The U.S. Centers for Disease Control and Prevention has reported another death and even more cases linked to Pseudomonas aeruginosa, a drug-resistant strain of bacteria, found in artificial tears or eyedrops.

The bacteria strain has been found in 81 people — four of whom have died from infections, according to specimens collected between May 2022 and April 2023, according to the CDC's most recent update.

Over 10 different brands of ophthalmic drugs were involved in these cases, the CDC said. But the most common was Ezri Care Artificial Tears, which the Food and Drug Administration warned consumers to stop purchasing in February.

The CDC confirmed a matching strain of Pseudomonas aeruginosa in opened bottles of the product and says it will test unopened bottles to test whether contamination occurred during manufacturing.

According to the FDA, Ezricare's parent company, an India-based pharmaceutical provider named Global Pharma Healthcare, had failed to provide appropriate microbial testing of its over-the-counter eye product. The same was true of another of the company's products, Delsam Pharma Artificial Eye Ointment, which the company voluntarily recalled shortly after.

The FDA said Global Pharma failed to use adequate, tamper-evident packaging and distributed the drugs without proper preservatives.

Global Pharma did not immediately respond to NPR's request for comment.

Two additional companies, Apotex Corp. and Pharmedica USA, recalled eyedrop products in February, though products from those companies had not been linked to infections at the time.

Per the CDC's latest update, infections have been identified in 18 states: California, Colorado, Connecticut, Delaware, Florida, Illinois, North Carolina, New Jersey, New Mexico, Nevada, New York, Ohio, Pennsylvania, South Dakota, Texas, Utah, Washington and Wisconsin.

Common symptoms of the bacterial infection include discharge from the eye, redness of the eye or eyelid, blurry vision, a sensitivity to light and eye pain.

In the most extreme cases, the infection can spread to other parts of the body, including the bloodstream. Four people have died due to infections, the CDC said. At least 14 others have experienced vision loss and four have undergone enucleation — the surgical removal of the eyeball.

Infections are generally treated with antibiotics, but the bacteria are becoming increasingly resistant to multiple drugs. The CDC does not recommend patients undergo testing for infection unless they have symptoms.

In 2017, a drug-resistant strain of the bacteria was believed to have caused an estimated 32,600 infections among hospitalized patients in the U.S., continuing a downward trend from 46,000 in 2012, the CDC said in an informational tip sheet.