The oral microbiome may harbor harmful bacteria in CF patients

P. aureginosa (green line) is the most common cause of infection for CF patients older than 18 years old.

By Ninjatacoshell (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Cystic fibrosis is a hereditary disease characterized by thick mucus secretions that obstruct the lungs and harbor harmful bacteria in a person’s airways. A common cause of death among CF patients is bacterial infection, usually by Pseudomonas aeruginosa, that subsequently leads to inflammation and respiratory failure. Scientists at the CF Reference Center in Roscoff, France were interested in a possible link between oral bacteria and lung bacteria of CF patients.  Specifically, they wondered if the mouth could harbor P. aeruginosa, which could then go on and inflame the lungs.  The results of their study were published in the Journal of Clinical Microbiology.

The researchers in France focused their study on detecting and measuring the genetic relatedness of P. aeruginosa in saliva and sputum (mucous) samples in 10 CF patients.  Of the 10 patients, 5 were chronically colonized (CC) by P. aeruginosa, with an average age of 23.8 years, and 5 were not colonized (NC), with an average age of 16.6 years. None of the patients had gingivitis or periodontitis.

No P. aeruginosa was detected in oral or sputum samples of NC patients, while 16 samples from the CC patients contained P. aeruginosa. Of the 16 sampled, six were salivary and ten were sputum. From these samples, the researchers discovered that the genetic make-up of the strain samples within each CC patient was more similar to other samples from the same patient than to those of other patients.

Overall, this study suggests that the oral cavity is a possible reservoir of P. aeruginosa and other bacteria that can infect the lungs. While this possibility is suggested by the discovery of similar P. aeruginosa strains in both saliva and sputum, it is not clear if the oral strains can actually descend and infect the lungs. As the article mentions, a longitudinal study that could follow the changes in bacterial colonization in CF patients would be beneficial. 

What exactly are antibiotics doing to our bodies?

We’ve talked a lot about antibiotics in the past as well as antibiotic resistant bacteria but it is still unknown exactly what all the effects of antibiotics are on the body and specifically our microbiome.  The increase in antibiotic resistance is a rising concern and this week President Obama and the White House announced that in their 2016 budget they would be doubling their investment in fighting antibiotic resistant bacteria to $1.2B this year. Antibiotics are essential for the treatment of bacterial infection; however, many individuals have adverse effects due to alterations of the microbiome and the increase of antibiotic resistance. These are very real concerns that are causing increasing public health issues and we are glad to see that this administration is continuing to make fighting antibiotic resistant bacteria a priority.

A study recently published in the journal Gut sought to further our understanding of the effects of antibiotics on the host. To look at the physiological effects of antibiotics, the scientists studied three groups of mice: regular germ-free mice; germ-free mice treated with antibiotics; and germ-free mice that were colonized with microbiota from antibiotic-treated normal mice. They found that the use of antibiotics influenced the host in three major ways: depletion of the overall microbiota; having a direct toxic effect on tissues in the host; and the increase of antibiotic resistant bacteria in the microbiota. The researchers also found that the antibiotic-resistant bacteria Pseudomonas aeruginosa were involved in mitochondrial damage, leading to mitochondria-dependent apoptosis (or programmed cell death) in the epithelial tissue of the intestines.

While antibiotics save lives and are incredibly important in fighting bacterial infection, they can also have very unpleasant effects such as local immunodeficiency and cell death. This study took an important, in depth look at the effects of antibiotics on the physiology of the host the effects on the microbiome.