Fecal Microflora in Healthy Infants Born by Different Methods of Delivery: Permanent Changes in Intestinal Flora After Cesarean Delivery :

The succession of bacterial populations in the large bowel of seven breast-fed and seven formula-fed infants was examined during the first year of life. The composition of the intestinal microflora varied according to the infant's diet. During the first week of life breast-fed and formula-fed infants were colonised by enterobacteria and enterococci followed by bifidobacteria, Bacteroides spp., clostridia and anaerobic streptococci. From week 4 until solid foods were given, breast-fed babies had a simple flora consisting of bifidobacteria and relatively few enterobacteria and enterococci. Formula-fed babies during the corresponding period were more often colonised by other anaerobes in addition to bifidobacteria and had higher counts of facultatively anaerobic bacteria. The introduction of solid food to the breast-fed infants caused a major disturbance in the microbial ecology of the large bowel as counts of enterobacteria and enterococci rose sharply and colonisation by Bacteroides spp., clostridia and anaerobic streptococci occurred. This was not observed when formula-fed infants began to take solids; instead, counts of facultative anaerobes remained high while colonisation by anaerobes other than bifidobacteria continued. At 12 months, the anaerobic bacterial populations of the large bowel of breast-fed and formula-fed infants were beginning to resemble those of adults in number and composition and there was a corresponding decrease in the number of facultative anaerobes. These changes are discussed in relation to changes in susceptibility to gastro-intestinal infection.

Human Lactobacillus sp strain GG (Lactobacillus GG) administered during acute rotavirus diarrhea has been shown to promote clinical recovery. To elucidate the immune mechanisms behind such a favorable outcome, the ELISPOT (solid phase enzyme-linked immunospot) assay of Ig- and specific antibody-secreting cells among circulating lymphocytes was used, giving indirect evidence of the immunologic events in the gut. After rehydration, 39 children with acute rotavirus diarrhea, mean age 16 (SD 6) mo, randomly received either a Lactobacillus GG fermented milk product (study group) or a pasteurized yogurt (placebo group). The duration of diarrhea was significantly shorter in the study group than in the placebo group [mean 1.1 (SD 0.6) versus 2.5 (SD 1.4)d, p = 0.001]. Lactobacillus GG therapy was associated with a significantly enhanced nonspecific humoral response during the acute phase of the infection, reflected in the IgG, IgA, and IgM Ig-secreting cell numbers. At convalescence, 90% of the study group versus 46% of the placebo group had developed an IgA specific antibody-secreting cell response to rotavirus (p = 0.006). The results indicate that Lactobacillus GG promotes recovery from rotavirus diarrhea via augmentation of the local immune defense. Furthermore, specific IgA response to rotavirus is endorsed, which is possibly relevant in protection against reinfections.

In a search for new strategies to improve oral vaccination, the effect of orally administered Lactobacillus casei strain GG (LGG) in conjunction with D x RRV rhesus-human reassortant live oral rotavirus vaccine was tested in 2-5-month-old infants. Infants who received LGG showed an increased response with regard to rotavirus-specific IgM secreting cells, measured using an ELISPOT technique, on day 8 after vaccination. In infants receiving LGG or placebo, respectively, a rotavirus IgM seroconversion was detected in 26/27 (96%), versus 23/27 (85%) cases (p = 0.15) and rotavirus IgA seroconversion was detected in 26/28 (93%) versus 20/27 (74%) cases (p = 0.05). These findings suggest that LGG has an immunostimulating effect on oral rotavirus vaccination. The clinical significance of LGG-enhanced immune responses to oral vaccines should be further evaluated.