From the Guidelines

The most common organism in a diabetic foot ulcer is Staphylococcus aureus, an aerobic gram-positive coccus.

Diabetic foot infections are often polymicrobial, but Staphylococcus aureus is the most frequently isolated pathogen, whether alone or in combination 1.
Aerobic gram-positive cocci, especially Staphylococcus aureus, are the predominant pathogens in diabetic foot infections 1.
Other organisms, such as Streptococci, Enterococci, and Gram-negative bacilli, may also be present, especially in chronic or previously treated infections 1.
The presence of MRSA (methicillin-resistant Staphylococcus aureus) is more common in patients who have recently received antibiotic therapy, have been previously hospitalized, or reside in a chronic care facility 1.
Obligate anaerobic species are most frequently isolated from ischemic or necrotic wounds or those that involve deep tissues, and are rarely the sole pathogen 1.
The diagnosis and management of diabetic foot infections require a multidisciplinary approach, including wound care, antibiotic therapy, and surgical interventions, as well as patient education and empowerment 1.

From the Research

The most common organism found in diabetic foot ulcers is Staphylococcus aureus, as identified in several studies 2, 3, 4, 5.
According to a study published in the Journal of Medical Microbiology, Staphylococcus aureus was identified as the most prevalent pathogen in diabetes-related foot pathologies, accounting for 25% of all samples 2.
A meta-analysis published in BMC Infectious Diseases also found that Staphylococcus aureus was the most common organism isolated from diabetic foot infections, with a prevalence of 18.0% 3.
Other studies have also reported Staphylococcus aureus as the most common isolate, with frequencies ranging from 19% to 38.6% 6, 4, 5.
However, it's worth noting that the frequency of other organisms, such as Pseudomonas aeruginosa and Escherichia coli, can also be significant in diabetic foot ulcers 6, 4, 5.

The prevalence of Staphylococcus aureus in diabetic foot ulcers can vary depending on the study, but it is generally reported to be around 20-30% 2, 3, 4.
A study published in the Journal of Family Medicine and Primary Care found that Staphylococcus aureus was the most common isolated organism in diabetic foot infections, accounting for 27.7% of all isolates 4.
Another study published in the Journal of Ayub Medical College found that Staphylococcus aureus was the most common isolate, accounting for 38.6% of all isolates 5.

Pseudomonas aeruginosa is another common organism found in diabetic foot ulcers, with frequencies ranging from 15.4% to 35% 6, 4, 5.
Escherichia coli is also a common isolate, with frequencies ranging from 6% to 16.9% 6, 4.
Other organisms, such as Enterococcus spp. and methicillin-resistant Staphylococcus aureus (MRSA), can also be present in diabetic foot ulcers 3, 6, 5.