Intersecting Pathologies: Cutaneous Diphtheria in a Diabetic Patient

Abstract Corynebacterium diphtheriae , a Gram-positive bacillus, is the pathogen responsible for respiratory and cutaneous diphtheria. Cutaneous diphtheria presents as chronic, non-healing ulcers and is notably more common in individuals with compromised immunity, such as those with diabetes. Diabetes, particularly with poor glycemic control, increases the risk of infections due to weakened immunity and a higher susceptibility to skin injuries. This case report describes a 75-year-old male with a history of hypertension and uncontrolled type 2 diabetes mellitus, who presented with non-healing ulcers on both feet. The ulcers were characterized by purulent discharge and poor general hygiene. Microbiological analysis, including Gram staining and culture, confirmed the presence of C . diphtheriae . Antimicrobial susceptibility testing indicated that the isolate was susceptible to cotrimoxazole and tetracycline but resistant to several other antibiotics. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) enabled rapid and precise identification of the organism, expediting appropriate treatment decisions. Based on these findings, the patient was treated with cotrimoxazole and showed clinical improvement. The case highlights the importance of early identification and appropriate treatment of cutaneous diphtheria to prevent severe systemic complications and transmission. Prompt and accurate diagnosis is also crucial for minimizing the spread of the infection within communities. Additionally, the role of MALDI-TOF MS in rapid diagnosis is emphasized, helping in prompt and early identification; antibiotic stewardship is essential as the right choice of the drug for treatment should be started only after performing antimicrobial susceptibility testing due to the rise in resistant strains.