Short-chain fatty acid and organic acid concentrations in feces of healthy human volunteers and their correlations with anaerobe cultural counts during systemic ceftriaxone administration.

Short-chain fatty acid (SCFA) and organic acid concentrations and (an)aerobe cultural counts were determined simultaneously in fresh feces from 10 human volunteers before, during, and after 5 days of single-dose ceftriaxone administration. The changes and the correlation coefficients between these variables were tested to be significant (P less than 0.05). to investigate whether significant changes in the intestinal microflora could be predicted by significant changes in SCFA/organic acid concentrations. Multivariate analysis was used with the same objective. Significant decreases in most SCFA, total SCFA (0.01 less than P less than 0.02), and pyruvic acid (0.02 less than P less than 0.05) concentrations in feces were found on day 3 of treatment and also on day 5, with the exception of the pyruvic acid concentrations. Lactic acid concentrations, however, were significantly increased (0.01 less than P less than 0.02) on day 5. All anaerobic cultural counts were significantly decreased (P less than 0.05) on days 3 and 5 of treatment except those for Clostridium difficile agar, which were only decreased on day 5. Highly significant correlations were found on day 3 between the total anaerobe counts (P less than 0.001), the Bacteroides counts (P less than 0.001), and propionic acid, of which the latter had a predictive value during treatment. The results of multivariate analysis were significant but did not have a predictive value. From this study we can conclude that propionic acid concentrations during ceftriaxone treatment in healthy volunteers have a predictive value for the Bacteroides cultural counts. The results of this study must be confirmed by those from patients treated with ceftriaxone.