1179 Characterization of the Bacterial Makeup and Quantitative Distribution in Patients With Suspected Small Intestine Bacterial Overgrowth (SIBO): A Meta-Analysis

Abstract

INTRODUCTION: Small Intestinal Bacterial Overgrowth (SIBO) is associated with abnormally high bacterial counts in the small intestine and clinical features such as diarrhea, constipation, abdominal pain, distension and bloating. A meta-analysis of studies of endoscopic samples from patients with suspected SIBO was performed to estimate the distribution of bacterial colony forming units (CFU) and identify the bacterial populations in these patients. METHODS: A literature search was performed to find studies of the jejunum or duodenum culture aspirates from patients with suspected SIBO using keywords: SIBO (or SBBO), culture aspirate and CFU. A total of 10 studies met the inclusion criteria. The CFU distribution was estimated using a log-spline smoothing technique in the statistical package R. Top bacterial population identified in aspirates of these patients was reviewed. RESULTS: The studies used in the meta-analysis including the number and type of subjects, the region where the culture aspirate sample was taken, and the type of CFU data presented was summarized in Table 1. A histogram of the estimated CFU distribution using the first five papers with actual CFU counts was shown in Figure 1. The spike at zero showed that approximately 26% of patients had sterile cultures. Sensitivity analyses using the first seven papers and all ten papers yielded similar estimated distributions to Figure 1, particularly in terms of the proportion of subjects with CFU counts between 104 and 106. The proportion of subjects in the tails of the distributions (sterile samples or CFU counts >1010) had larger variations between the three fitted distributions presumably due to differences in counting methodologies. The top bacterial species cultured and identified from jejunal aspirates was summarized in Table 2. CONCLUSION: Using a standard diagnostic threshold >105 CFU, only 24% of patients with suspected SIBO would test positive; while lowering the threshold to >104 CFU increases the positive call rate to 33%. As expected, bacterial culture identification was unable to clearly distinguish a single contributing organism. Limitations to this work are substantial and include variability in sampling regions, contamination, difficulty culturing and counting bacteria, lack of standardization in procedures and reproducibility. Given these limitations, there is consensus that novel tools are needed for evaluating patients with suspected SIBO.