described more fully in Chapter 4.
Some of the ‘normal resident’ bacteria described below (S. faecal is, for example) have a borderline status – normally they do no harm, but they have been implicated in infection – of the bladder, for example – in some cases.
We have to remember that there is a delicate symbiotic (mutually beneficial) relationship between us and the organisms that have lived inside us for millions of years, but in the end they are looking after their own best interests and not ours; we benefit from them when all the environmental conditions are as they ought to be. One of the factors which can seriously disrupt the environment in which these bacteria live is the use of antibiotics, which while killing ‘bad’ bacteria do harm to the ‘good’ ones as well (not all antibiotics do this to the same degree, as will be seen in Chapter 4).
BIFIDOBACTERIUM BIFIDUM
These friendly bacteria inhabit the intestines – with a greater presence in the large intestine (the colon) than the small intestine. They also live in the vagina. In breastfed babies together with B, infantis and B. longum they form 99 percent of the flora of the intestines, but gradually reduce in numbers as we age. Their major roles are:
LACTOBACILLUS ACIDOPHILUS
This natural inhabitant of the intestines also lives in the mouth and vagina. Its main site of occupation is the small intestine. Its major roles are:
BIFIDOBACTERIUM LONGUM
This is a natural inhabitant of the human intestines and vagina. It is found in larger numbers in the large intestine than the small intestine. Together with other bifidobacteria, this is the dominant organism of breastfed infants (making up 99 percent of the microflora). In adolescence and adult life the bifidobacteria are still the dominant organism of the large intestine (when health is good). Among its main benefits are:
BIFIDOBACTERIUM INFANTIS
This is a natural inhabitant of the human infant’s digestive tract (as well as of the vagina, in small quantities). Its presence is far greater in the bowel of breastfed infants compared with bottle-fed infants. Among its main benefits are:
LACTOBACILLUS BULGARICUS
This extremely useful friendly bacteria is not a resident of the human body, but a ‘transient’. Once it enters the body through food (yogurt, for example) it remains for several weeks before being passed, but while in the body it performs useful tasks. L. bulgaricus is a yogurt culture, as is the other main yogurt-making culture, Streptococcus thermophilus (see below), and is therefore found in some yogurts and cheeses if they have not been sterilized to kill their bacterial cultures to enhance shelf-life – after manufacture. It performs a number of useful roles, such as:
