An alarming outbreak of extensively drug-resistant bacteria linked to eye drops has now sickened 68 people across 16 states, according to the latest update from the Centers for Disease Control and Prevention. At least 16 people have been hospitalized, eight have lost vision, and four have had their eyeballs surgically removed (enucleation). One person has died, which was reported earlier.

The agency first released a health alert on the outbreak February 1. At that point, the outbreak had sickened 55 people in 12 states, with the one death reported in a Washington patient. In an update emailed to Ars on February 22, the CDC said the case count had reached 58, with five cases of vision loss and one enucleation.

The continued rise in cases and severe outcomes highlights the challenge of fighting the germ behind the outbreak, which is an extensively drug-resistant form of Pseudomonas aeruginosa. It has the unwieldy name of Verona Integron-mediated Metallo-β-lactamase (VIM) and Guiana-Extended Spectrum-β-Lactamase (GES)-producing carbapenem-resistant Pseudomonas aeruginosa—or VIM-GES-CRPA, for short.

The VIM-GES-CRPA outbreak strain is rare and has never been seen in the US before. Health officials think it was brought into the country in contaminated eye drops manufactured by Global Pharma, a Chennai, India-based manufacturer. The products were sold under the brand names EzriCare Artificial Tears and Delsam Pharma’s Artificial Eye Ointment, which were available nationwide via Amazon, Walmart, and other retailers.

Both products have been recalled, and the Food and Drug Administration put out separate warnings for consumers to immediately stop using the products. The agency noted that Global Pharma has had multiple manufacturing violations, including "lack of appropriate microbial testing, formulation issues (the company manufactures and distributes ophthalmic drugs in multi-use bottles, without an adequate preservative), and lack of proper controls concerning tamper-evident packaging."

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Widespread threat

VIM-GES-CRPA can be difficult to shake even if the eye drops are quickly ditched. The bacteria can lie low, sometimes spreading stealthily, which is particularly problematic in health care facilities with vulnerable patients. Of the 68 cases so far, 37 are linked to clusters in four health care facilities.

"Patients can carry these organisms on or in their body without showing signs of illness—this is called asymptomatic colonization," Marissa Grossman, a CDC Epidemic Intelligence Service Officer, told Ars last month. "This attribute helps facilitate their silent spread in health care facilities." Once a case is found in a health care facility, the CDC and other health officials recommend screening patients to find silent carriers, which is how some of the cases in the current outbreak were found, Grossman said. Most of the health care-linked cases had exposure to the eye drops, but some did not, suggesting person-to-person transmission, she said.

Antibiotic sensitivity testing suggests at least one newer antibiotic is still effective at treating the VIM-GES-CRPA strain. But Grossman noted that the germ's widespread distribution in the US via the eye drops is "concerning."

"To-date, extensively drug-resistant Pseudomonas with genes that rapidly spread resistance, like VIM and GES, have been rare in this country, and typically associated with person-to-person spread in health care facilities," she said. "The widespread introduction of the outbreak strain, which has not been seen before in the US, threatens to undermine efforts to prevent these highly resistant organisms from becoming more common."

Anyone who has used the recalled eye drops and has signs of an eye infection should seek medical care immediately. But, Grossman adds that "at this time, there is no recommendation for testing of patients who have used this product and who are not experiencing any signs or symptoms of infection."

This month, the FDA posted recall notices for two other types of eye drops—from Pharmedica and Apotex—for non-sterility concerns, but they have not been linked to the VIM-GES-CRPA outbreak.