May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
The Bactericidal Effectiveness of an EnhancedTobramycin-Dexamethasone Formulation
Author Affiliations & Notes
  • C. C. McCormick
    Microbiology, Univ of Mississippi Med Center, Jackson, Mississippi
  • C. L. Balzli
    Microbiology, Univ of Mississippi Med Center, Jackson, Mississippi
  • A. R. Caballero
    Microbiology, Univ of Mississippi Med Center, Jackson, Mississippi
  • A. Tang
    Microbiology, Univ of Mississippi Med Center, Jackson, Mississippi
  • R. J. O'Callaghan
    Microbiology, Univ of Mississippi Med Center, Jackson, Mississippi
  • Footnotes
    Commercial Relationships  C.C. McCormick, Alcon Laboratories, F; C.L. Balzli, Alcon Laboratories, F; A.R. Caballero, Alcon Laboratories, F; A. Tang, Alcon Laboratories, F; R.J. O'Callaghan, Alcon Laboratories, F.
  • Footnotes
    Support  Alcon Laboratories
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 846. doi:https://doi.org/
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      C. C. McCormick, C. L. Balzli, A. R. Caballero, A. Tang, R. J. O'Callaghan; The Bactericidal Effectiveness of an EnhancedTobramycin-Dexamethasone Formulation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):846. doi: https://doi.org/.

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

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Abstract

Purpose: : To compare the bactericidal effectiveness of Tobradex ophthalmic suspension to a new formulation containing half the concentration of dexamethasone enhanced with novel suspension technology using rabbit models of Staphylococcus aureus and Pseudomonas aeruginosa keratitis.

Methods: : Eyes were intrastromally injected with 100 colony forming units (CFU) of methicillin-sensitive S. aureus (MSSA; 8325-4) or methicillin-resistant S. aureus (MRSA; strain 70490) or 1000 CFU P. aeruginosa (27853). S. aureus infected eyes were treated every hour from 10 to 15 hours postinfection (PI) with a single drop of formulation. Eyes infected with Pseudomonas were treated at 16 hours PI with a single drop every 15 minutes for one hour and then every hour from 17 to 22 hours PI. Tested were untreated eyes (n = 12 per strain) and eyes treated with dexamethasone (0.1%, Maxidex; n = 6 per strain), tobramycin (0.3%, Tobrex; n = 6 per strain), the standard combination of tobramycin (0.3%) and dexamethasone (0.1%) (Tobradex, n = 6 per strain) or a new formulation of tobramycin (0.3%) and dexamethasone (0.05%) with pharmaceutical-grade xanthan gum (Tobradex ST; n = 6 per strain). Corneas were cultured 1 hour after the last treatment to determine the log CFU ± SEM per cornea.

Results: : Corneas in untreated eyes infected with MSSA or MRSA at 16 hours PI had 6.73 ± 0.1 and 6.95 ± 0.08 logs of bacteria, respectively; for P. aeruginosa, 7.55 ± 0.09 logs of bacteria were present at 23 hours PI. All eyes treated with Maxidex had no significant reduction in CFU as compared to the untreated control (P ≥ 0.15). Eyes treated with Tobrex had a significant reduction in CFU in MSSA-infected or MRSA-infected corneas (P = 0.002 and 0.04, respectively). Tobrex did not significantly reduce the CFU of P. aeruginosa (P = 0.09). Tobradex formulation significantly reduced the CFU in either Staphylococcus model (P ≤ 0.008), but not in the Pseudomonas model (P = 0.07). The Tobradex ST formulation in both Staphylococcus models significantly reduced the CFU per cornea relative to untreated eyes (P ≤ 0.003) and relative to eyes treated with the Tobradex formulation (P ≤ 0.01). The Tobradex ST in the Pseudomonas model also caused a significant reduction in CFU as compared to untreated controls (P = 0.007) and to eyes treated with the Tobradex formulation (P = 0.03).

Conclusions: : The Tobradex ST formulation is effective for S. aureus and P. aeruginosa keratitis in a rabbit model.

Keywords: keratitis • Staphylococcus • pseudomonas 
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