For preterm, low-birth-weight infants, probiotic formulations containing Lactobacillus and Bifidobacterium strains appear to be superior to single-strain probiotics and to other multiple-strain formulations for reducing the risk of all-cause mortality, according to the findings of a network meta-analysis of randomized clinical trials.
The results of a prior Cochrane review indicated that probiotics can help prevent severe necrotizing enterocolitis and all-cause mortality in preterm infants, but the most effective formulations remained unclear. Therefore, Rebecca L. Morgan, PhD, MPH, and her associates searched MEDLINE, EMBASE, Science Citation Index Expanded, CINAHL, Scopus, Cochrane CENTRAL, BIOSIS Previews, and Google Scholar through Jan. 1, 2019, to identify studies of single-strain and multistrain probiotic formulations in preterm, low-birth-weight neonates. A total of 63 studies involving 15,712 infants met inclusion criteria. “We used a frequentist approach for network meta-analysis and [a] GRADE approach to assess certainty of evidence,” they noted.
“High-certainty” evidence indicated that combination therapy with one or more Lactobacillus species and one or more Bifidobacterium species significantly reduced all-cause mortality, compared with placebo (odds ratio, 0.56; 95% confidence interval, 0.39-0.80), wrote Dr. Morgan, of McMaster University, Hamilton, Canada, and her coinvestigators. This was the only intervention to have moderate- or high-quality evidence for a reduction in mortality, the researchers wrote in Gastroenterology.
They added that, among the probiotic formulations with moderate- or high-quality evidence for efficacy, compared with placebo, those containing at least one species of Lactobacillus and at least one species of Bifidobacterium, and the single-strain probiotics containing Bifidobacterium animalis subspecies lactis, Lactobacillus reuteri, or Lactobacillus rhamnosus significantly reduced the risk of severe necrotizing enterocolitis (Bell stage II or higher), with statistically significant odds ratios of 0.35, 0.31, 0.55, and 0.44, respectively.
Three formulations were associated with “low-” or “very low-certainty” evidence for a reduction in risk for severe necrotizing enterocolitis, compared with placebo: Bacillus plus Enterococcus species, Lactobacillus plus Bifidobacterium plus Enterococcus species and Bifidobacterium plus Streptococcus salivarius subspecies thermophilus. Estimated odds ratios were 0.23 (risk difference, –4.9%), 0.28 (RD, –4.9%), and 0.38 (RD, –3.9%), respectively.
“The combinations of Bacillus species and Enterococcus species, and one or more Bifidobacterium species and S. salivarius subspecies thermophilus, might produce the largest reduction in necrotizing enterocolitis development,” the investigators wrote. “Further trials are needed.”
Compared with placebo, no probiotic formulation significantly improved the third primary outcome in the meta-analysis, culture-confirmed sepsis. However, several formulations were associated with moderate- or high-quality evidence for efficacy on secondary outcome measures. Compared with placebo, combinations of Lactobacillus and Bifidobacterium and Saccharomyces boulardii were associated with a significant decrease in the number of days to reach full feeding (mean reduction, 3.3 days; 95% CI, 5.9-0.7 days). Compared with placebo, single-strain therapy with B. animalis subspecies lactis or Lactobacillus reuteri was associated with a shorter duration of hospitalization, with mean reductions of 13.0 days (95% CI, 22.7-3.3 days) and 7.9 days (95% CI, 11.6-4.2 days), respectively.
“Multicenter and large randomized controlled trials should be prioritized to distinguish between the efficacy of single- and multiple-strain probiotics among preterm infants,” Dr. Morgan and her associates concluded. Such studies would further clarify the safety of probiotic formulations in this “fragile population,” they wrote. “Although the primary concern of live microbe administration, intestinal barrier translocation leading to sepsis, is decreased by several probiotic formulations, sound clinical judgement should be exercised.”
Partial support was provided by Mitacs Canada, in partnership with Nestlé Canada. The funder was not involved in designing or conducting the study or writing the manuscript. Dr. Morgan reported having no relevant conflicts of interest. One coinvestigator disclosed ties to AbbVie, Ferring, Janssen, and Takeda.
SOURCE: Morgan RL et al. Gastroenterology. 2020 Jun 24. doi: 10.1053/j.gastro.2020.05.096.