Table 4.
Minimal inhibitory concentrations to penicillin of Streptococcus pneumoniae mutants and transformants
| Strain or transformant | Description | MIC to PG (μg/ml)a |
|---|---|---|
| R6 | Wild type | 0.023 |
| CCRI1974 | S. pneumoniae, sensitive clinical isolate | 0.023 |
| R6M1 | R6 clone selected in vitro for PG resistance | 2.0 |
| R6M2 | R6 clone selected in vitro for PG resistance | 2.0 |
| 1974M1 | 1974 clone selected in vitro for PG resistance | 2.0 |
| 1974M2 | 1974 clone selected in vitro for PG resistance | 2.0 |
| CP1250 | S. pneumoniae that contains a spontaneous mutation in the rpsL gene that confers resistance to SM | |
| R62x-M1 | R6-WT transformed with pbp2x PCR fragments from R6M1 (contains all three missense mutations present in PBP2x of R6M1) | 0.06 |
| R62x-M2 | R6-WT transformed with pbp2x PCR fragments from R6M2 (contains just three mutations - Q281P, A369V, R384G - out of five mutations present in PBP2x of R6M2) | 0.06 |
| R62x2b-M1 | R62x-M1 transformed with pbp2b PCR fragments from R6M1 so all missense mutations present in PBP2b of R6M1 transformed into this transformant | 0.125 |
| R62x2b-M2 | R62x-M2 transformed with pbp2b PCR fragments from R6M2 so all missense mutations present in PBP2b of R6M2 transformed into this transformant | 0.125 |
| R62x2b-M2, 1a::Janus | R62x2b-M2 knocked out in pbp1a by Janus cassette, KMRSMS | 0.125 |
| R6SmR, 2x2b1a-M2, | R62x2b-M2, 1a::Janus subjected to second step transformation with pbp1a of the Janus cassette with pbp1a of R6M2, KMSSMR | 0.125 |
| R6SmR, 2x2b1a,spr1178-M2, | R62x2b1a-M2 transformed with spr1178 PCR fragments from R6M2 (contains a Q28* nonsense mutation in spr1178), SMR | 0.125 |
| R62x2b,spr1254-M2 | R62x2b-M2 transformed with pstB PCR fragment from R6M2 (contains a T205I mutation in PstB) | 0.125 |
| R62x2b, spr1254, spr1178-M2 | R62x2b-M2 transformed with spr1178 and pstB PCR fragments from R6M2 (contains the substitutions Q28* in spr1178 and T205I in PstB) | 0.125 |
| R6M1SmR,1a-WT | R6M1 co-transformed with a pbp1a PCR fragment from R6-WT and a rpsL streptomycin resistance marker, SMR | 1.0 |
| R6ko in spr1178 | R6-WT knocked out in spr1178, CMR | 0.023 |
| R6ko in spr1254 | R6-WT knocked out in spr1254, KMR | 0.023 |
| R6spr1888::janus | R6-WT knocked out in spr1888 by Janus cassette, KMRSMS | 0.023 |
aResults are the average of at least three independent measurements. Asterisks indicate nonsense mutations. PG, penicillin; KM, kanamycin; SM, streptomycin.