Antibiotic Resistance in Chimps

There's an interesting news story about antibiotic resistance in wild chimpanzee populations that claims to have found transfer of resistant Escherichia coli from humans to wild animals.

According to the article:

To do the study, the UI researchers, working with colleagues from Makerere University in Uganda and McGill University in Canada , examined 2 of the communities of chimpanzees living in the Kibale park. One of them has been under study by scientists for more than 2 decades. The other is visited regularly by ranger guides who shepherd tourists in the park. The researchers collected samples of E. coli bacteria from the chimpanzees and from the human scientists and guides. They also collected samples of E. coli from villagers who live about 3 and 15 miles (5-24 km.) from the park and have little if any contact with the chimps.

Goldberg said the researchers looked at E. coli because the bacterium is a good model system for such a study. It's common in animals and huomans and it can be a serious health threat in some forms. Scientists also know much about E. coli on a molecular, genetic level -- more than any other bacterium -- and about antibiotic resistance in E. coli. That's important because the UI researchers and their colleagues basically compared the genetic fingerprints of the various samples to see if there were similarities. They found that E. coli from people who worked in proximity to the chimpanzees was more like the E. coli from the chimps than bacteria from the villagers who have little or no contact with the animals.

Goldberg said you might expect some limited "background level" of antibiotic resistance in the chimps from natural factors. But in this case, specific strains of resistance proved to be significantly similar among the animals and the people who work with them. While antibiotics are used frequently among humans in the area, they've never been used in the local wildlife, indicating that the resistance found in the chimpanzees jumped from people, he said. And that's without the 2 actually touching. Goldberg said the transmission probably occurred environmentally, through contact by each with water sources and the like. He said the findings have prompted the researchers, who already took precautions to avoid contact, to be even more careful. Another goal of the study is to provide the Ugandans who manage Kibale with information they can use to minimize the human impact on the wildlife there, through measures such as limiting the number of people in the park and the time they spend in it.

The researchers are now looking for similarities in bacteria and antibiotic resistance in people from farms around the park whose crops are raided by Kibale chimpanzees and other monkeys.

One of the frustrating things about work that is described in the popular press is that it is impossible to assess the validity of the research. But I'll try anyway. I'm actually not surprised that some strains are shared between humans and wild chimps. A study by Eric Routman and Dan Hartl from 1985 found that wild baboons had very different E. coli and lower frequencies of resistance compared to human-associated baboons (ones that picked through garbage dumps) and people. Nonetheless, there were common strains and there were resistant strains. Given that you can find antibiotic resistant E. coli in very remote areas such as the Galapagos, I'm not that surprised. Unfortunately, we need numbers to figure this out: a couple of strains in common is the minimum I would expect to see, especially if the genotyping methods used are not very fine scale.

That raises the issue of what exactly is 'significant' exchange. Is it greater than zero? I'm not sure what the null hypothesis is.

Still, I'll be curious to see what the actual data are.