What is already known
The correlation between gut microbiota and airway immunity in cases of allergies or asthma is well-known. Supplementation of lactobacilli at an early age has also been demonstrated to influence the entire gut microbiota. Which is the impact in children with cystic fibrosis, however, remains to be investigated.
What this research adds
In this study, the impact of a daily supplement of L. rhamnosus GG in children affected by cystic fibrosis is evaluated by analysing faecal samples.
Bifidobacteria showed a general increase in children taking the supplement with a parallel improvement in lung symptoms and intestinal inflammation, compared to children with a microbiota not dominated by Bifidobacteria.
The probiotic L. rhamnosus GG appears to increase the amount of Bifidobacteria in the intestine and may result in a better clinical course in cases of childhood cystic fibrosis.
This is the conclusion of a study by Kathryn J. Ray and colleagues from the University of California, San Francisco (USA), recently published in BMC Pulmonary Medicine.
Cystic fibrosis and gut microbiota
Mucus overproduction, typical of cystic fibrosis, not only affects the respiratory system, but also the digestive system. Hence, the general low BMI and intestinal dysbiosis.
The administration of antibiotics for frequent infections affects the balance of the bacterial community and, consequently, the immune response.
In the context of this disease, however, the role of L. rhamnosus GG (LGG) remains controversial. Researchers have therefore assumed that supplementation of LGG alters the gut microbiota in paediatric patients, but that, in some, this impact is not sufficiently evident to influence the balance of the local microbiota and/or the course of the disease.
To test this, 22 children with cystic fibrosis received the LGG supplement daily for one year, while 28 controls were treated only with placebo. Moreover, their bacterial profile by collecting salivary and faecal samples and analysing their general health. Here are the main evidences.
The study results
Starting from a general observation:
● Staphylococcus aureus, Pseudomonas aeruginosa and Stenotrophomonas maltophilia were found to be the predominant pathogens in sputum.
● Most subjects at baseline showed a predominance of Bifidobacteria (32%, N = 16) or Bacteroides (18%, N = 9), followed at a distance by Prevotella (8%, N = 4), Lactobacillus (6%, N = 3), Enterococcus (4%, N = 2) Acidaminococcus (2%, N = 1), Blautia (2%, N = 1), Collinsella (2%, N = 1), Coprococcus (2%, N = 1), Faecalibacterium (2%, N = 1), Parabacteroides (2%, N = 1), Proteus (2%, N = 1), Ruminococcus (2%, N = 1) and unidentified genera (16%, N = 8).
Did the LGG supplementation therefore alter the microbiota?
● No significant change in terms of alpha diversity between the two groups was registered, although a trend towards an increase was seen in the placebo group.
● Faecal beta diversity was associated with dominant gender and clinical outcome at 12 months.
● At 12 months, predominance was reconfirmed for Bifidobacterium (29%; N = 22) and Bacteroides (19%, N = 15).
● Subjects with a predominance of Bifidobacterium had a lower concentration of faecal calprotectin, a marker of inflammation, and a lower need for antibiotics.
● The distribution of the dominant genera was shown to vary according to whether LGG was supplemented or not. In the supplemented group, a transition was seen at 12 months to profiles mainly dominated by Bifidobacterium (N = 4). This was followed by Faecalibacterium (N = 2), Collinsella (N = 1), or Acidaminococcus (N = 1). In the placebo group, however, Bacteroides (N = 4), Parabacteroides (N = 1), Streptococcus (N = 1), Enterococcus (N = 1), Ruminococcus (N = 1), Proteus (N = 1), or Bifidobacterium (N = 1) dominated.
To sum up, a supplement of LGG would seem to favour the proliferation of Bifidobacterium, providing a plausible explanation for the improved clinical and immunological response to disease in some of these children, compared to their placebo counterparts.
The small sample size, as the authors themselves claim, could however limit the significance and reproducibility of the results. Further and wider studies are therefore necessary to validate the contribution of L. rhamnosus GG in the context of childhood cystic fibrosis.