Intravitreal Daptomycin in a Case of Bilateral Endogenous Endophthalmitis

Bacterial endophthalmitis is a devastating intraocular infection that, in its most severe form, can result in complete loss of vision in the affected eye. In patients with endogenous bacterial endophthalmitis, 69% have a final visual acuity worse than counting fingers.¹ Visual outcomes are directly related to the infecting bacteria, with eyes infected with coagulase-negative Staphylococcus faring much better than those infected with Staphylococcus aureus, Streptococcus, and gram-negative organisms.² With the emergence of drug-resistant bacteria, increasing the arsenal of safe and effective antibiotics for treatment is of particular importance. We report a case of bilateral endogenous methicillin-resistant S aureus endophthalmitis treated successfully with intravitreal injections of daptomycin.

A 69-year-old previously well woman who was retired, married, and caregiver to her chronically ill husband was taken to the emergency department by her daughter with an acute onset of confusion, disorientation, and generalized malaise. Her medical history included a remote history of angina, intermittent pleurisy, a total abdominal hysterectomy with bilateral salpingo-oophorectomy, and cataract surgery in the left eye. Her only medication was estrogen replacement. There was no illicit drug use, recent dental work, or indwelling venous catheter. The patient was admitted to the hospital for workup of altered mental status and eventually found to have bacterial endocarditis with methicillin-resistant S aureus. The bacterial isolate had an intermediate resistance to vancomycin hydrochloride (minimum inhibitory concentration, 4-8 μg/mL). Magnetic resonance imaging of the brain showed multiple bilateral acute ischemic changes, and echocardiography revealed mitral valve endocarditis.

The ophthalmology service was consulted for evaluation of the patient's blurred vision. At initial examination, the patient's visual acuity was at least counting fingers OU and intraocular pressures were normal. Findings on anterior segment examination at the bedside were normal except for a few posterior synechiae in the right eye, moderate nuclear sclerotic cataract in the right eye, and a well-centered posterior chamber intraocular lens in the left eye. No hypopyon was noted. There was a moderate vitreous haze in both eyes with a small area of retinitis along the superior temporal arcade of the left eye. Otherwise, the optic nerve, macula, and periphery were grossly normal in each eye. Given the clinical setting, a diagnosis of bilateral endogenous endophthalmitis was made.

The patient's initial general health and mental state precluded both vitrectomy and intravitreal injection. She was treated with topical atropine, prednisolone, and vancomycin. Two days after the initial examination, intravitreal daptomycin (200 μg/0.1 mL) was administered without complication. She was also receiving intravenous daptomycin for endocarditis treatment. During the week following injection, the vitreous cleared completely in both eyes and the retinitis resolved. The patient required no further ocular intervention. At follow-up 2 months after the initial injection, visual acuity was 20/20 OU.

Daptomycin is a lipopeptide antibiotic that causes concentration-dependent depolarization of the bacterial cytoplasmic membrane, which inhibits protein synthesis. Since its introduction in 2003, it has been used to treat complicated skin and soft-tissue infections, endocarditis, and osteomyelitis.³ A recent safety and efficacy study showed that daptomycin can be administered safely in a dose of 200 μg in adult belted rabbits, and daptomycin killed 99.9% of gram-positive bacteria within 6 to 8 hours.⁴ Another report showed that therapeutic intravitreal concentrations greater than the minimum inhibitory concentration for methicillin-resistant S aureus can be achieved following intravenous administration of daptomycin.⁵ The bactericidal activity of daptomycin and the ability to cross the blood-ocular barrier make it a useful alternative to vancomycin and fluoroquinolone antibiotics.

To our knowledge, this is the first report of intravitreal daptomycin being used to successfully treat bacterial endophthalmitis. Future studies evaluating the safety and efficacy of daptomycin in treating endophthalmitis are warranted.

Correspondence: Dr Buzzacco, Department of Ophthalmology and Visual Sciences, The Ohio State University Medical Center, 915 Olentangy River Rd, Ste 5000, Columbus, OH 43212 (dominic.buzzacco@osumc.edu).