Naturally occurring Class A ss-lactamases from the Burkholderia cepacia complex

Abstract

Chromosomally encoded ss-lactamases from the Burkholderia cepacia complex species (formerly Pseudomonas cepacia) were characterized. Cloning and sequencing identified an Ambler class A ss-lactamase (PenB) from B. cenocepacia. It shares 82% amino acid identity with the PenA ss-lactamases previously identified from B. multivorans 249. Its expression was dependent upon a LysR-type regulatory protein. Its narrow-spectrum hydrolysis activity mostly included penicillins but also included expanded-spectrum cephalosporins and aztreonam at lower levels. In that study, Pen-like ss-lactamases (PenC, PenD, PenE, PenF) that shared 63 to 92% identity with PenB from B. cenocepacia were identified from other Burkholderia species. The corresponding ss-lactamase genes might be used as genetic tools for accurate Burkholderia species identification.

FIG. 1.

Nucleotide sequence of the 1,740-bp fragment of pBcSau13 containing the penB1- and penRB-coding regions. The deduced amino acid sequences are designated in single-letter code. The putative and overlapped promoter sequences are represented by −35 and −10 regions (in boldface and underlined). The start and stop codons of these genes are also in boldface, and the putative RBS sequence is underlined. The critical motifs for class A ß-lactamases are bracketed.

FIG. 2.

Dendrogram obtained for representative class A ß-lactamases by neighbor-joining analysis. The alignment used for tree calculation was performed with the ClustalX program. Branch lengths are drawn to scale and are proportional to the number of amino acid changes. The distance along the vertical axis has no significance. The amino acid identity of each ß-lactamase compared to the amino acid sequence of PenB1 from B. cenocepacia is indicated in parentheses. The acquired ß-lactamases of gram-negative organisms (GenBank accession numbers are indicated in parentheses) are TEM-1 (AAG47772), SHV-1 (AAD18054), CTX-M-1 (CAJ01342), LAP-1 (ABK58097), CARB-2 (Q03170), CARB-5 (AAF61417), GES-1 (AAL82589), BEL-1 (AAZ04368), BES-1 (AAF61147), SCO-1 (ABL75133), PER-1 (CAF18433), and TLA-1 (AAD37403), whereas the others are naturally occurring ß-lactamases, such as FAR-1 from Nocardia farcinica (AAB81957), SED-1 from Citrobacter sedlakii (AAK63223), and OXY-1 from Klebsiella oxytoca (P22391).