Makindo Medical Notes

About

• Shigellosis, also known as Bacillary Dysentery, caused by Shigella species. Transmitted primarily through the fecal-oral route.

Epidemiology

• More common in tropical regions with inadequate sanitation.
• Outbreaks seen in closed settings such as mental health facilities, residential schools, and institutional environments.
• Spread facilitated by unwashed hands following defecation, making hand hygiene critical for prevention.

Aetiology

• Highly acid-resistant, meaning as few as 10 organisms can cause infection.
• Produces cytotoxins that cause inflammation and tissue destruction, leading to diarrhoea.
• Shigella bacteria are gram-negative rods that primarily invade colonic epithelial cells.

Microbiology

• S. dysenteriae: Causes the most severe form of the disease.
• S. flexneri
• S. boydii
• S. sonnei: Causes milder cases of shigellosis.

Infections from Shigella sonnei are usually mild. However, S. dysenteriae can cause a fulminant form of the disease that may lead to death within 48 hours.

Clinical

• Acute onset with symptoms like watery diarrhoea, fever, abdominal pain, and malaise.
• Some cases involve bloody diarrhoea, tenesmus, and mucus in stools.
• About one-third of patients may experience vomiting. Most cases are self-limiting.

Complications

• Rectal prolapse
• Toxic megacolon or bowel obstruction
• Reiter's syndrome, especially in HLA-B27 positive patients
• Haemolytic uraemic syndrome (HUS)

Differential Diagnosis

• Inflammatory bowel disease
• Other causes of bloody diarrhoea, such as amoebic dysentery or Campylobacter infection

Investigations

• Stool culture: Confirms the diagnosis and identifies the specific Shigella species.
• Sigmoidoscopy: May be indicated in severe or persistent cases to evaluate mucosal involvement.
• Markedly elevated WCC in some cases.

Management

• Hand hygiene: Rigorous hand-washing is essential to prevent transmission.
• Rehydration therapy: Oral rehydration is the first line; IV fluids may be needed in severe cases.
• Antibiotics: Due to multi-drug resistance, antibiotics like Ciprofloxacin 500 mg twice daily for 3 days are often used.
• Antimotility agents: Generally avoided as they may prolong symptoms and increase infectivity risk.