Irritable bowel syndrome (IBS) is a functional disorder characterised by abdominal pain or digestive discomfort. A feature of these symptoms is that they are often associated with a change in stool frequency or are temporarily relieved by defecation. IBS is a real public health concern owing to its high frequency in adulthood – around 6 to 10% of the general population in western countries – and its severity, which varies but can often be very pronounced [DAPOIGNY 2009; MALINEN, KROGIUS-KURIKKA et al. 2010]. IBS may thus lead to serious physical and mental consequences for the patient and a deterioration of their quality of life [AMOURETTI, LE PEN et al. 2006]. The consequences to society are also of concern, because IBS is a source of absenteeism and health expenditure [LEONG, BARGHOUT et al. 2003; PARE, GRAY et al. 2006; DAPOIGNY 2009].
IBS is defined according to the precise criteria of “ROME III”, the current classification of functional digestive disorders [DROSSMAN 2006]. This classification also details the existence, within IBS, of sub-groups which are defined by significant symptom differences. Patients are thus believed to fall into four groups, according to whether an acceleration or a decrease of bowel movement is predominant, and according to stool consistency [WHITEHEAD 1999].
Intestinal ecosystem alterations seem to play a leading role in this disorder. Several experimental or indirect facts testify to that effect, even though anomalies in intestinal flora composition cannot be readily interpreted as the cause of IBS rather than the consequence of other implicated mechanisms [BARBARA, STANGHELLINI et al. 2004; MALINEN, RINTTILA et al. 2005; QUIGLEY, FLOURIE 2007; SPILLER 2007].
Probiotic products have long been used, particularly in gastroenterology, to restore or maintain digestive ecosystem homoeostasis [CARAMIA 2008].
Not all persons suffering from IBS seek medical advice [DAPOIGNY 2009], and a portion of them self-prescribe. Irritable bowel syndrome (IBS) is nevertheless the number one digestive complaint when seeing a general practitioner [THOMPSON, HEATON, et al. 2000]. For gastroenterologists, to whom IBS patients are often referred, this pathology concerns 30% to 40% of consultations [OLDEN 2002]. Other specialists (psychiatrists, rheumatologists, etc.) are also concerned due to the frequent presence of other extradigestive symptoms (thoracic, musculo-osteo-articular pain, chronic fatigue, etc.) which also generate substantial IBS health expenditure [JOHANSSON, FARUP et al.; SPIEGEL, KANWAL et al. 2005]. All therapists concerned view IBS and other digestive functional disorders as difficult problems with major psychological – and sometimes even psychiatric – components, often rendering their diagnosis uncertain or their treatment disappointing [THOMPSON, HEATON et al. 2000].
The diversity of digestive disorders for which an organic cause is not determined led the medical community to establish an international and systematic classification of these functional pictures, allowing their physiopathological mechanisms to be understood in a more specific manner, and resulting in the development of rational treatments tailored to each one. In accordance with the ROME III classification, around 25% of patients are observed to have IBS with a predominance towards either diarrhoea (“IBS-D”), constipation (“IBS-C”) or alternating diarrhoea and constipation (“mixed IBS: IBS-M”); one last form being made up of “unsubtyped cases”.
Certain experimental facts combined with the clinical observations make of IBS-D a form for which the intestinal flora’s involvement is believed to play a leading role.
Regarding intestinal flora, three recent studies showed that patients from the IBS-D group presented with particularities in their digestive microbiota, which distinguished them not only from normal subjects but also from other IBS patients. Indeed, for these patients, the luminal and mucosal flora composition have a lower bacterial biodiversity [CARROLL, RINGEL-KULKA et al. 2011]. Please note that these qualitative observations specific to the IBS-D subgroup, come in addition to the general finding of a lower quantitative representation of the Lactobacillus and Bifidobacteria strains characteristic of the dysbiosis observed in the majority of IBS patients [BALSARI, CECCARELLI et al. 1982, SI, YU et al. 2004]. The most comprehensive study to date examined the faecal flora of 27 IBS patients and compared it to that of 20 healthy control subjects using real time PCR [KASSINEN, KROGIUS-KURIKKA et al. 2007]. Comparisons between IBS sub-groups revealed that the Lactobacillus concentration was significantly lower in the diarrhoea group than in the constipation group (though not significant compared to the control). Bifidobacterium concentrations tended towards decrease in the diarrhoea form compared to the constipation control but this decrease was not significant.
Differences between IBS sub-groups were also noted in relation to gut sensitivity. As an example, a greatly lowered perception threshold to rectal distension seems to be one of the main characteristics of IBS-D, in particular for women [XIAO, LIU 2004]. The tolerance to distension is lower in IBS-D patients. Overall, the higher digestive sensitivity observed in group IBS-D patients could originate from the existence of an inflammatory state combined with mucosal hyperpermeability [ZHOU, ZHANG et al. 2009; RAO, CAMILLERI et al. 2011].
Current IBS treatment is based on an array of dietary or medicinal, psychotherapeutic and alternative measures [ATKINSON, SHELDON et al. 2004] aiming for the symptomatic relief of pain, bowel movement disorder anomalies and the psychological consequences of these symptoms [FORD, TALLEY et al. 2008; BRANDT, CHEY et al. 2009]. These measures are numerous and cannot be described, or even listed, in the context of this protocol. None of these measures are specific to IBS [BRANDT, CHEY et al. 2009], nor to the IBS-D subgroup – with the exception of the non-specific medicinal treatment of diarrhoea symptoms.
Recent data on intestinal flora disturbances in IBS, as well as the hypothesis that the bacterial colonisation of the small intestine potentially plays a role, aroused interest for new therapeutic approaches: probiotics, prebiotics, antibiotics. Recent meta-analyses confirmed the value of probiotics in IBS, but they also very clearly showed that their effects were strongly linked to the strain used [MCFARLAND, DUBLIN 2008; NIKFAR, RAHIMI et al. 2008; FORD, TALLEY et al. 2009; HOVEYDA, HENEGHAN et al. 2009][FORD, TALLEY et al. 2008; BRANDT, CHEY et al. 2009].
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