Increasing incidence of Gram-negative organisms in bacterial agents isolated from diabetic foot ulcers

In the present study, we sought to identify the bacterial organisms associated with diabetic foot infections (DFIs) and their antibiotic sensitivity profiles.

We retrospectively reviewed the records of wound cultures collected from diabetic patients with foot infections between May 2005 and July 2010.

We identified a total of 298 culture specimens (165 [55%] wound swab, 108 [36%] tissue samples, and 25 [9%] bone samples) from 107 patients (74 [69%] males and 33 [31%] females, mean age 62 ± 13 yr) with a DFI. Among all cultures 83.5% (223/267) were monomicrobial and 16.4% (44/267) were polymicrobial. Gram-negative bacterial isolates (n = 191; 61.3%) significantly outnumbered Gram-positive isolates (n = 121; 38.7%). The most frequently isolated bacteria were Pseudomonas species (29.8%), Staphylococcus aureus (16.7%), Enterococcus species (11.5%), Escherichia coli (7.1%), and Enterobacter species (7.1%), respectively. While 13.2% of the Gram-negative isolates were inducible beta-lactamase positive, 44.2% of Staphylococcus aureus isolates were methicillin resistant.

Our results support the recent view that Gram-negative organisms, depending on the geographical location, may predominate in DFIs.