Weeks after the US Centers for Disease Control and Prevention warned health care providers to stop using a popular brand of eye drops in the wake of infections that led to one known death, an additional two people have reportedly lost their lives.

As of March 14, 68 patients across 16 US states have been diagnosed with infections caused by a rare drug-resistant strain of the bacterium Pseudomonas aeruginosa.

In addition to the deaths, eight people have been reported to have lost their vision, with another four cases requiring at least one of their eyes to be surgically removed.

More than half of the cases were associated with clusters linked to four different healthcare facilities. One factor most of those in the outbreak had in common was their use the preservative-free brand of eye drops, EzriCare Artificial Tears, produced by an Indian pharmaceutical company called Global Pharma.

P. aeruginosa is a notable generalist of the bacterial kingdom, able to thrive just about anywhere from jet fuel to distilled water. Its ability to encase itself in a biofilm and hide from common disinfectants makes it a particularly persistent contaminant in many healthcare settings.

The particular strain of pathogen responsible for the outbreak is new to the US. A form of P. aeruginosa resistant to the antibiotic carbapenem (CRPA), it features two additional enzymes (coded VIM and GES) that boost its shielding even further by rendering a wide variety of β-lactam antibiotics harmless.

That makes the microbe, labeled VIM-GES-CRPA, especially hard to treat.

One case study tells a story of a 72 year old gentleman who presented with an ongoing infection and extreme vision loss in his right eye. After identifying the resistant strain in both his eye and his eye drops, medical specialists prescribed hourly doses of targeted antibiotics. In spite of several weeks of treatment and moderate improvements, the patient's infection remains and his vision is yet to return.

Tragically, a 68-year-old woman from Miami had to have her infected right eye removed last September following her purchase of the eye drops to ease the irritation brought on by her use of contact lenses.

By August her red and swollen eye was figured to be a scratched cornea and treated with the usual broad spectrum antibiotics. Over the course of the month she returned to doctors 10 times in pain that deprived her of sleep. Doctors had hoped to save her sight with a donated cornea, but by the time of the operation it was clear it was too late.

Shockingly, a connection between the eye drops and the infection was only made in January, when her clinic advised her to cease on advice from the CDC's initial notice on the outbreak.

The patient, now legally blind, is suing the manufacturer, distributors, and her healthcare provider. As her healthcare plan forced her to change products, she is including her insurer in the list of defendants.

EzriCare's US distributors claim in spite of there being no testing that confirms a link between their eye drops and the outbreak, they have pulled the product from the market. Global Pharma Healthcare has also issued a voluntary recall, following a recommendation by the US Food and Drug Administration based on a list of violations that includes inadequate microbial testing.

Carbapenem-resistant P. aeruginosa with a Verona integron-encoded metallo-β-lactamase resistance (VIM-CRPA) was already noted as an emergent strain in the US, particularly among so-called medical tourists undergoing surgery in Mexico.

The arrival of a variant with Guiana extended-spectrum-β-lactamase (GES) serves as a stark example of how superbugs are set to transform the medical landscape. Infections that were once routine to treat will increasingly lead to extreme cases of pain, disability, and death as therapies to curb their invasion become harder to find.

As the world opens to trade and travel, pockets of emerging pathogens will rapidly expand, carrying their flavor of resistance with them to spread into new populations.