Objective: To study the gut flora in infants who received fermented milk containing Lactobacillus casei and Streptococcus termophilus and its effect on secretory immunoglobulin levels.
Material and methods: An experimental, randomized, prospective, parallel group study was carried out. Thirty-five infants were included (18 in the treatment group and 17 in the control group) with a mean age of 2 years (SD: 0.6 years; range: 1-3 years). The experimental group received both fermented milk (0.5 l/day) containing L. casei and S. termophilus for 6 weeks and standard cow's milk for the following 6 weeks. The control group received standard cow's milk (0.5 l/day) for 12 weeks. Secretory IgA levels in saliva were evaluated in the experimental group at the start of the study (baseline levels) and 6 weeks later. In both groups, stools were collected to study gut flora at 0, 6 and 12 week.
Results: Secretory IgA levels significantly increased (p =0.0063) from a mean baseline value of 2.5 mg/dl to a mean of 3.4 mg/dl at 6 weeks. Gram-negative aerobic flora were decreased in the experimental group after 6 weeks compared with the control group (p =0.0203). The number of infants with Lactobacillus spp in their gut flora was greater in the experimental group than in the control group at week 6 and this difference was statistically significant (p =0.028) at week 12. Conclusion The present study provides evidence of L. casei survival in the gastrointestinal tract and of its effect of increasing secretory IgA.