline ingestion alters important microbial groups in the gut of Africanized honey bees

The aim of this study was to investigate putative shifts in the gut microbiota of Africanized honey bees (Apis mellifera scutellata x spp). Bees (1,000) were collected from hives in Areia-PB, Northeastern Brazil, placed into plastic chambers and kept under controlled temperature and humidity conditions. The control group (CON) was fed daily with syrup (10g) consisting of a 1:1 solution of demerara sugar and water, plus a solid protein diet (10g) composed of 60% soy extract and 40% sugar syrup. The tetracycline group (TET) was fed identically but with the addition of tetracycline hydrochloride (450 ug/g) to the sugar syrup. Bees were sampled from each group before (day 0), and after tetracycline exposure (days 3, 6 and 9). Amplicon (16S rRNA) libraries were prepared from DNA extracted from abdominal contents and high throughput sequenced using Illumina MiSeq. Downstream bioinformatic analyses were performed to determine Amplicon Sequence Variants (ASV) and microbial composition and diversity by means of alpha and beta-diversity and differentially abundant taxa across treatments and time points. Bee gut microbial composition and diversity differed significantly and increasingly over time and between CON and TET groups. The ingestion of tetracycline decreased abundances of Bombella and Fructobacillus, along with decreases in key core microbiota such as Snodgrassella, Gilliamella, Rhizobiaceae, and Apibacter. These alterations could potentially compromise bee health by affecting nutrient metabolism and pathogen defense. Considering the global ecological and economic importance of honey bees as pollinators, the environmental contamination by antimicrobial residues should be considered, especially in the case of drugs commonly used in livestock, such as tetracyclines.