Gel electrophoresis results for genomic DNA (gDNA) extracted from Clostridium difficile using three different QIAamp protocols. Gram-positive protocol (A), lanes 1 to 4: gDNA extracts from isolates 38A2 (lane 1 and 2) and 69B1 (lane 3 and 4). Each lane shows an independent extraction. Bacterial suspension protocol (B), lanes 1 to 3: gDNA extracts from isolate 38A2 obtained in three independent extractions. Optimized protocol (C), lanes 1 to 6: gDNA extracts from isolates 127A4, 161A1, 208A2, 208A3, 224C1, and 224A3, respectively. M, molecular-weight marker.