Abstract
Purpose :
Antibiotic resistance among pathogenic bacteria can hinder treatment of infections. Data from antibiotic resistance surveillance studies can provide clinicians with information to guide empiric therapy. The annual Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study is the only ongoing nationwide surveillance initiative focused exclusively on antibiotic resistance among common ocular pathogens. Here, we report on interim findings for bacterial isolates collected in 2021.
Methods :
As in prior years of the ARMOR study, participating clinical sites across the US submitted isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae cultured from ocular infections to a central laboratory for species confirmation and in vitro antibiotic susceptibility testing. Minimum inhibitory concentrations (MICs) for up to 16 antibiotics (10 drug classes) were determined using broth microdilution methodology and interpreted as per Clinical and Laboratory Standards Institute (CSLI) guidelines and breakpoints.
Results :
A total of 446 isolates were included in this interim analysis. Among staphylococci (167 S. aureus/178 CoNS), in vitro resistance was 53%/60% to azithromycin, 37%/37% to oxacillin/methicillin, and 31%/20% to ciprofloxacin; as well, 29% of CoNS exhibited trimethoprim resistance. Multidrug resistance (MDR; ≥3 antibiotic classes) was found among 32% of S. aureus (32%) and 40% of CoNS isolates (40%), with the rate of MDR more than doubled among methicillin-resistant (MR) isolates (81% and 84% among MR S. aureus [MRSA] and MRCoNS, respectively). All 84 P. aeruginosa isolates were resistant to polymyxin B, with <10% resistance to other drug classes. Among the 7 S. pneumoniae isolates, resistance to azithromycin and oral penicillin (both 43%) as well as tetracycline (29%) was detected. The 10 H. influenzae isolates exhibited no resistance to tested drugs.
Conclusions :
High rates of in vitro antibiotic resistance were observed among ocular staphylococci collected in 2021, with MR isolates demonstrating considerable MDR. Overall, these resistance profiles should be considered in combination with known ocular pharmacokinetic attributes of antibiotics. These preliminary findings appear consistent with 2020 ARMOR data.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.