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Penny A Asbell, Christine M Sanfilippo, Heleen H DeCory; Longitudinal Trends in Antibiotic Resistance Among Staphylococci Collected in the ARMOR Study. Invest. Ophthalmol. Vis. Sci. 2019;60(9):853.
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Staphylococci are known causative pathogens in ophthalmic infections, and numerous studies have demonstrated significant antibiotic resistance among these bacteria. The Antibiotic Resistance in Ocular MicRoorganisms (ARMOR) study is a nationwide surveillance study which evaluates in vitro antibacterial resistance among ocular pathogens. We examined antibiotic resistance trends over time among staphylococcal isolates collected to date in the ARMOR program.
Since Jan 2009, 2108 Staphylococcus aureus and 1721 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 were interpreted as susceptible or resistant based on established systemic breakpoints. Trends were evaluated using a Cochran-Armitage test for linear trends in a proportion.
Preliminary analysis confirm the previously reported decrease in methicillin resistance (MR) among S. aureus (P<0.001; 40% in 2018), but not among CoNS (P=0.762), with approximately half of CoNS exhibiting MR each year. In addition, decreased resistance was observed among S. aureus to azithromycin (62% to 60%), ciprofloxacin (39% to 30%), tobramycin (24% to 9%), and chloramphenicol (6.6% to 4.4%; P≤0.006 for all). Among CoNS, resistance to ciprofloxacin decreased (46% to 31%; P<0.001), while there was increased resistance to tobramycin (19% to 23%; P=0.036). As in previous years, a high proportion of methicillin-resistant staphylococci demonstrated multidrug resistance (≥3 antibiotic classes). In 2018, besifloxacin, moxifloxacin, gatifloxacin, ciprofloxacin, and levofloxacin MIC90s (in µg/mL) were 0.5, 4, 4, 64, and 16, respectively, for S. aureus, and 2, 32, 32, 64, and 128, respectively, for CoNS.
Longitudinal analyses confirm decreased MR among S. aureus, with additional decreases in resistance to macrolides, fluoroquinolones, aminoglycosides, and phenicols. In contrast, MR remains significant among CoNS, with a decrease observed in fluoroquinolone resistance and an increase observed in aminoglycoside resistance.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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