eMedicine Specialties > Infectious Diseases > Gastrointestinal Tract and Intra-abdominal Infections

Bacterial Overgrowth Syndrome: Treatment & Medication

Author: Pedro A Manibusan Jr, DO, Intern, Department of Internal Medicine, Tripler Army Medical Center
Coauthor(s): Joshua S Hawley, MD, Assistant Chief, Consulting Staff, Departments of Infectious Disease and Internal Medicine, Tripler Army Medical Center; 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; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Contributor Information and Disclosures

Updated: May 21, 2009

Treatment

Medical Care

General care in bacterial overgrowth syndrome (BOS) includes antibiotic therapy aimed at rebalancing enteric florae. Careful consideration must be taken to prevent total eradication of protective microorganisms. Instead, the goal should be directed at reducing symptoms. Initial antibiotic therapy should be broad and should cover both aerobic and anaerobic microorganisms. Community resistance patterns should also be considered.

  • Tetracycline was the mainstay of therapy, but its use as single agent has fallen out of favor in adult patients given community increases in bacterial resistance.
  • Bacterial sensitivities from duodenal intubations with nonidiopathic bacterial overgrowth syndrome support the use of amoxicillin-clavulanate. Amoxicillin-clavulanate appears to be 75% effective in patients with diabetes.
  • Clindamycin and metronidazole are useful in elderly patients with idiopathic bacterial overgrowth syndrome.
  • As outlined below, gentamicin, but not metronidazole, significantly improves intractable diarrhea in children younger than 1 year.8
  • Cholestyramine reduces diarrhea in infants and neonates with intractable diarrhea.20 Infants with 10-25 days of severe persistent diarrhea for which a cause could not be found despite an extensive infectious and immunologic workup were treated with cholestyramine and gentamicin or metronidazole. Cholestyramine and gentamicin significantly reduced stool weight within 4-5 days of therapy but had mild detrimental effects on fat and nitrogen absorption.
  • Recent studies have shown that monotherapy with rifaximin or norfloxacin may be beneficial.

The exact length of therapy is not clearly defined, as length of therapy should be tailored to symptom improvement.

  • Some patients may respond to short antibiotic courses (eg, 7-14 days).
  • However, given the underlying mechanism that produced the bacterial overgrowth syndrome, prolonged, repeat, or chronic antibiotic therapy is not uncommon.

Probiotic therapy has been shown useful in patients who do not respond to antibiotic therapy, but its role in bacterial overgrowth syndrome therapy is not clearly defined.

Dependent on clinical manifestations, treatment should include attention toward nutrient/vitamin replacement, if applicable.

Certain potential underlying abnormalities are amenable to treatment, as follows:

The following potential underlying diseases are not amenable to treatment, but prevention of their progression may be therapeutic:

  • Diabetic autonomic neuropathy
  • Scleroderma
  • Pseudoobstruction
  • Amyloidosis
  • Achlorhydria
  • Vagotomy

Surgical Care

In the absence of underlying structural abnormalities that limit normal bowel function, surgery is not generally unwarranted.

  • Repair postoperative strictures and blind loops; for example, a Billroth type II may need conversion to a Billroth type I.
  • Strictures, fistulae, and diverticula may require surgical correction.

Consultations

  • Patients refractory to standard medical or surgical treatment or those who have severe symptoms should be referred to a gastroenterologist/infectious disease specialist.

Medication

The goals of pharmacotherapy are to eradicate the infection, to reduce morbidity, and to prevent complications.

Antibiotics

Therapy should be directed against B fragilis.


Amoxicillin-clavulanic acid (Augmentin)

First-line antibiotic for bacterial overgrowth syndrome due to anatomic abnormalities and diabetes and for elderly patients with idiopathic bacterial overgrowth syndrome. Provides good gram-negative, gram-positive, and anaerobic coverage. Reduces number of bacteria in small bowel lumen.

Adult

875 mg PO bid

Pediatric

40 mg/kg/d PO divided bid

Probenecid increases serum levels; decreases efficacy of oral contraceptives; increases effect of anticoagulants

Documented hypersensitivity to same or other beta-lactam drugs

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Give for a minimum of 10 d to eliminate organism and prevent sequelae (endocarditis, rheumatic fever); following treatment, perform cultures to confirm eradication of streptococci


Clindamycin (Cleocin)

Works well in elderly patients with idiopathic bacterial overgrowth syndrome, especially if bile malabsorption coexists. Good anaerobic and gram-positive coverage, except enterococci.

Adult

300 mg PO q8h
600-2700 mg/d IV divided tid

Pediatric

30 mg/kg/d PO divided qid
40 mg/kg/d IV divided tid/qid

Enhances action of nondepolarizing muscle relaxants

Documented hypersensitivity; hepatic dysfunction; pseudomembranous colitis; other diarrhea

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Dose reduction with severe liver dysfunction; GI distress; pseudomembranous colitis; elevates LFT results; rash; Stevens-Johnson syndrome; granulocytopenia and thrombocytopenia


Gentamicin (Garamycin, Gentacidin)

Useful in neonates and infants with idiopathic bacterial overgrowth syndrome. Aminoglycoside that provides excellent aerobic gram-negative coverage in bowel when administered PO.
Not well absorbed PO. Studies have not established serum levels with enteral administration and compromise of intestinal lumen.

Adult

PO dose not established

Pediatric

50 mg/kg/d PO divided 4-6 times/d; not to exceed 360 mg/d

Coadministration with other aminoglycosides, cephalosporins, penicillins, and amphotericin B may increase nephrotoxicity; aminoglycosides enhance effects of neuromuscular blocking agents, thus, prolonged respiratory depression may occur; coadministration with loop diuretics may increase auditory toxicity of aminoglycosides; possible irreversible hearing loss of varying degrees may occur (monitor regularly)

Documented hypersensitivity (extremely rare)

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Parenteral administration is associated with increased risk for ototoxicity and nephrotoxicity; minimal oral absorption


Metronidazole (Flagyl)

First-line antibiotic for elderly patients with idiopathic bacterial overgrowth syndrome. Provides good anaerobic coverage.

Adult

500 mg PO bid/tid

Pediatric

30 mg/kg/d PO divided qid

Effects decreased by phenytoin and phenobarbital; alcohol induces disulfiramlike reaction; increases PT with warfarin; increases lithium serum levels and toxicity; serum level increased by cimetidine

Documented hypersensitivity; severe renal or liver failure

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

GI distress; discontinue if seizures or neuropathy develops


Tetracycline (Nor-tet, Panmycin)

Effective for patients with bacterial overgrowth syndrome. Provides anaerobic coverage.

Adult

500 mg PO qid

Pediatric

<8 years: Not recommended
>8 years: Not established

May interfere with efficacy of penicillins; increased PT in patients taking warfarin; antacids, calcium, iron, bicarbonate, and sucralfate decrease absorption

Documented hypersensitivity; children; severe renal and liver dysfunction

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

GI distress; photosensitivity; increased BUN, hepatotoxicity

More on Bacterial Overgrowth Syndrome

Overview: Bacterial Overgrowth Syndrome
Differential Diagnoses & Workup: Bacterial Overgrowth Syndrome
Treatment & Medication: Bacterial Overgrowth Syndrome
Follow-up: Bacterial Overgrowth Syndrome
References
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References

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  2. Bouhnik Y, Alain S, Attar A, et al. Bacterial populations contaminating the upper gut in patients with small intestinal bacterial overgrowth syndrome. Am J Gastroenterol. May 1999;94(5):1327-31. [Medline].

  3. Chalmers RA, Valman HB, Liberman MM. Measurement of 4-hydroxyphenylacetic aciduria as a screening test for small-bowel disease. Clin Chem. Oct 1979;25(10):1791-4. [Medline].

  4. Donald IP, Kitchingmam G, Donald F, Kupfer RM. The diagnosis of small bowel bacterial overgrowth in elderly patients. J Am Geriatr Soc. Jul 1992;40(7):692-6. [Medline].

  5. Gracey M, Burke V, Oshin A, et al. Bacteria, bile salts, and intestinal monosaccharide malabsorption. Gut. Sep 1971;12(9):683-92. [Medline].

  6. Gregg CR. Enteric bacterial flora and bacterial overgrowth syndrome. Semin Gastrointest Dis. Oct 2002;13(4):200-9. [Medline].

  7. Haboubi NY, Lee GS, Montgomery RD. Duodenal mucosal morphometry of elderly patients with small intestinal bacterial overgrowth: response to antibiotic treatment. Age Ageing. Jan 1991;20(1):29-32. [Medline].

  8. Hill ID, Mann MD, Househam KC, Bowie MD. Use of oral gentamicin, metronidazole, and cholestyramine in the treatment of severe persistent diarrhea in infants. Pediatrics. Apr 1986;77(4):477-81. [Medline].

  9. Hoverstad T, Bjorneklett A, Fausa O, Midtvedt T. Short-chain fatty acids in the small-bowel bacterial overgrowth syndrome. Scand J Gastroenterol. May 1985;20(4):492-9. [Medline].

  10. Kilby AM, Dolby JM, Honour P, Walker-Smith JA. Duodenal bacterial flora in early stages of transient monosaccharide intolerance in infants. Arch Dis Child. Mar 1977;52(3):228-34. [Medline].

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  12. Klish WJ, Udall JN, Rodriguez JT, et al. Intestinal surface area in infants with acquired monosaccharide intolerance. J Pediatr. Apr 1978;92(4):566-71. [Medline].

  13. Kocoshis SA, Schletewitz K, Lovelace G, Laine RA. Duodenal bile acids among children: keto derivatives and aerobic small bowel bacterial overgrowth [published erratum appears in J Pediatr Gastroenterol Nutr 1988 Jan-Feb;7(1):155]. J Pediatr Gastroenterol Nutr. Sep-Oct 1987;6(5):686-96. [Medline].

  14. Lin HC. Small intestinal bacterial overgrowth: a framework for understanding irritable bowel syndrome. JAMA. Aug 18 2004;292(7):852-8. [Medline].

  15. Mathias JR, Clench MH. Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine. Am J Med Sci. Jun 1985;289(6):243-8. [Medline].

  16. Meyers JS, Ehrenpreis ED, Craig RM. Small Intestinal Bacterial Overgrowth Syndrome. Curr Treat Options Gastroenterol. Feb 2001;4(1):7-14. [Medline].

  17. Nichols VN, Fraley JK, Evans KD, Nichols BL Jr. Acquired monosaccharide intolerance in infants. J Pediatr Gastroenterol Nutr. Jan 1989;8(1):51-7. [Medline].

  18. Saltzman JR, Russell RM. Nutritional consequences of intestinal bacterial overgrowth. Compr Ther. 1994;20(9):523-30. [Medline].

  19. Sherr HP, Sasaki Y, Newman A, et al. Detection of bacterial deconjugation of bile salts by a convenient breath-analysis technic. N Engl J Med. Sep 16 1971;285(12):656-61. [Medline].

  20. Tamer MA, Santora TR, Sandberg DH. Cholestyramine therapy for intractable diarrhea. Pediatrics. Feb 1974;53(2):217-20. [Medline].

  21. Virally-Monod M, Tielmans D, Kevorkian JP, et al. Chronic diarrhoea and diabetes mellitus: prevalence of small intestinal bacterial overgrowth. Diabetes Metab. Dec 1998;24(6):530-6. [Medline].

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Further Reading

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Keywords

bacterial overgrowth syndrome, BOS, acquired monosaccharide intolerance of infancy, blind-loop syndrome, blind loop syndrome, contaminated small bowel syndrome, small intestinal stasis syndrome, stagnant loop syndrome, fat malabsorption, protein malabsorption, carbohydrate malabsorption, vitamin malabsorption, malabsorption, neonatal chronic diarrhea, neonatal diarrhea

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Contributor Information and Disclosures

Author

Pedro A Manibusan Jr, DO, Intern, Department of Internal Medicine, Tripler Army Medical Center
Pedro A Manibusan Jr, DO is a member of the following medical societies: American College of Physicians, American Osteopathic Association, and Association of Military Osteopathic Physicians and Surgeons
Disclosure: Nothing to disclose.

Coauthor(s)

Joshua S Hawley, MD, Assistant Chief, Consulting Staff, Departments of Infectious Disease and Internal Medicine, Tripler Army Medical Center
Joshua S Hawley, MD is a member of the following medical societies: American College of Physicians, Armed Forces Infectious Diseases Society, Infectious Diseases Society of America, and Phi Beta Kappa
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.

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Medical Editor

Mark Raymond Wallace, MD, Infectious Disease Fellowship Director, Orlando Regional Healthcare; Clinical Professor of Medicine, Florida State University
Mark Raymond Wallace, MD is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Tropical Medicine and Hygiene, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Joseph F John Jr, MD, FACP, FIDSA, FSHEA, Clinical Professor of Medicine, Molecular Genetics and Microbiology, Medical University of South Carolina; Associate Chief of Staff for Education, Ralph H Johnson Veterans Affairs Medical Center
Disclosure: BioMerieux Honoraria Review panel membership; Cubist Honoraria Review panel membership; Pfizer Honoraria Speaking and teaching; Merck Stock dividends stock holdings

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD, Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center
Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Association of Professors of Medicine, Association of Program Directors in Internal Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation
Disclosure: Nothing to disclose.

 
 
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