A Gut Reaction to Antibiotics

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A Gut Reaction to Antibiotics

By Carol Potera

Sep 16, 2005, 20:47

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Is the explosive rise in asthma and allergies being seen especially

in children partially related to antibiotic use? Epidemiologic

studies have found strong connections between antibiotic treatment

and the later development of asthma and allergies. Yet, until

recently, no studies had looked at how the two are linked. Now

researchers at the University of Michigan in Ann Arbor have created

a mouse model that offers clues to the mechanism behind the

association.

Immunologist Huffnagle and colleagues are the first to

demonstrate in a mouse model that the disruption of beneficial

intestinal bacteria by antibiotics allows yeast to take hold and

flourish. They developed their mouse model specifically to study the

relationship between antibiotic use and allergies. When mice inhale

fungal spores known to trigger allergies in people, the allergic

reaction is more potent in mice with an overgrowth of yeast in their

guts.

In their studies, the Michigan researchers first treat mice for

several days with the broad-spectrum antibiotic cefoperazone to

destroy the gut flora. Then the mice are fed Candida albicans, a

yeast that commonly lives in people. " This represents the clinical

scenario of getting a yeast infection after taking antibiotics, "

says Huffnagle. Next, the mice are exposed nasally to spores of the

mold Aspergillus fumigatus (a major indoor contaminant) and to egg

white protein.

Results are showing that both allergens produce significant

increases in inflammation-related white blood cells in the lungs of

the mice, and they elevate blood levels of key markers of allergic

reactions, including IgE, interleukin-5, and interleukin-13. Mice

not treated with antibiotics show much milder reactions to the

allergens. The team's latest report appears in the January 2005

issue of Infection and Immunity. Future work with the model will

investigate the actions of other antibiotics (such as amoxicillin)

and allergens (such as pollen and dust mites).

How do changes in gut flora influence respiratory allergies? The

answer likely involves oral tolerance, Huffnagle theorizes. Upon

ingestion of allergens, the oral mucosa generate regulatory T cells,

which circulate to the respiratory tract, where they suppress

allergic reactions. " We live in a dirty world, and we swallow mold

spores, pollen, dust, and other allergens constantly, " says

Huffnagle. These oral allergens trigger immune responses that

instruct the rest of the body to be more tolerant of allergens so

allergic reactions don't occur. Moreover, other studies have

indicated that mice lacking gut flora cannot generate oral

tolerance. When the gut flora are restored, oral tolerance returns.

Huffnagle plans to evaluate over-the-counter probiotics--

concentrated supplements of beneficial bacteria--to identify which,

if any, work best for replenishing gut flora. " [Probiotics are a]

relatively new concept, and there's not a lot of precedent for their

use now, " says infectious disease specialist Bruce Klein of the

University of Wisconsin-Madison. If future studies show that

probiotics do replace flora, Klein adds, physicians may be inclined

to recommend their use. Eating yogurt with live cultures also

remains a good way to replenish gut flora following a course of

antibiotics.

Originally published by Envirnmental Health Perspectives in June,

2005. Republished with permission.