COMPARISON OF RESTRICTION-ENDONUCLEASE ANALYSIS, RIBOTYPING, AND PULSED-FIELD GEL-ELECTROPHORESIS FOR MOLECULAR DIFFERENTIATION OF CLOSTRIDIUM-DIFFICILE STRAINS

A combined clinical and molecular epidemiologic analysis of 46 strains of Clostridium difficile, including 16 nosocomial isolates from one w ard (outbreak ward) plus 17 other nosocomial isolates and 13 community -acquired isolates, was performed. HindIII digests of total cellular D NA were analyzed by restriction enzyme analysis (REA) and ribotyping; SmaI digests were analyzed by pulsed-field gel electrophoresis (PFGE). Isolates were assigned to typing groups on the basis of the profiles detected; isolates with closely related profiles were assigned to subg roups. The 16 isolates from the outbreak ward were resolved by both RE A and PFGE into five distinct groups; 13 isolates represented two REA groups and three PFGE groups and two isolates were resolved as distinc t groups by both techniques. DNA obtained from one isolate was persist ently partially degraded, precluding analysis by PFGE. Seventeen spora dic nosocomial isolates were resolved by REA and PFGE into comparable numbers of groups (i.e., nine groups) and subgroups (i.e., 15 and 14 s ubgroups, respectively), with two isolates not evaluable by PFGE. The 13 epidemiologically unrelated community-acquired isolates were assign ed to 11 groups by REA and to 12 groups by PFGE. Overall, ribotyping i dentified only nine groups among the 46 isolates. We conclude that REA and PFGE have comparable discriminatory powers for epidemiologic typi ng of C. difficile isolates and that ribotyping is appreciably less di scriminatory. For a few isolates, partial DNA degradation prevented an alysis by PFGE but not by REA or ribotyping; the cause of the degradat ion is unknown.