SEP 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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58 EW CORNEA September 2013 Cornea editor's corner of the world Taking a look at MRSA from around the globe by Vanessa Caceres EyeWorld Contributing Writer Studies in different populations glean clinical implications R eports of methicillin-resistant Staphylococcus aureus (MRSA) infections in the community and in hospital settings are increasing overall in medicine, and ophthalmology is no exception. This is a growing concern as this organism and other bacterial pathogens develop resistance against our limited available armamentarium of antibiotics. MRSA infections may target the cornea, conjunctiva, eyelids, lacrimal system, and orbit, and pose greatest risk should there be any intraocular surgery that allows the organism to enter the eye to cause endophthalmitis. Another worrisome trend seems to be that ophthalmic MRSA patients tend to be younger than other MRSA patients. Data on MRSA infections being on the rise does not only come from the U.S., but also internationally. This month's "Cornea editor's corner of the world" includes discussion of MRSA studies that were performed in California, Taiwan, and Canada. Ching-Hsi Hsiao, MD, Alejandro Lichtinger, MD, and Malena Amato, MD, discuss MRSA trends with respect to ocular infections, antibiotic response, and recommendations for managing these clinical cases. Clara C. Chan, MD, cornea editor I t's well known in medicine, including ophthalmology, that methicillin-resistant Staphylococcus aureus (MRSA) infections are on the rise and increasingly resistant to antibiotics. Yet how do regional or population-based differences play a role in the kind of bacteria seen and treatment response? Here's a summary of MRSA-focused studies from three entirely different settings—Taiwan, Toronto, and a U.S.-based pediatric population. We then share clinical applications to apply from the studies. Tracking ocular MRSA infections in Taiwan There is a high prevalence of MRSA in Taiwan, which was part of the motive behind a 10-year retrospective study led by Ching-Hsi Hsiao, MD, Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou, Taiwan, and published last year in Ophthalmology.1 Investigators examined both community-associated (CA) and healthcare-associated (HA) isolates of ocular infections caused by MRSA to find any trends. All isolates were seen at Chang Gung Memorial Hospital, a large referral center in Taiwan. Over the 10-year study period, there were 274 MRSA ocular infections—181 from CA MRSA and 93 HA MRSA cases. Community-associated MRSA most commonly caused lid disorders, keratitis, conjunctivitis, and lacrimal system disorders. In contrast, HA MRSA most frequently caused keratitis, although the presentation of keratitis decreased over the past five years. The majority of cases from both HA and CA MRSA were resistant to antibiotics such as clindamycin and erythromycin. Community-associated cases were more sensitive to sulfamethoxazole/trimethoprim; both HA and CA MRSA were resistant to penicillin but susceptible to vancomycin and teicoplanin. The investigators noted that the patients in the CA MRSA group were younger and more likely to be female, although they weren't sure if that is significant. MRSA infection after LASIK Source: David Ritterband, MD The investigators said their study is the largest reported case series of ocular MRSA infections. "We urge ophthalmologists to obtain cultures, determine susceptibility in such patients, and choose appropriate empiric therapy based on antimicrobial resistance patterns in their region," the investigators concluded. Analyzing bacterial keratitis in Toronto A Toronto-based study that also was published in Ophthalmology last year reported on bacterial keratitis isolates in the city over an 11-year period.2 Of 1,701 total corneal scrapings, investigators found a pathogen in 977 samples. The most common finding was bacterial keratitis. Although the investigators found a large number of Gram-positive isolates compared with Gram-negative isolates (684 versus 213), they found a decreasing trend in the Gram-positive isolates. "Gram-negative bacteria seem to respond very well to the antibiotics we routinely use, but this is not the case with the Gram-positive bacteria that are still much more common," said lead investigator Alejandro Lichtinger, MD, now with Instituto de Ciencias Oftalmológicas, Hospital Angeles de las Lomas, Huixquilucan, Mexico. MRSA was found in 1.3% of the S. aureus isolates, but methicillin- resistant coagulase-negative Staphylococcus (MRCNS) was found in 43% of CNS isolates. "There is no doubt that MRSA is causing more infections around the world," Dr. Lichtinger said. "From our study and the work of others, we found that MRSA and MRCNS are becoming more common in ophthalmology and as an etiologic agent in bacterial keratitis." There was increasing resistance to methicillin, from 28% during the study's first four years to nearly 39% in the study's final three-year period. The MRSA and MRCNS isolates were resistant to cefazolin, but all isolates were sensitive to vancomycin. Resistance to other antibiotics varied. "Getting proper smears for stains and cultures is extremely important as it can guide us down the road if things get complicated and help us target our antibiotics according to the sensitivities and rule out fungal or other type of infections," Dr. Lichtinger said. Examining ocular MRSA infections in children A California-based study published in the June issue of the Journal of the American Association for Pediatric Ophthalmology and Strabismus tracked trends in ophthalmic MRSA in children. Like the other studies profiled here, it was a retrospective review

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