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Heleen H DeCory, Christine M Sanfilippo, Penny A Asbell; Eight-Year Longitudinal Trends in Methicillin Resistance and Resistance to Other Antibiotics Among Staphylococci From the ARMOR Surveillance Study. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3874.
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© ARVO (1962-2015); The Authors (2016-present)
Staphylococci are common causative pathogens in ophthalmic infections, with numerous studies demonstrating significant antibiotic resistance among these bacteria. The Antibiotic Resistance in Ocular MicrooRganisms (ARMOR) study is a nationwide surveillance study on antibacterial resistance levels among ocular pathogens now in its 8th continuous year. Previous ARMOR data suggested that methicillin resistance (MR) among staphylococci, while high, may have plateaued and could be decreasing. Here, we examined antibiotic resistance trends over time among staphylococci isolates collected in ARMOR through the time of abstract submission to determine if this trend continued in 2016.
From Jan 2009 through Oct 2016, 1597 Staphylococcus aureus and 1400 coagulase-negative staphylococci (CoNS) were collected in ARMOR. Minimum inhibitory concentrations (MICs) were determined by broth microdilution according to Clinical and Laboratory Standards Institute guidelines, and MICs were interpreted as susceptible, intermediate, or resistant based on established systemic breakpoints. Longitudinal trends were evaluated using a Cochran-Armitage test for linear trends in a proportion.
Eight-year trend analysis confirmed MR is decreasing among S aureus (from 39% to 27%; P<0.001) but not among CoNS (P=0.090) with nearly half of CoNS still demonstrating MR. Further analysis showed decreased resistance among S aureus to azithromycin (62% to 47%), ciprofloxacin (39% to 25%), and tobramycin (24% to 9%), and among CoNS to ciprofloxacin (46% to 30%; P<0.001 for all), while there was increased resistance among CoNS to trimethoprim (26% to 37%; P=0.015). As in previous years, a high proportion of methicillin resistant staphylococci demonstrated multidrug resistance (≥3 antibiotic classes), although no staphylococci demonstrated vancomycin resistance. 2016 MIC90s (in µg/mL) for besifloxacin, moxifloxacin, gatifloxacin, ciprofloxacin, and levofloxacin, were 1, 4, 8, 64, and 32, respectively, for S aureus, and 2, 32, 32, 64, and 128, respectively, for CoNS.
Eight-year trend analyses confirm that among S aureus, MR and resistance to macrolides, fluoroquinolones, and aminoglycosides has decreased. In contrast MR has remained high among CoNS, and there was a notable increase in resistance to trimethoprim. These trends may inform treatment choices.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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