April 2009




Alternative customized prophylaxis?

by Matt Young EyeWorld Contributing Editor


Two views of post-op endophthalmitis Source: Nick Mamalis, M.D.

The European Society of Cataract & Refractive Surgeons’ endophthalmitis study, published in the Journal of Cataract & Refractive Surgery in 2006, was a landmark one, finding that the failure to inject intracameral cefuroxime for cataract surgery led to a 4.92-fold increased risk of endophthalmitis.

That study is a commendable one, but other clinical researchers are looking at ways to customize their own prophylaxis regimens to prevent endophthalmitis. The fruits of such labor were reported online in October 2008 in the journal Eye. Researchers at the Ophthalmic Institute Laboratory, Department of Ophthalmology, Gregorio Marañón University, General Hospital, Madrid, Spain, took pre-op conjunctival cultures of consecutive patients undergoing cataract surgery over the period of a year. They determined what bugs the patients had within their conjunctiva, which is known to be the main source of bacteria causing endophthalmitis. Interestingly, they found that cefuroxime wouldn’t have been a particularly good prophylaxis for these patients based on the organisms present. Further, the antibiotics they recommended as prophylaxis based on their results—and again, these are custom results for their clinic—are old antibiotics.

What they did

Researchers analyzed 1,940 patients for this study. Of the 4,391 microbes that researchers isolated, 94.2% of bacteria were Gram-positive and 5.3% were Gram-negative.

The bacteria isolated were as follows: • Staphylococci (CNS): 88.3% • Diphtheroids: 58.1% • Propionibacteria: 31% • Streptococci: 23.1% • Staphylococcus aureus: 10.2% • Haemophilus plus Gram-negative diplococcic: 7.5% Other Gram-negative rods: 4.5% • Enterococci: 2% “The Enterococci-Staphylococci profile was the most resistant,” reported lead study author Elisa Fernandez-Rubio, Ph.D., clinical analyst, Ophthalmic Institute Laboratory, Department of Ophthalmology, Gregorio Marañón University, General Hospital. Further, it was resistant to erythromycin in 47.4% of cases, methicillin in 42.8%, ciprofloxacin in 23.1%, tetracycline in 18.4%, gentamicin in 15.7%, levofloxacin in 15.1%, tobramycin in 14.8%, chloramphenicol in 3.7%, rifampicin in 1.6%, and fusidic-acid in 0.6%. “We found that no single antibiotic tested here had ‘in vitro’ activity for eradicating the whole conjunctival bacteria of our patients,” Dr. Fernandez-Rubio reported. Antibiotics tested comprised a near A to Z list of ocular antibiotics, from amikacin to vancomycin, although moxifloxacin was not included.

“Staphylococci (the most prevalent conjunctival bacteria) and the conjunctival seasonal bacteria (Streptococci, Haemophilus, Neisseria, and Moraxella) presented a very low ‘in vitro’ resistance to old antibiotics, such as chloramphenicol or rifampicin,” Dr. Fernandez-Rubio reported. “If only one of these two antibiotics were given as cataract surgery prophylaxis, only about 5% of our patients harbouring on their conjunctiva Gram-negative rods, different from Haemophilus, and/or Enterococci would be unprotected from [post-op endophthalmitis].”

Further, Dr. Fernandez-Rubio commented that the clinic’s Gram-negative rods were “quite resistant to cefuroxime.” “Therefore, independently of the antibiotics form of administration used, cefuroxime seems to be a worse choice for our patients’ cataract prophylaxis than for the Swedish patients,” Dr. Fernandez-Rubio reported. “Levofloxacine [sic] would be the best choice for eradicating the whole Gram-negative bacteria and most Enterococci of our patients, but not for eradicating their CNS and Streptococci.”

Based on the clinical findings, Dr. Fernandez-Rubio, suggested a two-phase prophylaxis for cataract surgery: “In the first prophylaxis phase, the most prevalent conjunctival bacteria (Staphylococci and the seasonal bacteria group) could be eradicated with chloramphenicol or rifampicin, administering it preoperatively for 3 days until 1 [hour] before the operation. In the second prophylaxis phase, we suggest giving levofloxacin eye-drops from 1 [hour] before the operation until 6 days afterwards, for eradicating the small quantity of Enterococci and Gram-negative rods, because the visual outcome of the [post-op endophthalmitis] cases caused by these bacteria is the most serious.”

Dr. Fernandez-Rubio noted that antibiotic resistance could vary depending on climate and patient characteristics. Spain is one of the warmest European countries, and climate differs markedly from Sweden, for instance. Notably, CNS methicillin resistance found by these researchers (48.7%) “was rather higher than this resistance that was in Sweden (6.8% in the conjunctival bacteria and 4.5% among the bacteria isolated in their [post-op endophthalmitis] cases after cataract operation),” Dr. Fernandez-Rubio noted. Dr. Fernandez-Rubio did not comment, however, on whether climate had some bearing on this. Although some surgeons might question the usage of older antibiotics, even for the purpose of prophylaxis, the researchers’ analysis of their own patients’ conjunctival bacteria in an effort to better understand their antibiotic resistance patterns and tailor cataract surgery prophylaxis accordingly is unique and worthy of mention. Mark Packer, M.D., clinical associate professor of ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, Ore., seemed skeptical of any sudden upswing in the usage of chloramphenicol based on the results of this study. “It’s generic,” he said. “Who’s going to market that exactly?”

Meanwhile, rifampicin is “thought of as an anti-tuberculosis drug in my experience,” Dr. Packer said. “If someone had unknown pneumonia, that would be something we put the patient on.” Further, he said, although it’s an interesting idea to figure out what comprises a clinic’s typical and not-so-typical conjunctival flora, Dr. Packer said he’s confident in the use of Zymar (gatifloxacin, Allergan, Irvine, Calif.) or Vigamox (moxifloxacin, Alcon, Fort Worth, Texas) prophylactically for most people. Dr. Packer did, however, say that randomly culturing patients that come in for cataract surgery might be reasonable in the wake of a case of endophthalmitis to re-evaluate the efficacy of prophylaxis.

Editors’ note: Dr. Fernandez-Rubio has no financial interests related to this study. Dr. Packer has financial interests with Alcon (Fort Worth, Texas).

Contact information

Fernandez-Rubio: mfernandezr.hgugm@salud.madrid.org
Packer: 541-687-2110, mpacker@finemd.com

Alternative customized prophylaxis? Alternative customized prophylaxis?
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