F. Laurent et al., Biochemical-genetic analysis and distribution of FAR-1, a class A beta-lactamase from Nocardia farcinica, ANTIM AG CH, 43(7), 1999, pp. 1644-1650
From genomic DNA of the clinical isolate Nocardia farcinica VIC, a 1.6-kb S
au3AI fragment was cloned and expressed in Escherichia coli JM109. The reco
mbinant strain expressed a beta-lactamase (pI, 4.6), FAR-1, which conferred
high levels of resistance to amoxicillin, piperacillin, ticarcillin, and c
ephalothin. The hydrolysis constants (k(cat), K-m, K-i, and 50% inhibitory
concentration) confirmed the MIC results and showed that FAR-1 activity is
inhibited by clavulanic acid and at a low level by tazobactam and sulbactam
, Moreover, FAR-1 beta-lactamase hydrolyzes aztreonam (at a low level) with
out significant activity against ceftazidime, cefotaxime and imipenem. FAR-
1 mature protein of molecular mass ca 32 kDa, has less than 60% amino acid
identity with any other class A beta-lactamases, being most closely related
to PEN-A from Burkholderia cepacia (52%). A bla(FAR-1)-like gene was found
in all studied N. farcinica strains, underlining the constitutive origin o
f this gene.