Microbial profile of diabetic foot osteomyelitis from the northwest of England.

Background: Osteomyelitis of the diabetic foot is a common and challenging complication affecting patients with diabetic foot ulcers and infections. The complexity of these infections lies in their polymicrobial nature, high rates of persistence and recurrence. This study examined the microbiological profile of diabetic foot osteomyelitis from a teaching hospital in Northwest England and their resistance patterns to understand its impact on infection persistence and to direct effective treatment.

Methods: A retrospective review of 105 patients who underwent surgical management for diabetic foot osteomyelitis between 2019 and 2024. We analysed three consecutive culture samples for each patient to assess for the microbiological profile and resistance patterns of these infections and to monitor infection recurrence and persistence rates.

Results: A total of 105 patients were identified. Infection eradication was noted in 42% of the cohort, infection persistence in 18%, and late infection recurrence in 40%. Polymicrobial growth was evident in 72% of our study sample. Gram-positive bacteria made up the majority of the bacterial isolates in all 3 culture samples, 74.81% in sample 1, 69.31% in sample 2, and 55.1% in sample 3. Staphylococcus aureus was the most prevalent gram-positive bacteria, at 52.38% in sample 1, 36.19% in sample 2, and 18.09% in sample 3, followed by Haemolytic Streptococcus, Enterococcus and Corynebacterium. The frequently identified gram-negative bacteria were Pseudomonas in sample 1 (7.61%), E. coli and Proteus in sample 2 (5,71%), Pseudomonas and Proteus in sample 3 (2.85%). Gram-positive bacteria were resistant to penicillin and macrolides with resistance of staphylococcus aureus to clarithromycin identified among all 3 culture samples. Gram-negative bacteria were most resistant to amoxicillin. Staphylococcus aureus was responsible for infection persistence in most of our cohort (12/19) 63.15%. Among those patients, Staphylococcus was resistant to clarithromycin in 6 of the cases. The 5-year mortality rate for our study sample was 32.38%.

Conclusion: This study highlights the prevalence of polymicrobial growth and multi-drug resistant pathogens in the scope of diabetic foot osteomyelitis. It highlights the predominance of Staphylococcus aureus and its resistant strains among patients affected by diabetic foot osteomyelitis in Greater Manchester.