Induction of lipid A modification genes in Pseudomonas aeruginosa cells tolerant to a commercially available contact lens disinfection solution.

Abstract

Introduction. Pseudomonas aeruginosa has a high propensity to develop drug resistance and is a leading cause of bacterial keratitis, particularly amongst contact lens (CL) wearers. Although CL wearers are advised to regularly disinfect their CLs with fresh multi-purpose disinfection solutions, adherence is often poor. This raises the possibility that P. aeruginosa may develop resistance to multi-purpose disinfection solutions when exposed to sub-inhibitory concentrations of disinfection solutions.Aim. We therefore investigated the survivability of a CL-associated keratitis isolate of P. aeruginosa (PA76203) in a commercially available multi-purpose disinfection solution (Opti-Free RepleniSH) when pre-treated with a sub-inhibitory concentration of solution.Methodology. Survival of PA76203 in 100% (v/v) disinfectant solution was evaluated for up to 6 h with both untreated control cultures and cultures pre-treated with 30% (v/v) solution, using bacterial colony count data. Transcriptomic and proteomic analysis of the model strain P. aeruginosa PAO1 was conducted to evaluate genes and proteins associated with growth in 30% (v/v) solution.Results. Untreated PA76203 was undetectable in the disinfection solution after 10 min incubation, whereas pretreated PA76203 was detectable at 6 h (P<0.05), indicating the acquisition of a tolerance phenotype. Transcriptomic and proteomic data from PAO1 treated with a sub-inhibitory concentration of disinfectant revealed 85 significantly differentially expressed genes and 342 differentially abundant proteins, respectively. Genes and proteins involved in LPS lipid A modifications (including arnA, which encodes the first functional enzyme in a lipid A modification operon) were shown to be upregulated in the pre-treated condition compared to the untreated control. The tolerance phenotype was not maintained in a strain of P. aeruginosa with a non-functional arnA gene.Conclusion. Exposure of P. aeruginosa to sub-inhibitory concentrations of disinfection solution enhances tolerance to previously lethal concentrations of solution and is positively associated with upregulation of genes involved in LPS lipid A modifications.