Probiotics and Antibiotics

Gut Flora

Bacteria are very small organisms (microbes) that are normally in the gut (intestines). There are over 500 different kinds known to live in the gut. Most bacteria are in the large intestine (colon) where they achieve concentrations of several billion. These “normal” bacteria have important functions in life: 

• They protect against infection by “bad”, or pathogenic, bacteria
• They help the immune system of the gut to develop
• They produce a variety of substances, including some essential vitamins, that have an important nutritional value

Together, the normal bacteria are often referred to as the gut flora. A variety of factors may disturb the mutually beneficial relationship between the flora and its host (our intestines), and disease may result. Additionally, some bacteria can cause infection. These are called pathogens.

Antibiotics

Antibiotics are medicines that destroy bacteria. They can change the balance of the number and kind of gut bacteria. Changing the normal balance may put some people at risk for IBS.

On the other hand, if there are too many or the wrong kinds of bacteria in the small intestine, antibiotics may make IBS symptoms better. In one line of investigation short-term therapy with antibiotics has been shown to reduce gas-related symptoms among a group of patients with bloating and flatulence, who did not have evidence of small intestinal bacterial overgrowth (SIBO).

Probiotics

Some kinds of bacteria, in the right amount, can be helpful. These are called probiotics. In some people, changing the kind of gut bacteria with probiotics may make symptoms of IBS better. The best evidence relates to a particular organism, Bifidobacterium infantis 35624. Studies have shown this strain to be superior to placebo in relieving the main symptoms of the irritable bowel syndrome (abdominal pain/discomfort, distension/bloating and difficult defecation).

Gut Flora and IBS

We still do not know the exact role bacteria may have in IBS. Whether or not these effects come about through subtle and perhaps localized changes in the number or type of bacteria in the colon and/or small intestine, it is evident that manipulation of the flora, whether through the administration of antibiotics or probiotics, deserves further attention in IBS. More medical research is needed.