MRSA orbital cellulitis is an aggressive disease and generally caused by external trauma or injury that seeds the gram-positive organism posterior to the orbital septum, although it can also be caused endogenously through systemic infection. Bilateral blindness from community-associated MRSA orbital cellulitis has also been seen in the literature. This was reported in an otherwise healthy incarcerated 44-year-old man and developed fever and chills two days after squeezing a pustule on his nares. There were no additional risk factors such as HIV, diabetes, steroid use, or hospitalization. By Day 11 he progressed to bilateral no-light-perception and cavernous sinus thrombosis. Our case report involves an episode of MRSA panophthalmitis that we believe disseminated endogenously secondary to the patient’s infected central line. Our patient also suffered from common risk factors that predisposed him to severe infection including poorly controlled diabetes, renal dysfunction on hemodialysis in addition to the infected central line.
A work up for EBE should include systemic evaluation including CBC, CMP, ESR/CRP, and blood cultures along with ophthalmic consultation. In cases of MRSA endogenous endophthalmitis, blood cultures have much greater diagnostic yield than vitreous cultures with sensitivity of 76% and 56%, respectively.3 Although most literature supports a vitreous tap in the initial work-up and management of suspected EBE, only 12% of vitreous cultures grew MRSA. In contrast, in a study of 17 cases of MRSA EBE, 100% of patients had blood cultures positive for MRSA.7 In cases of MRSA EBE secondary to infected catheters or central lines, the hardware was removed upon treatment initiation. It is unclear if this is beneficial, but it is recommended that these devices be removed in the setting of any MRSA bacteremia.
While there are very few reported cases of MRSA EBE, intravenous administration of vancomycin was the common choice of antibiotic for treatment. However, systemic vancomycin has an unpredictable penetration into the brain-retinal barrier and into the vitreous body. Studies of general endophthalmitis cases showed that vancomycin penetration was poor in the vitreous one and five hours after 1 IV gram dose with the highest serum concentration of 20%.8 Whereas perhaps in cases of endogenous endophthalmitis with greater systemic infection and theoretically meningeal inflammation, IV vancomycin may have better penetration.8 As such, IV antibiotics are a cornerstone of EBE, but they are not recommended in cases of exogenous or localized endophthalmitis.
Other IV antibiotics have been utilized with varying success in MRSA endogenous endophthalmitis including: daptomycin, ceftaroline, and linezolid.1 Daptomycin has a very poor ocular penetration, estimated to be around 28%, but is favorable in that it is not metabolized by kidneys as many of these patients have kidney dysfunction.8 Studies have shown very favorable intravitreal penetration at Linezolid as another potential antibiotic with fair ocular penetration; however, it is bacteriostatic and doesn't directly eliminate bacteria. Linezolid has been used in MRSA endogenous endophthalmitis with success but it is not recommended as a first line antibiotic due to side effects of bone marrow suppression and optic neuropathy. Of all antibiotic classes, fluoroquinolones have greatest penetration of the vitreous when given intravenously; however, there is a high resistance for this class of antibiotics among MRSA so they are not recommended as first line in MRSA endogenous endophthalmitis.8 Ceftaroline has shown promising results in a case series of MRSA endogenous endophthalmitis with recent studies have found it to have better vitreous penetration and a better side effect profile than vancomycin, daptomycin, and linezolid.1
The prognosis for MRSA EBE is usually poor, but it is difficult to prognosticate because the few publications on MRSA EBE involved are case series. Studies have shown retinal detachment as a common sequelae of MRSA EBE; the rate of retinal detachment has been estimated between 53 to 75%.1,7 Both studies however did not find a significant correlation between poor visual acuity (> 20/200) and presence of a retinal detachment.
One large retrospective study found that 47% of patients had a final visual acuity worse than 20/200. Furthermore this study found that poor visual acuity was not significantly affected by phakia status, diabetes mellitus, overall systemic illness, or development of retinal detachment, like the two studies above.7 The significant difference between patients who recovered with a visual acuity less than 20/200 versus worse than 20/200 (p = 0.02) was time of admission to endophthalmitis diagnosis.7 A literature review of case reports and case series of EBE, not specific to MRSA EBE, found that 44% resulted in total blindness while 25% required evisceration or enucleation in the end.3