Trends in Antibiotic Resistance Among Ocular Microorganisms in the United States From 2009 to 2018

Importance

Antibiotic resistance in ocular infections can affect treatment outcomes. Surveillance data on evolving antibacterial susceptibility patterns inform the treatment of such infections.

Objective

To assess overall antibiotic resistance profiles and trends among bacterial isolates from ocular sources collected during 10 years.

Design, Setting, and Participants

This cross-sectional study of longitudinal data from the ongoing, nationwide, prospective, laboratory-based surveillance study, the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) study, included clinically relevant isolates ofStaphylococcus aureus, coagulase-negative staphylococci (CoNS),Streptococcus pneumoniae,Pseudomonas aeruginosa,andHaemophilus influenzaecultured from patients with ocular infections at US centers from January 1, 2009, to December 31, 2018.

Main Outcomes and Measures

Minimum inhibitory concentrations were determined for various combinations of antibiotics and species. Odds ratios (ORs) were determined for concurrent antibiotic resistance; analysis of variance and χ²tests were used to evaluate resistance rates by patient age and geographic region; Cochran-Armitage tests identified changing antibiotic susceptibility trends over time.

Results

A total of 6091 isolates (2189S aureus, 1765 CoNS, 590S pneumoniae, 767P aeruginosa, and 780H influenzae) from 6091 patients were submitted by 88 sites. Overall, 765S aureus(34.9%) and 871 CoNS (49.3%) isolates were methicillin resistant and more likely to be concurrently resistant to macrolides (azithromycin:S aureus: OR, 18.34 [95% CI, 13.64-24.67]; CoNS: OR, 4.59 [95% CI, 3.72-5.66]), fluoroquinolones (ciprofloxacin:S aureus: OR, 22.61 [95% CI, 17.96-28.47]; CoNS: OR, 9.73 [95% CI, 7.63-12.40]), and aminoglycosides (tobramycin:S aureus: OR, 18.29 [95% CI, 13.21-25.32]; CoNS: OR, 6.28 [95% CI, 4.61-8.56]) compared with methicillin-susceptible isolates (P < .001 for all). Multidrug resistance was observed among methicillin-resistantS aureus(577 [75.4%]) and CoNS (642 [73.7%]) isolates. Antibiotic resistance amongS pneumoniaeisolates was highest for azithromycin (214 [36.3%]), whereasP aeruginosaandH influenzaeisolates showed low resistance overall. Differences in antibiotic resistance were found among isolates by patient age (S aureus:F = 28.07,P < .001; CoNS:F = 11.46,P < .001) and geographic region (S aureus:F = 8.03,P < .001; CoNS:F = 4.79,P = .003;S pneumoniae:F = 8.14,P < .001;P aeruginosa:F = 4.32,P = .005). Small changes in antibiotic resistance were noted over time (≤2.5% per year), with decreases in resistance to oxacillin/methicillin (oxacillin: −2.16%; 95% CI, −3.91% to −0.41%;P < .001) and other antibiotics amongS aureusisolates, a decrease in ciprofloxacin resistance among CoNS (−1.38%; 95% CI, −2.24% to −0.52%;P < .001), and an increase in tobramycin resistance among CoNS (0.71%; 95% CI, –0.29% to 1.71%;P = .03). Besifloxacin retained consistently low minimum inhibitory concentrations.

Conclusions and Relevance

Antibiotic resistance may be prevalent among staphylococcal isolates, particularly among older patients. In this study, a few small differences in antibiotic resistance were observed by geographic region or longitudinally.