FIG. 4.

Phylogeny of ESBLs. Representative sequences of various ESBLs were obtained from GenBank. The PC1 (class A, S. aureus enzyme), IMP-1 (class B, metallo-enzyme), and ACT-1 (class C, AmpC-type enzyme) β-lactamases were included for comparison. Signal peptides were identified with SPSScan and removed prior to alignment. Sequences were aligned using Clustal X (168). Trees were constructed with Clustal X, which uses the neighbor-joining method, with a bootstrap value of 1,000. The IMP-1 sequence was used to root the tree. Trees were visualized with TREEVIEW (118).