Screening and comparison of in vitro-induced resistant and clinically resistant Stenotrophomonas maltophilia strains for eravacycline resistance-related genes

Jie WuJiarong SongJunchang Cui^*

• People's Liberation Army General Hospital, Beijing, China

OBJECTIVE: To identify genes related to eravacycline resistance in Stenotrophomonas maltophilia (Sm) and to provide a theoretical basis for the study of eravacycline resistance mechanisms in Sm and the development of new antibiotics. METHODS: The study employed an integrated omics approach: (1) In vitro antimicrobial susceptibility profiling via broth microdilution to determine baseline MICs for eravacycline and comparator drugs; (2) Induction of resistance in clinical Sm isolates (WJ_4, WJ_14, WJ_18) with low eravacycline MICs through serial passage in escalating drug concentrations; (3) Transcriptome sequencing (RNA-seq) and whole-genome sequencing (WGS) of in vitro-induced resistant strains (WJ_4a, WJ_14a, WJ_18a) and a clinical high-MIC isolate (WJ_97); (4) Bioinformatics analyses, including differential gene expression screening (with |log2(fold change)| > 2 and FDR-adjusted p < 0.05), SNP detection via GATK, and copy number variation (CNV) quantification using CCNE-acc to identify and compare resistance-related genetic alterations. RESULTS: Stable eravacycline-resistant strains were successfully induced, exhibiting 8to 32-fold MIC increases. Transcriptome analysis revealed consistent upregulation of efflux pump genes (smrA, smeD, smeE, smeF) across all induced strains. CNV analysis demonstrated significant smeDEF locus amplification, while nonsynonymous mutations in smeD, smeE, and smeF occurred in WJ_14a (44 mutations) and WJ_18a (3 mutations) but not WJ_4a. The clinical strain WJ_97 showed distinct resistance architecture, including 65 upregulated nonsynonymous mutations (e.g., frameshift in smeF), mutations in smeR, adeF, and vanY-mediated target alteration, alongside a diverse resistance gene profile (41.4% inactivating enzymes, 34.4% efflux pumps). Global downregulation of cyclic AMP receptor protein (CRP) suggested synergistic multidrug resistance mechanisms.CONCLUSIONS: Eravacycline resistance in Sm is primarily driven by dysregulation of the smeDEF efflux complex, with in vitro-induced strains relying on CNV amplification and/or coding mutations, while clinical isolates combine these with accessory pathways.This work provides the evidence for CNV as a core resistance driver and highlights evolutionary divergence under clinical pressure, informing future antibiotic development and resistance surveillance strategies.