Table 1. Strains used in this study and mutations detected in penicillin binding proteins, gdpP and acrB genes.
| Strains | MecA | Driver for selection | MIC to CFTR* | MIC to AMP** | MIC to NAF*** | PBP1 | PBP2 | PBP3 | pbp4 promoter | PBP4 | GdpP | AcrB |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Colna | (+) | 1 S | 16 R | 128 R | ||||||||
| CRT# | (+) | CFTR | >64 R | 256 R | >256 R | G631S | 724602_724603insT (-377); 724500_724590del (-275) | N138K | ||||
| Colnexb# | (-) | <0.25 R | 0.25 S | 0.5 S | ||||||||
| CmTcc# | (-) | CFTR | >64 R | >256 R | >256 R | D156N | 724602_724603insT (-377); 724624T>G (-399) | T201A; F241L | H443Y | |||
| SF8300exd# | (-) | 0.25 S | 0.25 S | 0.5 S | ||||||||
| SRT# | (-) | CFTR | >64 R | >256 R | 64 R | 716955_716965del (-301) | N138K; H270L | Y306X | ||||
| SRB# | (-) | CFBP | 4 R | 4 S | 8 S | H499R; E567K | Y437C; V445L; Q453R; M559I | W228X | E183V; F241R | T509A | ||
| Sgape | (-) | 0.5 S | <0.25 S | 0.5 S | E183A; F241R | N182K | I960V | |||||
| SgapT# | (-) | CFTR | 64 R | >256 R | >256 R | H499R | 717031_717032insT (-377) | N138I; E183A; R200L; F241R | N182K | I960V | ||
| Spf | (-) | 0.25 S | 0.25 S | 1 S | E183A; F241R | |||||||
| SpT# | (-) | CFTR | >64 R | >256 R | >256 R | G581D | 716675del (-21); 717031_717032insT (-377) | N138I; E183V; T201A; F241R | N214del |
*CFTR = ceftaroline; CLSI breakpoints are ≤1 S, 2 I, ≥4 R (CLSI document M100-S23; ISBN 1-56238-865-7)
**AMP = ampicillin; CLSI breakpoints are ≤8 S, ≥16 R (CLSI document M100-S23; ISBN 1-56238-865-7)
***NAF = nafcillin; CLSI breakpoints are ≤8 S, ≥16 R (CLSI document M100-S23; ISBN 1-56238-865-7)
#Strains sequenced in this study
aParental strain of CRT
bCol strain with mecA excised
cColnex strain containing exogenous mecA plasmid (pYK20); mecA plasmid was evicted after ceftaroline selection (Chan L 2015 AAC)
dSF8300 strain with mecA excised, parental strain of SRT and SRB
eSF8300ex strain in which PBP4 (E183A, F241R), GdpP (N182K) and AcrB (I960V) mutations analogous to those in the CRB strain (Banerjee, et al. 2010 AAC) were introduced
fSF8300ex strain in which PBP4 (E183A, F241R) mutations analogous to those in the CRB strain (Banerjee, et al. 2010 AAC) were introduced
Abbreviations: MIC = minimal inhibitory concentration; R = resistant; S = susceptible, susc = susceptibility; CFTR = ceftaroline; CFBP = ceftobiprole.