TABLE 2.

β-Lactamase contents of isolates, mating, β-lactamases in transconjugant strains, oxyiminocephalosporin-hydrolyzing activities of β-lactamases, ESBL genes identified by PCR, and sequencing of blaCTX-M-3 genes

SpeciesCenter(s)No. of isolatespIs of β-lactamases in clinical isolatesaMatingβ-Lactamases in transconjugantsa (pIs)ESBL gene(s) identified by PCRNo. of gene sequencesb
K. pneumoniaeBB, CZ, SU, SZ, WA I, WA II, WO218.4, 7.6, 5.4+8.4, 5.4CTX-M8
K. pneumoniaeWA VI, WR38.4, 7.6, 5.4CTX-M3
K. pneumoniaeWA IV18.4, 5.4CTX-M
K. pneumoniaecWA V18.4, 8.2, 7.6, 5.4+8.4, 8.2, 5.4CTX-M, SHV
K. pneumoniaedSU68.4 8.2, 7.6, 5.4+8.4, 5.4CTX-M, SHV
K. pneumoniaeeSZ18.4 8.2, 7.6, 5.4CTX-M, SHV1
K. pneumoniaefCZ28.4, 7.6, 6.0, 5.4+6.0CTX-M, TEM
K. pneumoniaegKR18.4, 7.6, 6.0, 5.4CTX-M
K. oxytocaBB, WR28.4, 5.4+8.4, 5.4CTX-M1
K. oxytocaBB18.4, 5.4CTX-M
E. coliBB, CZ, GD, KR, SU, SZ, WA I, WA III, WA V, WO, WR178.4, 5.4+8.4, 5.4CTX-M9
E. coliBB18.4, 5.4CTX-M
E. cloacaeWA I, WO, WR58.4, 5.4+8.4, 5.4CTX-M2
E. cloacaehCZ, WA IV28.4, 5.4+8.4, 5.4CTX-M
E. cloacaeiKA18.4, 8.0, 5.4+8.4, 5.4CTX-M
C. freundiiCZ, WA I, WA III, WA V58.4, 5.4+8.4, 5.4CTX-M1
C. freundiijSU, WA V28.4, 5.4+8.4, 5.4CTX-M1
C. freundiikWA V18.4, 5.4CTX-M
C. freundiiWA I28.4, 7.0, 5.4+8.4, 5.4CTX-M
C. freundiiWO18.4, 7.0, 5.4CTX-M
S. marcescensCZ18.4, 5.4+8.4, 5.4CTX-M
S. marcescensCZ, WA IV, WO39.0,l 8.4, 5.4CTX-M
S. marcescensmCZ, WA I, WA V39.0, 8.4, 5.4+8.4, 5.4CTX-M
M. morganiiWO18.4, 5.4+8.4, 5.4CTX-M1
  • a pI values in boldface refer to β-lactamases that were found to hydrolyze only cefotaxime in the bioassay experiment, whereas pI values which are in boldface and underlined represent enzymes that hydrolyzed both cefotaxime and ceftazidime.

  • b Numbers of blaCTX-M-3 genes sequenced in particular groups of isolates.

  • c K. pneumoniae isolate WA V 7888.

  • d K. pneumoniae isolates SU 8406, SU 8815, SU 8912, SU 9148, SU 9161, and SU 972.

  • e K. pneumoniae isolate SZ 2941.

  • f K. pneumoniae isolates CZ 9455 and CZ 9459.

  • g K. pneumoniae isolate KR 3443; this isolate was not tested for the presence of a blaTEM gene.

  • h E. cloacae isolates CZ 8320 and WA IV 838.

  • i E. cloacae isolate KA 3663.

  • j C. freundii isolates SU 9050 and WA V 3324.

  • k C. freundii isolate WA V 3570.

  • l The pI ∼9.0 β-lactamases of these isolates produced “weak” IEF bands and were negative by the bioassay under the conditions used.

  • m S. marcescens isolates CZ 9424, WA I 4172, and WA V 3033.