Antibiotic Resistance High in Ocular Isolates Study

A surveillance study conducted at multiple centers across the United States in 2020 found a high level of antibiotic resistance among ocular isolates from infected eyes. These findings were presented during Academy 2021 presented by the American Academy of Optometry held in Boston November 3-6, 2021.

Resistance to antibiotics is an ongoing concern across many branches of medicine, including optometry. Despite the prevalence of resistant organisms, culturing and testing for resistance in eyes with ocular infections is not routine practice. Instead, treatment decisions are often chosen based on empirical knowledge.

The prospective, multicenter study, ARMOR, is the only surveillance study of antibiotic resistance among common ocular bacterial pathogens. Participating centers (N=25) located in 17 states collected ocular isolates of Haemophilus (H) influenzae, coagulase-negative staphylococci (CoNS), Staphylococcus (S) aureus, Streptococcus (S) pneumoniae, and Pseudomonas (P) aeruginosa. These samples underwent in vitro susceptibility testing at an independent, central laboratory. Bacteria were classified as resistant, susceptible, or intermediate as defined by the Clinical and Laboratory Standards Institute methodology.

A total of 598 isolates were collected in 2020, in which resistance was observed among 233 CoNS, 216 S aureus, 110 P aeruginosa, 23 S pneumoniae, and 16 H influenzae samples.

CoNS and S aureus had the greatest resistance to azithromycin (59% and 57%) followed by oxacillin (43% and 33%) and ciprofloxacin (25% and 32%), respectively. In addition, 29% of CoNS were resistant to trimethoprim.

Multidrug resistance to ≥3 drug classes was observed among 40% of CoNS and 33% of S aureus isolates. For strains with methicillin resistance, 76% of CoNS and 73% S aureus were multidrug resistant.

For P aeruginosa, all samples were resistant to polymyxin B and ≤5% resistant to other drugs.

The S pneumoniae isolates were resistant to tetracycline (43%), oral penicillin (35%), and azithromycin (23%).

No resistance was observed among the H influenzae isolates.

These findings indicated that antibiotic resistance was relatively common among ocular infection causative organisms. Multidrug resistance was particularly high among methicillin-resistant CoNS and S aureus. These findings should be taken into consideration when making empiric-based decision-making for patients who present with an ocular infection.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Sanfilippo C, DeCory H, Asbell P. 2020 results from the antibiotic resistance monitoring in ocular microorganisms (ARMOR) surveillance study. Poster presented at: American Academy of Optometry 2021;November 3-6, 2021; Boston. Board #23.