Overview
Bacterial infections of the cornea (bacterial keratitis) are a major cause of sight loss worldwide. There are around 6000 cases of bacterial keratitis every year in the UK. Pseudomonas aeruginosa is a type of bacteria that’s linked to severe infections that can lead to sight loss. Wearing contact lenses is a key risk factor for these infections.
The research team has collected hundreds of samples of this bacteria that have come from patients with keratitis. They have shown in a pilot study that some strains of the bacteria linked to severe infection are resistant to a common contact lens disinfectant. But the contact lens industry uses a different strain of the bacteria when they are testing disinfectant solutions, one that is not linked to eye infections and that is easily killed. And we don’t know how common the severe strains are.
In this study, the team is finding out how common the resistant strain of Pseudomonas aeruginosa is in their samples from patients, and also whether it is also resistant to contact lens solutions with different active ingredients. They will also study the resistant strain to find out what makes it harder to kill.
Results from the study will provide evidence for improving contact lens solution testing and could also help with designing better ways to disinfect contact lenses.
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Scientific summary
Emerging resistance of keratitis-associated Pseudomonas aeruginosa to contact lens disinfection solutions
Bacterial infections of the cornea are a major cause of visual loss world-wide, with approximately 6000 UK cases of bacterial keratitis per year. Pseudomonas aeruginosa is associated with severe infections that can lead to loss of sight and it has been demonstrated that contact lens use is a key risk factor for such infections. Through the UK Microbiology Ophthalmic Group (MOG), the team has collected 658 isolates of P. aeruginosa associated with keratitis (2003-2012), and have linked clinical metadata. In a pilot study, they have shown that some strains associated with severe infections exhibit enhanced resistance to a commonly used contact lens disinfection solution, whereas the industry reference strain, which is not associated with eye infections, was readily killed. However, the prevalence of this emerging resistance phenotype is not known.
In this study, the team’s aim is to determine the prevalence of this phenotype amongst their wider collection of P. aeruginosa associated with keratitis, and test whether the enhanced resistance phenotype also applies to other contact lens disinfection solutions where the active ingredient differs.
Finally, using RNAseq approaches to study the transcriptome of the resistant strain during exposure to the disinfection solution, coupled with quantitative PCR assays, they will determine the mechanism of resistance. Using these approaches they will (i) determine the extent of the emerging threat of resistant P. aeruginosa, thus providing an evidence base for improved testing procedures, and (ii) provide data that will help in the design of improved disinfection regimes in order to counter this emerging threat.