Bacillary Dysentery – Comprehensive Medical Guide
Overview
Bacillary dysentery (also called shigellosis) is an acute intestinal infection caused by the bacteria of the genus Shigella. The disease is characterized by inflammation of the colon and the passage of bloody or mucus‑laden stools. It is highly contagious; a very small number of organisms (as few as 10–100) can cause infection, making it a common cause of diarrheal outbreaks in settings where hygiene is compromised.
Who it affects: Children under five, travelers to endemic regions, people living in crowded or low‑sanitation environments, and individuals with weakened immune systems are most vulnerable.
Prevalence: According to the World Health Organization (WHO), Shigella accounts for an estimated 80–165 million cases of dysentery worldwide each year, resulting in roughly 600,000 deaths, the majority of which occur in children younger than five in low‑income countries.1 In high‑income nations, incidence is lower (≈ 2–10 cases per 100,000 persons annually) but still significant among travelers and institutionalized populations.2
Symptoms
Symptoms usually begin 1–3 days after exposure (incubation period) and can range from mild to severe.
- Diarrhea – Frequent, large‑volume stools that may be watery at first and become bloody or contain mucus.
- Abdominal cramps – Sharp or crampy pain often intensifying before a bowel movement.
- Fever – Low‑grade to high fever (38–40 °C / 100–104 °F).
- Tenesmus – A persistent urge to defecate even when the rectum is empty.
- Nausea and vomiting – More common in children.
- Fatigue & weakness – Resulting from fluid loss and electrolyte imbalance.
- Dehydration signs – Dry mouth, decreased urine output, dizziness, sunken eyes.
- Blood or pus in stool – Indicates more severe mucosal damage.
- Weight loss – Usually short‑term but can be notable in prolonged illness.
Most healthy adults recover within a week, whereas children and immunocompromised patients may experience prolonged or severe disease.
Causes and Risk Factors
Primary cause
Infection is caused by ingestion of Shigella bacteria (four main species: S. sonnei, S. flexneri, S. dysenteriae, and S. boydii). The organisms invade the lining of the colon, trigger an inflammatory response, and produce toxins that damage cells.
Transmission routes
- Fecal‑oral spread – Contaminated hands, food, or water.
- Person‑to‑person – Particularly in daycare centers, schools, prisons, and nursing homes.
- Travel – Consumption of raw vegetables, unpasteurized milk, or street food in endemic areas.
- Sexual contact – Especially receptive anal intercourse (a recognized risk among men who have sex with men).
Risk factors
- Living in or traveling to regions with poor sanitation (e.g., parts of South Asia, Sub‑Saharan Africa, Latin America).
- Age < 5 years (immature immunity and higher exposure in daycare).
- Immunosuppression (HIV, chemotherapy, organ transplant).
- Recent use of antibiotics that disrupt normal gut flora.
- Crowded living conditions and inadequate hand‑washing facilities.
Diagnosis
Clinical suspicion is based on the characteristic history (sudden onset of bloody diarrhea, recent travel, or outbreak exposure). Laboratory confirmation guides therapy, especially antibiotic choice.
Stool testing
- Culture – Gold standard; stool is plated on selective media (e.g., MacConkey, XLD) to isolate Shigella.
- PCR (polymerase chain reaction) – Rapid detection of Shigella DNA; increasingly used in high‑resource settings.
- Fecal leukocytes – Presence of white blood cells supports invasive bacterial cause.
- Ova & parasite exam – Excludes other causes of dysentery (e.g., Entamoeba histolytica).
Additional tests (if indicated)
- Complete blood count (CBC) – May show leukocytosis.
- Electrolyte panel – Assesses dehydration and electrolyte loss.
- Blood cultures – Reserved for severe disease or immunocompromised patients.
Treatment Options
Management combines rehydration, antimicrobial therapy (when appropriate), and symptom control.
Rehydration
- Oral rehydration solution (ORS) – First‑line for mild‑moderate dehydration (WHO‑recommended glucose‑electrolyte solution).
- Intravenous fluids – Needed for severe dehydration, persistent vomiting, or shock.
Antibiotic therapy
Antibiotics shorten the duration of symptoms and reduce bacterial shedding, but resistance is common. Choice should be guided by local susceptibility patterns.
- Ciprofloxacin 500 mg PO bid for 3 days – Historically first‑line, but resistance up to 30 % in some regions.3
- Azithromycin 500 mg PO daily for 3 days – Preferred for macrolide‑sensitive strains, especially in children.
- Ceftriaxone 2 g IV daily – Reserved for severe illness or when oral agents cannot be used.
- Rifampin – Occasionally used in outbreak settings with multidrug‑resistant strains.
Antibiotics are NOT recommended for mild disease in otherwise healthy adults because they may increase risk of resistance and have limited benefit.
Symptomatic care
- Antimotility agents (e.g., loperamide) are generally avoided, as they may prolong bacterial clearance and increase risk of toxic megacolon.
- Acetaminophen for fever/pain (avoid NSAIDs if risk of gastrointestinal bleeding).
Adjunctive measures
- Probiotics (e.g., Lactobacillus rhamnosus GG) – Some evidence for modest reduction in diarrhea duration.4
- Zinc supplementation (20 mg daily for children) – Recommended by WHO for acute diarrhea.
Living with Bacillary Dysentery
While most cases resolve quickly, patients may need practical strategies to manage symptoms and prevent spread.
Hydration & nutrition
- Drink ORS or clear fluids (broth, diluted juice) frequently – aim for 150 ml/kg/day in children.
- Consume a bland diet: bananas, rice, applesauce, toast (BRAT) after the acute phase.
- Avoid caffeine, alcohol, high‑fat or high‑fiber foods until diarrhea subsides.
Hygiene practices
- Wash hands with soap & water for at least 20 seconds after using the toilet and before eating.
- Disinfect bathroom surfaces with a bleach solution (1 part 5.25 % bleach to 9 parts water) daily during illness.
- Use separate towels for the patient and change them daily.
Work / school considerations
- Adults should stay home until 48 hours after the last unformed stool.
- Children may return to daycare/school after 24 hours without fever and with formed stools.
Follow‑up
- Re‑evaluate if symptoms persist >7 days, if blood persists, or if dehydration signs develop.
- Consider repeat stool culture for resistant organisms if no improvement after appropriate antibiotics.
Prevention
Because only a few organisms are needed to cause infection, strict hygiene and safe food/water practices are essential.
- Hand hygiene – Wash hands with soap and water; alcohol‑based rubs are less effective against Shigella when hands are visibly soiled.
- Safe water – Drink treated or boiled water; avoid ice in areas with questionable water quality.
- Food safety – Eat fully cooked foods, peel fruits/vegetables yourself, avoid raw salads in high‑risk settings.
- Sanitation – Ensure proper sewage disposal and latrine cleanliness.
- Traveler’s advice – Use bottled water, avoid street‑vend food without heating, and carry ORS packets.
- Vaccines – No licensed vaccine is currently available, but several candidates are in clinical trials (e.g., live‑attenuated Shigella flexneri 2a).
Complications
Most people recover without sequelae, but untreated or severe disease can lead to:
- Severe dehydration – Electrolyte imbalance, renal failure.
- Hemolytic‑uremic syndrome (HUS) – Rare, more associated with S. dysenteriae toxin production.
- Septicemia – Bacterial translocation into bloodstream, especially in immunocompromised hosts.
- Reactive arthritis – Post‑infectious joint inflammation, may develop weeks after gastrointestinal symptoms.
- Chronic carrier state – Small subset may harbor organisms for months, posing a public‑health risk.
When to Seek Emergency Care
- Signs of severe dehydration: rapid heartbeat, low blood pressure, dizziness, fainting, or < 2 years old with no wet diapers for >6 hours.
- Persistent high fever (≥ 39.5 °C / 103 °F) despite antipyretics.
- Bloody stools accompanied by severe abdominal pain or swelling.
- Inability to keep fluids down (continuous vomiting).
- Confusion, lethargy, or seizures.
- Symptoms lasting > 10 days or worsening after initial improvement.
References:
- World Health Organization. Shigellosis Fact Sheet. 2022. https://www.who.int/news-room/fact-sheets/detail/shigellosis
- Cleveland Clinic. Shigella infection (shigellosis). 2023. https://my.clevelandclinic.org/health/diseases/15246-shigella-infection
- Centers for Disease Control and Prevention. Antibiotic Resistance in Shigella. 2021. https://www.cdc.gov/shigella/antibiotic-resistance.html
- Allen SJ, et al. Probiotics for treating acute infectious diarrhoea. Cochrane Database Syst Rev. 2010;CD003054.