Bone cultures in diabetic foot infection is the most accurate method to identify causative pathogen, while there is only 30% concordance between superficial wound swab and bone biopsy cultures. Diabetic foot infection is commonly polymicrobial, therefore report on the bone biopsy culture may come with several updates before it is finalized. Our study is aimed to describe how often additional pathogens were identified after patients’ discharge on antibiotics therapy for diabetic foot osteomyelitis, and evaluate microbiological appropriateness of antibiotic regimen upon discharge based on the final result of the bone culture.
Medical records of the patients 18 year-old or older, who had inpatient bone biopsy, deep tissue debridement or amputation for diabetic foot infection, were reviewed from Jan 2014 through Dec 2015 in Rochester Regional Health System. Antibiotic regimens for the patients discharged before final culture result were evaluated for microbiological appropriateness by two reviewers trained in infectious diseases.
A total of 198 procedures were screened, 158 procedures met inclusion criteria, out of which 74 patients with 80 procedures (51%) were discharged before the final culture result was available. Average time from procedure to the final culture report was 6 days, and from discharge to the final culture was 3.7 days. In most of the cases (70%, 56 out of 80) the patients were discharged on empiric regimen discordant with final culture result. Predominant organisms were Gram positive bacteria 74%, with Gram negatives 24%, and yeast 2%. Most infections were polymicrobial (81%), mixed with anaerobic bacteria in 37%. The most frequent isolates were Staphylococcus aureus (15%), Corynebacterium (14%), anaerobic Gram positive cocci (12%) and Staphylococcus epidermidis (8%). All negative Gram stains (31%, 25 out of 80) had positive growth on culture.
Half of the patients with diabetic foot osteomyelitis, who underwent bone biopsy, were discharged before final culture results were available. Most of them were discharged on empiric regimen discordant with final culture. This data suggests that careful outpatient follow up on the final culture would likely result in modification of antibiotics therapy to target newly reported pathogen.
H. K. Kim,