Escherichia coli Cellulitis in a Patient With Waldenström Macroglobulinaemia: A Case Report.

Escherichia coli cellulitis is rarely reported, typically affecting immunocompromised individuals. The management of such cases presents significant challenges, as these patients often exhibit resistance to the empirical antibiotics commonly used for cellulitis. Furthermore, identifying E. coli in blood cultures necessitates additional investigations to rule out alternative sources of infection, such as biliary, urinary, or deep-seated collections. We present the case of a 79-year-old woman with Waldenström macroglobulinaemia, AL amyloidosis, and secondary immunosuppression who developed E. coli cellulitis. The diagnosis was confirmed via positive blood cultures, and no alternative sources of E. coli bacteraemia were identified. She was successfully treated with co-amoxiclav and flucloxacillin. This case underscores the importance of considering uncommon pathogens in immunocompromised patients and tailoring antimicrobial therapy based on microbiological sensitivity.