DIAGNOSIS OF BACTERIAL OVERGROWTH
Diagnosis of IBO is based on clinical and bacteriological analysis.
- On the clinical level, since direct or indirect bacteriological evidence
is sometimes hard to provide, diathesis and symptoms (diarrhoea, ballooning,
malabsorption, infections) should be considered first.
- On the bacterial level, qualitative and quantitative analysis may be
done by examining the duodenal and/or jejunal flora by the corresponding tubage
technique, along with analysis of the pharyngeal flora. A concentration (C)
> 106/ml is evidence of IBO; the type of germ is determined by gelose cultures
in a laboratory experienced in identification and quantification techniques
such as these.
The limits to this diagnostic approach are the examination duration, contamination
of the sampling probe, the difficulty of demonstrating anaerobes, the quality
of bacterial counts and in vitro cultures and, lastly, the sampling site compared
to the seat of overgrowth. The result of this is false negatives and false positives.
Coprocultures, unless they isolate a abundant monomorphic flora such as a particular
strain of pathogenic enterobacteria, are of limited interest.
Indirect methods based on bacterial metabolism include duodenal
tubage and assaying of non-conjugated bile acids or volatile fatty acids, urine
assays (indicanuria and free phenols/24h) and breath tests using labelled glycocholate
(CO2), 14C-xylose (CO2), lactose or lactulose (H2). The methods are limited
by the use of stable or radioactive isotopes, the effect of the caecum, and
acceleration of transit resulting from a dose of lactulose. Moreover, not all
bacteria produce hydrogen.
In practice
Diagnosis is based on analysing the diathesis, proper sampling of duodenal flora,
examining the transit time (carmine) both before and during an H2 breath test
on an empty stomach and every 15 minutes after a dose of lactulose. Sometimes,
the therapeutic test will provide the retrospective "evidence" of
IBO.
TREATMENT
Outside antibiotic treatment, surgery is indicated for removing
an obstacle or a blind loop or for carrying out an enterostomy. Human milk stimulates
motricity and provides bacteriostatic factors.
Antibiotic treatment depends on various strategies which will depend
on habits, experience, anatomical or functional indication, as well as the germs
involved. It could be monotherapy (erythromycin, tetracyclines, metronidazole),
bitherapy (colimycine 500,000 units and metronidazole 10 mg/kg) 3 times/day
or (erythromycine 10 mg/kg and metronidazole 10 mg/kg) 3 times/day or even total
digestive decontamination (DD); the risk of total DD, however, is the emergence
of multiresistant strains.
The criteria of effectiveness for total, partial or selective DD is based
on analysis of clinical improvement, measurement of absorption (steatorrhoea
and stool weight), the H2 breath test, duodenal flora and/or coprocultures.
Total DD may be performed as emergency treatment for septicaemia of digestive
origin (translocation) which is not rapidly brought under full control by systemic
antibiotic treatment. This is often the most effective stand, but means a total
DD lasting according to aetiology and continuation of the systemic antibiotic
treatment.
The use of so-called substitution "floras" or "probiotics"
is believed to be effective; they are currently being assessed.
Digestive mucus modifiers could be a useful therapeutic approach
because of their capacity to intervene in bacterial adhesion mechanisms. The
interactive mechanisms between mucin and bacteria are said to let the latter
resist the binding and penetration of micro-organisms and toxins present in
the intestinal lumen.
Index de la page .