Abstract
Purpose :
Staphylococci are known causative pathogens in ophthalmic infections, and antibiotic resistance among these bacteria is of clinical concern. The Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study is a nationwide surveillance study on in vitro antibacterial resistance levels among ocular pathogens now in its 14th year. Here, we examined resistance trends over time among staphylococcal isolates collected from 2009 through 2022 to date in ARMOR.
Methods :
As in prior years, participating US clinical sites submitted isolates of Staphylococcus aureus and coagulase-negative staphylococci (CoNS) from ocular infections as part of ARMOR. Isolates were sent to a central laboratory for species confirmation, and minimum inhibitory concentrations (MICs) were determined and interpreted for up to 16 different antibiotics based on Clinical and Laboratory Standards Institute methods and breakpoints. Cochran-Armitage tests for linear trends in a proportion were used to evaluate longitudinal trends in resistance.
Results :
A total of 2999 S. aureus and 2575 CoNS were included in this analysis, and several small but significant trends were noted (all P<0.001). In vitro resistance decreased to methicillin/oxacillin (S. aureus, 39% in 2009 to 18% in 2022; CoNS, 50% in 2009 to 37% in 2022), and to ciprofloxacin (S. aureus, 39% in 2009 to 17% in 2022; CoNS, 46% in 2009 to 20% in 2022). Additionally, among S. aureus, resistance to azithromycin decreased (62% in 2009 to 46% and 9% in 2022), as did resistance to tobramycin (24% in 2009 to 9% in 2022), while in contrast an increase in chloramphenicol resistance was observed (7% in 2009 to 3% in 2022, peaking at 30% in 2021). Cumulative multidrug resistance (MDR; ≥3 antibiotic classes) was observed in 30% of S. aureus and 41% of CoNS, and in 76% and 79% of methicillin-resistant isolates thereof, respectively.
Conclusions :
In this longitudinal analysis of staphylococci collected in ARMOR, in vitro resistance has remained prevalent, despite trends of decreasing resistance for several antibiotics. Overall, MDR was common, especially among methicillin-resistant strains. These resistance data, in combination with known ocular pharmacokinetics of antibiotics, should be considered when selecting empiric treatment for staphylococcal eye infections.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.