Harmful Bacteria Replace Beneficial Ones in Guts of CF Patients, Study Finds

Cystic fibrosis (CF) patients have a higher amount of harmful gut bacteria and increased levels of intestinal inflammation than healthy people, according to researchers.

Their study, “Altered intestinal microbiota composition, antibiotic therapy and intestinal inflammation in children and adolescents with cystic fibrosis,” was published in the journal PLOS One.

CF predominantly affects the lungs, but it can also cause gastrointestinal complications. The CFTR protein defect (the cause of CF) is abundant in the gastrointestinal tract of patients and affects the normal structure of the intestine. This defect could influence the diversity of the bacteria present in the gut (also called the gut microbiome).

Previous studies have shown that CF patients have a less diverse gut microbiome than healthy individuals.

Now, researchers investigated the impact of antibiotic use on gut inflammation and bacterial composition in CF patients.

The team used a molecular imaging method — fluorescence in situ hybridization — to detect and identify bacteria in fecal matter collected from 19 CF patients and 17 healthy people (controls).

The median age of the CF patients was 3, and in healthy controls was 4. CF patients were divided into two groups based on whether or not they used antibiotics.

Researchers noted a significant decrease in the Bacteroides, Eubacterium rectale, Faecalibacterium prausnitzii, and Firmicutes bacteria in CF patients compared to healthy controls. These bacteria are usually considered markers of a healthy intestinal microbiome.

Clostridium difficile (bacterium associated with severe intestinal inflammation) and Escherichia coli (some strains of this bacterium are associated with diarrhea, urinary tract infections, and respiratory illness) were found in markedly higher numbers in CF patients.

Similarly, a high number of Pseudomonas aeruginosa was also detected in CF patients. P. aeruginosa is an aggressive bacterium associated with lung infections.

A similar change in microbiome diversity was observed in all CF patients regardless of antibiotic use. Although frequent use of antibiotics did not appear to influence the gut microbiome in CF, there was a noticeable shift in the gut population from beneficial to harmful bacteria.

Fecal calprotectin is a marker for intestinal inflammation. The researchers found that the median level of fecal calprotectin per gram of fecal matter was significantly higher in the overall CF patient group and CF patients on antibiotic therapy, compared to the control group.

Although levels of fecal calprotectin in CF patients on antibiotic therapy were higher than in those not using antibiotics, the difference was not significant.

The researchers acknowledged some limitations of the study. The number of participants analyzed was insufficient to determine the significance of antibiotic therapy on CF gut microbiome.

Also, the bacteria analyzed in the study were selected based on their influence on intestinal health and their role in CF, so they provided a limited view of the entire gut microbiome.

Still, “the results of the present study confirm the presence of intestinal inflammation in patients with CF and suggest that the disease may be related to changes in the colonization of some microorganisms,” the researchers wrote.