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59 EW CORNEA December 2014 by Maxine Lipner EyeWorld Senior Contributing Writer bacteria at particular concentra- tions." Investigators then introduced these suspensions to the lens solu- tion. They took samples at 1-min- ute, 5-minute, 10-minute, 2-hour, 4-hour, and 24-hour time points and examined them to determine how many of the bacteria were still alive. "We were testing the viability," Prof. Winstanley said, adding that one of the strains included was the industry standard strain for Pseudomonas aeruginosa. While only 9 Pseudomonas strains out of approximately 2,000 in the collection were tested, all were associated with real infections, he said. "The main finding was that the industry standard strain was completely killed within 10 minutes," he said. Meanwhile, one of the other strains was still going reasonably strong after 4 hours, and another survived more than 2 hours, Prof. Winstanley reported. Investi- gators do not know how common such long-term survival in solution is. "But certainly 1 out of 9 is a reasonable hit rate," he said. Some strains of Pseudomonas can be resilient to antibiotic treatment. "Indeed, this particular strain is quite resistant to antibiotics and was associated with a particularly severe case of keratitis also," Prof. Winstanley said. This could potentially have clinical implications for those who do not rigidly stick to recommended guidelines for soaking their lenses, Prof. Winstanley said. Currently, the recommended timeframe for keep- ing lenses in solution is 6 hours. Unfortunately, one weakness of the study is that it was not designed with a 6-hour time point to check bacterial viability in the solution, Prof. Winstanley said. Instead, growth was checked at 4 hours and then again at 24 hours. "We can't be 100% sure that the solution would have failed [with this particular hardy strain], but it was probably getting quite close, and if people don't stick rigidly to the regimen, there would be a potential risk," Prof. Winstanley said. Take-home message "The main take-home message is that the standard strains that the companies are using to test the Longer survival found for certain Pseudomonas isolates C ontact disinfecting solution is the first line of defense against keratitis infections for those who wear lenses. However, new research presented at the 2014 Society for General Microbiology meeting in Liverpool, U.K. indicates that a hardier isolate of Pseudomonas aeruginosa may survive for a lon- ger time than the usual test strain, according to Craig Winstanley, PhD, professor of bacteriology, University of Liverpool. This may potentially put users who do not follow recom- mendations and give their lenses just a perfunctory soak at risk for infection, he said. "There are more than 30,000,000 contact lens users in the U.S. and about 3,000,000 in the U.K.," Prof. Winstanley said, adding that while it is difficult to pin down exactly how many Pseudomonas infections are contact lens-related, lens use is one of the largest risk factors associated with Pseudomonas keratitis in particular. For years, Prof. Winstanley and fellow investigators have been collecting isolates from 8 different eye hospitals in the U.K. "We've collected a few thousand Pseudomo- nas isolates associated with severe infections," he said. Because this is an organism that causes a range of infections, investigators have been mining the various strains from the collection, trying to determine whether there is something in par- ticular about Pseudomonas aeruginosa that causes outbreaks in the eye, Prof. Winstanley explained. In one of many studies, inves- tigators decided to take from the collection genotypically different Pseudomonas isolates associated with real eye infections and test these for their survival over time in contact lens solutions. Testing Pseudomonas in solution "What we did was very similar to what the manufacturers would do in that we made suspensions of bacteria," Prof. Winstanley said. "The suspensions were of Considering the strain on contact lens solutions A hardier strain of Pseudomonas aeruginosa may survive longer than expected in contact lens solution, with the potential for causing corneal ulcers such as this. Contact patients who simply give their lenses a quick soak may be putting themselves at risk for severe keratitis infections. In a recent study, investigators tested 9 Pseudomonas strains in their collection, which were all associated with real keratitis infections. Source (all): Craig Winstanley, PhD continued on page 60