Table 4. Distribution of C. difficile Strains, According to Epidemiologic Category.
| Strain | Community-Associated CDI (N = 735) | Health Care–Associated CDI (N = 629) |
|---|---|---|
| no. of cases (%) | ||
| NAP1 | 138 (18.8) | 193 (30.7) |
| NAP1-related† | 13 (1.8) | 20 (3.2) |
| NAP2 | 13 (1.8) | 10 (1.6) |
| NAP3 | 3 (0.4) | 12 (1.9) |
| NAP4 | 84 (11.4) | 65 (10.3) |
| NAP5 | 3 (0.4) | 6 (1.0) |
| NAP6 | 56 (7.6) | 27 (4.3) |
| NAP7 | 25 (3.4) | 13 (2.1) |
| NAP7-related‡ | 2 (0.3) | 2 (0.3) |
| NAP8 | 5 (0.7) | 1 (0.2) |
| NAP9 | 22 (3.0) | 9 (1.4) |
| NAP10 | 21 (2.9) | 15 (2.4) |
| NAP11 | 79 (10.7) | 63 (10.0) |
| NAP12 | 9 (1.2) | 16 (2.5) |
| Unnamed§ | 245 (33.3) | 163 (25.9) |
| Could not be typed¶ | 17 (2.3) | 14 (2.2) |
Molecular typing was performed with the use of pulsed-field gel electrophoresis (PFGE). PFGE types represented the following ribotypes on polymerase-chain-reaction assay, according to an analysis that was performed on a random sample of 35 of the most prevalent NAP (North American PFGE) types: NAP1, 027; NAP4, 020; NAP6, 002; NAP7, 078; and NAP11, 106.
This strain has characteristics of NAP1 (i.e., positive for toxins A and B and C. difficile binary toxin with a 18-bp deletion in tcdC) but does not meet the 80% cutoff for relatedness on PFGE.
This strain has characteristics of NAP7 (i.e., positive for toxins A and B and C. difficile binary toxin with a 39-bp deletion in tcdC) but does not meet the 80% cutoff for relatedness.
The strains in the unnamed category include 80 PFGE types that do not fall within NAP1 through NAP12.
DNA from these samples produced no bands on PFGE after three attempts.