A Case of Recurrent Bacteremic Cellulitis Caused by Citrobacter koseri

We encountered a rare case of recurrent <i>Citrobacter koseri</i> cellulitis with bacteremia in an 82-year-old woman with a history of surgery for cervical cancer and chronic lower limb lymphedema. She was admitted with cellulitis in the right lower leg and subsequently developed septic shock. Blood cultures revealed <i>C. koseri</i>, which was treated successfully with meropenem. Eight months later, she developed septic shock and cellulitis while hospitalized for lumbar compression fractures. Again, blood cultures yielded <i>C. koseri</i>. She recovered after treatment with cefmetazole but experienced a third episode of <i>C. koseri</i> cellulitis with bacteremia, which was treated with cefazolin. Long-term prophylactic cefalexin was initiated because of the frequent relapses. Although dementia-related nonadherence led to three further cellulitis episodes without bacteremia, a switch to once-daily levofloxacin improved adherence and prevented further recurrences. <i>Citrobacter koseri</i> is an uncommon cause of cellulitis and typically occurs in immunocompromised individuals. Risk factors in this case included lymphedema, cirrhosis, and multiple comorbidities. The formation of biofilm may have contributed to the recurrences. This case highlights the limitations of penicillin-based prophylaxis for Gram-negative cellulitis and suggests cefalexin as an alternative in selected cases. With population aging, Gram-negative soft tissue infections may become more common, increasing the need for preventive strategies tailored to resistant pathogens.