TABLE 1.

Drug sensitivities of mutant TEM-1 alleles

Amino acid substitutionMIC (μg/ml)Improvement for cefotaximea
AmpicillinPiperacillinCephalothinCefotaxime
No plasmid24160.0625
pBR3224,0964,0961280.0625
TEM-1 (estimated)b0.012
A42G4,0964,0962560.0625c
G92S4,0964,0962560.0625
E104K4,0964,0961280.2521
M182T4,0964,0962560.0625
G238S d 1,024 128 64 0.5 42
R241H4,0964,0962560.0625
A42G, E104K8,1924,0962560.2521
G92S, E104K8,1924,0962560.0625
E104K, M182T8,1928,1925120.12510
E104K, R241H4,0962,0482560.0625
A42G, G238S2,0481,0242564333
G92S, G238S2,048256640.542
E104K, G238S 2,048 256 128 8 667
M182T, G238S2,0485121282167
G238S, R241H2,048256640.542
G238S, E104K, A42G 2,048 1,024 512 64 5,333
G92S, E104K, G238S2,0482561288667
E104K, M182T, G238S4,0961,024256322,667
E104K, G238S, R241H20482562568667
A42G, G92S, E104K, G238S4,0961,02451212810,667
A42G, E104K, M182T, G238S 4,096 4,096 2,048 1,024 85,333
A42G, E104K, G238S, R241H4,0961,02451212810,667
A42G, G92S, E104K, M182T, G238S4,0961,02451212810,667
A42G, E104K, M182T, G238S, R241H 4,096 1,024 512 256 21,333
A42G, G92S, E104K, M182T, G238S, R241H2,0481,02451225621,333
  • a The improvement for cefotaxime is relative to the estimated cefotaxime MIC for TEM-1.

  • b See text for estimation of the cefotaxime MIC for the wild-type TEM-1 gene.

  • c —, the cefotaxime MIC is indistinguishable from that for the host; therefore, relative resistance cannot be calculated.

  • d Data for mutations with the highest resistance to cefotaxime in their class (single mutation, double mutation, etc.) are highlighted in boldface.