Glenn Gibson and his colleagues at the Institute of Food Research in Reading
added liquid from a culture of bifidobacteria to cultures of E. coli.
鈥淚f you have a Petri dish containing E. coli 0157:H7, a gap appears if
you add extracts from bifidobacteria,鈥� says Gibson. His team is now trying to
identify the antibiotic involved.
E. coli 0157:H7, which can contaminate beef and dairy products,
killed 18 people in Lanarkshire in an outbreak that began before Christmas. A
second Scottish outbreak, in Arbroath, had claimed one more life as New
杏吧原创 went to press.
All the people killed in the two Scottish outbreaks were elderly, and
Gibson鈥檚 results may help explain why old people are especially vulnerable to
E. coli poisoning. Beyond middle age, populations of bifidobacteria in
our gut deplete rapidly (see
Figure). 鈥淲e know that bifidobacteria decrease
markedly in this section of the population, so might there be a link with
vulnerability?鈥� asks Gibson. Certainly, as bifidobacteria populations decline,
those of potentially harmful bacteria, such as E. coli and
Streptococcus, surge.
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Gibson and his colleagues are seeking ways to make bifidobacteria flourish in
the large intestine. One option is to eat commercially available yoghurts
containing cultures of live bifidobacteria, but Gibson is not convinced by this
approach. 鈥淚鈥檓 not a fan of these live yoghurts because it鈥檚 asking a lot for
them to get right through the gut to the large intestine,鈥� he says.
Instead, Gibson favours promoting the growth of existing colonies by
supplementing people鈥檚 food with fructo-oligosaccharides, carbohydrates that are
easily digested by bifidobacteria but not by humans or harmful bacteria. His
team has demonstrated that bifidobacteria become the dominant microorganisms in
the large intestine of subjects who consume around 15 grams of
fructo-oligosaccharides per day, ousting potentially harmful bacteria such as
Clostridium, which can cause diarrhoea. But researchers have yet to
test whether the dietary supplements can restore elderly people鈥檚 diminished
populations of bifidobacteria.
Gibson says that it would be impossible for people to consume 15 grams of
fructo-oligosaccharides from a normal diet. 鈥淲e only take in around 3 or 4 grams
a day,鈥� he says. But it should be feasible to supplement foods such as biscuits
with fructo-oligosaccharides, Gibson says.