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Speaker: Incidence of atypical organisms increasing
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NEW ORLEANS — The incidence of atypical organisms is on the rise, and the organisms are likely to appear in ophthalmologists’ offices, Kristin M. Hammersmith, MD, said here at Cornea Subspecialty Day preceding the American Academy of Ophthalmology meeting.
Hammersmith referred to Acanthamoeba keratitis as a “particularly pesky” organism. There was a marked increase in incidence starting in 2004 and peaking in 2007 with the outbreak related to Complete MoisturePlus (Abbott Medical Optics), she said.
The incidence of fungal keratitis also began increasing in 2004, peaking with the outbreak linked to Renu with MoistureLoc (Bausch + Lomb).
Kristin M. Hammersmith
Infection related to both of these organisms has since decreased, but the number of other types of filamentous fungal cases has increased, she said, including atypical Mycobacteria, Nocardia and Microsporidia.
“When we treat these patients, we often go into automatic pilot,” Hammersmith said. “However, the clinician should look for signs that we may be headed for a different infection.”
Hammersmith used the example of a contact lens wearer who appears to have herpes simplex.
“Acanthamoeba keratitis (AK) is misdiagnosed as herpes in three-fourths of our patients,” she said. “What’s different is they have more inflammation, more pain than you would expect with herpes, and the biggest difference is they just don’t get better with regular herpes therapy. Epithelial keratitis gets better quickly. Think about AK in these patients and any patient who is a contact lens wearer with nonspecific keratitis. It’s easy to diagnose, but harder to cure.”
Hammersmith also advised caution in cases in which the borders are irregular or feathery.
“Fungal keratitis is more commonly seen in more temperate climates and in response to ocular trauma,” she said. “Patients have multifocal infiltrates, satellite lesions and a dry leather appearance. If they have pigment, it’s helpful, but that’s uncommon. They can often be deep into the cornea.
“These patients can have a lot of inflammation and diplopia,” she continued, “but they don’t have external inflammation and not a lot of hyperemia.”
Hammersmith noted that just because a patient gets better with antibiotics does not mean it is a bacterial infection.
“There are several case reports of an antifungal effect of antibiotics, specifically fluoroquinolones,” she said. “If you don’t have a culture, you don’t know the organisms.
“In our postop patients, be suspicious for atypical Mycobacteria,” Hammersmith continued.
She recommended culturing when in doubt, referring if the patient is not responding to therapy and avoiding the temptation to start a steroid if there is uncertainty.
Disclosure: Hammersmith has no relevant financial disclosures.