Diabetes Mellitus and Infectious Diseases: Current Evidence and Clinical Implications

Diabetes mellitus predisposes individuals to a broad spectrum of infections. People with diabetes face a 1.5- to 4-fold increased risk of both common and severe infections, and infections remain the leading cause of morbidity and mortality. Chronic hyperglycemia impairs neutrophil chemotaxis, oxidative burst, and complement activation, while vascular insufficiency and neuropathy compromise tissue perfusion and barrier integrity. These defects, together with altered skin, mucosal, and gut microbiota, influence the marked susceptibility to urinary tract infections (especially renal abscess and emphysematous pyelonephritis), osteomyelitis, diabetic foot infections, pneumonia (including influenza), tuberculosis, skin and soft tissue infections, and lifethreatening syndromes such as emphysematous cholecystitis and rhino-orbital mucormycosis that are almost exclusive to people with diabetes. Outcomes from infections are worse in diabetes. Although the core therapeutic principles align with those for patients without diabetes, management should be individualized. Glycemic control should balance infection risk and hypoglycemia; antimicrobial dosing should account for renal function and drug interactions; and strict antimicrobial stewardship is required. If needed, prompt debridement and multidisciplinary intervention are necessary to mitigate complications and reduce mortality. Preventive care relies on comprehensive vaccination (influenza, pneumococcus, severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], hepatitis B, herpes zoster, and Tdap/Td) and regular foot surveillance with offloading to avert ulceration.