The role of infection in irritable bowel syndrome

Abstract

A clinically distinct subset of Irritable Bowel syndrome (IBS) could be induced or exaggerated by bowel infection that is called post-infective IBS (PI-IBS) which is characterized by diarrhea predominant symptoms with less psychiatric illness. The purpose of this work was to study whether some bowel infections contribute to the pathogenesis of IBS and whether the treatment of such infections reduces IBS symptoms. 100 patients with symptoms suggestive of IBS according to Rome II Criteria were chosen from Internal Medicine outpatient clinic-Al Hussein university hospital. They were 64 females and 36 males, aged 18-52 years old with mean age 38,2  3,6 years. They were submitted to: full clinical examination and frequent stool examinations (direct smear and culture) before, soon after and six months after administration of drug therapies for common stool-positive associated bowel infections (diloxanide for E. histolytica, metronidazole for Giardia lamblia, Ketoconazole for Candida, ciprofloxacin for Salmonella and neomycin for Pseudomonas). Results obtained showed that 24% of patients had diarrhea predominant symptoms, 13 patients (54%) out of them had history suggestive of acute gastroenteritis. 80 patients had initial positive stool examination and continued the post treatment six months follow up study. Out of them, 13 patients had stool positive for Salmonella typhi mixed with E. histolytica; ten of them (76.9%) showed a statistically significant persistent clinical and laboratory improvement after ciprofloxacin therapy (P < 0.01). So Salmonella typhi may be implicated in IBS pathogenesis. Six patients showed isolated Giardia lamblia infection; four of them (66.7%) showed a statistically significant persistent clinical and laboratory improvement after metronidazole thereby (P < 0.05). Giardia lamblia parasite may be considered in triggering or exaggerating IBS symptoms. 24 patients had isolated E. histolytica infection; only one of them (4.2%) showed sustained clinical and Laboratory improvement after diloxanide therapy -statistically insignificant result- (P > 0.05). This finding makes the correlation between E. histolytica infection and IBS is unlikely. 20 patients had isolated Candida overgrowth on stool examination; eight of them (40%) showed a statistically significant clinical and laboratory improvement after Ketoconazole therapy (P < 0.05). Therefore Candida overgrowth may induce or exaggerate IBS symptoms. Finally, no growth was noticed for shigella sp. or E. coli, this may exclude the role of such organisms in IBS pathogenesis.