Why are older people more likely to become seriously ill or even die from pneumonia? It turns out the cause may have as much to do with the gut as it does with the lungs.
That’s according to new research from Rachel McMahan, PhD, research assistant professor of gastroenterology, trauma, and endocrine surgery at the University of Colorado School of Medicine and Holly Hulsebus, graduate student in immunology at the University of Colorado School of Medicine. CU.
In an article published in March in the journal Frontiers of agingthe researchers — along with lead author Elizabeth J. Kovacs, PhD, professor of GI, trauma and endocrine surgery — examined the bacterium Streptococcus pneumoniaein in animal models, studying changes in gut microbial populations after infection.
“Streptococcus pneumoniae is normally carried in the nasal passages of healthy adults. People with healthy immune systems can just live with it, and it doesn’t cause any problems,” says Hulsebus. weakened people, including the elderly, tend to become more susceptible because their immune systems cannot really control the bacteria that are normally present.These bacteria can leave the nose and move to other places in the body.They can cause ear infections, and they can also spread to the lungs and cause pneumonia.
The role of leaky gut
In addition to increased morbidity and impaired lung function following Streptococcus pneumoniae infection in older mice, the researchers also found elevated levels of gut-derived bacteria in the lungs, suggesting that the bacteria that migrate from the intestine to the lungs could be partially responsible for the poor outcome in the elderly.
A likely reason for this migration, McMahan says, is that as we age, our guts become “leaky” because the mechanisms the body has in place to keep gut bacteria in place begin to break down. This is similar to what happens with burn patients and people who abuse alcohol. The problem is compounded by the fact that inflammation in the body naturally increases with age, leading to more pro-inflammatory bacteria being present in the gut.
In their published study, funded by the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health, the researchers found high levels of the bacteria family Enterobacteriaceae – a gut-specific bacterium which includes E. coli – in the lungs of elderly, but not young animal models, infected with Streptococcus pneumoniae. As Enterobacteriaceae are associated with increased inflammation, the researchers also found higher levels of neutrophils, a type of inflammatory immune cell, in the lungs of aged infected animal models.
“Our working theory is that as you age, you have an increased baseline inflammatory response, which then induces the gut to be more pro-inflammatory,” McMahan says. “It causes potentially pathogenic bacteria to leak into the gut into the organs, and then things can go downhill quickly.”
New strategies to fight infection
Older adults are nearly five times more likely to be hospitalized with pneumonia, and pneumonia mortality rates can exceed 50%, depending on comorbidities or underlying health conditions. With the world’s rapidly growing population of people over 65, it’s important to find new ways to fight serious infections.
Focusing on the gut, McMahan says, can help researchers find new ways to combat increased lung inflammation.
Strategies like probiotics and a healthy diet could help control gut bacteria in older adults, she says, as could medications that protect against leaky gut. Future research from the lab includes studying the effectiveness of microbiome transplants or fecal transplants that replace bacteria in the aging gut with those from younger animals.
The gut-lung axis has long been studied in the context of diseases such as acute respiratory stress disorder, but the new paper from the CU School of Medicine researchers is among the first to describe how aging can contribute to the problem.
“We show that as you age, you specifically get an expansion of these bacteria and that the gut-lung axis may be impaired,” McMahan says.