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ARMOR study identifies increased antibiotic resistance
Ongoing research demonstrates trends in ocular pathogens throughout the nation, but experts recommend evaluating susceptibility locally and in-office.
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The latest results from the Antibiotic Resistance Monitoring in Ocular Microorganisms surveillance study indicate that non-susceptibility is increasing, according to a presentation this spring at the annual Association for Research in Vision and Ophthalmology meeting.
“At this year’s ARVO meeting, my colleagues and I reported year-over-year comparisons of susceptibility rates based on 2013 data on 496 bacterial isolates collected from 22 participating sites and preliminary 2014 data on 141 isolates from seven participating sites,” Penny Asbell, MD, MBA, lead ARMOR study author, told Primary Care Optometry News.
Asbell said that the objective of the study is to equip health care providers with current antimicrobial susceptibility patterns so they can make informed treatment decisions.
She continued: “The survey included the organisms most frequently implicated in bacterial eye infections, including Streptococcus pneumoniae, Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Pseudomonas aeruginosa and Haemophilus influenzae.”
Results from the 2014 data showed high levels of antibiotic resistance among ocular pathogens.
“Similar to previous years, we observed high levels of antibiotic resistance – full and intermediate resistance,” Asbell, a professor of ophthalmology at Icahn School of Medicine at Mount Sinai, said. “Preliminary data indicate that approximately one in two S. pneumoniae isolates was resistant to penicillin, and that two in five were resistant to azithromycin. During this period, tobramycin resistance among CoNS appeared to increase, whereas resistance rates for azithromycin remained stable.”
Additionally, non-susceptibility of S. aureus isolates to oxacillin, ciprofloxacin and azithromycin decreased in 2014, and non-susceptibility of P. aeruginosa isolates to polymyxin B, imipenem and ciprofloxacin emerged in 2014, as detailed by Asbell and colleagues in the ARVO abstract. Multi-drug resistance among CoNS and methicillin-resistant CoNS increased in 2014 and decreased among S. aureus and methicillin-resistant S. aureus (MRSA).
The latest data imply that antibiotic resistance among common ocular pathogens is a significant problem, Asbell said. Understanding resistance as well as trends is vital information for clinicians.
“While it is important to consider the ARMOR data when making treatment decisions, clinicians must consider each case individually,” she explained. “The effect of treatment often depends upon a combination of factors, including the pathogen, the choice of antibiotic and, importantly, the patient.”
What’s next for ARMOR
Bausch + Lomb, which initiated the study in 2009, told PCON that the company plans to continue research.
“The study is the only multicenter, national survey of antibiotic resistance patterns among bacteria specific to eye care,” Calvin Roberts, MD, chief medical officer for Bausch + Lomb, said. “This ongoing surveillance study, now in its seventh consecutive year, is designed to provide health care professionals with information about evolving trends in antimicrobial susceptibility patterns to help guide treatment decisions.”
He continued: “The ARMOR study is part of Bausch + Lomb’s dedication to doctors, and we are committed to funding and providing this survey each year. We believe this is a very valuable study for the clinical community, because it is one of the only sources of information about the changing resistance patterns of significant ocular pathogens, and it is important to understand trends to help clinicians determine treatment options for their patients.”
Asbell told PCON that the researchers have submitted their 5 years of data for publication and will present at the American Academy of Optometry meeting in October. They will also begin their seventh year of research.
“Antibiotic resistance is a topic of significant and increasing concern in the health care community and one that authorities in the U.S. and around the world are actively monitoring,” she said. “Continuous surveillance of this trend is particularly important, because we often treat the infection before the pathogen has been identified and because, many times, the pathogen is never identified.”
Asbell said that unsuccessful treatment with antibiotics can threaten patients’ sight and accelerate the growth of resistant bacteria strains.
“We all bear some responsibility for continued vigilance regarding resistance patterns and care in therapeutic selection,” she said.
Direct applications in optometry
Richard Mangan, OD, FAAO, a member of the PCON Editorial Board, said that tracking isolates and susceptibility patterns, as done in the ARMOR study, helps clinicians appreciate issues with multi-drug resistance and determine therapy courses in terms of empirically treating eye and adnexa related infections.
“The ARMOR data tells us that there is increasing resistance to third- and fourth-generation fluoroquinolones,” he said in an interview. “These agents have historically been the go-to drug for eye doctors when treating empirically. Because of important tracking data, we know that when faced with a potentially sight-threatening infection, it is best to start with fortified antibiotics.
“These are antibiotics that are compounded at higher strengths than are available commercially,” he noted. “If, for example, the patient is high risk for MRSA or MRSE [methicillin-resistant Staphylococcus epidermidis], I would typically order fortified vancomycin 33 mg/mL every hour.”
Mangan explained that the ARMOR study results illustrate the importance of eye care providers obtaining culture and sensitivity reports on higher-risk infections.
“The ARMOR study is helpful in understanding trends in bacterial resistance and certainly gives doctors a better idea of how to start treatment in patients at risk for resistance, such as nursing home patients or those on dialysis,” he told PCON. “With that said, we always want to know exactly what organism we’re dealing with.”
Mangan said that this is done with a culture taken from ocular tissue, which can be performed in several ways.
“One way is to use a culturette to collect organisms,” he said. “It is placed into a tube containing transport media that is designed to maintain the viability of the organisms during transit to the lab. Once at the lab, they transfer the organism to differing growth plates. Once the microorganism grows out to a certain level, they can test it against varying antibiotics to see what it is sensitive and not sensitive to.”
The lab will then issue a report detailing the resistance levels the organism has to various antibiotics, Mangan said.
“This helps the clinician determine whether he or she is on the right track with their treatment,” he explained. “In general, the entire process takes a few days. In the meantime, the patient is treated empirically, meaning a clinician’s best guess based on case history, nature of the infection and likelihood of treatment adherence.”
Mangan said that while many optometrists have culturettes in their offices, it is best to refer patients who are potentially dealing with a severe or sight-threatening infection to a corneal specialist or referral center.
“They are usually equipped with culture plates and can collect tissue samples for microscopic examination,” he said. “This may save a little time in determining what the organism is but, in most cases, patients still have to be started on aggressive, empirically derived therapy.
“When confronted with a sight-threatening infection, knowing what organism you are dealing with is critical,” Mangan continued. “What is equally important is knowing what drug or drugs they may or may not respond to. The ARMOR data is invaluable in understanding trends in antibiotic resistance, but every area of the country has its own, more specific resistance problem.”
Asbell also offered advice for optometrists in selecting antibiotics and managing ocular infections.
“Some best practices that can help clinicians manage this issue and improve patient care are to pay close attention to infection control protocols that can decrease the risk of nosocomial infections, avoid over prescribing, engage in post-treatment monitoring and consider class switching and combination treatment,” she said.
“Additionally, clinicians should consult local antibiograms,” she added. “The hospital antibiogram is a periodic summary of antimicrobial susceptibilities of local bacterial isolates submitted to the hospital’s clinical microbiology laboratory. These tools can be used to assess local susceptibility rates, aid antibiotic therapy selection and monitor resistance trends over time within an institution.” – by Chelsea Frajerman Pardes
- Reference:
- Asbell PA, et al. Antibiotic Resistance Among Ocular Pathogens – Results from the ARMOR Surveillance Study 2013-Present. Poster presented at: Association for Research in Vision and Ophthalmology meeting; May 3, 2015; Denver, CO.
- For more information:
- Penny Asbell, MD, MBA, is a professor of ophthalmology at Icahn School of Medicine at Mount Sinai, director of the Cornea Service and Refractive Surgery Center, and the lead ARMOR study author. She can be reached at penny.asbell@mssm.edu.
- Richard Mangan, OD, FAAO, is a consultative optometrist and a member of the PCON Editorial Board. He can be reached at eyeam4uk@aol.com.
- Calvin Roberts, MD, is the chief medical officer for Bausch + Lomb. He can be reached at Calvin.W.Roberts@Bausch.com.
Disclosures: Asbell is a consultant to Bausch + Lomb. Mangan reports no relevant financial disclosures. Roberts is an employee of Bausch + Lomb.