Isolation and Identification of Bacteria Associated with Irritable Bowel Syndrome

Abstract

Background: Irritable bowel syndrome (IBS) represents a multifactorial functional gastrointestinal disorder which affects approximately 10-15% of the world's population. It has been demonstrated that microbial disturbances are a crucial part of its etiology and sustainment. Unfortunately, a lack of complete bacteriological profiling of stool specimens of patients from some geographic locations exists. Objective: The objective of the work is isolation and identification of bacterial species from stool specimens of patients diagnosed with irritable bowel syndrome and the comparison of their profiles with those of healthy control subjects as well as the determination of the resistance of the isolated strains to various antimicrobial drugs. Methods: Stool specimens were taken from 80 patients who met the Rome IV Irritable bowel syndrome diagnostic criteria and 40 healthy age- and sex-matched control subjects. Traditional bacteriological cultures were followed by sequencing of the 16S RNA gene in order to definitively establish the species of isolates. Antibiotic susceptibilities were measured according to CLSI criteria via the Kirby-Bauer disk diffusion test. Results: In total, 248 bacterial isolates have been identified in stool specimens of IBS patients, while only 98 isolates have been found in controls. Among isolates obtained from IBS patients, the most frequent included E. coli (31.5%), K. pneumoniae (18.1%), E. faecalis (14.1%), B. fragilis (11.3%), lactobacilli (9.3%), bifidobacteria (7.7%), along with other lesser represented bacterial strains A decrease in the number that is statistically significant of lactobacilli and bifidobacteria (p<0.01) was found in IBS patients. Regarding antibiotic resistance, Enterobacteriaceae showed significant resistance to ampicillin (58.4%) and tetracycline (47.6%). Conclusions: It has been found that IBS patients have significant dysbiosis in terms of reduced numbers of beneficial bacteria with concomitant colonization by pathogenic bacteria.