Approach to the Patient With Infectious Colitis

Herbert L. DuPont

Curr Opin Gastroenterol. 2012;28(1):39-46.

Treatment

Patients with infectious colitis usually will benefit by receiving an antimicrobial drug directed against the causative agent. Laboratory study will be important to identifying the cause of the colitis.

Nonspecific Treatment

Patients with infectious colitis such as others with diarrhea of small bowel origin will benefit by paying attention to fluid and salt administration to meet losses from illness and to keep up with continuing losses. Occasionally intravenous fluid administration will be needed. Symptomatic therapy with antimotility therapy (e.g., loperamide) is generally not indicated in infectious colitis and can be dangerous if given without specific treatment.^[26] There is no evidence that the antimotility drugs are harmful in inflammatory diarrhea if given with proper antimicrobial treatment designed to treat the bacterial enteric infection.^[27•,28] For possible STEC infection in which specific therapy is not available, antimotility drugs can potentiate the development of HUS.^[29••]

Antimicrobial Therapy

In Table 2 recommended antimicrobial therapy for the various forms of infectious colitis are provided. Making an etiologic diagnosis (Table 1) is important for developing a plan for therapy.

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Table 1. Etiologic diagnosis of patients with infectious colitis suspected in patients with acute diarrhea and any of the following: fever, dysentery (passage of grossly bloody stools, often with mucus), fecal markers of inflammation, ^a or colonic mucosal inflammation on endoscopy
Etiologic agent	Routine stool examination	Specialized stool examinations that must be requested	Specialized stool examinations that are available in research laboratories
Shigella	Identified routinely with stool culture	Not needed, employ standard stool culture	Not needed
Campylobacter	Identified routinely with stool culture	Not needed, employ standard stool culture	Not needed
Salmonella	Identified routinely with stool culture	Not needed, employ standard stool culture	Not needed
STEC	May or may not be part of normal stool culture exam	Should be requested when patient is passing grossly bloody stools looking for Escherichia coli O157:H7 and Shiga toxins directly in stool [1]	If positive, additional study will be needed at a local or state health department laboratory^b
EAEC	Not available	Not available	Performed only in research laboratories
EIEC	Not available	Not available	Performed only in research laboratories using PCR methods, or Sereny guinea pig eye test
Aeromonas	Should be identified routinely with stool culture	Advisable to request that the laboratory look for in dysenteric diarrhea	Few research labs are working with this organism
Vibrio (noncholera) spp. (e.g.V. parahemolyticus)	Not part of normal stool culture exam	Should be requested when organism suspected based on vehicle of transmission (shellfish, seafood)laboratory will culture on salt-containing media	Few research labs are working with this organism
Yersinia enterocolitica	Should be identified routinely with stool culture if present in stools in high concentration	Should be requested when suspected based on epidemiology and the stool can be processed by incubating the culture at 25 and 28°C	Few research labs are working with this organism
Enterotoxigenic Bacteroides fragilis	Not available	The toxin is detected by PCR and the organism is isolated by microbiologic culture methods	The importance of this organism has not been established
Clostridium difficile	Stool test for C. difficile toxin (EIA, PCR or cytotoxin by tissue culture) or microbiologic culture	Many diagnostic laboratories are moving to sensitive PCR methods	Not needed
Entamoeba histolytica	Identified routinely when parasite test ordered by direct microscopy or by commercial EIA tests	Not needed	Research laboratories can differentiate between pathogenic and nonpathogenic Entamoeba
Schistosoma mansoni colitis	Stool examination for characteristic eggs	EIA available	Endoscopic evaluation may be required to establish diagnosis^[2•]
Cytomegalovirus	Not available	Mucosal biopsy material can be examined histologically and/or the virus can be cultured	Not needed

EAEC, enteroaggreagative Escherichia coli; EIA, enzyme immunoassay; EIEC, enteroinvasive Escherichia coli; PCR, polymerase chain reaction; STEC, Shiga toxin-producing Escherichia coli; TCBS, thiosulfate citrate bile sucrose agar.
^aFecal leukocytes or positive test for lactoferrin or calprotectin.
^bIf the stool is negative for O157 but Shiga toxin positive, isolated Escherichia coli strains will have to be tested for serotype and confirmed to be toxigenic and organism will need to be serotyped and submitted to a local health laboratory for analysis for pulsed field gel electrophoresis (PFGE) to determine whether it is part of an epidemic.

Table 2. Antimicrobial therapy of infectious colitis in adults
Etiologic agent	Recommended treatment	Comments
Shigella spp.	Ciprofloxacin 750 mg (or other fluoroquinolone) once day for days; or azithromycin 500 mg once day for days	Secondary spread is common in families because of the low inoculum size required to cause infection; fluoroquinolone resistance is being reported.
Campylobacter jejuni	Azithromycin 500 mg once day for days; or erythromycin 500 mg four times day for 3–days	Fluoroquinolone resistance is widespread. Azithromycin resistance is being seen.
Salmonella (nontyphoid)	For milder illness, none; for possible bacteremic disease, levofloxacin 500 mg (or other fluoroquinolone) once a day for (if immunocompetent) or 14 days (if immunocompromised*)	Bacteremic disease is considered if: febrile or toxic, at extremes of age (≤months or ≥65 years of age)patient has sickle cell anemia, cancer or AIDS#2;or is on steroids or is undergoing hemodialysis or has inflammatory bowel disease.
Shiga toxin producing E. coli (STEC)	None	Antibiotics or antimotility agents may encourage production of Shiga toxin and increase risk of HUS.
Enteroaggregative E. coli	Rifaximin 200 mg three times day for 3 days	Fluoroquinolones or azithromycin are equally effective.
Enteroinvasive E. coli	Treat as for Shigella	This is an unusual cause of foodborne outbreaks.
Aeromonas spp.	Treat as for Shigella	This infection is most common in tropical and semitropical areas.
Travelers' diarrhea complicated with fever or dysentery (uncertain agent)	Treat as for Shigella	As bacterial agents cause most cases of travelers' diarrhea, empiric antimicrobial therapy is given.
Vibrio spp. (noncholera)	Treat as for Shigella	Causes watery diarrhea and dysentery usually associated with shellfish and seafood consumption.
Yersinia enterocolitica	Treat as for Shigella	Causes acute watery diarrhea, fever, and dysentery and an 'appendicitis'-like picture.
Clostridium difficile	Metronidazole 500 mg three times day for milder cases or oral vancomycin 125 mg four times day for more severe illness; either drug is given for 10–14 days	Recurrences are common and may require prolonged treatment with oral vancomycin or other approach^[4]Fidaxomicin was recently licensed for therapy in the USA.
Entamoeba histolytica	Metronidazole 750 mg three times day for 5–10 days and luminal amebicide: paromomycin 500 mg three times day for 10 days, iodoquinol 650 mg three times day for 20 days, or diloxanide furoate 500 mg three times day for 10 days	It is necessary to treat the infectious trophoite phase with metronidazole to improve symptoms and the cyst phase of the parasite to prevent disease recurrence.
S. mansoni colitis	Praziquantil 40 mg/kg body weight in single dose	Cure rates in field studies have been approximately 85%
Cytomegalovirus	Ganciclovir mg/kg intravenously for 14 days	Diarrhea may persist after treatment suggesting longer-term treatment will be necessary.

STEC, Shiga toxin-producing Escherichia coli.

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