LOSS OF CAPSULAR POLYSACCHARIDE EXPRESSION IN S. aureus CONTRIBUTES TO BONE DAMAGE DURING OSTEOMYELITIS

DECURGEZ, GISELA; ANA-KATHARINA E. GEHRKE; CINTIA D. GONZALEZ; MARIÁNGELES NOTO LLANA; BARBEITO JIMENA; DANIEL O. SORDELLI; GOMEZ MARISA INES

Puerto Madryn

Congreso; XX Congreso de la Sociedad Argentina de Microbiología General; 2025

SAMIGE

Staphylococcus aureus adapts to the bone environment during osteomyelitis (OM). Although it is recognized that this ability can contribute to bacterial persistence, the impact on the pathogenesis of the disease remains unclear. A higher proportion of isolates lacking capsular polysaccharide (CP) expression are found in chronic vs. acute OM, suggesting CP is downregulated during disease. This study aimed to experimentally determine whether CP expression is lost during OM and assess its impact on disease pathogenesis. We used a murine OM model with intratibial challenge of clinical isolates expressing type 5 CP [(Hu25a, Hu107f (CP+)], a non-typeable isolate [Hu107c (NT)], or a genetically modified strain lacking CP (CP-). Bone colonization and CP expression were evaluated at 48 hours (n=9), 14 days (n=13) and 9 weeks (n=17) after inoculation in the bone matrix (BMX) and bone marrow (BMW).Mice inoculated with Hu25a (CP+) exhibited persistent colonization with a trend to higher bacterial persistence in the BMX: BMX (89% (48h), 69% (14d), 59% (9w)); BMW (83% (48h), 62% (14d), 29% (9w)). By day 14, CFU counts were significantly lower in BMW vs. BMX (p