June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Interim Analysis of Antibiotic Resistance from Bacterial Pathogens Collected in the 2020 ARMOR Study
Author Affiliations & Notes
  • Christine M Sanfilippo
    Medical Affairs, Bausch and Lomb Rochester, Rochester, New York, United States
  • Heleen H DeCory
    Medical Affairs, Bausch and Lomb Rochester, Rochester, New York, United States
  • Penny A Asbell
    Ophthalmology, The University of Tennessee Health Science Center, Memphis, Tennessee, United States
  • Footnotes
    Commercial Relationships   Christine Sanfilippo, Bausch Health US, LLC (E); Heleen DeCory, Bausch Health US, LLC (E); Penny Asbell, Bausch Health US, LLC (C)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 717. doi:
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      Christine M Sanfilippo, Heleen H DeCory, Penny A Asbell; Interim Analysis of Antibiotic Resistance from Bacterial Pathogens Collected in the 2020 ARMOR Study. Invest. Ophthalmol. Vis. Sci. 2021;62(8):717.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose : When treating bacterial infections of the eye, knowledge of the antibiotic resistance profile of causative bacteria may aid in selection of the most suitable treatment. Now in its twelfth consecutive year, the ongoing Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study is the only nationwide surveillance study focused exclusively on common ocular pathogens. This interim analysis reports on the antibiotic susceptibility of ocular isolates collected to date in 2020.

Methods : Clinically relevant isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae cultured from ocular infections were submitted to a central laboratory for in vitro antibiotic susceptibility testing as part of ARMOR. Minimum inhibitory concentrations (MICs) were determined per Clinical and Laboratory Standards Institute broth microdilution methods for up to 16 antibiotics (from 10 drug classes), and isolates were classified as susceptible or resistant based on established interpretative criteria.

Results : A total of 366 isolates from 20 US sites were analyzed. Staphylococci exhibited high levels of in vitro resistance to azithromycin (57-62%), oxacillin/methicillin (36-46%), and ciprofloxacin (25-33%); trimethoprim resistance (28%) was also observed among CoNS. Multidrug resistance (MDR; ≥3 antibiotic classes) was common among S. aureus (39%) and CoNS isolates (43%), with a substantial proportion of methicillin-resistant isolates exhibiting MDR (78% and 75%, respectively). Although S. pneumoniae isolates demonstrated resistance to azithromycin (47%) as well as oral penicillin and tetracycline (both 41%), no resistance to fluoroquinolones was detected. Resistance to polymyxin B and the fluoroquinolones was low (<2%) among P. aeruginosa, and no resistance to tested drugs was observed among H. influenzae isolates.

Conclusions : Preliminary results from the 2020 ARMOR study indicate continued high levels of in vitro antibiotic resistance among staphylococci, with considerable MDR especially in methicillin-resistant strains. Combined with other clinical information, these surveillance data can help guide the selection of antibiotics for empiric management of ocular infections.

This is a 2021 ARVO Annual Meeting abstract.


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