Effects of triclosan on the normal intestinal microbiota and on susceptibility to experimental murine colitis

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Evidence suggests that alterations in the intestinal microbiota may be a factor in symptoms of inflammatory bowel disease. Triclosan, an antibacterial agent found in consumer products, is detectable in wastewater and in urine from sample human populations. The current study determined whether low level exposure to triclosan, mimicking environmental exposure, alters intestinal bacterial populations and susceptibility to colitis. Mice were given triclosan in the drinking water (10 μg/ml) for 5 days, followed by induction of colitis by 3% dextran sulfate sodium (DSS). Fecal bacteria were cultured to determine CFUs of total anaerobes, lactobacilli, and coliforms. Fecal DNA was analyzed by PCR and denaturing gradient gel electrophoresis (DGGE) using universal primers targeting the 16S rRNA gene. Colitis was assessed by disease activity index, histological scoring, and RT‐PCR for cyclooxygenase‐2. Clinical colitis scores were increased with DSS but were not altered by triclosan treatment. Total anaerobes were increased by DSS but were not altered by triclosan, while lactobacilli were decreased by triclosan and DSS. DGGE analysis indicated a shift in the fecal bacterial population with DSS that was altered by triclosan + DSS. We conclude that low‐level exposure to triclosan does not significantly alter susceptibility to DSS colitis, but that it may alter the composition of the intestinal microbiota.