Secondary outcomes measured at the beginning and the end of the trial are as follows:
There was no significant statistical difference in the number and mean duration of hospitalization for pulmonary exacerbations between the 2 groups. Furthermore, the 2 groups did not statistically differ for the number of gastrointestinal infections (Table 1). There was also no difference in bacterial strains and semiquantitative analysis of sputum bacteria between pre- and posttreatment sputum in the 2 groups (data not shown). Table 2 reports the secondary outcome measures in the 2 groups, expressed as mean (standard deviation) Δ values before and after the trial; there was no statistically significant difference in all of the variables analyzed.
There is sound clinical evidence that different probiotic strains can improve chronic intestinal inflammation, diarrhea, food allergy–related diseases, and extraintestinal disorders (32). Interactions between probiotics and intestinal mucosa through modulation of the gut immune system seem to be crucial both for the intestinal and extraintestinal effects (33,34).
LR ATCC55730 is a heterofermentative probiotic bacterium widely administered as a dietary supplement; its clinical usefulness and safety have been clearly shown in different clinical trials in patients with gastrointestinal disorders (35,36). Interestingly, experimental data also show the properties of LR strains to colonize both upper and lower intestinal mucosa as well as to modulate intestinal immunological response (37,38). It is noteworthy that an anti-inflammatory intestinal activity by different LR strains has been documented through inhibition of colitis in transgenic IL-10-deficient mice and reduction of the TNF-α expression levels in a mouse model of colitis (38). Furthermore, some LR strains exhibit a potent inhibitory effect on TNF-α-induced IL-8 expression in human intestinal epithelial cells (39), whereas LR 100–23 strain elicits an increased number of regulatory T cells in a murine gut model (40). Recently, a randomized placebo-controlled trial in children with ulcerative proctitis has shown that LR ATCC55730 was able, at the level of the rectal mucosa, to increase the expression of IL-10 (a downregulator cytokine) and to decrease that of proinflammatory cytokines, such as TNF-α, IL-1β, and IL-8 (41).
The use of probiotics in CF is rational because these patients are exposed to high numbers of medications and large-spectrum antibiotics, causing an altered composition of the intestinal microbiota. Interestingly, a certain degree of intestinal inflammation as well as increased intestinal permeability has been reported in these patients (42).
Our study shows that LR ATCC55730 administered per os in patients with CF is effective in reducing the risk of pulmonary exacerbations as well as the number of upper respiratory tract infections. This evidence, confirmed by other studies (23,24), has a clinical weightiness because respiratory exacerbations in CF lead to progressive pulmonary insufficiency with gradual functional deterioration that ultimately affects long-term prognosis (3).
Although there is a traditional view that probiotics can be helpful by improving intestinal permeability, it is widely agreed that the main intestinal and extraintestinal effects of probiotics are mediated by the interaction with the gut immunity (43,44). Furthermore, a gut–lung axis of probiotic action has recently been proposed; this notion is based on the assumption that the interaction of probiotic strains with gut-associated lymphoid tissue, such as Peyer patch cells, leads to enhancement of innate and adaptive respiratory immunity. Several mechanisms have been suggested: increase of the IgA-secretory cells in the bronchial mucosa; activation of natural killer (NK) cells (the main components of the host nonspecific cell-mediated immunity) and expansion of T-regulatory cells; production of antibacterial compounds; inhibition of virulence factors; and increase of the phagocytic activity of alveolar macrophages (45–47). Thus, our results and those of other reports support the view that certain Lactobacillus strains influence the immune responses beyond the gastrointestinal tract.
We also observed a significant reduction in the number of upper respiratory tract infections (URTIs), mostly otitis, in our patients with CF treated with LR. Our data are supported by a recent Cochrane review (48), showing that in 14 randomized controlled studies, probiotics were superior to placebo in reducing the number of subjects experiencing acute episodes of URTIs and, consequently, the use of antibiotics. Two different studies showed that feeding infants with a milk formula containing Lactobacillus GG resulted in a significant reduction of the risk of URTIs (17,49).
It is worth noting that the 2 groups enrolled in our study did not differ in the number and duration of hospital admissions for pulmonary exacerbations as well as episodes of gastrointestinal infections. We cannot exclude that the effectiveness of home treatments may have contributed to this result (50). Moreover, we did not observe a change in the FEV1 following probiotic administration, in agreement with other studies (24–52). Lack of improvement of FEV1 could be related to the chronicity of pulmonary disease with consequent irreversible damage. It has been suggested that the markers of inflammation in induced sputum may be more sensitive than pulmonary function tests to determine the effectiveness of therapies as well as to reveal mechanisms underlying inflammation and infections (53–55). It is commonly held that sputum induction in CF is a safe and reproducible way to obtain airway secretions for analysis in patients with CF; this tool is also less expensive and more comfortable than bronchoalveolar lavage (56).
Among markers of inflammation, IL-8 has been reported to be released by CF cells and highly induce mucosal inflammation (57–59). Therefore, we analyzed pre- and posttrial concentrations of IL-8 and TNF-α both in the induced sputum and serum of patients and did not find any significant variation.
In conclusion, we have shown that long-term administration of a LR strain, with documented anti-inflammatory and immunomodulatory properties, reduces the rate of pulmonary exacerbations and upper respiratory tract infections in patients with CF. Because of the complexity of the intestinal immune system and the specificity of the probiotic strains in the interaction with the intestinal epithelium, future studies should be focused on peculiar markers of inflammation when mechanisms of the probiotics effects will be investigated.
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