A novel extended-spectrum ?-lactamase, SGM-1, from an environmental isolate of Sphingobium sp.

ABSTRACT: SGM-1 is a novel class A ?-lactamase from an environmental isolate of Sphingobium sp. containing all of the distinct amino acid motifs of class A ?-lactamases. It shares 77 to 80% amino acid sequence identity with putative ?-lactamases that are present on the chromosome of all Sphingobium species whose genomes were sequenced and annotated. Thus, SGM-type ?-lactamases are native to this genus. Antibiotic susceptibility testing classifies SGM-1 as an extended-spectrum ?-lactamase, conferring the highest level of resistance to penicillins. Although SGM-1 contains the conserved cysteine residues characteristic of class A carbapenemases, it does not confer resistance to the carbapenem antibiotics imipenem, meropenem, or doripenem but does increase the MIC of ertapenem 8-fold. SGM-1 hydrolyzes penicillins and the monobactam aztreonam with similar catalytic efficiencies, ranging from 10(5) to 10(6) M(-1) s(-1). The catalytic efficiencies of SGM-1 for cefoxitin and ceftazidime were the lowest (10(2) to 10(3) M(-1) s(-1)) among the cephalosporins tested, while the catalytic efficiencies against all other cephalosporins varied from about 10(5) to 10(6) M(-1) s(-1). SGM-1 exhibited measurable but not significant activity toward the carbapenems tested. SGM-1 also showed high affinity for clavulanic acid, tazobactam, and sulbactam (Ki < 1 ?M); however, only clavulanic acid significantly reduced the MICs of ?-lactams.

SUBMITTER: Lamoureaux TL 

PROVIDER: S-EPMC3719716 | biostudies-other | 2013 Aug

REPOSITORIES: biostudies-other