Bacterial diversity and inflammatory response at first-time visit in younger and older individuals with diabetic foot infection (DFI)

Aim Infection of a diabetic foot ulcer (DFU) is common. More than the half of DFUs become infected and 15-20% of them necessitate amputation in course of treatment. Diabetic foot infection (DFI) is therefore the major cause for non-traumatic lower limb amputation in Germany. Prompt and effective treatment of DFI is mandatory to safe limbs and lives. We investigated if there are relevant differences in evoked inflammatory response between different species and age-separated groups. We further investigated if there is an impact of ulcer localization on bacterial diversity. Methods For a 12-month period, we investigated 353 individuals with infected DFU, their laboratory results and bacterial diversity at first-time visit in a Diabetic Foot Care Center in Southern Germany. Results The ulcer microbiota was dominated by gram-positive species, primaryStaphylococcus aureus. The gram-negative sector was mainly formed byPseudomonas aeruginosaandEnterobacteriaceae(Proteus spp., Enterobacter spp.,Escherichia coliand Klebsiella spp.). With increase in age,P. aeruginosaandS. aureusbecame more frequent, whileStreptococcidecreased. Ischemic and/or deep wounds were more likely to bear gram-negative species. Inflammatory response did not differ between gram-positive and gram-negative species, whileStreptococciand Proteus spp. induced the highest serum inflammation reaction in their category.Streptococci, Enterobacter spp. andE. coliwere more frequent in summer, while Enterococci spp.,coagulase-negative StaphylococciandP. aeruginosawere more prevalent in winter half-year. DFIs of the forefoot and plantar side are mostly caused by gram-positive species, whileEnterobacteriaceaewere most frequent in plantar ulcerations. Conclusion Gram-positive species dominate bacterial spectrum in DFI. With increase in age,S. aureus,StreptococciandPseudomonas aeruginosabecame more frequent. The inflammatory response did not differ significantly between different species, but gram-negative species were slightly but not significant more frequent in ischemic wounds. Climatic distinction like summer or winter half-year as well as foot ulcer localization seems to influence bacterial diversity in DFUs.