A novel CTX-M beta-lactamase (CTX-M-8) in cefotaxime-resistant Enterobacteriaceae isolated in Brazil.
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.
Bonnet
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R
Laboratoire de Bactériologie, Faculté de Médecine, 63001 Clermont-Ferrand Cedex, France. Richard.Bonnet@u-clermont1.fr
Sampaio
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Labia
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De Champs
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Sirot
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Chanal
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Sirot
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D001938:Brazil; D002439:Cefotaxime / Q000494:pharmacology*; D018550:Cephalosporin Resistance / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D018014:Gene Transfer Techniques; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams / Q000494:pharmacology
D001426:Bacterial Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; D047090:beta-Lactams; C412610:blaCTX-M-8 protein, Citrobacter amalonaticus; D001618:beta-Lactamases; D002439:Cefotaxime