Dynamics of the gut microbiome and resistome in response to prophylactic antibiotic treatment in post-surgical giant pandas

For giant pandas, the ecological impact of prophylactic postoperative antibiotics on their gut microbial communities and resistome is not well characterized. Here, we assessed the impact of intravenous cefotaxime administration by analyzing longitudinal fecal samples from five giant pandas via 16 S rRNA sequencing (n = 304 samples) and shotgun metagenomics (n = 22 samples). 16 S-based analysis revealed that antibiotic exposure significantly altered bacterial community structure, resulting in a pronounced increase in the abundance of Pseudomonadota (from 50% ± 24% to 60% ± 38%; P < 0.001) and a reduction in Shannon diversity (from 2.8 ± 0.4 to 2.4 ± 1.3; P < 0.05). In contrast, metagenomic analysis indicated that cefotaxime exposure did not significantly increase the overall diversity of antimicrobial resistance genes (ARGs) or virulence factor genes (VFGs). However, we observed a marked expansion in the diversity of the CTX-M β-lactamase family (bla_CTX-M), which persisted into the recovery phase. We also recovered 10 metagenome-assembled genomes (MAGs) harboring both ARGs and VFGs, identifying them as potential antibiotic-resistant pathogens (ARPs). Their abundance, however, remained unchanged throughout treatment. These findings provide new insights into the effects of short-term antibiotic exposure in giant pandas, highlighting its transient effect on microbial community structure and a limited effect on resistome diversity.