In this Article, in the section entitled ‘Quantitative real-time PCR’ within the Supplementary Methods, the probe for the Bacteroides fragilis 16S real-time PCR reaction was listed incorrectly as 5ʹHEX-AGGGACTGGAAGGCTTTACTGCTTC-3ʹBHQ1. The correct probe for Bacteroides fragilis 16S should be listed as 5ʹHEX-ACACGTATCCAACCTGCCCTTTACTCG-3ʹBHQ1. The mistake was a result of a copy and paste error with a different primer set targeting a B. fragilis toxin gene. All qPCR reactions were performed using the correct probe, and therefore no data were affected.