eMedicine Specialties > Gastroenterology > Colon

Gastroenteritis, Bacterial: Differential Diagnoses & Workup

Author: Jennifer Lynn Bonheur, MD, Attending Physician, Division of Gastroenterology, Lenox Hill Hospital
Coauthor(s): Mukul Arya, MD, Associate Professor of Internal Medicine, Assistant Director of Therapeutic Endoscopy, Department of Gastroenterology and Internal Medicine, Wyckoff Heights Medical Center/Weill Medical College; Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston; M Akram Tamer, MD, Program Director, Professor, Department of Pediatrics, University of Miami
Contributor Information and Disclosures

Updated: Feb 19, 2009

Differential Diagnoses

Adenoviruses
Food Poisoning
Amebiasis
Gardnerella
Appendicitis
Gastroenteritis, Viral
Campylobacter Infections
Giardiasis
Celiac Sprue
Isosporiasis
Cholera
Lower Gastrointestinal Bleeding
Clostridium Difficile Colitis
Meckel Diverticulum
Colon Cancer, Adenocarcinoma
Microsporidiosis
Colonic Polyps
Salmonellosis
Colovesical Fistula
Shigellosis
Crohn Disease
Short-Bowel Syndrome
Cryptosporidiosis
Ulcerative Colitis
Diverticulitis
Food Allergies

Workup

Laboratory Studies

  • A stool pH of 5.5 or below or the presence of reducing substances indicates carbohydrate intolerance. This is usually transient in nature.
  • Enteroinvasive infections of the large bowel cause leukocytes, predominantly neutrophils, to be shed into stool. Absence of fecal leukocytes does not eliminate the possibility of enteroinvasive organisms; however, the presence of fecal leukocytes eliminates consideration of enterotoxigenic E coli, Vibrio species, and viruses.
  • Examine any exudate found in the stool for leukocytes. Such exudates highly suggest inflammatory bowel disease, which could be infectious or of another origin.
  • Below, Table 3 lists common bacteria and the optimal culture media for their growth.

Table 3. Common Bacteria and Optimum Culture Media

Open table in new window

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Table
OrganismDetection MethodMicrobiological Characteristics
Aeromonas speciesBlood agarOxidase-positive, flagellated GNB
Bacillus speciesBlood agarFacultatively aerobic, spore-forming GPR; beta-hemolytic; reduces nitrates; ferments carbohydrates
Campylobacter speciesSkirrow agarRapidly motile, curved GNR; Campylobacter jejuni 90% of infections, Campylobacter coli 5% of infections
C difficileCCFE agar, EIA for toxin, LA for proteinAnaerobic, spore-forming GPR; toxin-mediated diarrhea; produces pseudomembranous colitis
C perfringensNone availableAnaerobic, spore-forming GPR; toxin-mediated diarrhea
E coliMacConkey, EMB, or SM agarLactose-producing GNR
Listeria speciesBlood agarFlagellated GPB
Plesiomonas speciesBlood agarOxidase-positive GNR
Salmonella speciesBlood, MacConkey, EMB, XLD, or HE agarNonlactose, non–H2S-producing GNR
Shigella speciesBlood, MacConkey, EMB, XLD, or HE agarNonlactose and H2S-producing GNR; verotoxin (neurotoxin)
Staphylococcus speciesBlood agarHeat-stable, preformed toxin-mediated GPC
Vibrio speciesBlood or TCBS agarOxidase-positive, motile, curved GNB
Y enterocoliticaCIN agarNonlactose-producing, oval GNR
OrganismDetection MethodMicrobiological Characteristics
Aeromonas speciesBlood agarOxidase-positive, flagellated GNB
Bacillus speciesBlood agarFacultatively aerobic, spore-forming GPR; beta-hemolytic; reduces nitrates; ferments carbohydrates
Campylobacter speciesSkirrow agarRapidly motile, curved GNR; Campylobacter jejuni 90% of infections, Campylobacter coli 5% of infections
C difficileCCFE agar, EIA for toxin, LA for proteinAnaerobic, spore-forming GPR; toxin-mediated diarrhea; produces pseudomembranous colitis
C perfringensNone availableAnaerobic, spore-forming GPR; toxin-mediated diarrhea
E coliMacConkey, EMB, or SM agarLactose-producing GNR
Listeria speciesBlood agarFlagellated GPB
Plesiomonas speciesBlood agarOxidase-positive GNR
Salmonella speciesBlood, MacConkey, EMB, XLD, or HE agarNonlactose, non–H2S-producing GNR
Shigella speciesBlood, MacConkey, EMB, XLD, or HE agarNonlactose and H2S-producing GNR; verotoxin (neurotoxin)
Staphylococcus speciesBlood agarHeat-stable, preformed toxin-mediated GPC
Vibrio speciesBlood or TCBS agarOxidase-positive, motile, curved GNB
Y enterocoliticaCIN agarNonlactose-producing, oval GNR

CCFE = cycloserine-cefoxitin-fructose-egg; CIN = cefsulodin-irgasan-novobiocin; EIA= enzyme immunoassay; EMB = e-methylene blue; GNB = gram-negative bacillus; GNR = gram-negative rod; GPB = gram-positive bacillus; GPC = gram-positive cocci; GPR = gram-positive rod; H2S = hydrogen sulfide; HE = Hektoen enteric; LA = latex agglutination; SM = Sorbitol-MacConkey; TCBS = thiosulfate-citrate-bile-sucrose; XLD = xylose-lysine-deoxycholate.

  • The following is a list of the different culture media used to isolate bacteria. A high index of suspicion is needed to choose the appropriate medium.
    • Blood agar - All aerobic bacteria and yeast; detects cytochrome oxidase production
    • MacConkey EMB agar - Inhibits gram-positive organisms; permits lactose fermentation
    • XLD agar and HE agar - Inhibit gram-positive organisms and nonpathogenic gram-negative bacilli; permit lactose fermentation and H2S production
    • Skirrow agar - Selective for Campylobacter species
    • SM agar - Selective for enterohemorrhagic E coli
    • CIN agar - Selective for Y enterocolitica
    • Thiosulfate-citrate-bile-sucrose agar - Selective for Vibrio species
    • CCFE agar - Selective for C difficile
  • Stool cultures are useful when positive, but the yield is usually low.
    • Refrigerate stool that is not cultured within 2 hours of collection at 4°C, or place it in a transport medium.
    • Always culture stool for Campylobacter, Salmonella, and Shigella species, especially if stool leukocytes or gross blood is found in the stool.
  • Serotype Salmonella for S typhimurium DT104, particularly if the gastroenteritis is associated with raw milk or cheese ingestion. S typhimurium DT104 is a multidrug-resistant organism, and antibiotic sensitivities are crucial to guide therapy.10,11
  • Preformed toxin from Bacillus or Staphylococcus species may cause rapid-onset gastroenteritis. In such cases, the bacteria may not exist in the gastrointestinal tract; therefore, culture the food ingested by the person.
  • Bloody diarrhea with a history of ground beef ingestion should raise the suspicion for enterohemorrhagic E coli. If E coli is found in the stool, type it to determine if it is O157:H7. Report cases of E coli O157:E7 gastroenteritis (and other infectious problems) to the state health department.
  • History of raw seafood ingestion or foreign travel should prompt additional screening for Vibrio and Plesiomonas species.
  • The leukocyte count is usually not elevated in viral and toxin-mediated diarrhea. Leukocytosis is seen with enteroinvasive bacteria. Shigella characteristically causes marked bandemia with variable total WBC count.
  • Antilisteriolysin O (ALLO) is positive during the convalescent phase of the illness and when invasive disease has occurred.

Procedures

  • Identification of pseudomembranes in the colon by direct visualization is diagnostic for C difficile; however, the yield may be low.

More on Gastroenteritis, Bacterial

Overview: Gastroenteritis, Bacterial
Differential Diagnoses & Workup: Gastroenteritis, Bacterial
Treatment & Medication: Gastroenteritis, Bacterial
Follow-up: Gastroenteritis, Bacterial
References
Further Reading
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References

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  8. Lee LA, Gerber AR, Lonsway DR, et al. Yersinia enterocolitica O:3 infections in infants and children, associated with the household preparation of chitterlings. N Engl J Med. Apr 5 1990;322(14):984-7. [Medline].

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  10. Cody SH, Abbott SL, Marfin AA, et al. Two outbreaks of multidrug-resistant Salmonella serotype typhimurium DT104 infections linked to raw-milk cheese in Northern California. JAMA. May 19 1999;281(19):1805-10. [Medline]. [Full Text].

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Keywords

bacterial gastroenteritis, gastroenteritis, diarrhea, traveler's diarrhea, acute gastroenteritis, viral infection, improper diet, malabsorption syndrome, enteropathy, inflammatory bowel disease, Salmonella, Shigella, Campylobacter, Aeromonas, Escherichia coli, E coli, vomiting

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Contributor Information and Disclosures

Author

Jennifer Lynn Bonheur, MD, Attending Physician, Division of Gastroenterology, Lenox Hill Hospital
Jennifer Lynn Bonheur, MD is a member of the following medical societies: American Gastroenterological Association, American Society for Gastrointestinal Endoscopy, New York Academy of Sciences, New York Society for Gastrointestinal Endoscopy, and Sigma Xi
Disclosure: Nothing to disclose.

Coauthor(s)

Mukul Arya, MD, Associate Professor of Internal Medicine, Assistant Director of Therapeutic Endoscopy, Department of Gastroenterology and Internal Medicine, Wyckoff Heights Medical Center/Weill Medical College
Mukul Arya, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Medical Association, and American Society for Gastrointestinal Endoscopy
Disclosure: Nothing to disclose.

Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston
Richard E Frye, MD, PhD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, Child Neurology Society, and International Neuropsychological Society
Disclosure: Nothing to disclose.

M Akram Tamer, MD, Program Director, Professor, Department of Pediatrics, University of Miami
M Akram Tamer, MD is a member of the following medical societies: American Medical Association and Florida Medical Association
Disclosure: Nothing to disclose.

Medical Editor

John Gunn Lee, MD, Director of Pancreaticobiliary Service, Associate Professor, Department of Internal Medicine, Division of Gastroenterology, University of California at Irvine School of Medicine
John Gunn Lee, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, and American Society for Gastrointestinal Endoscopy
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Simmy Bank, MD, Chair, Professor, Department of Internal Medicine, Division of Gastroenterology, Long Island Jewish Hospital, Albert Einstein College of Medicine
Disclosure: Nothing to disclose.

CME Editor

Alex J Mechaber, MD, FACP, Associate Dean for Undergraduate Medical Education, Associate Professor of Medicine, University of Miami Miller School of Medicine
Alex J Mechaber, MD, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Chief Editor

Julian Katz, MD, Clinical Professor of Medicine, Drexel University College of Medicine; Consulting Staff, Department of Medicine, Section of Gastroenterology and Hepatology, Hospital of the Medical College of Pennsylvania
Julian Katz, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Geriatrics Society, American Medical Association, American Society for Gastrointestinal Endoscopy, American Society of Law Medicine and Ethics, American Trauma Society, Association of American Medical Colleges, and Physicians for Social Responsibility
Disclosure: Nothing to disclose.

 
 
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