The outbreak of a lethal drug-resistant bacteria strain linked to an alleged eye drop manufacturing breakdown is one of the biggest health stories in 2023. A report from the American Society of Microbiology details how this complicated case came to light.
In February 2023, the ophthalmic sector was on high alert as a contaminated artificial tears brand was linked to a host of serious adverse reports in the US. The latest update from the US Food and Drug Administration stated 14 patients had suffered vision loss, an additional four required enucleation (surgical removal of the eye), and four deaths.
In total, 81 infected patients have been identified in 18 states, according to the latest data.
Authorities allege the outbreak originated from contaminated artificial tears manufactured in India. The infections have been caused by carbapenem-resistant Pseudomonas aeruginosa – a rare strain of extensively drug-resistant bacteria that had never been found in the US previously. Multidrug-resistant bacteria like this have been labelled “one of the most concerning threats in modern medicine”.
The FDA and Centers for Disease Control issued an urgent product recall on 2 February 2023 for Global Pharma Healthcare and its artificial tears lubricant eye drops, distributed to US consumers as EzriCare Artificial Tears and Delsam Pharma Artificial Tears, due to possible contamination. But as it turns out, tainted bottles had been causing problems long before then.
Recently in Antimicrobial Agents and Chemotherapy, an interdisciplinary group of researchers and physicians in Cleveland, Ohio, describe a case of a 72-year-old female from November 2022 that helped expose the mysterious source of the outbreak at the time.
According to a report in the American Society of Microbiology (ASM), P. aeruginosa is a pathogenic, gram-negative bacterium that’s resistant to treatment with most antibiotics. It can cause swimmer’s ear – a painful infection of the outer ear canal – and more serious conditions, especially in people with compromised immune systems.
But the case in Cleveland was unusual, stated Dr Morgan Morelli, the study’s first author and an infectious disease fellow at University Hospitals Cleveland Medical Center.
“I’ve never recovered it from an eye,” she told the ASM. Because P. aeruginosa isn’t usually found in eye infections, she said, finding the right diagnosis was a challenge. “It required a lot of thinking and digging to figure out what was going on. And we never thought it was related to a global manufacturing issue.”
The elderly woman in this case presented to an outpatient eye clinic with unilateral vision loss. She was found to have a large corneal ulcer with hypopyon. She was referred to the hospital’s emergency department where she was evaluated by ophthalmologists. They cultured the infection, prescribed a combination of strong antibiotic eye drops, and sent her home. But the next day, the eye was worse, prompting a referral to a corneal specialist.
The patient had noticed a yellow discharge on her pillow, and she hadn’t been swimming: “We wondered if she’d accidentally touched something, or there was some freak accident, to explain the infection,” Morelli said.
At that point, Morelli said her case was referred to microbiologists and infectious disease experts at the hospital. Infectious disease specialist Dr Scott Fulton asked the patient’s husband to bring in her eye drops for testing. A sample from the patient was sent to the lab of Dr Robert Bonomo, an expert in gram-negative, drug-resistant bacteria at Case Western Reserve University School of Medicine.
Then, Morelli said, the pieces came together. Bonomo’s lab identified a P. aeruginosa isolate that matched genetic material found in the EzriCare artificial tear eye drops she’d been using. Then researchers connected the eye infection to the contaminated drops.
Because the bacteria was resistant to any antibiotics that could be delivered via the eye, this was problematic for the patient’s treatment plan. She was prescribed a strong antibiotic, intravenous cefiderocol, that has some activity against gram-negative bacterium, as well as two other topical antibiotics, polymyxin B ophthalmic solution and doxycycline. The injury to her eye improved, Morelli told ASM, but it’s unclear whether the patient will ever regain total vision.
According to the case study, the patient was discharged from hospital after two weeks and continued with the treatment regime. She had complete resolution of the hypopyon with improvement in the epithelial defect. However, two months after her initial presentation, she developed low intraocular pressure and was found to have choroidal detachment. At the time of publication, the vision potential in the eye remains poor, given the extent of her injuries.
Since issuing the warning in February, the CDC has identified infectious cases due to P. aeruginosa as early as autumn 2022.
Morelli said people may still have the contaminated eye drops on the shelf at home, but she hoped ophthalmologists and optometrists who may be the first physicians to see future patients with this infection will know what to look for.
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