# Comparative metagenomic characterization of gut microbiota and antibiotic resistome in multi-facility SPF mice

## TL;DR

This study compares gut microbes and antibiotic resistance genes in lab mice from different facilities, showing how environment affects microbial diversity and resistance patterns.

## Contribution

The study provides a high-resolution metagenomic comparison of gut microbiota and antibiotic resistomes in SPF mice across multiple facilities.

## Key findings

- Microbial communities in SPF mice varied significantly by facility rather than mouse strain.
- Facility-specific differences in antibiotic resistance mechanisms were identified, such as target alteration or protection.
- Bacillota, Bacteroidota, and Pseudomonadota were major carriers of antibiotic resistance genes.

## Abstract

Specific pathogen-free (SPF) mice are pivotal preclinical models linking basic microbiology to clinical translation, yet comprehensive high-resolution profiling of their gut microbiome, especially antibiotic resistance genes (ARGs), remains limited. To address this gap, metagenomic sequencing was conducted on cecal contents from C57BL/6 and BALB/c SPF mice from five Shanghai laboratory animal facilities, generating 141 Gbp high-quality sequencing data. From 1,761,909 predicted genes, 1,048,575 non-redundant genes were identified for analysis. Taxonomic annotation identified Bacillota (73.0%), Bacteroidota (16.6%), and Actinomycetota (2.9%) as dominant phyla. At the genus level, microbial communities varied markedly across facilities, with Muribaculaceae prevailing in SHA/SHD and Blautia or Enterococcus enriched in SHB/SHE. Beta diversity analysis showed communities clustered by facility, indicating breeding environment had a stronger impact on gut microbiota diversity than host strain. KEGG, COG, and GO functional annotation revealed broad metabolic and molecular diversity. Antibiotic resistome profiling identified 11 ARG categories, predominantly associated with glycopeptides (18.1%) and tetracycline (11.3%) resistance. The most enriched ARG carriers were Pseudomonadota (acrD, emrB, mdtB etc.), Bacillota (tet(44), tet(M), tet(O) etc.), Bacteroidota (tet(Q), mel, tet(X) etc.), and Actinomycetota (rpoB, ileS). Furthermore, ARGs resistance mechanisms varied between facilities with distinct beta-diversity clustering: SHB and SHE mice mainly employed antibiotic target alteration against glycopeptides, whereas SHA, SHD, and SHC-C57BL/6 primarily utilized antibiotic target protection against tetracyclines. This study presents a high-resolution comparison of gut microbiota and ARGs in SPF mice from multiple facilities, highlighting facility-dependent microbial and resistome variation and providing valuable references for preclinical microbiological standardization and risk assessment.

The online version contains supplementary material available at 10.1186/s12866-025-04699-6.