The pathogens that cause common eye infections now show alarming levels of antibiotic resistance and, in some cases, multidrug resistance, according to a recent study published in JAMA Ophthalmology.
Researchers conducted their antibiotic resistance surveillance study at an independent central laboratory, using more than 3,200 ocular isolates submitted by 72 clinical centers across 36 states. The isolates — which were collected from January 2009 through December 2013 — were infected with the most common pathogens known to cause eye infections, including Staphylococcus aureus.
The study revealed:
1. Nearly half of the S. aureus-infected samples were resistant to methicillin, as were the samples containing a related bacteria called coagulase-negative staphylococci.
2. Together, S. aureus (1,169 samples) and CoNS bacteria (99 samples) made up roughly two-thirds of the total samples collected.
3. Approximately one-third of the S. aureus and CoNS samples were resistant against antibiotics fluoroquinolones, aminoglycosides and macrolides. All staphylococcal isolates were susceptible, however, to vancomycin.
4. Staphylococcal isolates from elderly patients were more likely to be resistant to methicillin than younger patients, as were S. aureus isolates collected from the southern U.S.
5. Although the levels of resistance were higher than the researchers hoped, they did find the levels of methicillin resistance did not increase during the five-year study period.
The fact that the trend in resistance remained flat over the five-year study is a good sign, but "resistance remains high for S. aureus and CoNS isolates, with many strains demonstrating multidrug resistance consistent with reports for nonocular staphylococcal isolates in the literature," concluded the study authors. "Until rapid diagnostic methods are available to guide treatment choices, clinicians should consider these data to guide the empirical treatment of ocular infections."
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