Streptococcus agalactiae is a predominant cause of prosthetic joint infections in adults with specific risk factors.

This retrospective cohort study examined 1,454 adults within the CRIOAc registry across six university hospitals in the West Region. The analysis focused on Streptococcus agalactiae infections compared to other streptococcal species, aiming to identify risk factors for bone and joint infections (BJIs). The study population included cases of prosthetic joint infections (PJIs), diabetic foot osteitis, and other infection types.

S. agalactiae was the predominant species among streptococcal BJIs, accounting for 423 of 1,454 cases (29%). The cohort had a high prevalence of comorbidities, with obesity affecting 378 patients (26%) and diabetes mellitus affecting 343 patients (24%). Prosthetic joint infections were observed in 653 cases (45%).

Specific associations were identified through logistic regression analysis. Arteriopathy was identified as a specific risk factor with an odds ratio of 4.16 (95% CI: 1.64-11.24, p=0.003). Obesity was also identified as a specific risk factor with an odds ratio of 2.57 (95% CI: 1.41-4.78, p=0.002).

Regarding infection characteristics, diabetic foot osteitis was significantly more associated with S. agalactiae infections (11% versus 7%, p=0.05). Lower-limb infections and chronic infections were more frequently observed in S. agalactiae cases (57% versus 49%, p=0.04). Polymicrobial infection was slightly more frequent (56% versus 48%, p=0.1). Results remained consistent in a sensitivity analysis excluding diabetic foot-related osteitis. No safety data or adverse events were reported.

The study acknowledges that data on S. agalactiae infections remain scarce. Because this is an observational study, the identified factors represent associations rather than proven causation. These results highlight S. agalactiae as a prominent and distinct pathogen in complex streptococcal BJIs, particularly in patients with arteriopathy or obesity.