Table 3.
The 20 traits with the greatest differential in percent positives between NMEC and HFEC isolates
| Gene/traita | No. (%) of isolates containing trait |
Chi-square value | P | |
|---|---|---|---|---|
| NMEC (n = 85) | HFEC (n = 204) | |||
| aec35 | 64 (75.3) | 4(2) | 179.33 | <0.0001 |
| ompTp | 57 (67.1) | 8 (3.9) | 137.20 | <0.0001 |
| hlyF | 53 (62.4) | 8(3.9) | 123.02 | <0.0001 |
| cvaC | 49 (57.6) | 8 (3.9) | 109.38 | <0.0001 |
| etsA | 54 (63.5) | 14 (6.9) | 107.08 | <0.0001 |
| cvaA | 61 (71.8) | 29 (14.2) | 92.67 | <0.0001 |
| etsB | 52 (61.2) | 17 (8.3) | 92.18 | <0.0001 |
| cvaB5′ | 58 (68.2) | 27 (13.2) | 87.42 | <0.0001 |
| iss | 48 (56.5) | 15 (7.4) | 84.91 | <0.0001 |
| sfaS | 42 (49.4) | 14 (6.9) | 69.53 | <0.0001 |
| iutA | 68 (80) | 55 (27) | 69.04 | <0.0001 |
| 2093 | 55 (64.7) | 33 (16.2) | 66.72 | <0.0001 |
| 2101 | 55 (64.7) | 33 (16.2) | 66.72 | <0.0001 |
| cdtB | 32 (37.7) | 5 (2.5) | 66.58 | <0.0001 |
| tsh | 28 (32.9) | 2 (0.9) | 65.88 | <0.0001 |
| 2103 | 55 (64.7) | 34 (16.7) | 64.71 | <0.0001 |
| 2095 | 55 (64.7) | 34 (16.7) | 64.701 | <0.0001 |
| cvaB3′ | 55 (64.7) | 35 (17.2) | 64.71 | <0.0001 |
| 2078 | 33 (38.8) | 7 (3.4) | 63.02 | <0.0001 |
| papG1* | 48 (56.5) | 28 (13.7) | 56.56 | <0.0001 |
The traits are listed in descending order based on the magnitude of the chi-square value, with the most powerful trait being aec35, which contributes to the virulence of APEC BEN2908. The next 8 traits have been found among the PAIs of large APEC virulence plasmids. The tenth trait listed, sfaS, occurs in just under half of the NMEC isolates examined. The next two traits, 2093 and 2101, were originally found in a genomic island of APEC O1 and have not previously been ascribed a function or associated with ExPEC virulence. The remaining traits had smaller differences in prevalence rates and thus lower chi-square values, either because they occurred relatively more frequently in HFEC isolates or relatively less frequently in NMEC isolates than the more discriminating traits. Interestingly, many of the better-studied NMEC virulence traits, such as gimB, ibeA, or cnf1, did not make this list, suggesting that there is much yet unknown about NMEC pathogenesis.