RNAseq transcriptome analysis of K. pneumoniae MS6671 and E. coli MS8345 treated with PBT2

The emergence of colistin resistance in carbapenem-resistant and extended-spectrum ß-lactamase (ESBL)-producing bacteria is a significant threat to human health, and new treatment strategies are urgently required. Here we investigated the ability of the safe-for-human use ionophore PBT2 to restore antibiotic sensitivity in several polymyxin-resistant, ESBL-producing, carbapenem resistant Gram-negative human pathogens. PBT2 was observed to resensitize Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa to last-resort polymyxin class antibiotics, including a 'next generation' polymyxin derivative, FADDI-287. To gain additional insight into the potential mechanism of action of PBT2, we analyzed the transcriptome of K. pneumoniae and E. coli in the presence of sub-inhibitory concentrations of PBT2. Treatment with PBT2 was associated with multiple stress responses in both K. pneumoniae and E. coli. Significant changes in the transcription of transition metal ion homeostasis genes were observed in both strains. Overall design: For each species of bacteria, 2 sample conditions were analyzed. Sample conditions included: 1) bacterial treatment with cation-adjusted Muller Hinton broth (CA-MHB; reference sample); or 2) CA-MHB+PBT2 (7 µM for E. coli and 64 µM for K. pneumoniae).