Characterization of an extended-spectrum class C beta-lactamase of Citrobacter freundii.
Microbiol Immunol
; 45(4): 277-83, 2001.
Article
in En
| MEDLINE
| ID: mdl-11386417
ABSTRACT
Citrobacter freundii GC3 is a clinical isolate which showed moderate resistance to oxyimino beta-lactams such as ceftazidime and aztreonam. This drug resistance was due to an extended-spectrum class C beta-lactamase encoded by chromosomal gene(s). The GC3 beta-lactamase showed high amino acid sequence homology to a known C. freundii beta-lactamase, i.e., 346 of 361 amino acids were identical with those of C. freundii GN346 beta-lactamase (Tsukamoto, K. et al, Eur. J. Biochem. 188, 15-22, 1990). Asp198 was the only dissimilar amino acid found in the omega loop region, known as the hot spot for extended-spectrum resistance in class C beta-lactamases (Haruta, S. et al, Microbiol. Immunol. 42, 165-169, 1998). However, Asp198 was eliminated as a cause of the extended-spectrum resistance by the substitution of Asn for Asp198. Subsequent investigation suggested that the moderate resistance to oxyimino beta-lactams is attributable to the replacement of amino acids on the enzyme's surface area, far from the active-site. Some or all of the replacements are assumed to delicately modify the active-site configuration. The GC3 beta-lactamase is the first example of an extended-spectrum class C beta-lactamase in which mutations are independent of the omega loop.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Beta-Lactamases
/
Citrobacter freundii
Limits:
Humans
Language:
En
Journal:
Microbiol Immunol
Year:
2001
Document type:
Article
Affiliation country:
Japón