The death toll has now climbed in the outbreak of extensively drug-resistant bacteria that was linked to recalled eye drops, the Centers for Disease Control and Prevention announced Tuesday, confirming two more deaths in people infected by Pseudomonas aeruginosa.

Eight people have lost their vision and four have had their eyeballs removed, according to the CDC’s latest update, out of 68 patients identified across 16 states with the bacteria. One death had previously been reported in a Washington state man.

A total of three eye products have been recalled – all imported from Indian firm Global Pharma Healthcare Private Limited – as health authorities raced to investigate the outbreak suspected to be linked to opened eye drops that were purchased online and in retailers, as well as obtained through ophthalmologist offices.

Two eye products from other manufacturers have also been recalled in recent weeks for unrelated contamination concerns. 

The Pseudomonas aeruginosa strain in the outbreak is exceedingly rare and had never before been seen in the U.S. It is especially challenging for doctors to treat given it has developed resistance to a dozen different antibiotics. 

News of the outbreak’s growing toll comes as the CDC says researchers at the University of California at San Diego have identified a bacteriophage that might work to treat the extensively drug-resistant bacteria.

The university’s Center for Innovative Phage Applications and Therapeutics has previously touted so-called “phage” therapies that it developed to save patients with infections caused by drug-resistant bacteria. 

These kinds of treatments work by deploying viruses that aim to attack bacteria, fending off infections that traditional antibiotic drugs fail to stamp out.

It is unclear how many patients, if any, have so far been treated with the bacteriophage identified for the current outbreak. The center did not immediately return a request for comment.