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Methicillin-resistant ocular infections of increasing concern
MRSA cases in hospital settings are known to be common, but community-acquired infections are also on the rise.
The rate of methicillin-resistant Staphylococcus aureus eye infections appears to be increasing, experts say, and surgeons are encountering more cases, particularly after refractive and cataract surgeries.
 Eric D. Donnenfeld |
“MRSA and MRSE (methicillin-resistant Staphylococcus epidermis) are the No. 1 infectious disease concerns for ophthalmology for the foreseeable future, and the problem will only get worse over the next couple of years,” OSN Cornea/External Disease Section Editor Eric D. Donnenfeld, MD, told Ocular Surgery News in a telephone interview. “It’s something that every clinician needs to be aware of and needs to be ready to treat because we will all be seeing methicillin-resistant infections in the near future.”
With awareness and vigilance, however, Francis S. Mah, MD, said clinicians can stay on top of these infections.
“I do think that it is something you do have to be aware of and be conscientious about, but it isn’t something that’s going to be overwhelming,” he said.
“Most of the infections are not more virulent than conventional infections,” Dr. Donnenfeld said. In a study published in the American Journal of Ophthalmology of 13 MRSA cases after refractive surgery, Dr. Donnenfeld and colleagues cited decreased vision and pain or irritation as the primary symptoms. They also noted that corneal epithelial defects, focal infiltrates, edema, conjunctival infection, purulent discharge and hypopyon were seen in eyes with MRSA infections upon slit-lamp biomicroscopic examination.
“[These infections] present the same way endophthalmitis usually presents or a LASIK infection presents,” Dr. Donnenfeld said. “The difference is that they do not always respond to conventional antibiotics.”
Associated diagnoses, procedures
According to Dr. Donnenfeld, MRSA and MRSE are “the most common cause of infections following all forms of anterior segment surgery,” including cataract surgery, LASIK and PRK.
In the study by Dr. Donnenfeld and colleagues, eight patients had underdone LASIK, one had undergone a LASIK enhancement and two had undergone PRK.
Dr. Mah said that MRSA isolates are being found specifically in cases of blepharitis, conjunctivitis, keratitis and endophthalmitis.
In a study published in the American Journal of Ophthalmology, Julie Freidlin, MD, and colleagues found that 88 of 915 S. aureus isolates registered in the clinical laboratory database at the F.I. Proctor Foundation in San Francisco between July 1998 and July 2006 were methicillin resistant. Of the 41 patients with these 88 isolates, 78% had blepharoconjunctivitis, 14.6% had keratitis, 2.4% had cellulitis, 2.4% had dacryocystitis and 2.4% had endophthalmitis.
Uday Devgan, MD, FACS, predicted that the two biggest areas of concern moving forward will be keratitis development after LASIK and endophthalmitis development after intraocular surgery, including cataract surgery and refractive lens exchange.
“For me, the huge worry is endophthalmitis, given the volume of intraocular surgery that we do, and the endophthalmitis can be really visually devastating,” he said. “It can progress very, very quickly, especially with a virulent organism like MRSA, and you can end up with permanent, extreme vision loss.”
Possible explanations
“There are a variety of reasons why methicillin resistance is increasing,” Dr. Donnenfeld said.
Both Dr. Donnenfeld and Dr. Devgan noted that physicians are prescribing increasing numbers of antibiotics for patients.
“Ophthalmologists are only a small part of the problem because the use of topical antibiotics has minimal impact on resistance compared to the use of systemic antibiotics,” Dr. Donnenfeld said.
As a result, “the bacteria are getting more and more evolved, and so they’re becoming resistant to more and more of our treatments,” Dr. Devgan said.
“Probably far and away the most significant problem is the use of antibiotics in poultry,” Dr. Donnenfeld said. He explained that farm animals such as chickens and cows are given antibiotics before they are slaughtered. The antibiotics in the poultry and beef are then eaten by consumers and contribute to the number of resistant strains of bacteria.
In terms of drugs widely prescribed for patients, Dr. Mah pointed specifically to fluoroquinolones.
“Fluoroquinolones, which have really dominated empiric therapy and therapy of ocular infection … really do a fantastic job against gram-negative bacteria,” he said.
“If there’s going to be an Achilles’ heel for fluoroquinolones, it’s going to be the methicillin-resistant Staph aureus,” he said.
Dr. Mah also noted that a perceived increase in the incidence of MRSA may result because clinicians previously did not see cases like this.
“It might be just a bias as far as we’re doing such a great job with the other bacteria, such as Pseudomonas, that what’s left uncovered is the Staph aureus, so maybe the actual case numbers are not increasing, but the percentages of Staph aureus infections are increasing,” he said.
Nosocomial vs. community-acquired
In their study, Dr. Donnenfeld and colleagues found that nine of the patients worked in health care settings or had been exposed to a health care setting.
“It’s a much more significant problem in patients who work in hospital environments,” he said.
“The incidence of MRSA, just as a normal flora in these patients, is extremely high,” Dr. Devgan said.
Of the Staph aureus found in nosocomial infections, approximately two-thirds are methicillin-resistant, Dr. Mah said.
“The organisms that are hospital-based may be a little more virulent just because in the hospital there’s such an incredible number of sick patients who are getting such strong regimens of various antibiotics,” Dr. Devgan said. “The hospitals almost breed these very virulent, multi-drug resistant forms.”
“On the other hand, methicillin-resistant staph is also becoming common in the general population,” Dr. Donnenfeld said.
For those not working in health care settings, Dr. Mah said MRSA prevention methods are basic. Postoperative patients should make sure to follow up with their clinicians by reporting any unexpected ocular symptoms.
“Community-acquired [MRSA] tends not to be quite as virulent and not quite as resistant, but they do not respond as well to conventional antibiotics, so we need to be aware that there are these infections out there,” Dr. Donnenfeld said. “We need to be ready to culture to make certain we have the right diagnosis, and we need to be able to treat with antibiotics that are effective against methicillin resistance.”
Preoperative measures
Dr. Donnenfeld and Dr. Mah recommended aggressively treating any infection present before ocular surgeries.
“The etiology of the organisms that cause endophthalmitis and LASIK and PRK infections overwhelmingly come from the patient’s own endogenous lid flora,” Dr. Donnenfeld said. “When I see a patient who has blepharitis preoperatively, I aggressively treat the blepharitis to reduce the risk of contamination and reduce the bacterial load in the eyelid.”
He specifically recommended hot compresses and the use of lid scrubs such as SteriLid (Advanced Vision Research).
In known MRSA carriers, Dr. Mah recommended prescribing a bacitracin ointment, sulfa drops or an oral agent such as Zyvox (linezolid, Pfizer).
“I would say the No. 1 thing [for patients] is just take the medications the way the doctors prescribe them,” Dr. Donnenfeld said.
Dr. Devgan said that an effective presurgical preparation with povidone-iodine is essential. The conjunctiva, conjunctival cul-de-sac, eyelid and eyelid margin should all be addressed, he said.
He also pointed to the need for appropriate draping.
“There shouldn’t be any eyelashes or lid margin accessible to your surgical field when you’re doing the surgery,” he said.
As for patients exposed to health care settings, Dr. Mah said additional steps are warranted.
“Their surgeons [can] take extra precautions against MRSA by either adding a prophylactic agent, which has known efficacy for MRSA or doing an extra lid prep, or using a day or so of antibiotics that are going to be more effective against methicillin-resistant Staph aureus,” he said.
Dr. Devgan also recommended using a lid sterilizer and adding an additional antibiotic such as Polytrim (polymyxin B-trimethoprim, Allergan) before surgery in health care workers.
“I also recommend treating lid margin and meibomian gland disease with AzaSite (azithromycin, Inspire) prior to any surgical procedure, and this also can have a beneficial effect of reducing the ocular flora exposure,” he said.
“It may seem like overkill, but if you can prevent one patient from losing vision from endophthalmitis, I think it was all worth it,” he said.
Action after surgery
After surgery, fourth-generation fluoroquinolones can be effective against confirmed MRSA infections; however, some MRSA strains have developed resistance to these drugs, the experts said.
“Gatifloxacin (Zymar, Allergan) and moxifloxacin (Vigamox, Alcon) are probably some of the best anti-infectives that are commerically available, however against MRSA, their coverage is … probably 70% or 80%, which is good but less than even a couple years ago” Dr. Mah said.
“They won’t treat all methicillin resistance, and we have to be aware of that and be able to culture and treat with other antibiotics,” Dr. Donnenfeld said.
“The most common and probably the best acknowledged antibiotic for treating methicillin-resistant organisms is now vancomycin,” he said. “Because methicillin resistance is becoming so common, I routinely treat all of my LASIK and PRK infections with vancomycin on initial presentation while we’re waiting for culture reports to return.”
Dr. Mah, however, warned that drugs such as gentamicin, sulfacetamide, bacitracin and vancomycin can be highly toxic and tend to have less penetration into the cornea and anterior chamber than the fourth-generation fluoroquinolones. As a compromise, he recommended combining one of these drugs with a fourth-generation fluoroquinolone when there is a concern for MRSA in an infection.
In patients who develop MRSA who were not previously at risk, Dr. Mah recommended immediate aggressive treatment with sulfacetamide, vancomycin or bacitracin in addition to a fourth-generation fluoroquinolone.
“You use your big guns, and then you can always back down once you’ve gotten the infection under control,” he said.
“These are all just suggestions,” Dr. Mah said. “There are no written rules.”
The keys, he said, are that patients be aware of the risk of infection and that they take every possible measure to help prevent infection.
For more information:
- Uday Devgan, MD, FACS, can be reached at the Maloney Vision Institute, 19021 Wilshire Blvd. #900, Los Angeles, CA 90024; 310-208-3937; fax: 310-208-0169; e-mail: devgan@ucla.edu. Dr. Devgan is a consultant to Allergan and Inspire.
- Eric D. Donnenfeld, MD, can be reached at OCLI, 2000 North Village Ave., Rockville Centre, NY 11570; 516-766-2519; fax: 516-766-3714; e-mail: eddoph@aol.com. Dr. Donnenfeld consults for Advanced Vision Research, Allergan, Alcon, Bausch & Lomb, InSite and Inspire.
- Francis S. Mah, MD, can be reached at University of Pittsburgh Medical Center, Eye and Ear Institute, 203 Lothrop St., 8th Floor, Pittsburgh, PA 15213; 412-647-2200; fax: 412-647-5119; e-mail: mahfs@upmc.edu. Dr. Mah is a consultant for Alcon, Allergan, InSite and InSpire.
References:
- Freidlin J, Acharya N, Lietman TM. Spectrum of eye disease caused by methicillin-resistant Staphylococcus aureus. Am J Ophthalmol. 2007;144:313-315.
- Solomon R, Donnenfeld ED, Perry HD. Methicillin-resistant Staphylococcus aureus infectious keratitis following refractive surgery. Am J Ophthalmol. 2007;143:629-634.
- Jessica Loughery is an OSN Staff Writer who covers all aspects of ophthalmology.