Development of a Six-Stage Culture System for Simulating the Gastrointestinal Microbiota of Weaned Infants

The development of a six-stage culture system simulating the microbial community present in the intestine of weaned infants is described. Plate counts of selected fecal indicator-organisms revealed high concentrations in the culture liquid of the simulator and these data paralleled those in infant feces. The metabolic patterns of the microbiota present in the model and the infant feces, compared by means of BIOLOG, revealed similar carbon utilization profiles. A genetic ? ngerprinting by means of Denaturing Gradient Gel Electrophoresis generated a more complex banding pattern in the culture system than in infant feces. The three vessels representing the colon showed similar DGGE patterns, indicating a high stability of the dominant microbial species. Yet, high variability in terms of the dominant bacteria was observed in infant stools. The fermentative capacity of the in vitro system, characterized by the concentration of volatile fatty acids and ammonium, was in accordance with the in vivo data. The enhanced production of propionate in vitro is probably due to the high concentration of fermentable sugars in the culture medium and hence, a high fermentation rate. The elevated concentration of propionate, as well as valerate and caproate in vitro suggests conditions favoring Megasphaera sp. fermentation. The data concerning microbial diversity and activity warrants further exploration of the in vitro model as a tool for studying the impact of newly developed infant formulas, functional foods and pharmaceuticals on the gastrointestinal microbiota of infants. Keywords: intestinal microbiota, gut fermentation, infant, culture system.