Shigella Infection

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Shigella infection, also known as shigellosis, is a bacterial infection caused by a group of bacteria called Shigella. It primarily affects the intestines and can cause severe diarrhoea and dysentery.

Aetiology

Shigella infection is caused by bacteria of the genus Shigella, which are transmitted through:

• Consumption of contaminated food or water
• Direct person-to-person contact
• Contact with contaminated surfaces

Pathophysiology

The pathophysiology of Shigella infection involves:

• Ingestion of Shigella bacteria.
• The bacteria invade the intestinal mucosa, causing inflammation and ulceration.
• Shigella produce toxins, including Shiga toxin, which contribute to the severity of the disease.
• This results in diarrhoea, abdominal pain, and in severe cases, dysentery (bloody diarrhoea).

Risk Factors

• Consumption of contaminated food or water
• Poor hygiene practices
• Living in or travelling to areas with poor sanitation
• Close contact with an infected person
• Young children in daycare settings
• Immunocompromised individuals

Signs and Symptoms

The signs and symptoms of Shigella infection include:

• Diarrhoea (which may be bloody)
• Abdominal pain and cramping
• Fever
• Nausea and vomiting
• Tenesmus (a painful sensation of needing to pass stools even when the bowels are empty)

Investigations

Specific investigations to diagnose Shigella infection include:

• Stool culture: To isolate and identify Shigella species.
• Full blood count (FBC): To check for elevated white blood cell count and other markers of infection.
• Blood cultures: In cases of suspected systemic infection.
• Polymerase Chain Reaction (PCR): To detect Shigella DNA in stool samples.

Management

Primary Care Management

• Rehydration: Oral rehydration solutions to prevent dehydration from diarrhoea.
• Antidiarrhoeal medications: Such as loperamide may be used in non-severe cases, but generally avoided to allow the infection to clear.
• Antibiotics: Typically not required for mild cases, but may be considered for severe or prolonged infections, or in immunocompromised individuals. Common antibiotics include ciprofloxacin or azithromycin.
• Hygiene advice: Emphasising hand washing and safe food handling practices to prevent spread and reinfection.

Specialist Management

• Hospitalisation: For severe cases, particularly if dehydration, sepsis, or complications arise.
• Intravenous fluids: To manage severe dehydration and maintain electrolyte balance.
• Further investigations: In cases of complications such as reactive arthritis or haemolytic uraemic syndrome (HUS), specialist referral and further investigations may be necessary.
• Public health measures: Reporting cases to public health authorities to monitor and prevent outbreaks.

References

1. NHS (2024) Shigella infection. Available at: https://www.nhs.uk/conditions/shigella/ (Accessed: 24 June 2024).
2. Centers for Disease Control and Prevention (2024) Shigella - Shigellosis. Available at: https://www.cdc.gov/shigella/index.html (Accessed: 24 June 2024).
3. World Health Organization (2024) Shigella. Available at: https://www.who.int/news-room/fact-sheets/detail/shigella (Accessed: 24 June 2024).
4. British Medical Journal (2024) Shigella infection: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h3655 (Accessed: 24 June 2024).

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