Irritable Bowel Syndrome Linked to Gut Bacteria

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newswise

CS CEDARS-SINAI

Physician Definitively Links

Irritable Bowel Syndrome

(IBS) and Bacteria in Gut

Released: 5/25/2012 8:00 AM EDT

Source: Cedars-Sinai Medical Center

Newswise — LOS ANGELES (May 25, 2012)

An overgrowth of bacteria in the gut has been definitively

linked to Irritable Bowel Syndrome in the results of a

new Cedars-Sinai study which used cultures from the

small intestine. This is the first study to use this “gold

standard” method of connecting bacteria to the cause

of the disease that affects an estimated 30 million

people in the United States.

Previous studies have indicated that bacteria play a role

in the disease, including breath tests detecting

methane – a byproduct of bacterial fermentation in the

gut. This study was the first to make the link using

bacterial cultures.

The study, in the current issue of Digestive Diseases

and Sciences, examined samples of patients’ small

bowel cultures to confirm the presence of small

intestinal bacterial overgrowth – or SIBO – in more than

320 subjects. In patients with IBS, more than a third

also were diagnosed with small intestine bacterial

overgrowth, compared to fewer than 10 percent of those

without the disorder. Of those with diarrhea-

predominant IBS, 60 percent also had bacterial

overgrowth.

“While we found compelling evidence in the past that

bacterial overgrowth is a contributing cause of IBS,

making this link through bacterial cultures is the gold

standard of diagnosis,” said Mark Pimentel, MD,

director of the Cedars-Sinai GI Motility Program and an

author of the study. “This clear evidence of the role

bacteria play in the disease underscores our clinical

trial findings, which show that antibiotics are a

successful treatment for IBS.”

IBS is the most common gastrointestinal disorder in the

U.S., affecting an estimated 30 million people. Patients

with this condition suffer symptoms that can include

painful bloating, constipation, diarrhea or an alternating

pattern of both. Many patients try to avoid social

interactions because they are embarrassed by their

symptoms. Pimentel has led clinical trials that have

shown rifaximin, a targeted antibiotic absorbed only in

the gut, is an effective treatment for patients with IBS.

“In the past, treatments for IBS have always focused on

trying to alleviate the symptoms,” said Pimentel, who

first bucked standard medical thought more than a

decade ago when he suggested bacteria played a

significant role in the disease. “Patients who take

rifaximin experience relief of their symptoms even after

they stop taking the medication. This new study

confirms what our findings with the antibiotic and our

previous studies always led us to believe: Bacteria are

key contributors to the cause of IBS.”

The study is a collaboration with researchers at

Sismanogleion General Hospital in Athens, Greece,

and at the University of Athens.

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DIGESTIVE DISEASES AND SCIENCES

Volume 57, Number 5 (2012), 1321-1329, DOI:

10.1007/s10-7

ORIGINAL ARTICLE

The Prevalence of Overgrowth by Aerobic

Bacteria in the Small Intestine by Small

Bowel Culture: Relationship with

Irritable Bowel Syndrome

Emmannouil Pyleris, Evangelos J.

Giamarellos-Bourboulis, Dimitrios Tzivras, Vassilios

Koussoulas, Charalambos Barbatzas and Mark

Pimentel

Abstract

Objectives

Many studies have linked irritable bowel syndrome (IBS)

with small intestinal bacterial overgrowth (SIBO), although

they have done so on a qualitative basis using breath tests

even though quantitative cultures are the hallmark of

diagnosis. The purpose of this study was to underscore the

frequency of SIBO in a large number of Greeks necessitating

upper gastrointestinal (GI) tract endoscopy by using

quantitative microbiological assessment of the duodenal

aspirate.

Methods

Consecutive subjects presenting for upper GI endoscopy

were eligible to participate. Quantitative culture of aspirates

sampled from the third part of the duodenum during upper

GI tract endoscopy was conducted under aerobic

conditions. IBS was defined by Rome II criteria.

Results

Among 320 subjects enrolled, SIBO was diagnosed in 62

(19.4%); 42 of 62 had IBS (67.7%). SIBO was found in 37.5%

of IBS sufferers. SIBO was found in 60% of IBS patients

with predominant diarrhea compared with 27.3% without

diarrhea (P = 0.004). Escherichia coli, Enterococcus spp and

Klebsiella pneumoniae were the most common isolates

within patients with SIBO. A step-wise logistic regression

analysis revealed that IBS, history of type 2 diabetes

mellitus and intake of proton pump inhibitors were

independently and positively linked with SIBO; gastritis was

protective against SIBO.

Conclusions

Using culture of the small bowel, SIBO by aerobe bacteria is

independently linked with IBS. These results reinforce

results of clinical trials evidencing a therapeutic role of

non-absorbable antibiotics for the management of IBS

symptoms.