A novel CTX-M beta-lactamase (CTX-M-8) in cefotaxime-resistant Enterobacteriaceae isolated in Brazil

Antimicrob Agents Chemother. 2000 Jul;44(7):1936-42. doi: 10.1128/AAC.44.7.1936-1942.2000.

Abstract

To estimate the diversity of extended-spectrum beta-lactamases in Brazil, 18 strains from different species of the family Enterobacteriaceae exhibiting a positive double-disk synergy test were collected by a clinical laboratory from several hospitals in Rio de Janeiro, Brazil, in 1996 and 1997. Four strains (Proteus mirabilis, Enterobacter cloacae, Enterobacter aerogenes, and Citrobacter amalonaticus) hybridized with a 550-bp CTX-M probe. The P. mirabilis strain produced a CTX-M-2 enzyme. The E. cloacae, E. aerogenes, and C. amalonaticus isolates harbored a bla gene which was identified by cloning and sequencing as a bla(CTX-M) gene. E. coli HB101 transconjugants and the E. coli DH5alpha transformant harboring a recombinant plasmid produced a CTX-M beta-lactamase with an isoelectric point of 7.6 conferring a resistance phenotype characterized by a higher level of resistance to cefotaxime than to ceftazidime, as observed with the other CTX-M enzymes. The deduced protein sequence showed a novel Ambler class A CTX-M enzyme, named CTX-M-8, which had 83 to 88% identity with the previously described CTX-M enzymes. The phylogenic study of the CTX-M family including CTX-M-8 revealed four CTX-M types, CTX-M-8 being the first member of a new phylum of CTX-M enzymes. The evolutionary distances between the four types of CTX-M were large, suggesting that the four clusters branched off early from a distant unknown enzyme and that intermediate enzymes probably existed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins*
  • Base Sequence
  • Brazil
  • Cefotaxime / pharmacology*
  • Cephalosporin Resistance / genetics*
  • Cephalosporins / pharmacology
  • Cloning, Molecular
  • DNA, Bacterial / analysis
  • Enterobacteriaceae / drug effects
  • Enterobacteriaceae / enzymology*
  • Enterobacteriaceae / genetics
  • Gene Transfer Techniques
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Sequence Homology, Amino Acid
  • beta-Lactamases / classification
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism
  • beta-Lactams / pharmacology

Substances

  • Bacterial Proteins
  • Cephalosporins
  • DNA, Bacterial
  • beta-Lactams
  • blaCTX-M-8 protein, Citrobacter amalonaticus
  • beta-Lactamases
  • Cefotaxime