Assessment of intestinal microbiota modulation ability of Bifidobacterium strains in in vitro fecal batch cultures from preterm neonates.

Microbial colonization of the infant gut is essential for the development of the intestine and the immune system. The intestinal microbiota of full-term breast-fed infants is considered as the health standard for newborns. A culture medium containing formula milk was designed, which allowed a balanced growth of intestinal microorganisms and was used to perform fecal batch cultures from preterm babies. Sixteen Bifidobacterium strains and fructooligosaccharides (FOS) were tested for their ability to modulate in vitro the intestinal microbiota. The production of short chain fatty acids (SCFA) was measured by Gas Chromatography and the levels of some anaerobe (Bifidobacterium and Bacteroides groups) and facultative anaerobes (Enterobacteriaceae, Enterococcaceae, Weissella group, and Klebsiella pneumoniae) were determined by quantitative PCR. Results were referred to a fecal negative control culture without microorganisms or FOS added. Strains that in fecal cultures counteracted better the aberrancies previously found in feces of preterm babies, as compared with full-term breast-fed infants, were selected. The three Bifidobacterium bifidum strains tested in this work promoted the most suitable shifts in SCFA and in the ratio of variables facultative anaerobes to anaerobes. Two Bifidobacterium breve strains complied with the requirement for facultative anaerobes and anaerobes and one of them also promoted a suitable shift of SCFA. Bifidobacteria behaved similarly as FOS regarding the microbial profiles in fecal cultures but the production of lactic and acetic acid was much lower. B. breve and B. bifidum strains selected represent promising candidates for their assessment in more complex in vitro and in vivo models.