Lack of Correlation between Bristol Stool Scale and Quantitative Bacterial Load in Clostridium difficile Infection

Decision to test for Clostridium difficile infection (CDI) is usually made when patients have loose stools with Bristol stool score of ≥5. We aimed to assess the relationship between bacterial load of C. difficile and Bristol stool scale, as well as stool frequency in stool samples collected from patients infected with the organism. Samples were collected at baseline, during therapy, and at the end of therapy. Spearman correlation test was used to evaluate these relationships. No correlation between Bristol stool scale and fecal load of C. difficile was found for both spores and vegetative cells at all time points as counts were persistently high (P = non-significant). Weak positive correlations were found between stool frequency and fecal load of C. difficile spores and vegetative cells (r(s) = 0.22 and 0.24, P = 0.04 and 0.03, respectively). These findings indicate that quantitative colony counts were sufficiently high to detect C. difficile, irrespective of stool consistency, and suggest that semiformed stool should be sought for the pathogen in symptomatic patients with frequent stools.