CHICAGO, April 3 (Xinhua) -- Apes in U.S. zoos host bacterial communities in their intestinal tracts that are more similar to those of people who eat a non-Western diet than to the gut makeup of their wild ape cousins, according to a study posted on the website of Washington University in St. Louis on Wednesday.

To learn about the apes' gut microbiomes, the researchers followed apes in known groups and discreetly collected fecal samples from 18 wild chimpanzees and 28 wild gorillas in Nouabale-Ndoki National Park in the Republic of Congo. They also collected fecal samples from 81 people who lived on the outskirts of the park.

Meanwhile, the researchers obtained fecal samples from 18 chimpanzees and 15 gorillas living at either the Saint Louis Zoo or the Lincoln Park Zoo in the United States.

The researchers identified the kinds of bacteria and the antibiotic genes present in the gorilla, chimpanzee and human samples, and compared the results to publicly available data on people who live in the United States, Peru, El Salvador, Malawi, Tanzania, or Venezuela and follow hunter-gatherer, rural agriculturalist, or urban lifestyles.

The gut microbiomes of people whose data was included in the study fell into two groups. In one were hunter-gatherers and rural agriculturalists who typically eat a diet heavy in vegetables and light in meat and fat; this group included the people from the outskirts of the national park in Congo. In the second group were urban people who eat a meat-rich Western diet. Wild gorillas and chimpanzees formed a third group distinct from both human groups. But captive apes fell into the first group; they were most similar to people who ate non-Western diets.

The researchers found that contact with people shapes the gut microbial communities, or microbiomes, of gorillas and chimpanzees.

The researchers also identified several previously unknown antibiotic resistance genes in the wild apes and people from Congo, including one that confers resistance to colistin, an antibiotic of last resort.

"Rare sampling opportunities of wild apes like in this study gives us a look into the future," said Tayte Campbell, then a graduate student at Washington University. "When we find these novel antibiotic resistance genes in the environment, we can study them and possibly find ways to inhibit them before they show up in human pathogens and make infections very difficult to treat."

"It would be very interesting to expand this research across a broader range of conservation contexts, such as commercial logging zones and tourist operations," said David Morgan, an honorary research scientist at Washington University. "With the arrival of human activities and associated anthropogenic disturbances, wild apes may be exposed to antibiotic resistance genes. We don't know much about how antibiotic resistance spreads through natural environments, so that could have implications for human public health that we don't yet understand. That's something we'd like to investigate."

The study has been published online in The ISME Journal.