Shigellosis is another common cause of diarrhoea, particularly in developing countries. This article throws light on the clinical symptoms found in shigellosis and prompt management of this common illness.

Introduction

Shigella infection (shigellosis) is caused by gram-negative, non-motile, non-encapsulated facultative anaerobic bacilli. There are 47 serotypes belonging to four serogroups namely, A (S. dysenteriae); B (S. flexneri); C (S. boydii); and D (S. sonnei). The disease is endemic in developing countries particularly in areas with poor sanitation.

Mode of transmission

The mode of transmission is by faecal-oral route. It can spread via water-borne or food-borne transmission. It is a common cause of diarrhoea in children in developing countries. After entering the intestines the bacteriae multiply in the large intestine. The bacteriae produce enterotoxins and also cause cell injury by directly invading the colonic mucosa. Invasion of the colonic mucosa and inflammatory colitis are the hallmarks of shigellosis. 

Signs and symptoms

The classical presentation of shigellosis is:

• Watery diarrhoea, vomiting with mild to moderate dehydration
• Dysentery with a small volume of bloody, mucoid stools, and abdominal pain (cramps and tenesmus)

The other symptoms associated with shigellosis are: 

• Fever
• Nausea and vomiting
• Mild abdominal discomfort or severe diffuse colicky abdominal pain
• Anorexia
• Lethargy
• Rare symptoms are: delirium, encephalopathy, anuria, seizures, meningismus, and coma

On clinical examination, the following signs are seen in shigellosis: 

• Pyrexia
• Tachycardia
• Tachypnoea
• Hypotension
• Distended abdomen with hyperactive bowel sounds
• Tenderness particularly in the lower abdomen (due to the involvement of sigmoid colon and rectum)

Diagnosis 

• Stool examination: Presence of leukocytes and blood. Isolation and identification of the organisms by stool culture
• Complete blood count (CBC): Leukocytosis; in some cases, leukopenia is present, anaemia and thrombocytopenia might be seen
• Liver function test: In severe cases, there could be a mild increase in bilirubin
• Renal function: Patients with dehydration may have increased levels of blood urea nitrogen (BUN) and creatinine
• Inflammatory markers: Increase in erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) might be present
• Blood culture: Positive blood culture is seen in children and is associated with poor prognosis
• Stool alpha-1 antitrypsin: In the acute phase of shigellosis the levels are high
• ELISA and Polymerase chain reaction: Not routinely done. ELISA is used to detect S. dysenteriae type-1 toxin in stool, and PCR is used to identify the virulent genes of Shigella

Management 

1. Hydration: Management of dehydration, metabolic acidosis, and significant potassium loss is the first consideration to treat diarrhoea caused by shigellosis. Oral rehydration treatment is effective and safe. In patients with vomiting or severe dehydration, intravenous fluid replacement is recommended for correction of fluid and electrolyte balance.
2. Antibiotics:
   1. The following antibiotics are recommended in the paediatric age group-
      1. Ampicillin (2 g/day for 5 days)
      2. Trimethoprim (8 mg/kg/day) and sulfamethoxazole (40 mg/kg/day)
      3. Azithromycin
      4. Cefixime and ceftibuten in cases with resistance to common antibiotics
      5. Pivmecillinam
      6. Ceftriaxone (single dose or for five days) as parenteral administration in cases with severe infection, immunodeficiency or inability to take oral medications
   2. In adults, the following antibiotics are recommended-
      1. Fluoroquinolone
      2. Third-generation cephalosporin in cases of resistance to common antibiotics or patients with immunodeficiency such as HIV infected patients
      3. Second-generation cephalosporin
      4. Ampicillin
      5. Trimethoprim-sulfamethoxazole
3. Antimotility drugs: Lloperamide, paregoric or diphenoxylate are not recommended as they cause intestinal stasis, promote bacterial invasion thereby prolonging the infection and increasing the shedding of the organism.

Prevention

Frequent handwashing with soap and water especially after defecation and before food preparation or consumption is crucial for the prevention of spread of the disease. Food handlers should not engage in food preparation as long as there is a positive stool culture. Consumption of safe and effective faeces disposal is recommended.