Some antibiotics alter gut differently

ANN ARBOR, Mich., June 19 (UPI) -- U.S. researchers say they found, in studies in mice, two different types of antibiotics can cause moderate to wide-ranging changes in the gut's "good bacteria."

University of Michigan scientists said that it's common knowledge that a set of thousands of different kinds of microbes lives in the gut -- a distinctive mix for each person. However, antibiotics temporarily disturb the normal balance.

Senior author Dr. Vincent B. Young and colleagues used sequence analysis of 16S rRNA-encoding gene libraries to profile the bacterial communities in the gut.

Mice, which normally develop a diverse set of microbes after being born without one, were given either cefoperazone, a broad-spectrum cephalosporin antibiotic, or a combination of three antibiotics -- amoxicillin, bismuth and metronidazole. The scientists then observed changes in the gut microbiota after the antibiotics were stopped or six weeks later.

"Both antibiotic treatments caused significant changes in the gut microbial community," Young said in a statement. "However, in the mice given cefoperazone, there was no recovery of normal diversity. In other mice given the amoxicillin-containing combination, the microbiota largely recovered, but not completely."

Young cautions against concluding that supplements of probiotics are safe and effective for everyone looking for a way to restore healthy gut microbes after antibiotics -- an individual's specific health needs and vulnerabilities have to be considered.

The findings were published in the June issue of Infection and Immunity.