Re: “Oral Administration to Nursing Women of Lactobacillus fermentum CECT5716 Prevents Lactational Mastitis Development: A Randomized Controlled Trial” by Hurtado et al. ( Breastfeed Med 2017;12:202–209)

To the Editor:

We would like to point out several items that we believe invalidate the authors' conclusions in the article “Oral Administration to Nursing Women of Lactobacillus fermentum CECT5716 Prevents Lactational Mastitis Development: A Randomized Controlled Trial” by Hurtado et al. ¹

There is an incongruence between the objective of the study, the method, and the conclusion: the stated objective is “to evaluate the preventive effect of oral administration of Lactobacillus fermentum CECT5716 on mastitis incidence in lactating women”; however, the study was done on “women who received preventive dose of antibiotic in the context of delivery.” Therefore, the conclusion should not state results as “an efficient strategy to prevent development of lactational mastitis in women,” but “in women who received preventive dose of antibiotic in the context of delivery.”

The high rate of cesarean section among the recruited women (both in the control and the experimental groups) is surprising: 31.4% and 34.7%, respectively, both higher than the average in Spain (26.7% in 2015). The high incidence in both groups of mixed feeding (49.4% and 54.3%), pacifier use (30.5% and 31.2%), and sucking difficulties (26% and 29%) makes it doubtful that the study participants received effective breastfeeding support, resulting in a high incidence of difficulties known to be predisposing factors for mastitis. ²

The distribution of previous episodes of mastitis in the study women among the control and experimental groups should have been more homogeneous, or even an exclusion criterion, it being a known risk factor for subsequent mastitis. Women in the control group had a higher incidence of previous mastitis (17.3%) than those of the probiotic group (11.5%) with a statistically very low p (p 0.126), low enough as to possibly alter results.

The basal characteristics shown pertain to the women originally included in the study (322 in the control group and 303 in the probiotic group), but there is no information about the women who were finally studied (152 and 139, respectively) and whether there were statistical differences among the groups.

The high incidence of women who discontinued breastfeeding is surprising (53% in the control group, 54% in the probiotic group), barely explained in the discussion. And there were no comparing data between women who discontinued breastfeeding and those who did not. The percentage of breastfeeding discontinuation is similar in both groups: 23.6% (76 of 322) in the control group and 21.6% (70 of 303) in the probiotic group. Therefore, taking probiotics was not effective for maintaining breastfeeding.

The mastitis rate presented is 20%, very high compared with that in other studies, ² so the study group might have suffered selection. The global recurrence rate, 26%, is also much higher than that in the literature. Recurrence rate was 33% in the control group and 12.5% in the probiotic group. We wonder why the women in this study had so many mastitis and so many recurrences (both globally and by groups) and whether there were correct breastfeeding support interventions for these women. There is no information about the treatment the women received for their mastitis, nor is there mention of a unified protocol to manage those episodes in the women studied.

The abstract does not mention that there were no statistical differences (p 0.058) in the percentage of mothers who had mastitis in both groups.

The authors mention a statistically significant lowering of Staphylococcus spp. in the probiotic group, but not whether it is Staphylococcus aureus or Staphylococcus epidermidis. Since S. aureus is the main etiological agent for mastitis, ² it is an important distinction, more so because these authors have previously declared that S. epidermidis is the main causal agent for mastitis. ³

Some authors, including those in the PROLAC group, have a conflict of interest, having ties to the company that owns the patent and markets the probiotic under study. This company, Biosearch Life, has signed an agreement to license its strain of L. fermentum to Nestle in December 2017. It is to be marketed at a global level as “nutritional complement for breastfeeding women for maintaining healthy breastfeeding.” ⁴

The recommendation for lactating women to take probiotics to prevent mastitis, based on such unclear evidence, could be a dangerous marketing operation, as such a recommendation could delay or interfere with evidence-based interventions and be economically onerous for families. ⁵