Tracking Antibiotic Resistance and Endophthalmitis

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Staphylococcus epidermidis, a coagulase-negative, gram-positive coccus, is the most common cause of culture-proven endophthalmitis. Researchers at Bascom Palmer Eye Institute in Miami set out to describe the features and antibiotic resistance profiles of endophthalmitis cases that occurred at their institution from 2006-2016.¹ They then compared the data to findings of a similar case review from the prior decade.²

Cataract surgery accounted for nearly half (49%) of the cases caused by methicillin-sensitive and methicillin-resistant S. epidermidis, they found. Intravitreal injections were the second most common procedure (22%) linked to the inflammation.¹

Of the 96 cases of endophthalmitis and culture-positive S. epidermidis (96 eyes), 89 (93%) were treated with intravitreal vancomycin and ceftazidime. The remaining 7 (7%) received intravitreal vancomycin and amikacin.

Study specifics. The findings in­cluded the following:

• All isolates were sensitive to vanco­mycin in both decades.
• Resistance to methicillin was present in 53% of eyes, compared to 60% in the previous series.
• Resistance to the fluoroquinolone moxifloxacin has increased to 66% of eyes, compared to 31% in the previous decade.
• Visual acuity was not significantly different between those eyes that were methicillin- or moxifloxacin-sensitive and those that were resistant. At last examination, 33% of all eyes achieved 20/40 or better, and 29% achieved less than 5/200.

The challenge ahead. The vancomy­cin outcomes are “encouraging,” given the drug’s effectiveness against all study isolates over time, said coauthor Harry W. Flynn Jr., MD, at Bascom Palmer. Eyes such as those evaluated in the study “are usually responsive to treat­ment and generally have a favorable visual prognosis,” he said.

He cautioned, however, that ophthalmologists cannot presume a rosy prognosis going forward. “In the future, it is reasonable to assume that routine use of intracameral vancomycin prophy­lactically may contribute to vancomycin resistance.”

With regard to methicillin resistance, he noted, “It is reasonable to hypoth­esize that methicillin sensitivity rates have remained stable given the lack of selective pressure, since methicillin is not a commonly used ophthalmic antibiotic.” As for fluoroquinolone re­sistance, he added, “With increasing use of fluoroquinolones, it is not surprising that resistance to this antibiotic class has increased.”

Even so, Dr. Flynn cautioned against connecting any rise in drug resistance to the increased prophylactic use of fluoroquinolones for endophthalmitis. Intracameral antibiotics are not used at Bascom Palmer, and the study “was not designed to determine the cause of increasing S. epidermidis resistance to fluoroquinolones,” he said. Nonetheless, he noted, “the concept that intracameral fluoroquinolones given at the time of cataract surgery will prevent postoperative infection should be chal­lenged.”

—Miriam Karmel

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1 Yannuzzi NA et al. Ophthalmology Retina. 2018;2(5):396-400.

2 Miller DM et al. Ophthalmic Surg Lasers Imag­ing. 2007;38(16):446-451.

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Relevant financial disclosures—Dr. Flynn: None. This study was supported in part by grants from the NIH and Research to Prevent Blindness. No conflicting relationship exists for any author.

For full disclosures and the disclosure key, see below.

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