Development of heat-resistant CFU of 53 <i>C. difficile</i> strains.

<p>CFU following heat treatment (60°C for 25 min) were determined after (A) 0h; (B) 24h; (C) 48h; and (D) 120h incubation in BHIS broth. The BI/NAP1/027 strains were originally isolated from North America (N.A.), the UK, or the rest of Europe. The data represent the average of three independent experiments and error bars indicate the standard errors of the means. The solid line represents the average CFU/ml of all 53 isolates at 20h, the dotted line represents the average CFU/ml of the BI/NAP1/027 group, and the dashed line represents the average CFU/ml of the non-BI/NAP1/027 group. The detection limit for colony counts was 50 CFU/ml.