Biochemical-Genetic Analysis and Distribution of FAR-1, a Class A β-Lactamase from Nocardia farcinica

Abstract

From genomic DNA of the clinical isolate Nocardia farcinica VIC, a 1.6-kb Sau3AI fragment was cloned and expressed in Escherichia coli JM109. The recombinant strain expressed a β-lactamase (pI, 4.6), FAR-1, which conferred high levels of resistance to amoxicillin, piperacillin, ticarcillin, and cephalothin. The hydrolysis constants (kcat ,Km , Ki , 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 β-lactamase hydrolyzes aztreonam (at a low level) without 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 β-lactamases, being most closely related to PEN-A fromBurkholderia cepacia (52%). Abla FAR-1-like gene was found in all studiedN. farcinica strains, underlining the constitutive origin of this gene.

Determination of antimicrobial susceptibility patterns of Nocardia spp. from clinical specimens by Etest

“…Their hydrolytic activity is inhibited partially by clavulanic acid, but almost not at all by sulbactam and tazobactam, which probably explains the lack of activity of piperacillin + tazobactam against most Nocardia isolates. Resistance to ceftriaxone and to imipenem does not seem to be mediated by β‐lactamases, but rather by decreased affinities of penicillin‐binding proteins for these molecules [26].…”

Resistance gene pool to co-trimoxazole in non-susceptible Nocardia strains

“…Descriptions of resistance determinants in Nocardia – β-lactamases – or possible determinants – second gyrase B, an extra copy of rpo B-, detected by partial or whole genome sequencing ( Laurent et al, 1999 ; Poirel et al, 2001 ; Vera-Cabrera et al, 2013 ), led us to examine, in clinical strains strongly resistant to SXT, the diversity of acquired antimicrobial resistance determinants commonly detected in clinical and environmental bacteria and the presence of integrons as vehicles of the resistance gene recruitment.…”

Molecular Identification and Susceptibility Pattern of Clinical Nocardia Species: Emergence of Nocardia crassostreae as an Agent of Invasive Nocardiosis

“…One strain was intermediately susceptible to cefotaxime. Resistance to cefotaxime and imipenem does not appear to be mediated by beta-lactamase, but rather by decreased affinities of penicillin binding-proteins for these molecules (55).…”