eMedicine Specialties > Infectious Diseases > Gastrointestinal Tract and Intra-abdominal Infections
Bacterial Overgrowth Syndrome: Treatment & Medication
Updated: May 21, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
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:
- Infectious diarrhea
- Malnutrition
- Malabsorption
- Hypothyroidism
- Inflammatory bowel disease
- Immunodeficiency
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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Further Reading
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
Treatment & Medication: Bacterial Overgrowth Syndrome