Connecting the dots: the elderly, frailty and the microbiome

Published: April 6th 2017

A pilot study of microbial genes in pensioners living in an assisted care facility in Atlantic Canada has shed new light – and more than a few surprises – on the state of residents’ microbiome.

There is a known link between the gut microbiome and factors like diet, immune development, infectious diseases, and even living conditions. But little is known about the relationship between gut microbes and frailty.

Frail individuals are more vulnerable to poor health and are at a greater risk for accidents and illness. Could the microbiome of aging and frail individuals provide information that could contribute to better health outcomes?

This was a key question of a recent pilot study conducted with 47 pensioners in Northwoodcare, an assisted living facility in Halifax. The study, led by Dr. Rob Beiko and Dr. Kenneth Rockwood of Dalhousie University, looked at the changing composition of the community of bacteria that live in the gastrointestinal tract – collectively known as the gut microbiome – in relation to the participants’ age, health and lifestyles.

Beiko and Rockwood set out to explore how age and frailty affect the gut microbiome, specifically pinpointing what bacteria are present or absent and determining whether the microbiome in aging and frail individuals changes over time. Their hope was that the information gathered from the study could ultimately help in developing better techniques for frailty assessment and inform health care and quality of life decisions for frail individuals.

Study participants, aged 65-98, were scored on the Clinical Frailty Scale, a global clinical measure of fitness and frailty in elderly people. In the process, extensive information was gathered on their health and lifestyles. Then, subjects’ stool samples were collected once a week for five weeks and microbial genes were analyzed to see if their gut microbiomes showed associations with frailty.

Obtaining both high- and low-resolution sequencing through Dalhousie University’s Integrated Microbiome Resource (IMR) “made life a lot easier for us,” says Beiko, the Canada Research Chair in Bioinformatics, at the university’s Faculty of Computer Science. The study relied on the IMR’s Illumina MiSeq and NextSeq sequencers to identify the bacteria and the functions they play.

‘we can look for specific things that can influence critical decision making’ – Dr. Rob Beiko

A unique feature of the study was that Northwood’s subjects shared the same type of housing, environment and diet, although they differed widely in their health status and prescribed drugs. A surprising finding, says Beiko, was that “living in the same facility does not lead to anyone having the same or even similar (microbe) species profiles.”

Contrary to previous studies carried out by others, the research showed that older adults and frailer subjects had as much bacterial diversity as their younger and less frail counterparts. Furthermore, with few exceptions, most subjects’ microbiomes were relatively stable during the five-week period of the study.

Exceptions, though, were sometimes dramatic. One subject showed wild instability with Pseudomonas, a potentially opportunistic pathogen, and with Akkermansia, a bacterium associated with weight loss and anti-inflammation. The Pseudomonas appeared in week one but disappeared by week two, never to return for the rest of the sampling period. Meanwhile, Akkermansia turned up in week two and grew in abundance each week until it became dominant in week five.

“We don’t know if there is any sort of casual relationship, but it’s interesting that the pathogen goes away and then other things that might be good, actually bloom afterwards,” says Beiko. This observation, and others like it, have become key motivators for expanding the study to see if more examples of these phenomena can be found.

Another important finding in a few individuals was the presence of bacterial genes that confer resistance to certain antibiotics. These results dovetail with a new Genome Canada study, headed by Beiko and managed by Genome Atlantic, which is developing a quick and practical way to identify antimicrobial-resistant genes in patients’ samples. In the hands of a clinician, the resulting information would take the guesswork out of prescribing effective antibiotics in an era of increasing bacterial resistance.

For Beiko, the most encouraging takeaway was confirmation of the potential for harnessing microbiome analysis for clinical application. “One of the most immediate benefits of screening the microbiome is that we can look for specific things that can influence critical decision making,” he says.

The results from the pilot study are now driving applications for multi-year studies to characterize explore the relationship between frailty and the microbiome for subjects living in a wider array of environments. Beiko and his informatics lab team continue to probe sequencing data, and develop more complex models and tools to uncover the patterns buried in enormous bacterial diversity. “The relationship between aging, frailty and the microbiome is very complicated,” he says, “but we’re starting to see the big picture and we know where to look next.”