738. Spatiotemporal Patterns of Antimicrobial Resistance of Outpatient Staphylococcus aureus Isolates in the United States, 2010-2019

Abstract Background Oral non-beta-lactam antibiotics are commonly used for empiric therapy of Staphylococcus aureus infections, especially in outpatient settings. However, little is known about geographic heterogeneity in the prevalence and temporal trends of antibiotic resistance among different regions in the US. We aimed to characterize the spatiotemporal patterns of drug-resistance prevalence of S. aureus using the nationwide surveillance data from the Veterans Health Administration (VHA) system. Methods Utilizing a dataset of 383,514 S. aureus isolates obtained in outpatient settings in the VHA from 2010-2019, we explored the spatiotemporal variation of S aureus resistance to clindamycin, tetracyclines, trimethoprim-sulfamethoxazole, and macrolides, stratified by methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA), and subdivided by regions of the United States (Northeast, Midwest, South, and West). Results Over the ten-year study period there was a national decrease in the proportion of S. aureus isolates which were MRSA, from 54% to 39% (Figure 1). Amongst MRSA isolates (Figure 2, panels A-D), we observed stability of clindamycin resistance (from 24.5% to 31.1%), an increase in tetracycline resistance (from 3.9% to 13.1%), an increase in trimethoprim-sulfamethoxazole resistance (from 2.7% to 9.3%), and a decrease in macrolide resistance (from 72% to 60%). For MSSA (Figure 2, panels E-H), we observed relative stability of resistance over time for all four drug classes. Regional analysis (Figure 3) demonstrated that the Northeastern US had slightly higher rates of clindamycin resistance than other regions but lower rates of tetracycline resistance, while the South had notably higher rates of trimethoprim-sulfamethoxazole resistance than other regions, particularly amongst MRSA isolates. Figure 1 Frequency of S. aureus isolates by year (A), proportion of S. aureus isolates resistant to methicillin (B), and proportion of S. aureus isolates resistant to methicillin by region (C) Figure 2 Proportion of S aureus isolates resistant to Clindamycin, Tetracyclines, Trimethoprim-Sulfamethoxazole, and Macrolides, stratified by MRSA (panels A-D) and MSSA (panels E-H) Figure 3 Proportion of S aureus isolates resistant to Clindamycin, Tetracyclines, Trimethoprim-Sulfamethoxazole, and Macrolides, stratified by MRSA (panels A-D) and MSSA (panels E-H), subdivided by region Conclusion Even though the prevalence of MRSA is decreasing nationally, there are variable levels of co-resistance to non-beta-lactam antibiotics amongst S. aureus isolates. There was some regional variability in co-resistance amongst MRSA isolates, but less so for MSSA isolates. Further studies are needed to better understand which biological mechanisms mediate these differences. Disclosures Michihiko Goto, MD MSCI, Merck & Co.: Grant/Research Support