Fig. 4.

Beta-lactam resistance determinants have additive effects and appear in a consistent order. The left-hand panel shows that the candidate determinants against the beta-lactam drug class often appear in a consistent order. For example, the mutation at site 551 of PBP2X tends to appear in backgrounds that already carry mutations in PBP2B. The plot was generated according to the method and plotting convention of [28], where each row represents an isolate, and those isolates that fit the nested pattern are shown in pink. Results show that 93.5% (634/678) of our isolates fit the nested pattern. The right-hand plots show the log MIC values for these 634 isolates, comparing isolates carrying different numbers of candidate determinants.