Table 2.
Classification schemes and characteristics of β-lactamases.
| Ambler Classification | Functional Scheme | Representative Enzyme | Relevant Bacteria | Transfer Origin | Substrate | Reference |
|---|---|---|---|---|---|---|
| Class A | 2b | TEM-1, TEM-2, and SHV-1 | E. coli, N. gonorrhoeae, P. aeruginosa, H. influenzae, and K. pneumoniae | Plasmid-mediated | Penicillin and narrow-spectrum cephalosporins | [6] |
| 2be | CTX-M, SHV-2, TEM-10, and GES-1 | E. coli, K. pneumoniae, C. freundii, and other Enterobacteriaceae | Chromosome-encoded and plasmid-mediated | Penicillin, aztreonam, narrow and extended-spectrum cephalosporins | [33,35] | |
| 2br | TEM-30, SHV-72 | K. pneumoniae, E. coli, | Plasmid-mediated | Penicillin | [7] | |
| 2c | PSE (CARB) | V. cholerae, E. coli, S. enterica, P. aeruginosa, and S. typhimurium | Chromosome-encoded | Penicillin and carbenicillin | [36] | |
| 2f | KPC-2, KPC-3, GES-2, GES-11, NMC-A, IMI-1, SFC-1, and SME-1 | K. pneumoniae, E. cloacae, A. baumannii, P. aeruginosa, and S. marcescens | Chromosome-encoded and plasmid-mediated | Penicillin, cephalosporins, aztreonam, and carbapenems | [10,37] | |
| Class B | 3 | IMP, VIM, NDM, CphA, and L1 | A. baumannii, P. aeruginosa, K. pneumoniae, A. hydrophila, and S. maltophilia | B1: Plasmid-mediated (mainly) B2 and B3: chromosome-encoded |
Penicillin, cephalosporins, and carbapenems | [38,39] |
| Class C | 1 | CMY, FOX, MIR, ACT, and DHA | C. freundii, E. cloacae, S. marcescens, P. aeruginosa, K. pneumoniae, and M. morganii | Chromosome-encoded and plasmid-mediated | Penicillin, aztreonam, cephamycin, and cephalosporins (except cefepime) | [40] |
| Class D | 2d | OXA-23, OXA-40, OXA-48, OXA-51, and OXA-58 | A. baumannii, E. coli, E. cloacae, K. pneumoniae, P. aeruginosa, and other Enterobacteriaceae | Plasmid-mediated (mainly) and chromosome-encoded | Penicillin, cephalosporins, and carbapenems | [10,41] |
A. baumannii, Acinetobacter baumannii; A. hydrophila, Aeromonas hydrophila; C. freundii, Clostridium freundii; E. coli, Escherichia coli; E. cloacae, Enterobacter cloacae; H. influenzae, Haemophilus influenzae; K. pneumoniae, Klebsiella pneumoniae; M. morganii, Morganella morganii; N. gonorrhoeae, Neisseria gonorrhoeae; P. aeruginosa, Pseudomonas aeruginosa; S. marcescens, Serratia marcescens; S. maltophilia, Stenotrophomonas maltophilia; S. enterica, Salmonella enterica; S. typhimurium, Salmonella typhimurium; V. cholerae, Vibrio cholerae.