FIG. 2.

RT-PCR products with specific fliD primers fliD-Nter and fliD-Cter and RNA isolated from nonflagellated C. difficile strains. Lanes: 1, 1-kb ladder (Amersham-Pharmacia Biotechnology); 2, strain 79685 (positive control); 3, RNA from C. sordellii (negative control); 4, strain ATCC 43596 (reference serogroup C. strain); 5, strain 54637; 6, strain 54828; 7, strain 51936; 8, strain 1075; 9, strain ATCC 43597 (reference serogroup D strain); 10, strain 55944; 11, strain SE956; 12, strain ATCC 43600 (reference serogroup H strain); 13, strain ATCC 43601 (reference serogroup I strain); 14, strain 54823; 15, strain 55684; 16, strain 52356; 17, strain 57207; 18, strain 20356. To confirm the purity of the RNA preparation and the specificity of the target RNA, an RNA sample treated with RNase was submitted to an RT-PCR as described in the text. Furthermore, the absence of genomic DNA contamination in the RNA samples was verified by PCR with fliD gene-specific N-terminal and C-terminal primers. No amplified products were detected in these two control experiments.