July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
In Vitro Susceptibilities of Methicillin-Susceptible and Resistant Staphylococci to Traditional Agents Compared to a Novel Fluoroquinolone
Author Affiliations & Notes
  • James Lin
    Ophthalmology, University of Miami, Miami, Florida, United States
  • Kenneth Fan
    Ophthalmology, University of Miami, Miami, Florida, United States
  • Nathan Pirakitikulr
    Ophthalmology, University of Miami, Miami, Florida, United States
  • Darlene Miller
    Ophthalmology, University of Miami, Miami, Florida, United States
  • Harry Flynn
    Ophthalmology, University of Miami, Miami, Florida, United States
  • Footnotes
    Commercial Relationships   James Lin, None; Kenneth Fan, None; Nathan Pirakitikulr, None; Darlene Miller, None; Harry Flynn, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 837. doi:https://doi.org/
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      James Lin, Kenneth Fan, Nathan Pirakitikulr, Darlene Miller, Harry Flynn; In Vitro Susceptibilities of Methicillin-Susceptible and Resistant Staphylococci to Traditional Agents Compared to a Novel Fluoroquinolone. Invest. Ophthalmol. Vis. Sci. 2019;60(9):837. doi: https://doi.org/.

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

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Abstract

Purpose : Endophthalmitis is a severe ocular infection that can have permanent, sight-threatening consequences. Delafloxacin is a newer, fourth generation fluoroquinolone that has seen utility in acute skin and skin-structure infections, specifically methicillin-resistant Staphylococcus aureus and epidermidis (MRSA, MRSE respectively). However, no reports have tested its utility for intraocular bacteria, where Staphylococci related infections are common. We utilize our large collection of culture-proven Staphylococcus vitreous samples to assess the in vitro efficacy of delafloxacin in comparison to the current standard of care.

Methods : Non-consecutive intravitreal isolates of culture-proven S. aureus and S. epidermidis were identified between 2014-2018. A standard inoculum (1x108 CFU/mL) for each isolate was inoculated in-vitro on Mueller-Hinton agar. Minimum inhibitor concentrations (MIC) were determined using E-test strips placed according to manufacturer’s instructions and susceptibilities were based on breakpoints from Clinical & Laboratory Standards Institute (CLSI) guidelines. Plates were incubated in a non-CO2 incubator and read after 18-24 hours. Antibiotic susceptibilities were obtained for glycopeptides such as telavancin and vancomycin as well as traditional and newer fluoroquinolones.

Results : Of 45 total isolates identified between 2014-2018, 13% were MRSA, 9% were methicillin-sensitive S. aureus (MSSA), 53% were methicillin-resistant S. epidermidis (MRSE), and 24% were methicillin-sensitive S. epidermidis (MSSE). 56% of patients were female. Among the fluoroquinolones, resistance rates were 61% for levofloxacin, 50% for moxifloxacin, and 12% for delafloxacin (p < 0.01). MIC90 values were lowest for delafloxacin (0.98 ug/mL) compared to levofloxacin (8.0 ug/mL) and moxifloxacin (8.0 ug/mL). For glycopeptides, both telavancin and vancomycin were 100% effective against all isolates with MIC90 values of 0.06 ug/mL and 0.75 ug/mL, respectively.

Conclusions : The increase in antibiotic resistance has led to the need for newer, more effective antibiotics for endophthalmitis and other ocular infections. No other study has investigated the efficacy of delafloxacin in ocular tissues. The current study demonstrates that delafloxacin may allow for improved antimicrobial coverage as compared to other fluoroquinolones for Staphylococcus-associated endophthalmitis.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

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