# Transcriptomic analysis of tigecycline-induced colistin collateral sensitivity in carbapenem-resistant Enterobacter cloacae complex

## TL;DR

This study explores how tigecycline treatment increases sensitivity to colistin in antibiotic-resistant bacteria by analyzing genetic and transcriptional changes.

## Contribution

The study identifies transcriptional and genetic mechanisms underlying tigecycline-induced colistin collateral sensitivity in carbapenem-resistant Enterobacter cloacae complex.

## Key findings

- Tigecycline exposure reduced colistin resistance in CRECC by inhibiting quorum sensing and biofilm formation.
- Transcriptomic analysis revealed 1,977 differentially expressed genes, including those involved in carbohydrate, amino acid, and ion metabolism.
- Lipopolysaccharide biosynthesis and modification genes were upregulated, contributing to increased colistin susceptibility.

## Abstract

Utilizing treatment strategies based on collateral sensitivity (CS) represents a promising approach to suppressing antibiotic resistance. Although the mechanism of CS between numerous drugs has been researched, the mechanism of CS between tigecycline and colistin remains unclear. Therefore, the purpose of our research is to investigate the possible mechanism by which tigecycline affects colistin CS in the Enterobacter cloacae complex. Tigecycline induction significantly reduced the minimum inhibitory concentration of carbapenem-resistant Enterobacter cloacae complex (CRECC) to colistin, and sequencing revealed a single-base deletion at the RamR binding site. Complementation experiments demonstrated that deletion of the RamR binding site increased the resistance of CRECC417 to colistin and tigecycline by 2-fold and 4-fold, respectively. Transcriptomic comparison analysis of strains before and after CRECC417 induction revealed a total of 1,977 genes with significant differences in expression. Genes associated with carbohydrate, amino acid, and inorganic ion metabolism were the most highly enriched. Furthermore, the observed increase in colistin susceptibility in CRECC417R can be attributed to the inhibition of quorum sensing and biofilm formation pathways, as well as increased expression levels of genes associated with lipopolysaccharide biosynthesis and modification.

Due to the overuse of antibiotics, antimicrobial resistance (AMR) has become a serious threat to global public health. Dosage regimens based on bacterial CS can reduce antibiotic use without reducing efficacy, thereby reducing antibiotic-related toxicity risks, expanding the scope of antibiotic application, and limiting the development of antibiotic resistance. In this study, we analyzed the drug resistance mutations and global transcriptional changes in CRECC after tigecycline induction through genomics and transcriptomics. Our study showed that tigecycline exposure significantly inhibited quorum sensing pathways and biofilm formation. There were significant changes in the transcriptional levels of genes related to cell membrane lipopolysaccharide synthesis and modification, but no mutations were found in genes related to colistin resistance. These findings provide valuable insights for further investigation into the CS between tigecycline and colistin.