TABLE 1.
Variations in the Ω loop of CTX-M β-lactamases from Enterobacteriaceae
| Variation in the Ω loop | CTX-M ESBLa |
||
|---|---|---|---|
| Group 1 | Group 2 | Group 9 | |
| R164G | M-72 | ND | ND |
| P167T | M-23 M-42 M-58 | M-74 | ND |
| P167S | M-52 M-62 | ND | M-19 M-99 |
| P167Q | M-54 | ND | ND |
| P167L | ND | ND | M-87 |
| P167A | ND | ND | M-126 |
| L169Q | ND | ND | M-93 |
| T171S | ND | M-4 M-6 M-7 | ND |
| P174Q | M-117 | ND | ND |
a
CTX-M ESBLs are assigned to five groups (groups 1, 2, 8, 9, and 25) based on identity of ≥95% for sequences belonging to the same group (20). No Ω loop variants were described for CTX-M β-lactamases belonging to groups 8 and 25. Sequences were obtained from the Lahey website (https://www.lahey.org/Studies/). ND, the variation was not detected in any variant of the group.