An outside researcher hired by Bausch & Lomb says that whatever is causing the recent outbreak among contact lens wearers of potentially blinding fungal eye infections, it is increasingly likely that consumers are not getting the microbes directly from the company's lens cleaning solution.
Tests have shown that at least four different strains of the microbe, the Fusarium fungus, from three genetically distinct families are involved, the researcher, David Geiser, director of the Fusarium Research Center at Pennsylvania State University, said in an interview on Friday.
Two of the strains are commonly found in sinks and drains, according to Geiser, a leading expert on Fusarium who has been retained by Bausch to provide independent assessments of the genetic make-up of microbes collected from victims and their lens gear.
The findings suggest that there is no single source of contamination for the infections, which have been reported primarily in Singapore, Hong Kong and the US among users of Bausch & Lomb's ReNu with MoistureLoc lens solution coming from a plant in Greenville, South Carolina.
US Food and Drug Administration officials declined to comment Friday on Geiser's assessment. But the agency's Web site posted an update saying that while it continued to confirm cases of Fusarium infections associated with products other than ReNu With MoistureLoc, "Our interest in the MoistureLoc product is based on the disproportionate number of cases of Fusarium keratitis associated with ReNu With MoistureLoc compared to the overall product market share."
As of Friday, the Centers for Disease Control in Atlanta had received 195 reports of Fusarium eye infections occurring in the US since last June, 102 of which had been confirmed in follow-up investigations.
"At this point, it is too early in the investigation to say whether a particular product or solution may be responsible for the outbreak," the CDC said.
On Tuesday, when the confirmed number had been 86 cases, the CDC said it had verified that 56 involved contact lens users and that 54 of them had used ReNu brand solutions -- mostly MoistureLoc -- from the Bausch factory in Greenville.
So far, though, neither Bausch nor federal regulators have found signs of Fusarium contamination at the factory, in production samples retained from lots shipped to customers or in unopened bottles returned by retailers, according to Praveen Tyle, the company's senior vice president for global research and development and chief scientific officer. And some countries that received MoistureLoc from Greenville, like Indonesia and the Philippines, have not reported any unusual increase in the infection rate.
"We are getting to the point where we think there isn't one answer to this," said Tyle, who is based at Bausch's headquarters in Rochester, New York.