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Joseph M Blondeau, Christine M Sanfilippo, Timothy W Morris, Jennifer Deane, Daniel F Sahm; In vitro Antibiotic Susceptibility Profile of Ocular Pathogens - Results from the First ARMOR Canada Surveillance Study. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2840.
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© ARVO (1962-2015); The Authors (2016-present)
The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study, which monitors the potency of a variety of antibiotics against ocular pathogens, was initiated in the USA in 2009. In recent years, clinical sites in Canada have participated in the study, and the results for 2012-2013 are presented here.
A total of 180 clinical isolates (65 Staphylococcus aureus, 57 coagulase-negative staphylococci (CoNS), 15 Pseudomonas aeruginosa, 24 Haemophilus influenzae, and 19 Streptococcus pneumoniae) were collected across 7 geographically distributed sites in Canada from patients with ocular infections. Broth microdilution susceptibility testing was performed for up to 16 antibiotics according to the Clinical and Laboratory Standards Institute guidelines. Isolates were categorized as susceptible or non-susceptible (intermediate and resistant) based on systemic breakpoints, where available.
Resistance among the staphylococci was highest for azithromycin (45-51%), oxacillin/methicillin (14-42%), and ciprofloxacin (29-33%); among the fluoroquinolones, besifloxacin had the lowest MIC90 values (1 µg/ml for S. aureus, 0.5 µg/ml for CoNS), equal to or more potent than that of vancomycin. More than 21% of the S. aureus isolates and over 43% of the CoNS isolates were non-susceptible to three or more drug classes. Methicillin-resistant isolates of S. aureus (MRSA) and CoNS (MRCoNS) were predominantly multi-drug resistant (89-92%). Among S. pneumoniae isolates, 32% were resistant to azithromycin and 16% were non-susceptible to imipenem, yet all were susceptible to the fluoroquinolones, ceftriaxone, chloramphenicol, and penicillin. While one H. influenzae isolate was non-susceptible to fluoroquinolones, and another showed intermediate resistance to chloramphenicol, no resistance was detected among the P. aeruginosa isolates.
This study provides the first report of susceptibility data against solely ocular isolates collected across Canada, and provides a baseline activity profile for relevant antibiotics against important ophthalmic pathogens. The information obtained from this surveillance study should be considered before initiating empiric treatment of common eye infections. Future monitoring in Canada is warranted to assess current resistance trends.
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