Intravenous treatment of experimental Staphylococcus aureus endophthalmitis: imipenem versus the combination of ceftazidime and amikacin

Abstract

IV IPM is more effective than is IV CAZ/AN in reducing the number of bacteria in an animal model of S.aureus endophthalmitis.

Intravitreal vancomycin and amikacin versus intravenous imipenem in the treatment of experimental Staphylococcus aureus endophthalmitis

“…As we have previously discussed [11], severe inflammation can be observed in the absence of viable microorganisms, and it is striking that the course of disease in the IV imipenem-treated eyes is superimposable with the course of disease in the control eyes. We speculate that delayed clearance of microorganisms and a consequently higher immunostimulatory load consisting of inflammatory bacterial cell wall constituents and metabolic products in the IV-treated group accounts for the massive immune response observed, which might conceivably contribute to the effect of S. aureus exotoxins in destroying intraocular structures.…”

“…However, in a previous study [11], we obtained promising results in treating experimental Staphylococcus aureus endophthalmitis with IV imipenem, compared with treatment with the EVS regime of IV ceftazidime and amikacin. This difference may be attributable to the superior vitreous penetration of imipenem compared with that of ceftazidime and amikacin [3].…”

“…In a previous study [11], we have found that IV imipenem is more efficacious in eradicating S.aureus from the vitreous than IV ceftazidime and amikacin, the antibiotics used by the EVS. Consequently, the present study was designed to determine the efficacy of IV imipenem in comparison with IO vancomycin and amikacin.…”

Modeling intraocular bacterial infections

“…In 1952, Leopold reviewed experimental rabbit endophthalmitis studies and concluded that antibiotics could not penetrate into the vitreous, but still recommended the use of prophylactic systemic antibiotics because of potential “spill-over into the intraocular fluids” during surgery. In 1987, Parrish and O’Day recommended systemic antibiotic prophylaxis for the treatment of traumatic endophthalmitis even though “…we are unaware of any experimental evidence that supports the efficacy of systemic antibiotics in prophylaxis of endophthalmitis….” Some antibiotics have been shown experimentally to reach therapeutic concentrations in the vitreous of rabbits in the model of penetrating eye trauma: intravenous cefazolin (Alfaro et al, 1992), intravenous ciprofloxacin (Alfaro et al, 1996b), combined topical and oral ciprofloxacin (Ozturk et al, 1999), combined topical and oral ofloxacin (Ozturk et al, 2000), and intravenous imipenem (Engelbert et al, 2003). Although some antibiotics do reach therapeutic concentrations in the vitreous, it is a widely held opinion that the use of systemic antibiotics alone is not an effective strategy for the treatment of exogenous or endogenous bacterial endophthalmitis.…”

“…In order to experimentally correlate clinical findings in the use of systemic antibiotics in the treatment of bacterial endophthalmitis, Engelbert et al (2004b) compared intravitreal vancomycin and amikacin and intravenous imipenem in the treatment of experimental S. aureus endophthalmitis in the rabbit. Intravenous imipenem was previously shown to have excellent penetration into the vitreous and was effective against experimental S. aureus endophthalmitis (Engelbert et al, 2003). When administered at 24 hours post-infection, a single intravitreal injection of vancomycin and amikacin sterilized the vitreous and preserved the retina and intraocular structures.…”