ACI-1 from Acidaminococcus fermentans: characterization of the first beta-lactamase in Anaerobic cocci.
Acidaminococcus fermentans belongs to the group of strictly anaerobic gram-negative cocci. All previously described Acidaminococcus strains are susceptible to beta-lactam antibiotics. An A. fermentans strain (RYC-MR95) resistant to penicillin and expanded-spectrum cephalosporin (amoxicillin and cefotaxime MICs, 64 microgram/ml) was isolated from a human perianal abscess. A fragment encoding a beta-lactamase from genomic DNA was cloned in Escherichia coli K-12 strain HB101, and the recombinant strain expressed resistance to amoxicillin (MIC, 1,024 microgram/ml) and cefotaxime (MIC, 4 microgram/ml). Clavulanic acid decreased the MICs to 8 and 0.03 microgram/ml, respectively. Analysis of the nucleotide sequence revealed a new class A beta-lactamase, ACI-1. In accordance with its biochemical properties, we propose to assign ACI-1 to functional group 2be. The ACI-1 enzyme (estimated pI 4.3) had <50% amino acid identity with any other class A beta-lactamases, the closest being ROB-1 from Haemophilus influenzae (44%). ACI-1 was closer to class A beta-lactamases from some gram-positive organisms (41 to 44% amino acid identity with Bacillus beta-lactamases) than to most class A enzymes from gram-negative organisms (TEM-1, 24.6%). The aci1 gene had a G+C content of 42.1%, in contrast with 56% G+C content for genomic DNA from A. fermentans, thus suggesting that aci1 may have been obtained by horizontal gene transfer.
Galán
J C
JC
Servicio de Microbiología, Hospital Ramón y Cajal, Instituto Nacional de Salud (INSALUD), 28034 Madrid, Spain.
Reig
M
M
Navas
A
A
Baquero
F
F
Blázquez
J
J
D000595:Amino Acid Sequence; D000667:Ampicillin / Q000494:pharmacology; D001483:Base Sequence; D003001:Cloning, Molecular; D003013:Clostridium / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010802:Phylogeny; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D000667:Ampicillin; C417269:beta-lactamase ACI-1; D001618:beta-Lactamases