Influence of microbial species on small intestinal myoelectric activity and transit in germ-free rats

The effect of an intestinal microflora consisting of selected microbial spe cies on myoelectric activity of small intestine was studied using germ-free rat models, with recording before and after specific intestinal colonizati on, in the unanesthetized state. Intestinal transit, neuropeptides in blood (RIA), and neuromessengers in the intestinal wall were determined. Clostri dium tabificum vp 04 promoted regular spike burst activity, shown by a redu ction of the migrating myoelectric complex (MMC) period from 30.5 +/- 3.9 m in in the germ-free state to 21.2 +/- 0.14 min (P< 0.01). Lactobacillus aci dophilus A10 and Bifidobacterium bifidum B11 reduced the MMC period from 27 .9 +/- 4.5 to 21.5 +/- 2.1 min (P< 0.02) and accelerated small intestinal t ransit (P< 0.05). Micrococcus luteus showed an inhibitory effect, with an M MC period of 35.9 +/- 9.3 min compared with 27.7 +/- 6.3 min in germ-free r ats (P< 0.01). Inhibition was indicated also for Escherichia coli X7 gnotob iotic rats. No consistent changes in slow wave frequency were observed. The concentration of neuropeptide Y in blood decreased after introduction of c onventional intestinal microflora, suggesting reduced inhibitory control. I ntestinal bacteria promote or suppress the initiation and aboral migration of the MMC depending on the species involved. Bacteria with primitive ferme nting metabolism (anaerobes) emerge as important promoters of regular spike burst activity in small intestine.