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

<b>Introduction.</b> <i>Pseudomonas aeruginosa</i> 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 <i>P. aeruginosa</i> may develop resistance to multi-purpose disinfection solutions when exposed to sub-inhibitory concentrations of disinfection solutions.<b>Aim.</b> We therefore investigated the survivability of a CL-associated keratitis isolate of <i>P. aeruginosa</i> (PA76203) in a commercially available multi-purpose disinfection solution (Opti-Free RepleniSH) when pre-treated with a sub-inhibitory concentration of solution.<b>Methodology.</b> 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 <i>P. aeruginosa</i> PAO1 was conducted to evaluate genes and proteins associated with growth in 30% (v/v) solution.<b>Results.</b> Untreated PA76203 was undetectable in the disinfection solution after 10 min incubation, whereas pretreated PA76203 was detectable at 6 h (<i>P</i><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 <i>arnA</i>, 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 <i>P. aeruginosa</i> with a non-functional <i>arnA</i> gene.<b>Conclusion.</b> Exposure of <i>P. aeruginosa</i> 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.