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Jack D Stringham, Darlene Miller, Harry W Flynn; Coagulase-Negative Staphylococcus (CoNS) Causing Endophthalmitis: A Decreasing Trend of Susceptibility Among Vancomycin and Fluoroquinolones. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):278.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the susceptibility of CoNS causing endophthalmitis to vancomycin and fluoroquinolones over time.
Microbiology records were reviewed to document trends in automated vancomycin MIC90 and percent inhibited using Vitek 2 data on vitreous isolates recovered from (1990-1994-baseline) in five-year increments to 2010-Oct2014. Parallel resistance for the fluoroquinolones (ciprofloxacin, levofloxacin and moxifloxacin) were also documented. Data for levofloxacin and moxifloxacin were only available for the last 4 periods (1995-1999, 2000-2004, 2005-2009, 2010-Oct2014).
Vancomycin MIC90 at base line (1990-1994, N=90) was <1ug/ml. 96% of the all isolates were inhibited at this concentration. The MIC90 (% susceptible) for the remaining periods were 1995-1999, N=75, <1 µg/ml (100%), 2000-2004, N=59, <2 µg/ml (90%), 2005-2009, N=73, <2 µg/ml (95%), and 2010-Oct2014, N=55, <2 µg/ml (100%). A significant decline in the percent of isolates susceptible to a vancomycin concentration of 1 ug/ml was observed in the last 3 periods when compared to baseline (96%), 2000-2004 (11%; p=0.00), 2005-2009 (8%; p=0.00) and 2010-Oct2014 (40%; p=0.00).<br /> <br /> Ciprofloxacin resistance increased from 14.6% (N=82) at baseline to 62.3% (N=61) for the last test period (p=0.00). Similar significant increases in resistance to levofloxacin and moxifloxacin were documented from the initial test period 1995-1999 to 2010-Oct2014. Resistance to levofloxacin increased from 17.4% (N=23) to 60.7% (N=61; p=0.00). Moxifloxacin resistance increased from 21.7% (N=23) to 62.3% (N=61; p=0.00).
CoNS isolates remain susceptible to vancomycin, but the concentration required to kill or inhibit 90% of the isolates has doubled over the last 24.5 years. Less than 40% of our CoNS isolates are susceptible in vitro to the fluoroquinolones, moxifloxacin included.
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