Chromosome-encoded extended-spectrum class A β-lactamase MIN-1 from Minibacterium massiliensis

Abstract

Minibacterium massiliensis strain CIP107820 is a recently discovered waterborne Gram-negative rod isolated from hospital water samples. It harbors a chromosomally located gene encoding an Ambler class A extended-spectrum β-lactamase termed MIN-1, sharing 56%, 54%, and 51% amino acid identities with β-lactamases LUT-1, KPC-2, and CTX-M-2, respectively. β-Lactamase MIN-1 hydrolyzes penicillins, narrow-spectrum cephalosporins, cefotaxime, and, less efficiently, cefepime, while ceftazidime and carbapenems are very poor substrates, and cephamycins and aztreonam are not hydrolyzed.

Fig 1

Comparison of the amino acid sequence of MIN-1 with those of the broad-spectrum ß-lactamases LUT-1 from Pseudomonas luteola (6), KPC-2 (15), CTX-M-2 (2), SFO-1 (10), BES-1 (3), BIC-1 (7), NMC-A (12), SME-1 (13), VEB-1 (19), TLA-1 (20), PER-1 (14), BEL-1 (16), GES-1 (18), SHV-1 (4), and an uncharacterized PenA β-lactamase from the genome of the betaproteobacterium Herminiimonas arsenicoxydans (11). In addition, dashes indicate the gaps between β-lactamases that were inserted to optimize the alignment. The conserved domains of class A β-lactamase are underlined (9). The arrow indicates the putative cleavage site for the leader peptide of MIN-1.

Fig 2

Seventeen amino acid sequences of class A Ambler β-lactamases were aligned using the ClustalW program and the BLOSUM62 matrix. Alignments were analyzed using PhyML, software that estimates neighbor-joining phylogenies. Trees were designed with MEGA4 software (8). At every node, the bootstrap value is indicated. See Fig. 1 legend for sequence references.