We report here the development of a useful method composed of a set of six multiplex PCRs and one simplex PCR for the rapid screening of the most frequently encountered beta-lactamases. This method allowed direct sequencing from the PCR products.

The establishment of bacterial communities in two healthy babies was examined for more than the first 10 months of life by monitoring 16S ribosomal DNA (rDNA) diversity in fecal samples by PCR and denaturing gradient gel electrophoresis (DGGE) and by analyzing the sequences of the major ribotypes. DGGE profiles of the dominant populations in the intestines of the infants were obtained by analyzing daily or weekly fecal samples. After delivery, the germfree infant gastrointestinal tracts were rapidly colonized, and the succession of bacteria in each ecosystem was monitored. During the first few days of life the profiles were simple, but they became more complex as the bacterial diversity increased with time in both babies. Clone libraries of amplified 16S rDNA fragments from baby feces were constructed, and these libraries allowed identification of the bacterial types by comparative DNA sequence analysis; the bacteria identified included members of the genera Bifidobacterium, Ruminococcus, Enterococcus, Clostridium, and Enterobacter. Species most closely related to the genera Bifidobacterium and Ruminococcus in particular dominated the intestinal microbiota based on the stability over time and the numbers, as estimated by the intensities of the bands. However, 19 of the 34 cloned rDNA sequences exhibited less than 97% identity with sequences of known bacteria or cloned sequences in databases. This study showed that using PCR-DGGE and 16S rDNA sequence analysis together resulted in a dynamic description of bacterial colonization in the infant intestinal ecosystem and allowed visualization of bacteria that are difficult to cultivate or to detect by other methods.

-The post-weaning period in pigs is characterized by an immediate but transient drop in feed intake resulting in severe undernutrition and growth check. This in turn affects various aspects of small intestinal architecture and function leading to gut-associated disorders and often diarrhea. Among these, villus atrophy and digestive enzyme activity depression have been documented. More recent investigations clearly demonstrate early signs of local inflammation including immune cell infiltration and increased pro-inflammatory cytokine gene expression, signs of cytoprotection through up-regulation of so-called heat shock proteins, indications of tissue alterations by proteases (stromelysin) and finally epithelial functional disorders in mineral absorption/secretion and permeability. This is followed by a regenerative phase, probably stimulated by feed intake resumption, resulting in down-regulation of many intestinal indicators. However, some of them then display new spatio-temporal adult-type adaptive patterns of maturation. A limited number of substances, particularly nitrogenous compounds and complex preparations of animal origin (colostrum, plasma) have proven to be successful, at least partly, in minimizing post-weaning intestinal disturbances. Thus further research in intestinal physiology, in association with microbiology and immunology, is warranted to strengthen our understanding of the mechanisms of gut disorders in order to provide a better rational basis for designing suitable alternatives to in-feed antibiotics for pigs. clairement montré des signes précoces d'inflammation incluant une infiltration cellulaire et l'expression accrue des gènes de plusieurs cytokines inflammatoires, une cytoprotection renforcée par la sur-expression des protéines du choc thermique, des indications d'altérations tissulaires par des protéases (stromélysines), et finalement des désordres fonctionnels épithéliaux d'absorption et de sécrétion minérales et de la perméabilité intestinale. Ceci est suivi par une phase de régénération intestinale, probablement stimulée par la reprise de consommation alimentaire, et conduisant à un retour à la normale de plusieurs indicateurs. Cependant, certains d'entre eux ont évolué vers des profils spatio-temporels adaptatifs de type adulte. Un nombre limité de substances, particulièrement des composés azotés et des produits animaux (colostrum, plasma) ont démontré leur capacité, au moins partielle, à minimiser les perturbations digestives post-sevrage. De nouvelles recherches en physiologie digestive, en association avec la microbiologie et l'immunologie, sont nécessaires pour renforcer notre compréhension des mécanismes des troubles digestifs. Ceci permettra de fournir des bases plus rationnelles pour développer des solutions alternatives satisfaisantes aux antibiotiques dans les aliments pour porcelets.intestin / nutrition / physiopathologie / porcelet / sevrage

We analysed the spatio-temporal sequence of events concerning the morphology, physiology and ecology of the gut of piglets during the 2 weeks following weaning, in order to provide a limited number of variables that could be relevant markers of the gut post-weaning changes. An experiment was conducted on sixty piglets fasted for 2 d, then administered a weaning diet with a moderate or a high content of wheat using controlled gastric feeding, and slaughtered at different time-points post-weaning. Sixty-nine variables were analysed by principal component analysis. The results showed that the temporal changes induced in the gut by weaning can be divided into two periods: an acute period happening immediately after weaning, followed after day 5 by a more progressive adaptative and maturational phase. The main factors of this adaptation were the refeeding process and the time, while the diet per se had little influence. The villus length, lactase activity, macromolecule fluxes across the jejunum and the plasma cholecystokinin were proposed as markers of the acute phase. The mass of the jejunum, the weight of the pancreas, the content of stomach, the trypsin activity and the theophylline-induced secretion in jejunum were related to the re-feeding. Markers proposed to follow the gut maturation were the maltase activity, the glucose absorption and the basal resistance in the ileum, the lactobacilli and enterococci in the colon, and the pH of colonic and caecal contents. These markers might be helpful to design suitable diets to limit post-weaning gut disorders in pigs.