EUS-Guided Detection of Multidrug-Resistant Shigella dysenteriae from Retroperitoneal Cyst Fluid: A Rare Gastroinfectious Entity

Abstract

Background: Shigella dysenteriae is an invasive enteric pathogen classically associated with bacillary dysentery.
Extraintestinal isolation is rare and typically occurs in immunocompromised hosts. Retroperitoneal cyst infections due
to Shigella have scarcely been reported. Emerging antimicrobial resistance among Shigella species further complicates
management.
Case Presentation: A 47-year-old immunocompetent male presented with abdominal pain and was found to have a
retroperitoneal aortocaval multiseptated cyst on imaging. Endoscopic ultrasound (EUS)-guided fine needle aspiration
yielded hemorrhagic cyst fluid. Microbiological culture grew multidrug-resistant Shigella dysenteriae. Antimicrobial
susceptibility testing, interpreted according to CLSI guidelines, revealed resistance to third-generation cephalosporins
and carbapenems. The patient was treated with culture-directed therapy and improved clinically.
Conclusion: This case highlights a rare extraintestinal presentation of multidrug-resistant Shigella dysenteriae and
underscores the importance of microbiological evaluation of cystic lesions and adherence to standardized susceptibility
testing guidelines.