Microbiological Distribution, Antimicrobial Susceptibility and Risk Factors of Polymicrobial Infections in Diabetic Foot.

Background: Diabetic foot infection (DFI) leads to poor prognosis and polymicrobial infections are usually the main cause. The study is to explore the microbiological distribution, antimicrobial drug susceptibility, and risk factors of polymicrobial infections in hospitalized patients with DFI.

Methods: This retrospective study included 160 patients with DFI in Wagner's grades 2, 3, and 4. Deep necrotic tissue was used to acquire specimens for microbiological culture. VITEK-2 system and MALDI-TOF mass spectrometry were used to identify the bacterial isolates. The Kirby Bauer method was used for drug susceptibility tests.

Results: A total of 202 pathogens were isolated. The proportion of gram-negative bacilli (GNB, 62.4%, 126 of 202) was higher than that of gram-positive cocci (GPC, 37.6%, 76 of 202). The most prevalent GPC was Staphylococcus aureus in every Wagner grade, while the most common GNB varied in different Wagner grades. Linezolid was the most effective antibiotic for GPC in different Wagner grades. Imipenem was the most effective antibiotic for GNB in Wagner grade 2. Amikacin was the most effective antibiotic for GNB in Wagner grades 3 and 4. Polymicrobial infections existed only in Wagner grades 3 and 4 and increased the risk of amputation (p < 0.01). History of antibiotics, duration of diabetic foot, CRP, and lower extremity arterial disease were the independent risk factors of polymicrobial infections (p < 0.05).

Conclusions: Clinicians should adjust the antibiotic as needed based on the results of drug susceptibility and clinical treatment effect among different Wagner grades. Particular attention should be given to the treatment of polymicrobial infections.