TABLE 4.
Prevalence of PMSCs in inlA among five EcoRI ribotypes associated with inlA PMSC mutations identified in this study
| Ribotypea and inlA PMSC mutation type | Molecular serogroup(s) (no. of isolates characterized)b | No. of inlA PMSC mutations (no. of isolates screened) among isolates obtained fromc:
|
Total | % Prevalence of inlA PMSCs among all isolates belonging to ribotype | |
|---|---|---|---|---|---|
| Humans | Food | ||||
| DUP-1039C | |||||
| 7 | 1 (7) | 0 (29) | 7 (28) | ||
| 4 | 3 (3) | 4 (29) | 10 (28) | ||
| 12 | 3 (2) | 1 (29) | 1 (28) | ||
| Total | 1 and 3 | 5 (29) | 18 (28)** | 23 (57) | 40.4 |
| DUP-1045B | 1 (10) | 1 (17) | 12 (17)** | 13 (34) | 38.2 |
| DUP-1062D | |||||
| 6 | 1 (8) | 0 (4) | 11 (28) | ||
| 5 | 1 (2) | 0 (4) | 2 (28) | ||
| Total | 1 | 0 (4) | 13 (28)* | 13 (32) | 40.7 |
DUP-1029A isolates were not characterized by the SNP genotyping assay because all DUP-1029A isolates available were shown by DNA sequencing to carry an inlA PMSC. Isolates belonging to ribotypes DUP-1041A, DUP-1048A, and DUP-1056A were not characterized by the SNP genotyping assay, as these ribotypes were very rare among isolates in the PathogenTracker database. Ribotype DUP-1039C isolates were associated with three PMSC mutations corresponding to separate serotypes. Ribotype DUP-1062D isolates were associated with two PMSC mutations that corresponded to the same serotype.
Serogroup 1 isolates were of serotype 1/2a or 3a, and serogroup 3 isolates were of serotype 1/2c or 3c. Up to 10 isolates belonging to each common ribotype newly associated with an inlA PMSC were characterized by molecular serotyping as described by Doumith et al. (4).
A total of 123 isolates, including 57 DUP-1039C isolates, 34 DUP-1045B isolates, and 32 DUP-1062D isolates, were screened by reactions 1 and 2 of the SNP genotyping assay. Asterisks indicate significant (**, P < 0.001) or marginal (*, P = 0.11) overrepresentation of L. monocytogenes isolates carrying an inlA PMSC. More than one inlA PMSC was present in some ribotypes, and statistical analysis was based on the detection of any PMSC in isolates belonging to each ribotype.