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Research Journal of Microbiology

Year: 2006 | Volume: 1 | Issue: 1 | Page No.: 1-22
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Authors

Jung Hun Lee

Sang Hee Lee

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Research Article

Carbapenem Resistance in Gram-negative Pathogens: Emerging Non-metallo-carbapenemases

Jung Hun Lee and Sang Hee Lee
Non-metallo-carbapenemases involved in acquired resistance are of Ambler molecular class A, C and D. Class A, clavulanic acid-inhibited carbapenemases are either chromosome-encoded (SME-1 to SME-3, IMI-1 to IMI-2, NMC-A) in Serratia marcescens and Enterobacter cloacae, or plasmid-encoded, such as KPC-1 to KPC-4 in Klebsiella and Enterobacter spp. and GES-2 (Pseudomonas aeruginosa), -4 (Klebsiella pneumoniae), -5 (Escherichia coli) and -6 (Klebsiella pneumoniae). In class C, imipenem resistance has been associated with porin loss and class C carbapenemases in Pseudomonas aeruginosa, Enterobacter spp. and Klebsiella pneumoniae. CMY-10 is a plasmid-encoded class C β-lactamase with a wide spectrum of substrates. Unlike the well-studied class C extended-spectrum β-lactamase from Enterobacter cloacae GC1, the Ω-loop does not affect the active site conformation and the catalytic activity of CMY-10. Instead, three amino acid deletion in the R2 active site appears to be responsible for the extended-spectrum activity of CMY-10. This observation demonstrates the hydrolyzing activity of CMY-10 toward imipenem with a long R2 substituent. CMY-10 is the only Ambler class C β-lactamase with carbapenemase activity without reduced uptake (porin loss) so far. Finally, class D carbapenemases are increasingly reported in Acinetobacter baumannii but compromise carbapenem susceptibility only marginally. The sources of the acquired non-metallo-carbapenemase genes remain unknown and these enzymes may remain underestimated as a consequence of the lack of their detection. The more three-dimensional structural information of these enzymes is necessary for the development of new inhibitors for non-metallo-carbapenemases or new β-lactam antibiotics.
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How to cite this article

Jung Hun Lee and Sang Hee Lee, 2006. Carbapenem Resistance in Gram-negative Pathogens: Emerging Non-metallo-carbapenemases. Research Journal of Microbiology, 1: 1-22.

URL: https://scialert.net/abstract/?doi=jm.2006.1.22

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