Bone Biopsy Microbiology Does Not Explain Clinical Severity in Diabetic Foot Osteomyelitis.

Diabetic foot osteomyelitis is the most frequent infection in diabetes-related foot ulcers, often associated with delayed healing, prolonged hospitalization, and increased risk of amputation. The contribution of microbiological factors to its clinical severity remains uncertain. While severe cases are often associated with soft tissue complications such as abscesses or necrotizing infections, it is unclear whether the bacterial profile influences infection severity. This study aimed to determine whether severe presentations are associated with a higher frequency of polymicrobial infections, multidrug-resistant organisms, or specific bacterial species. We conducted a secondary analysis of a prospective cohort of patients with moderate or severe diabetic foot infections confirmed to involve osteomyelitis through histopathological evaluation. Bacterial species isolated from bone biopsy cultures were compared between moderate and severe cases. Among 114 patients included, 73 were classified as moderate and 41 as severe. Bone cultures were positive in 101 cases, yielding 173 isolates. Staphylococcus aureus was the most frequently isolated species, followed by Enterococcus faecalis and Streptococcus agalactiae. No significant differences were found between severity groups in the distribution of individual species, polymicrobial cultures (46.6% in moderate vs 56.1% in severe; p = 0.435), or multidrug-resistant organisms (12.3% vs 12.2%; p = 1.000). A global comparison of species distribution also showed no statistical association with severity (p = 0.941). These findings suggest that severity is not explained by the microbiological profile identified through conventional aerobic cultures. Instead, host-related or anatomical factors may be more relevant, although the lack of anaerobic cultures may have underestimated microbial diversity.