Biochemical-Genetic Analysis and Distribution of DES-1, an Ambler Class A Extended-Spectrum β-Lactamase from Desulfovibrio desulfuricans

Desulfovibrio spp. are gram-negative anaerobes phylogenetically related to Bacteroides spp., which are rarely isolated and which are mostly isolated from intra-abdominal abscesses. Desulfovibrio desulfuricans clinical isolate D3 had a clavulanic acid-inhibited β-lactam resistance profile and was resistant to some expanded-spectrum cephalosporins. A β-lactamase gene, bla(DES-1), was cloned from whole-cell DNA of isolate D3 and expressed in Escherichia coli. Purified β-lactamase DES-1, with a pI value of 9.1, had a relative molecular mass of ca. 31 kDa and a mature protein of 288 amino acids. DES-1 was distantly related to Ambler class A β-lactamases and most closely related to PenA from Burkholderia pseudomallei (48% amino acid identity). It was weakly related to class A β-lactamases CblA, CepA, CfxA, and CfxA2 from other anaerobic species, Bacteroides spp. and Prevotella intermedia. Its hydrolysis spectrum included amino- and ureidopenicillins, narrow-spectrum cephalosporins, ceftriaxone, and cefoperazone. bla(DES-1)-like genes were not identified in phylogenetically related Desulfovibrio fairfieldensis isolates. However, they were found in some but not all D. desulfuricans strains, thus suggesting that these genes may be present in a given D. desulfuricans subspecies.