Gastroenteritis - Bacterial Management

Last updated: 23 April 2026
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Evaluation

Initial clinical evaluation of the patient with acute diarrhea should focus on the assessment of the severity of the illness, the need for rehydration, and the identification of likely causes based on history and clinical findings. A careful clinical evaluation is needed in order to provide a cost-effective evidence-based approach to initial diagnostic tests and treatment.

ASSESSMENT OF THE SEVERITY OF DEHYDRATION

The goals in the assessment of the severity of dehydration are to provide a starting point for treatment and to segregate which patients can safely be sent home for therapy, which ones should remain for observation during therapy, and which ones immediately need intensive therapy. Consider admitting the patient to the hospital if with severe dehydration, failed rehydration, serious alternative diagnoses, concerns regarding the caregiver's ability to administer rehydration therapy or to identify significant symptoms requiring a return visit.

Dehydration Assessment



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Minimal or No Dehydration

  • Consists of <3% loss of body weight (<5% in infants)
  • Normal heart rate (HR), respiratory rate (RR) and pulse volume
  • Normal eyes (non-sunken eyeballs) with the presence of tears and moist mucous membranes
  • Normal capillary refill (<2 seconds)
  • Normal to decreased urine output
  • Patient is well and alert
  • Drinks normally and not thirsty


Mild to Moderate Dehydration 

  • Consists of 6% loss of body weight (5-10% in infants)
  • Normal to increased heart rate and respiratory rate
  • Normal to decreased pulse volume
  • Slightly sunken eyes with decreased tears, and sticky mucous membranes
  • Delayed capillary refill
  • Decreased urine output
  • Patient may appear normal, listless, irritable or fatigued
  • Thirsty and drinks eagerly


Severe Dehydration

  • Consists of >9% loss of body weight (>10% in infants)
  • Tachycardia with bradycardia especially in severe cases, deep and/or rapid respirations
  • Thready to absent pulse
  • Deeply sunken eyes with absence of tears, and parched mucous membranes
  • Poor capillary refill (>3 seconds)
  • Minimal urine output (<0.3 mL/kg/hr in 16 hours) or no urine output in 12 hours
  • Patient may appear lethargic to comatose
  • Not able to drink or drinks poorly

Principles of Therapy

Management of acute diarrhea may be decided upon the history and presentation.

Rehydrate and Maintain Hydration

Dehydration is the primary cause of morbidity and mortality; thus, treatment goals include prevention of dehydration, treatment of dehydration when present, and reduction of the severity and duration of symptoms.

Oral rehydration therapy (ORT) encompasses two phases of treatment: Rehydration phase where electrolytes and water are administered as oral rehydration solution (ORS) to replenish fluid losses and should be performed rapidly within 3-4 hours; and the maintenance phase, where there is restoration of ongoing fluid and electrolyte losses and adequate dietary intake and should be continued until resolution of symptoms.

An age-appropriate diet (including solids) for rapid realimentation is recommended once an adequate degree of hydration is attained. Breastfeeding should be continued, especially for breastfed patients. Changes in formula milk or avoidance of milk-based products are not necessary.

Empiric Antibiotics for Traveler’s Diarrhea

The objectives of antimicrobial treatment of traveler’s diarrhea are shortening the illness and returning travelers to normal activities; routine use is not recommended. Eradication of enteropathogens from stool does not predict the clinical benefits of antimicrobial therapy. Traveler’s diarrhea is typically short-lived and self-limited, but many organisms that cause the infection can be treated with antibiotics. The choice of therapy should depend on epidemiologic data.

Empiric Antibiotics for Cholera

Rehydration is the mainstay of therapy. When antibiotics are administered to cholera patients, there is a reduction in stool volume loss and a shorter clinical course. Antibiotics administered should follow recent sensitivity data for V cholerae, if available.

Empiric Antibiotics for Bloody Diarrhea

Antipropulsives should be avoided, as these drugs may increase severity by delaying excretion of organisms and facilitating invasion of the mucosa. The usage of antibiotics should be judicious and not for all cases.

Pharmacological therapy

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Empiric Antibiotics for Traveler’s Diarrhea

Empiric treatment of traveler’s diarrhea has been the best approach, but its usefulness is being undermined by growing antibiotic resistance in many parts of the world.

Azithromycin

Azithromycin may be the treatment of choice for C jejuni infection for patients 2-8 years of age. This may be considered for severe traveler’s diarrhea associated with pathogenic E coli. Azithromycin is reported to be effective against traveler’s diarrhea in Southeast Asia.

Co-trimoxazole (Sulfamethoxazole [SMZ] and Trimethoprim [TM])

Historically, Co-trimoxazole is the drug of choice for the treatment of traveler’s diarrhea. Resistance of enterotoxigenic E coli (ETEC) and Salmonella sp to this drug limits its usefulness.

Fluoroquinolones

Example drugs: Ciprofloxacin, Levofloxacin

Fluoroquinolones may be considered for severe traveler’s diarrhea associated with pathogenic E coli or multi-resistant strains of Shigella sp, Salmonella sp, V cholerae or C jejuni.

Empiric Antibiotics for Cholera

Doxycycline and Tetracycline are preferred agents against V cholerae. These are not recommended in patients <8 years of age. Doxycycline may be considered in the presence of an isolate-susceptible epidemic. Co-trimoxazole, macrolides (eg Azithromycin, Erythromycin) and Ciprofloxacin are alternative drugs.

Empiric Antibiotics for Bloody Diarrhea

Antibiotics may reduce the duration of illness and shorten the carrier stage of patients with bloody diarrhea. Initiation of empiric antibiotics may be considered in special situations such as: Infants <3 months old with manifestations of bacterial infection; immunocompetent patients exhibiting signs and symptoms of Shigella infection (fever, abdominal pain, hematochezia); and those who recently traveled and with fever of ≥38.5°C and other signs of septicemia. Once EHEC or Shiga toxin-producing E coli (STEC) has been excluded by stool exam, empiric therapy with antibiotics can be started. Broad-spectrum antimicrobials should be started in patients with signs and symptoms pointing to sepsis as soon as specimens have been collected. Antibiotic therapy should be tailored once results become available.

Antibiotics following the local sensitivities for Shigella sp may be used as empiric therapy before waiting for culture and sensitivity results. Ciprofloxacin or any third-generation cephalosporin (eg Ceftriaxone, Cefotaxime) may be used as empiric therapy for infants <3 months of age and patients with central nervous system (CNS) manifestations, or Azithromycin and Pivmecillinam in pediatric patients, depending on the location, antimicrobial susceptibility data and travel history. There are reports on resistance to Ciprofloxacin in some countries (please refer to local guidelines for recommended antibiotics). Alternative agents to be considered depending on location and antimicrobial susceptibility data include fluoroquinolones, Nalidixic acid, Ampicillin and Trimethoprim/Sulfamethoxazole. There is widespread resistance to the following drugs: Ampicillin, Azithromycin, Co-trimoxazole, Chloramphenicol, Nalidixic acid, Tetracycline, Ciprofloxacin, Gentamicin and first- and second-generation cephalosporins.

Pathogen-Specific Treatment of Bacterial Diarrhea

Pathogen Preferred Agent(s) Alternative Agent(s) Remarks
Aeromonas/Plesiomonas spp Antibiotics not usually required 
Aeromonas sp: Antibiotics may be indicated in patients prone to septicemia (eg cirrhosis, immunocompromised patients)
Plesiomonas sp: Antibiotics may be required in severely ill or immunocompromised patients
Co-trimoxazole  Ciprofloxacin1
 Chloramphenicol
 Aminoglycosides
 Campylobacter spp Antibiotics not usually required; may be used in severely ill patients or traveler’s diarrhea

This is a self-limiting condition. Early treatment can shorten the duration of the illness and prevent any relapse.
Erythromycin
Azithromycin
Ciprofloxacin1		 Tetracycline or Doxycycline2
EHEC 0157:H7 Antibiotics and antipropulsives are contraindicated; may increase the chance of developing hemolytic uremic syndrome
Salmonella spp Cefotaxime
Ceftriaxone 		Ampicillin
Co-trimoxazole
Ciprofloxacin1
Chloramphenicol

Ceftriaxone may be considered in suspected septicemic cases. Follow available local epidemiologic data.
Shigella spp Cefotaxime
Ceftriaxone
Ciprofloxacin1
Co-trimoxazole 		Azithromycin

This is a self-limiting condition.

Yersinia spp Co-trimoxazole
Tetracycline or Doxycycline2 		Ciprofloxacin1
Antipseudomonal aminoglycosides
3rd generation cephalosporins (eg Cefotaxime) 		 

1Ciprofloxacin is not recommended in patients <18 years of age, except in cases when potential benefits outweigh the risks.
2Tetracycline and Doxycycline are contraindicated in patients <8 years of age.

Adjunctive Therapy

Antiemetic Agents

Example drug: Ondansetron

Antiemetic agents may be used in patients >4 years of age to decrease vomiting or help avoid the need for intravenous (IV) fluid but these may increase episodes of diarrhea.

Antisecretory Agents

Example drug: Racecadotril

Antisecretory agents may be used as an adjunctive therapy in acute diarrhea, to be given during the first 3 days. Studies showed decreased diarrhea duration and reduced stool output following administration of Racecadotril in children with acute diarrhea.

Bovine Colostrum



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Bovine colostrum contains antimicrobial peptides (eg lactoferrin, lactoperoxidase), immune-regulating and inflammatory cytokines, and growth factors that may help provide passive immunity by enhancing different immune functions (eg phagocytosis, antigen presentation, antimicrobial activity via antigen chelation, and inflammation control) in the GI tract. Studies showed that bovine colostrum improved clinical symptoms (eg reduced stool frequency, reduced occurrence and duration of diarrhea) in children with infectious diarrhea. Clinical benefit in the prevention and management of infectious diarrhea is currently undergoing clinical trials.

Probiotics 



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Probiotics have been shown to reduce the intensity and duration of diarrhea of acute infectious diarrhea in children. Example probiotics are Bacillus clausii, Bifidobacterium spp, Lactobacillus spp, and Saccharomyces boulardii. Bacillus clausii contributes to the recovery of the intestinal microbial flora altered during the course of microbial disorders of diverse origin. This is capable of producing various vitamins, in particular group B vitamins; hence, it contributes to correcting the consequent vitamin disorders caused by antibiotics and chemotherapeutic agents in general. Bifidobacterium spp is the most commonly used probiotic that is used to improve the health of the host when given in adequate amounts. Lactobacillus spp (eg Lactobacilllus rhamnosus, Lactobacillus reuteri) are lactic acid bacteria used as an adjunct to rehydration therapy in children with acute gastroenteritis. Saccharomyces boulardii is a yeast that is used as an adjunct to rehydration therapy in children with acute gastroenteritis. This is an intestinal replacement flora that acts as an antidiarrheal microorganism in the digestive tract. This transits in the digestive tract without colonizing it, rapidly attaining significant intestinal concentrations, which are maintained at a constant level throughout the administration period.

Zinc

Zinc should be given routinely as adjunctive therapy in children more than 6 months of age. Zinc supplementation given during an episode of diarrhea may decrease the duration and severity of diarrheal illness.

Other Agents

Antimotility agents should be avoided in patients with bloody diarrhea caused by Shigella sp. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) did not give any recommendations regarding the use of prebiotics and synbiotics in the treatment of acute gastroenteritis.

Investigational Agents

Human milk and gelatin tannate are being studied to determine their use in the management of gastroenteritis. 

Nonpharmacological

Rehydrate and Maintain Hydration

Oral Rehydration Solutions (ORS)

The oral rehydration solutions (ORS) formula recommended by the World Health Organization (WHO) is a concentration of 75 mEq/L sodium and 75 mmol/L glucose with a total osmolarity of 245 mOsm/L, or ½ teaspoon of salt and 6 teaspoons of sugar in 1 L of water. This has lower osmolarity that contains proportionally reduced sodium and glucose concentrations. The formulation has been shown to reduce vomiting and the need for intravenous (IV) fluids.

The WHO-recommended amounts to be given based on weight and age are as follows:

Weight Age Amount
(within the first 4 hours)
<5 kg (<11 lb) <4 months 200-400 mL
5-7.9 kg (11 lb - 17 lb, 7 oz) 4-11 months 400-600 mL
8-10.9 kg (17 lb, 10 oz - 24 lb) 12-23 months 600-800 mL
11-15.9 kg (24 lb, 4 oz - 35 lb) 2-4 years 800-1,200 mL
16-29.9 kg (35 lb, 4 oz - 65 lb, 15 oz)
 5-14 years 1,200-2,200 mL
≥30 kg (≥66 lb, 2 oz) ≥15 years
 2,200-4,000 mL

Oral rehydration solutions are the first-line treatment for patients with acute diarrhea accompanied by mild-moderate dehydration. This may also be considered in mild-moderately dehydrated patients with vomiting or severe diarrhea. Severe vomiting, abdominal ileus, altered mental status, gastrointestinal (GI) disease with absorption concerns, and a state of hemodynamic shock are contraindications to ORS.

Intravenous (IV) Fluids or Nasogastric (NG) Oral Rehydration Solutions (ORS)



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Intravenous (IV) fluids or nasogastric (NG) oral rehydration solutions (ORS) is given for 4-6 hours or until adequate hydration is achieved. Intravenous fluids are recommended in the following patients: Severely dehydrated; in whom oral hydration has failed due to severe vomiting or excessive stool output; patients in shock or with altered mental status; and patients with intestinal ileus or intestinal obstruction.  Nasogastric (NG) ORS may be given to moderately dehydrated patients who cannot tolerate oral administration of ORS and to children who are too weak and refuse to drink, which may cause insufficient hydration if only by oral intake. Nasogastric feeding allows continuous ORS administration at a slow and steady amount. A rehydrated state should be maintained by continuous replacement of losses.

Mild Dehydration

Administer 50-100 mL of oral rehydration solutions to children <2 years old, 100-200 mL to children 2-10 years old, or an unlimited amount for children >10 years old, after each loose stool or 20 mL/kg body weight/hour to replace estimated fluid deficit. Several trials support the use of nasogastric (NG) oral rehydration solution feeding even in patients with continuous vomiting or with oral ulcers. Continue breastfeeding or resume age-appropriate feeding. Rapid IV hydration may also be administered.

Moderate to Severe Dehydration

Start patient on rapid intravenous (IV) rehydration. Administer 20 mL/kg body weight of IV lactated Ringer’s solution or normal saline solution (0.9% NaCl) until pulse, perfusion, and mental status return to normal, followed by 100 mL/kg body weight of ORS for 4 hours or 5% dextrose ½ normal saline IV at two times maintenance fluid rates. Alternatively, give 100 mL/kg body weight.

For infants <1 year, give 30 mL/kg/body weight within the first hour, followed by 70 mL/kg/body weight within 5 hours. For children >1 year, 30 mL/kg/body weight IV fluid may be given within the first 30 minutes, followed by 70 mL/kg/body weight within 2.5 hours. Assess hydration every 15-30 minutes until hydration improves, then hourly thereafter. Administration of oral rehydration solutions may encourage early resumption of feeding. A study shows that giving ORS may lead to rapid resolution of acidosis compared to IV fluid.

Dietary Therapy

Dietary therapy depends on age and diet history. Breastfed patients should continue nursing on demand while formula-fed patients must continue their usual full-strength milk. Based on several trials, feedings with diluted formula are associated with protracted symptoms and delayed nutritional recovery. Lactose-free formulas are recommended in patients with documented and persistent lactose intolerance. Intake of the patient’s usual diet is recommended. Foods high in simple sugars should be avoided.

Patient/Parent Education



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Bacterial gastroenteritis is contagious. Good hygiene (eg handwashing and housekeeping) is needed, especially during outbreaks. Handwashing should also be observed in caregivers having contact with patients' feces to minimize potential transmission.

Advise the parent to continue feeding or breastfeeding both during and after illness. Breastfeeding in young children helps decrease the incidence of acute gastroenteritis and hospital admissions from diarrhea. Children should be encouraged to eat solid foods once dehydration has been corrected. Early refeeding with age-appropriate foods is beneficial. 

    Prevention

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    Traveler’s Diarrhea

    Travelers should avoid the following: Undercooked food except peeled fruits or vegetables, fruit salads, chicken salads, or lettuce; non-bottled beverages and unpasteurized dairy products; and ice in drinks made from unfiltered or unbottled water sources.

    Water Purification

    Travelers who are going to be living in rustic circumstances overseas will need to make arrangements for a safe water supply.

    Prophylactic Antibiotics

    Prophylactic antibiotics are effective but cannot be recommended unless the complications of diarrhea in a traveler or severe dehydration in a person with an underlying medical condition cause the benefits of antibiotic prophylaxis to outweigh the risks. These may also be given to asymptomatic people whose stools have been tested positive for Salmonella enterica subspecies enterica serovar typhimurium to reduce the spread of infection.

    Probiotics

    Probiotics may decrease the incidence of diarrhea in travelers. Examples of probiotics are Lactobacillus sp, Saccharomyces boulardii, and Bifidobacterium sp.

    Cholera

    Vibrio cholerae is spread through contaminated food and water. Prevention depends on interruption of fecal-oral transmission. Travelers to regions with cholera should follow precautions for the prevention of traveler’s diarrhea. Water can be treated with chlorine or iodine, by filtration or by boiling. A killed oral cholera vaccine may be given to children living in an endemic area and during outbreaks.

    Shigellosis

    Drinking water can be treated with chlorine or iodine, by filtration or by boiling. Good hygiene by strict handwashing should be practiced. Proper food preparation and refrigeration may help prevent the spread of Shigella infection. The occurrence of Shigella infection in daycare or school should prompt diagnostic investigation (eg stool culture, PCR tests) of students and staff members and isolation of infected students or personnel.

    Vitamin or Mineral Supplementation

    Zinc supplementation may be given to children 6 months to 12 years of age to prevent acute infectious diarrhea. Vitamin A supplementation may be given to infants and children >6 months of age to prevent acute infectious diarrhea.