Concept of human bowel flora as a healthy or sick organ

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Concept of human bowel flora as a

healthy or sick organ

 

Probiotic Therapy Research Centre

 

The Healthy Human Bowel Flora

 

The human flora is considered to be healthy if clinically the patient

is not suffering any disorders that might be related to it and

generally has painless, soft daily bowel movements without any

bleeding, and a normal amount of flatus. Furthermore, on examination

the normal components of the flora should be in their usual, accepted

qualitative/quantitative numbers and there should be no detectable

pathogens present. With such a working definition we can then move to

the description of what constitutes an unhealthy bowel flora.

 

 

The Unhealthy Human Bowel Flora

 

Each body organ responds to various disease processes in a limited

number of ways. The disease process affects the organ in question

which in turn may affect surrounding organs and the rest of the body.

For example obstruction of small blood vessels in the heart may lead

to an arrhythmia and perhaps death. Yet such vessel obstruction in

the lung or the brain will not cause arrhythmia but will have a

different pathological and clinical effect. Some organs develop

inflammatory responses (eg. dermatitis). The bowel flora can also

respond in a limited number of ways to disease processes. The bowel

flora is incapable of having a blood vessel obstructed or being

inflamed - albeit inflammatory cells can be detected in the flora.

Most organs can develop neoplastic changes. The bowel flora is not

capable of developing a benign or a malignant change in bacterial

cells as far as we know. However, the bowel flora is quite capable of

becoming infected by a variety of pathogens. Hence, its response is

generally limited to the proliferation of pathogenic bacterial (and

other) cells, toxin production, production of various bio-active (or

pro-inflammatory) molecules, gas production, as well as the

suppression of normal bacterial components and even loss of bacterial

components. As the result of infection the flora can directly affect

its immediate human tissues - the bowel - and at times other parts of

the body. The bowel may respond with excessive fluid secretion

(cholera), inflammation (colitis), pain or cramping (IBS), trapping

gas (bloating), partial paralysis (constipation as in botulism and

idiopathic constipation) among other responses. Various combinations

of these responses may also co-exist. The infected flora therefore

affects primarily the muscular container (bowel) in which the bowel

flora resides, but through the production of toxins and pro-

inflammatory products and the associated bowel inflammation it is

easier to understand how other parts of body may be affected. Having

understood how known infective bacteria (eg. shigella) can bring

about inflammation of the mucosal lining resulting in infective

colitis, it is easier for us to comprehend how 'idiopathic colitis'

could possibly be caused by a chronic faecal infection whose

pathogens are still to be discovered. Furthermore, infected bowel

flora can transmit infective agents that can then invade the bowel

wall eg. Mycobacterium tuberculosis causing TB of the distal small

bowel or the colon. In a similar fashion Mycobacterium avium

subspecies paratuberculosis can be transmitted by infected bowel

flora to the distal small bowel and colon resulting in Crohn's

disease. (see www.crohns.org)

 

Other parts of the body may suffer from the effects of flora

infection because of the severe nature of local colonic changes or

absorbed toxins. If there is colonic bleeding, frequency, mucus

production, and fluid loss for example, the entire body may be

affected by anaemia, tiredness, malaise or dehydration effects. Some

infective agents may secrete molecules which when absorbed may result

in anorexia, nausea, vomiting as well as profound weakness and even

death (botulism), called 'para-infective' phenomena.

 

Just as other body organs suffer infectious diseases and can be

treated with anti-microbial drugs, so infection of the bowel flora is

frequently treated for parasites or bacterial infections. In

situations of serious diseases of body organs, topping up of a

missing organ (eg. blood transfusion or skin graft) is resorted to.

At times, transplantation of the entire organ is necessary (eg.

heart, liver or bone marrow transplant). The bowel flora may also

be 'topped up' (probiotic use) and at times it can be fully

transplanted (Human Probiotic flora Infusion - HPI).

 

Infected Human Bowel Flora

 

The most common disease state which affects the bowel flora is

infection. In this condition, human stool or faecal flora becomes

infected with a pathogen or pathogens. Numerous pathogens can infect

the human flora. They can be viral, bacterial, fungal or helminthic.

Furthermore, such infections can be classified as acute, sub-acute or

chronic (persistent). From yet another angle, bowel flora infections

can be viewed as being detectable or undetectable. For example, in

adults many acute diarrhoeal episodes are clearly infective in

nature, yet in most situations we do not detect any pathogens. Many

chronic diarrhoeal states carry a similar infective mechanism. It is

the 'undetectable' group that holds much promise as an area where

research and the elimination of 'not-yet-described' infective agents

could bring about much change in the way we view the human flora.

Disorders we have not yet considered to be caused by the human flora

eg. IBS, constipation or inflammatory bowel disease (IBD) may indeed

be linked to flora imbalances.

 

Acute Infection of the Human Flora

 

There is an ever-expanding list of pathogens that have been thought

to cause acute infection of the flora. These generally cause

diarrhoea. Nonetheless it has to be remembered that the GI flora can

become acutely infected causing no symptoms - simply carrier status,

eg. Clostridium difficile or certain worms - and in some situations

can cause constipation, flatulence, anorexia and weight loss. Such

infections are well known. Examples of acute infections include viral

pathogens eg. rotavirus, Norwalk virus, enteric adenovirus,

calcivirus, astrovirus; bacterial pathogens eg. salmonella, shigella,

campylobacter, enterotoxigenic E. coli, Clostridium perfringens,

yersinia, vibrio, bacillus cereus and protozoa eg. cryptosporidium.

 

Persistent Infection of the Human Flora

 

Patients with persistent infection may present to the doctor with

many weeks to years of diarrhoea, bloating, flatulence, cramps and

incontinence as well as constipation. Apart from local bowel effects

of such chronic flora infections, distant symptoms outside the bowel

can be caused by pathogens and are called 'para-infective phenomena'.

They can include nausea and vomiting, tiredness, joint pains,

headaches, malaise, fevers, reflux and pain on swallowing among

others. Symptoms may be mild in some patients yet severe in others

for various reasons. Multiple infections can co-exist in some

patients. Examples of known persistent infections of the flora are

listed below. However, it has to be remembered that the overwhelming

majority of persistent bowel flora infections, perhaps 80%, are still

to be named and diagnosed because science has not yet identified and

described all pathogens.

 

Some examples of persistent bowel flora infections include C.

difficile, C. perfringens, Aeromonas sp., Entamoeba histolytica,

Dientamoeba fragilis, Giardia lamblia, Yersinia enterocolitica and

many other parasites. Candida albicans rarely plays a pathogenic

infective role in the bowel except in some situations of severe

immunodeficiency eg. AIDS.

 

Deficient Human Bowel Flora

 

The normal human bowel flora is made up of a large number of

different bacterial components including the Bacteroides species,

eubacteria, clostridia, bifidobacteria, E. coli and others. Unlike

the composition of blood which is well studied and known the

composition of the bowel flora has received comparatively little

research attention and remains poorly understood. At best no more

than 50% of the bacterial components have actually been cultured or

named and research is now heading towards DNA characterisation of

components to better describe the human flora. It has recently become

clear that some species of bacteria can be completely absent in the

bowel flora of some individuals. This has been especially documented

in those patients who, after antibiotic treatment, had complete

absence of Bacteroides species in association with chronic infection

with C. difficile.2 Bacteroides and E. coli deficiency has also been

observed in patients with irritable bowel syndrome and chronic

fatigue syndrome.3 Generally, deficient flora appears to be infected

or replaced with other pathogenic bacteria that fill the gap left by

the absent normal flora components.

 

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