Research report: Microbial profiles, resistance patterns, and clinical outcomes in diabetic foot ulcers: a prospective cohort study using the WIfI classification

A prospective study of adults with diabetes admitted to a tertiary hospital in Belo Horizonte, Brazil, found that microbial and resistance patterns differed across grades of foot infection and stages of amputation risk defined by the Wound, Ischemia and foot Infection, or WIfI, classification. Enterobacterales became more frequent as the amputation risk stage increased, while Enterococcus faecalis became less frequent. Carbapenem resistance did not rise steadily with infection grade, and major amputation increased from 0.0% in the lowest-risk stage to 32.4% in the highest.

The single-center cohort, which included 100 infected limbs from 98 patients, establishes associations within this hospital population but does not show that particular organisms caused the clinical outcomes. The researchers consecutively enrolled adults with diabetes who were admitted with a foot ulcer and a WIfI foot infection grade from 1 to 3 between February 2017 and March 2019. Deep tissue cultures yielded 133 isolates: 54.1% were Gram-negative, 43.6% Gram-positive and 2.3% fungi.

Staphylococcus aureus was the most frequent species, accounting for 23.3% of isolates. Cultures were monomicrobial in 71 of 100 limbs, meaning that only one species was identified in 71.0% of the sampled infected limbs. Several Enterobacterales were more frequent in grade 3 infection than in grade 2 infection.

Proteus mirabilis had an odds ratio of 15.00, a 95% confidence interval of 1.98 to 112.03 and a p-value of 0.011. Klebsiella pneumoniae and Klebsiella aerogenes each had an odds ratio of 16.78, with p-values of 0.039. The broad confidence interval for Proteus and the small study population indicate substantial uncertainty around these estimates.

When results were grouped by WIfI amputation risk stage, Enterobacterales rose from 13.6% of isolates in the very-low-risk stage to 40.5% in the high-risk stage. Enterococcus faecalis declined from 31.8% to 7.1% across the same stages. The broader decrease in Gram-positive bacteria did not reach statistical significance, so the findings support a species-level pattern rather than a general claim that all Gram-positive organisms became less common as risk increased.

Carbapenem resistance followed a different and non-linear pattern. Organisms with carbapenem resistance were isolated from 25.7% of limbs with grade 1 infection, 8.3% with grade 2 infection and 40.0% with grade 3 infection. Among the nine carbapenem-resistant isolates from grade 1 limbs, eight were non-fermenting Gram-negative bacilli.

The study authors concluded that this pattern does not indicate that carbapenem resistance was associated with greater infection severity. Clinical outcomes differed across the WIfI amputation risk stages. Major amputation occurred in 15 of the 100 infected limbs, or 15.0%, and the proportion increased from 0.0% in the lowest stage to 32.4% in the highest; the test for trend produced a p-value of 0.003.

Two of the 98 patients died in hospital, corresponding to 2.0%. Overall, the findings offer a detailed microbiological snapshot of infected diabetic foot ulcers treated at one Brazilian tertiary hospital. They should not be assumed to represent every hospital or region, and the observational design, relatively small cohort and low number of deaths limit broader generalization.

Subject of Research: Microbial profiles, antibiotic resistance and clinical outcomes in diabetic foot ulcers stratified by WIfI classification

Article Title: Microbial profiles, resistance patterns, and clinical outcomes in diabetic foot ulcers: a prospective cohort study using the WIfI classification

Article References: Cardoso, N. A., Cisneros, L. D. L., Machado, C. J., Procópio, R. J., Navarro, T. P., & Duani, H. (2026). Microbial profiles, resistance patterns, and clinical outcomes in diabetic foot ulcers: a prospective cohort study using the WIfI classification. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14404-1

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14404-1

Keywords: diabetic foot ulcers, foot infection, WIfI classification, Enterobacterales, Gram-negative bacteria, carbapenem resistance, amputation, clinical microbiology, prospective cohort, Brazil, Microbial, profiles