Table 1.

β-Lactamases present in the test strains

Species (no. of strains)No. of strains by β-lactamase group
ESBLaAmpCbHigh K1cOtherd
E. coli (31)15511
K. pneumoniae (31)e 18310
K. oxytoca (13)3046
 Total368427
  • a ESBLs belonging to Bush group 2be included TEM-3, TEM-4, TEM-5, TEM-6, TEM-7, TEM-8, TEM-9, TEM-10, TEM-12, SHV-2, SHV-4, SHV-5, and four other TEM- or SHV-derived ESBLs.

  • b Plasmid derivatives of AmpC β-lactamase (Bush group 1) included LAT-1, LAT-2, MIR-1, MOX-1, and FOX-1.

  • c High-level producers of the chromosomally encoded K1 β-lactamase (Bush group 2be) of K. oxytoca.

  • d Other β-lactamases were low-level K1 producers (Bush group 2be) in wild-type strains of K. oxytoca; TEM-1 (low and high level expression), TEM-2, SHV-1 (low and high level expression), and PSE-1 (Bush group 2); and TRC-1 (Bush group 2br).

  • e One strain of K. pneumoniaeproduced both an AmpC β-lactamase and an ESBL.