Shigella flexneri Outbreak at a Rehabilitation Center: First Report from Saudi Arabia

Abstract

Background: Shigella flexneri is a major cause of shigellosis in developing regions and is known to cause outbreaks in institutional settings. Transmission occurs via the fecal-oral route. It invades intestinal epithelial cells, causing diarrhea, systemic symptoms, and complications such as hemolytic uremic syndrome. This study aimed to characterize the clinical presentation, administered treatment, infection outcomes, and infection control measures during a local S. flexneri outbreak at a rehabilitation center. Methods: This case series at King Saud University Medical City (Oct-Dec 2024) investigated S. flexneri infections from a rehabilitation center. Stool and blood samples were cultured and analyzed using microbiological methods. Molecular studies were used to verify the genetic linkage between the isolates and to study their virulence genes. Results: Four cases of S. flexneri were included, involving patients with various comorbidities, residing in a rehabilitation center, and presenting with symptoms like fever and diarrhea. Laboratory investigations revealed leukocytosis, electrolyte imbalances, and elevated inflammatory markers. Imaging studies showed findings consistent with colitis in two cases. Patients were managed with IV fluids and targeted antibiotics, leading to symptom resolution. Molecular studies confirmed the genetic relatedness between the S. flexneri isolates, with virulence genes indicating cellular invasion and inflammation as primary drivers of disease severity. Outbreak management comprised contact isolation, environmental disinfection, and education. Conclusions: S. flexneri outbreaks in long-term care facilities pose challenges among bedbound patients. Diapers may facilitate transmission, and infections may cause severe complications. Robust infection control, identifying outbreak sources, and strengthening prevention strategies are essential to protect vulnerable populations.

Keywords: Saudi Arabia; Shigella spp.; outbreak; rehabilitation center.

Figure 1

Pulsed-field gel electrophoresis (PFGE) results. (a) A dendrogram of NotI-digested S. flexneri isolates was constructed based on cluster analysis. DNA relatedness was assessed using BioNumerics v7.5 software (Applied Maths, Sint-Martens-Latem, Belgium). The dendrogram was generated by comparing banding patterns using the unweighted pair group method with arithmetic averages (UPGMA), applying a 4% Dice similarity coefficient and 2% tolerance. Banding pattern interpretation followed Tenover’s criteria [35]. (b) A dendrogram of XbaI-digested S. flexneri isolates was generated based on cluster analysis. DNA relatedness was analyzed using BioNumerics v7.5 software (Applied Maths, Sint-Martens-Latem, Belgium). The dendrogram was constructed by comparing banding patterns with the unweighted pair group method using arithmetic averages (UPGMA), applying a 4% Dice similarity coefficient and 2% tolerance. Banding pattern interpretation followed Tenover’s criteria [35].

Figure 2

Virulence genes of Shigella flexneri isolates.