2602. Genetic Basis of Staphylococcus aureus Virulence

Background Although multiple different virulence factors have been identified for Staphylococcus aureus, there is limited information on genetic variation present between different strains of S. aureus in the clinical setting. To better define whether differing virulence factors could contribute to differing clinical manifestations of S. aureus infections we undertook a comparison of the frequency of virulence and antibiotic resistance genes present in S. aureus isolates from different clinical sites. Methods Whole-genome sequencing was performed on a convenience sample of S. aureus isolates from clinical or surveillance cultures obtained at an academic medical center over a 27-month period. Genomic assemblies were generated and annotated to define protein-coding regions. The prevalence of 28 genes previously defined as being associated with S. aureus virulence or antimicrobial resistance, including MSCRAMM genes, was then analyzed in relation to nine specific culture sources including only a single isolate from each culture source per patient using a likelihood ratio χ 2 analysis. Results There were 1286 S. aureus isolates with draft assemblies and annotations, and there was a statistically significant (P < 0.01) difference in gene frequencies between culture sources for 18 genes that included 13 of 19 virulence factors, 4 of 7 antibiotic resistance genes and 1 of 2 MSCRAMM genes. The most notable variation was seen for the presence of the sec, sep, entB, lukS, lufK, fosB, mecA, and ermA genes (all with P < 0.0001). There were also significant variations in overall gene frequency patterns between isolates from wound, blood, and respiratory isolates (P < 0.0001), as well as significant differences in the frequency of cna and hlY genes between surveillance and clinical isolates (P < 0.0001). Conclusion This study demonstrates a difference in the prevalence of virulence and antibiotic resistance genes in S. aureus isolates based on the culture source. As the culture location can be considered a surrogate for different types of infections (such as bacteremia, pneumonia, urinary tract infections) these differences in gene frequency may contribute to variation in the clinical manifestations of infections by differing S. aureus strains. Disclosures All authors: No reported disclosures.