1319. Evolution of Invasive and Colonizing Pediatric Staphylococcus aureus Isolates

Abstract

Abstract Background Staphylococcus aureus is the most common invasive bacterial pathogen in children. The constant evolution of S. aureus is a barrier to the development of successful interventions. A detailed understanding of the current molecular epidemiology of actively circulating, invasive S. aureus strains and a comparison to both colonization strains and historical invasive strains to determine which virulence factors and genetic lineages are preserved over time are important unmet needs in this field. Methods We compared four groups of S. aureus isolates: 45 invasive strains obtained during the epidemic methicillin-resistance S. aureus (MRSA) peak (2010-2012); 74 invasive contemporary strains (2015-2021); 61 colonizing strains from 2004; and 30 colonizing strains from 2021. Genetic relatedness (via clonal complex typing) and virulence factor presence were determined via whole genome sequencing. Results Among invasive isolates, the prevalence of clonal complex 8 (CC8) decreased significantly over time from 87% to 46% among typeable strains (p< 0.05, Fig.1). Similarly, the presence of Panton-Valentine leucocidin (PVL) decreased from 71% to 40% (p< 0.01). 56% of invasive isolates from 2010-2012 were MRSA, vs 37% from 2015-2021 (p= 0.05, Fig. 2). In contrast to PVL, the presence of leukocidins LukED and LukAB remained stably prevalent over time at 84% and 100% (Fig. 3). Colonization isolates overall remained diverse, with no dominant clonal complex (Fig. 1). Figure 1Figure 2Figure 3 Conclusion Invasive S. aureus molecular epidemiology has changed significantly over the past decade. The former dominance of CC8 and PVL-positive MRSA strains has shifted to a more diverse, predominantly MSSA group of contemporary strains. Other virulence factors (LukED, LukAB) have remained prevalent among invasive strains regardless of genetic lineage. Targets of intervention should be those that are preserved throughout the evolution of this major human pathogen. Disclosures All Authors: No reported disclosures.