Cow’s milk protein allergy (CMPA) is the most common food allergy in infancy. Non-IgE mediated (NIM) forms are little studied and the responsible mechanisms of tolerance acquisition remain obscure. Our aim was to study the intestinal microbiota and related parameters in the fecal samples of infants with NIM-CMPA, to establish potential links between type of formula substitutes, microbiota, and desensitization. Seventeen infants between one and two years old, diagnosed with NIM-CMPA, were recruited. They were all on an exclusion diet for six months, consuming different therapeutic protein hydrolysates. After this period, stool samples were obtained and tolerance development was evaluated by oral challenges. A control group of 10 age-matched healthy infants on an unrestricted diet were included in the study. Microbiota composition, short-chain fatty acids, calprotectin, and transforming growth factor (TGF)-β₁ levels were determined in fecal samples from both groups. Infants with NIM-CMPA that consumed vegetable protein-based formulas presented microbiota colonization patterns different from those fed with an extensively hydrolyzed formula. Differences in microbiota composition and fecal parameters between NIM-CMPA and healthy infants were observed. Non-allergic infants showed a significantly higher proportion of Bacteroides compared to infants with NIM-CMPA. The type of protein hydrolysate was found to determine gut microbiota colonization and influence food allergy resolution in NIM-CMPA cases.

The preterm infant gut has been described as immature and colonized by an aberrant microbiota. Therefore, the use of probiotics is an attractive practice in hospitals to try to reduce morbidity and mortality in this population. The objective of this pilot study was to elucidate if administration of two probiotic strains isolated from human milk to preterm infants led to their presence in feces. In addition, the evolution of a wide spectrum of immunological compounds, including the inflammatory biomarker calprotectin, in both blood and fecal samples was also assessed. For this purpose, five preterm infants received two daily doses (~10⁹ CFU) of a 1 : 1 mixture ofBifidobacterium brevePS12929 andLactobacillus salivariusPS12934. Bacterial growth was detected by culture-dependent techniques in all the fecal samples. The phylumFirmicutesdominated in nearly all fecal samples whileL. salivariusPS12934 was detected in all the infants at numerous sample collection points andB. brevePS12929 appeared in five fecal samples. Finally, a noticeable decrease in the fecal calprotectin levels was observed along time.

Some strains of species belonging to the genera Bifidobacterium and Lactobacillus are used in order to maintain health. Although these organisms have a long record of safe use, it is important to assess their safety and tolerance in potentially vulnerable populations, such as infants. The objective of this study was to evaluate the safety and tolerance of three probiotic strains (Bifidobacterium longum subsp. infantis R0033, Bifidobacterium bifidum R0071 and Lactobacillus helveticus R0052) in healthy infants aged 3 to 12 months. A multi-centre randomized, double-blind, placebo-controlled intervention study with 221 healthy full-term infants was conducted. Infants received either a placebo or one of the 3 probiotic strains (3×10⁹ cfu) daily during an 8 week intervention period. Growth (weight, height and head circumference), adverse events (AEs)/serious adverse events (SAEs), concentrations of D-lactic acid in urine samples, characteristics of the stools and use of medication were collected for safety evaluation. All 4 groups were homogeneous with respect to age, gender, feeding type, ethnicity, height, weight and head circumference at the start of the study. The results showed that changes in growth (weight, height and head circumference) were equivalent in all 4 groups. No SAEs were reported. Total number of AEs recorded was equivalent in all groups. Thus, the use of B. infantis R0033, L. helveticus R0052 and B. bifidum R0071 in infancy is safe, and well tolerated.

Post-weaning diarrhoea in piglets remains an important cause of economic losses for swine producers. Feed supplementation with probiotics is one of the alternatives to antibiotics used to reduce the impact of such gastrointestinal disease. The aim of the present study was to evaluate the effect of Ligilactobacillus salivarius PS21603 supplementation on the intestinal structure and the gut microbiota composition of weaned piglets. Safety and tolerance of L. salivarius PS21603 were previously evaluated in a 28-days study using 384 weaned piglets (28 ± 2 days old and 7.5 ± 1.5 kg) divided in three treatment groups: T1: Basal diet + L. salivarius PS21603 10⁹ cfu/day, T2: Basal diet + L. salivarius PS21603 10⁷ cfu/day, and T3: Basal diet (control group). For the present study, 16 piglets per treatment group were randomly selected and faecal samples were collected on day 0 (weaning) and 28 of study. At the end of study, three males and three females per treatment were euthanised. Intestinal morphometric values were measured after necropsy. Faecal counts of Escherichia coli were evaluated by culture techniques, and faecal microbiota composition was assessed by high-throughput sequencing. All data were analysed and compared between treatment groups. Supplementation with L. salivarius PS21603 caused an increase in the intestine length of piglets from T1 and in the villous height:crypt ratio of piglets from T2 (P < 0.05) compared to T3 on day 28. According to the Shannon Diversity Index, microbiota diversity increased on day 28 compared to day 0, with no significant differences observed between treatments. The main changes in the relative abundance of bacteria at the phylum, family, and genus levels were observed between different sampling time points. However, piglets from T1 and T2 had lower faecal E. coli counts than T3 on day 28 (P < 0.05). Moreover, supplementation with L. salivarius PS21603 modulated gut microbiota through a more optimal composition, reducing Escherichia and increasing Bifidobacterium relative abundance in piglets from T1 (P < 0.05) from the beginning to the end of the study. Therefore, the strain L. salivarius PS21603 has shown probiotic properties to be used as feed additive in the pig industry, along with good hygiene and farm management practices, for the prevention and/or treatment of post-weaning diarrhoea in piglets.

Background/Objectives: Infertility affects couples at reproductive age, with in vitro fertilization (IVF) being the most effective treatment. Success rates of IVF are influenced by several factors, including a healthy female reproductive system microbiome, which can improve implantation rates and pregnancy outcomes. This study evaluated the impact of Ligilactobacillus salivarius PS11610 on IVF outcomes. This strain showed antimicrobial activity against pathogens related to dysbiosis, commonly observed in women undergoing assisted reproductive treatment. Results: The administration of L. salivarius PS11610 at a dose of 1 × 10⁹ CFU every 12 h for at least one month before IVF procedures, particularly in the frozen embryo transfer (FET) group, appears to enhance the success rate of IVF. IVF procedures without embryo transfer showed no significant differences between the groups. However, there were statistically significant differences in the quality of embryos, specifically in category 2, which were higher in the group without L. salivarius PS11610 supplementation (p = 0.042). Similar results were seen in the IVF with embryo transfer group, where the quality of embryos in categories 2 and 3 was higher in the group without L. salivarius PS11610 (p = 0.019 and p = 0.05, respectively). IVF with FET showed notable improvements, where intake of L. salivarius PS11610 was associated with a significant increase in live birth infants (26.4% with L. salivarius PS11610 vs. 17.9% without, p = 0.034) and higher biochemical pregnancy rates (42.6% vs. 34%, p = 0.071). Conclusions: Despite some differences in embryo quality, the overall positive impact on pregnancy and birth outcomes highlights L. salivarius PS11610 as a promising supplement in assisted reproductive treatments.

The objective of this letter of reply is to provide answers to the doubts and critical issues that Martín Martinez and López Liñan