What is the appropriate treatment for dysentery?

Dysentery Treatment

Azithromycin is the first-line antimicrobial agent for dysentery, given as either a single 1000 mg dose or 500 mg daily for 3 days, but rehydration with oral rehydration solution (ORS) must be initiated immediately as the priority intervention to prevent mortality. 1, 2

Immediate Rehydration (Priority Over Antibiotics)

Fluid replacement takes absolute priority over antimicrobial therapy in preventing death from dysentery. 2

Assessment of dehydration severity:

• Mild (3-5% deficit): Slightly decreased skin turgor, dry mucous membranes 2
• Moderate (6-9% deficit): Sunken eyes, decreased urine output, tachycardia 2
• Severe (≥10% deficit): Shock, altered mental status, weak/absent pulse, poor perfusion 1, 2

Rehydration protocol by severity:

• Mild to moderate dehydration: Reduced osmolarity ORS at 50-100 mL/kg over 2-4 hours 1, 2
• Unable to drink but not in shock: Nasogastric ORS at 15 mL/kg/hour 1, 2
• Severe dehydration/shock: Isotonic IV fluids (lactated Ringer's or normal saline) immediately, then transition to ORS once pulse and perfusion normalize 1, 2

First-Line Antimicrobial Therapy

Azithromycin is superior to fluoroquinolones for dysentery due to widespread fluoroquinolone resistance in Campylobacter (exceeding 90% in some regions), Shigella, and other dysentery-causing pathogens. 1, 2

Azithromycin dosing options:

• Single 1000 mg dose (can split over first day to reduce nausea) 1, 2
• 500 mg daily for 3 days 1, 2

Rationale: Azithromycin demonstrates effectiveness against all major dysentery pathogens including Shigella, enteroinvasive E. coli, Campylobacter, Aeromonas, Plesiomonas, and Yersinia enterocolitica. 1, 2 Clinical trials in Thailand showed azithromycin superior to levofloxacin in settings with high fluoroquinolone resistance. 1

Alternative Antimicrobial Agents

Fluoroquinolones (ciprofloxacin 500 mg twice daily or levofloxacin 500 mg once daily for 3 days) may be considered only when:

• Local susceptibility patterns confirm low resistance rates 1
• Patient has not traveled to regions with high Campylobacter resistance 1
• Azithromycin is contraindicated or unavailable 1

However, fluoroquinolones carry significant concerns: Achilles tendon rupture risk (FDA black box warning), C. difficile infection risk, QT prolongation, and promotion of multidrug-resistant bacteria acquisition during travel. 1

Special Population Considerations

Infants <3 months with dysentery:

• Third-generation cephalosporin is preferred empiric therapy 1, 2
• Azithromycin is alternative depending on local resistance patterns 1, 2
• Fluoroquinolones are contraindicated in this age group 2

Immunocompromised patients:

• Empiric antimicrobial therapy warranted even with less severe presentation 1, 2
• Broader coverage may be needed 1

Critical Contraindications and Pitfalls

DO NOT use antimicrobials if Shiga toxin-producing E. coli (STEC) O157 or other Shiga toxin 2-producing STEC is suspected or confirmed, as antibiotics precipitate hemolytic uremic syndrome. 1, 2

DO NOT use rifaximin for dysentery—it is ineffective for invasive diarrheal illness and only works for noninvasive watery diarrhea. 1, 2

DO NOT use antimotility agents (loperamide):

• Absolutely contraindicated in children <18 years with dysentery 2
• Avoid in adults with dysentery if fever present or symptoms worsen 2

DO NOT treat asymptomatic contacts—they should follow infection prevention measures only. 1, 2

Nutritional Management

Resume normal diet immediately after rehydration—there is no justification for "bowel rest" or fasting. 1, 2

• Continue breastfeeding throughout the illness without interruption 2
• Provide energy-rich, easily digestible foods to maintain nutritional status 2
• For non-breastfed infants, give full-strength formula immediately after rehydration 2

Diagnostic Approach

Obtain stool culture before starting antibiotics to guide therapy modification. 1, 2

• Visual examination should confirm blood and mucus in stool 2
• Microscopy can identify Entamoeba histolytica trophozoites (important in developing countries) 2
• Testing for STEC/Shiga toxin is critical to avoid antibiotic use in these cases 1, 2

When to Modify or Discontinue Antibiotics

Modify or discontinue antimicrobial therapy when a specific organism is identified and either:

• The organism does not require treatment (e.g., STEC) 1
• Targeted therapy is more appropriate than empiric coverage 1
• Susceptibility testing indicates resistance to current agent 1