Table 1.
Prevalence of Virulence-Related Strain Features in Pharyngitis (n = 417) and Invasive (n = 236) GAS Isolates, Colorado, June 2016 to April 2017
| Strain Featurea | Description | Cramer’s Vb | Number (Percent) Pharyngitis Isolatesc | Number (Percent) Invasive Isolatesc | Fisher P Valued | CMH P Valuee |
|---|---|---|---|---|---|---|
|
| ||||||
| ERM | The erm genes associated with macrolide resistance | 0.7 | 31(7%) | 54 (23%) | <.001 | <.001 |
| TET | The tet genes associated with tetracycline resistance | 0.89 | 33 (8%) | 63 (27%) | <.001 | .005 |
| COVS_NULL | Inactivating mutations in the covS gene | 0.34 | 2 (0.5%) | 15 (7%) | <.001 | .008 |
| SOF | Serum opacity factor | 0.98 | 243 (58%) | 198 (84%) | <.001 | .689 |
| FBAA | Fibronectin-binding protein of group A streptococci type A | 0.99 | 287 (69%) | 225 (95%) | <.001 | 1 |
| SFB1 | Streptococcus pyogenes fibronectin-binding protein I | 0.98 | 304 (73%) | 138 (58%) | <.001 | .913 |
| PRTF2 | S pyogenes fibronectin binding protein | 1 | 246 (59%) | 166 (70%) | .004 | 1 |
| R28 | Homolog of a group B streptococcal adhesin | 0.98 | 75 (18%) | 25 (11%) | .013 | .879 |
| ENN | emm-like enn virulence gene | 0.97 | 248 (59%) | 196 (83%) | <.001 | .452 |
| MRP | emm-like mrp virulence gene | 0.99 | 249 (60%) | 202 (86%) | <.001 | 1 |
| SME_Z | Streptococcal mitogenic exotoxin | 0.96 | 350 (84%) | 162 (69%) | <.001 | .602 |
| SPE_K | Streptococcal pyrogenic exotoxin K | 0.91 | 98 (24%) | 17 (7%) | <.001 | .294 |
| SS_A | Streptococcal superantigen A | 0.99 | 132 (32%) | 15 (6%) | <.001 | .986 |
| SPE_A | Streptococcal pyrogenic exotoxin A | 0.94 | 79 (19%) | 22 (9%) | .001 | .053 |
| SPE_L | Streptococcal pyrogenic exotoxin L | 0.96 | 17 (4%) | 18 (8%) | .057 | .063 |
| SPE_M | Streptococcal pyrogenic exotoxin M | 0.96 | 17 (4%) | 18 (8%) | .057 | .063 |
| SPE_J | Streptococcal pyrogenic exotoxin J | 0.95 | 93 (22%) | 63 (27%) | .207 | 1 |
| SPE_H | Streptococcal pyrogenic exotoxin H | 0.94 | 78 (19%) | 36 (15%) | .265 | .239 |
| SPE_I | Streptococcal pyrogenic exotoxin I | 0.91 | 72 (17%) | 35 (15%) | .420 | .745 |
| SPE_C | Streptococcal pyrogenic exotoxin C | 0.83 | 302 (72%) | 169 (72%) | .824 | .028 |
| SPE_G | Streptococcal pyrogenic exotoxin G | 0.98 | 342 (82%) | 219 (93%) | <.001 | .979 |
| SDA1 | Virulence-associated DNAse | 0.89 | 94 (23%) | 36 (15%) | .026 | .627 |
| SIC | Streptococcal inhibitor of complement | 0.99 | 89 (21%) | 24 (10%) | <.001 | .899 |
| NADase 330-G | NADase 330-G is associated with active NADase. The G330D substitution is a common inactivating substitution. | 0.91 | 371 (89%) | 173 (73%) | <.001 | .713 |
| PNGA3 | Pnga 3 - Clade 3 up-regulated promoter of the nga operon | 0.98 | 265 (64%) | 74 (31%) | <.001 | .028 |
| CAPSULE | hasA hyaluronic acid synthetase operon determinant | 0.96 | 225 (54%) | 163 (69%) | <.001 | .374 |
| ROCA | rocA null mutations | 1 | 39 (9%) | 4 (2%) | <.001 | 1 |
Abbreviations: CMH, Cochran-Mantel-Haenszel; GAS, Group A Streptococcus.
a
A strain feature is either positive (presence) or negative (absence) in an isolate.
b
Association between strain feature and emm type.
c
Number (percent) of feature-positive isolates.
d
Fisher’s exact test.
e
Cochran-Mantel-Haenszel (CMH) test using emm type as the stratum.