Consider resistance before empirically treating eye infections
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BOSTON — Results from the ARMOR study indicate that about 70% of Staphylococcus organisms in the eye are resistant to commonly used antibiotics.
“Knowing this will help you be more selective in choosing your antibiotic,” researcher Penny A. Asbell, MD, FACS, MBA, told Healio.
Asbell and colleagues presented 10-year data from the Antibiotic Resistance Monitoring and Ocular micRoorganisms (ARMOR) study here at the American Academy of Optometry annual meeting.
Isolates for the study were collected from either the vitreous or aqueous fluid of patients with eye infections at 40 sites in more than 20 states, Asbell said. After being sent to a central lab, the isolates were tested to determine the organism and potential resistance patterns.
“The data is clean in the sense that it’s all handled exactly the same way by the independent laboratory,” she said.
Over the past 10 years, nearly 6,000 isolates have been collected and tested, Asbell said.
“We all know that a serious infection often leads to permanent loss of vision,” she said. “So, picking the right antibiotic to get going is key.”
She said the ARMOR data are useful in selecting an antibiotic before culture results are available.
“There’s a lot of resistance among the staph organisms; whether it’s S. aureus or coagulase-negative staph, we see nearly 50% of those isolates have significant resistance to some of the commonly used antibiotics,” Asbell said. “Specifically, they’re methicillin-resistant. And we find if they’re methicillin-resistant, they have a high likelihood to be resistant to other antibiotics as well.”
Asbell continued: “For instance, if you have a methicillin-resistant coagulase-negative staph, over 70% of those are resistant to ciprofloxacin and azithromycin, two commonly available topical antibiotics. And for the methicillin-resistant S. aureus, nearly 90% were resistant to ciprofloxacin and azithromycin.”
Researchers found moderate resistance to several agents among pneumococci and low resistance among gram-negative organisms, according to the study abstract.
Vancomycin continues to be effective; however, “it is not commercially available and needs to be compounded, which means it’s very unlikely to be immediately available,” Asbell said.
Besifloxacin is comparable to vancomycin and “significantly better than many of the other fluoroquinolones and the other medications we might use, so that might be an alternative,” she said.
Asbell said the “clinical evaluation is also going to be key to good patient care and trumps the laboratory data in terms of looking at efficacy of a particular antibiotic.”
She noted that when she first became involved in surveillance studies, researchers saw an “alarming increase in the number of methicillin-resistance S. aureus organisms. However, in the last couple of years, we’ve seen it plateau. That’s good news, but the question is, ‘Why?’ Maybe because there has been better stewardship of antibiotic use, not just for the eye, but for systemic use as well.”
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Sanfilippo C, et al. 2020 results from the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) surveillance study. Presented at: American Academy of Optometry annual meeting; Nov. 2-6, 2021; Boston.
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