Probiotics and prebiotics modulate the composition of the human gut microbiota. The beneficial effects may result from suppression of harmful microorganisms or stimulation of organisms which contribute in a positive way to the nutrition and health of the host. Both types of supplement represent an attempt to reconstitute the gut flora to its normal composition which has been adversely affected by dietary and environmental stresses.

The potential of amylose a constituent of starch, as a novel colonic drug delivery system has been investigated. In this study glucose was used as a model drug and incorporated into pellets (diameter 1.40–1.70 mm) that were prepared by extrusion and spheronisation. The behaviour of different glucose containing pellets coated with an amylose-Ethocel® mixture (ratio 1:4 w/ w) has been investigated in vitro. Dissolution release profiles of the formulation demonstrated in vitro gastric and small intestine resistance. High volatile fatty acid and carbon dioxide concentrations during in vitro fermentation studies showed that the formulation was susceptible to bacterial enzymatic attack.

The observation that certain starches naturally present in the diet resist pancreatic enzymes and reach the colon where they are fermented by bacterial amylases has been exploited to provide a coating for specifically targeting drugs to the human large intestine. A mixture of amylose, which is a fraction of starch that can be made resistant to pancreatic enzymes, and Ethocel (1:4 amylose:Ethocel) has been developed and [13C]glucose used as a surrogate for drug delivery. Eight healthy subjects were given, fasting, at 8 am amylose-Ethocel coated pellets containing 300 mg [13C]glucose together with a further capsule that contained amberlite resin labelled with 99mTC to act as a transit marker and outline for the anatomy of the gut. Subjects underwent gamma-scintigraphy at half-hourly intervals for 5 h and then at hourly intervals until 8 pm. Breath samples were taken for 13CO2, which was measured by gas isotope mass spectrometry, at half-hourly intervals for 5 h and then hourly until 2300 h, with two further breath samples the following morning before breakfast. Gamma-scintigraphy showed that 5% of the activity had arrived in the caecum at 3.5 h after oral dosage (range 2.5–4.75 h) with all the material in the colon after 7.1 h (4.5–10 h). Breath 13CO2 data were analysed by the cusum technique and by curve fitting to determine first appearance of 13CO2 in breath. The first rise in breath 13CO2 was at 3.5 h (range 2.0–6.0 h) with 1% accumulated recovery of breath 13CO2 at 6.2 h (5.2–7.3 h). Total 13CO2 recovery at 25 h was 37.5% (21.9–47.8%). A single subject given a dose of uncoated glucose showed a rise in breath 13CO2 at 30 min peaking at 1.5 h and a total recovery of 28% at 6 h. Accumulated recovery curves for 13CO2 in breath showed that pellet breakdown and glucose metabolism was occurring over a 15 h period with a delay of about 2.7 h between arrival in the caecum and significant (1%) breakdown of the pellets. Resistant amylose, a naturally occurring component of the diet combined with ethylcellulose, can therefore be used to coat pellets that allow controlled release of contents for targeted drug delivery to the large bowel during a 12–24 h period.

Viable counts and activities of sulfate-reducing bacteria were determined in the oral cavities of 12 healthy volunteers. Of these, 10 harboured viable sulfate-reducing bacteria populations. Six separate sites were sampled: the posterior tongue, anterior tongue, mid buccal mucosa, vestibular mucosa, supragingival plaque and subgingival plaque. Sulfate-reducing bacteria occurred in all areas, with the highest incidence in supragingival plaque. Viable counts and sulfate-reducing activities in each of the regions varied from 0 to 10(8) cfu (g wet weight)-1 and from 0 to 50 nmol (g wet weight)-1 h-1, respectively. As sulfate-reducing bacteria can be detected in the oral cavity, they may potentially be involved in terminal oxidative processes carried out by the microflora of the mouth.

The possibility of drug targeting to the colon by using a coating comprising amylose in glass form has been studied. Amylose is a naturally-occurring polysaccharide and possesses the ability to form gels and films. This ability has been used to formulate a coating by spraying it on to drugs in pellet form. However, amylose film strength is poor in water due to swelling and, under simulated gastro-intestinal conditions, allows drug release. With the incorporation of Ethocel(R) into the coat, drug release in vitro was suppressed over a period of 12 h. Further evaluation of the drug coated pellets was carried out in vitro in a batch culture fermenter containing faecal inoculum, simulating large bowel conditions. The coating was fermented and the drug released. The in vivo performance of coated C-13 glucose pellets in eight healthy human volunteers was evaluated using gamma scintigraphy and (CO2)-C-13 excretion in breath. Gamma scan photographs showed the mean arrival time of the pellets to be 3.5 h in the caecum (range 2.5 to 4.7 h). Breath (CO2)-C-13 was detected 3.7 h post-dosing and was not significant (1% recovery) until 6.4 h. Breath (CO2)-C-13 was not apparent before pellets had reached the caecum, with a delay of 2.9 h between caecum arrival and significant (CO2)-C-13 release.

Helicobacter pylori is arguably the commonest chronic infection in man. However, its route of transmission is unknown. We have isolated viable H pylori from the faeces of an infected individual from The Gambia. The organism was cultured on selective media after concentration of faecal bacteria by centrifugation in a buffer equilibrated with a microaerophilic gas mixture. Growth characteristics, microscopic appearances, and enzyme activities were the same as those of a typical gastric isolate of H pylori. Protein preparations derived from the new isolate and the typical strain were antigenically similar, and had very similar electrophoretic profiles (including two major protein bands of 62 and 26 kDa, corresponding to the urease enzyme subunits). With the same technique, organisms with the colony morphology, growth requirements, enzyme activities, and microscopic appearances of H pylori were isolated from the faeces of 9 of 23 randomly selected children aged 3-27 months from a Gambian village with a high prevalence of H pylori infection in early life. Faecal-oral transmission is probably important in the spread of infection in such communities.