Characterization of the AmpC ?-Lactamase from Burkholderia multivorans.

ABSTRACT: Burkholderia multivorans is a member of the Burkholderia cepacia complex, a group of >20 related species of nosocomial pathogens that commonly infect individuals suffering from cystic fibrosis. ?-Lactam antibiotics are recommended as therapy for infections due to Bmultivorans, which possesses two ?-lactamase genes, blapenA and blaAmpC PenA is a carbapenemase with a substrate profile similar to that of the Klebsiella pneumoniae carbapenemase (KPC); in addition, expression of PenA is inducible by ?-lactams in Bmultivorans Here, we characterize AmpC from Bmultivorans ATCC 17616. AmpC possesses only 38 to 46% protein identity with non-Burkholderia AmpC proteins (e.g., PDC-1 and CMY-2). Among 49 clinical isolates of Bmultivorans, we identified 27 different AmpC variants. Some variants possessed single amino acid substitutions within critical active-site motifs (? loop and R2 loop). Purified AmpC1 demonstrated minimal measurable catalytic activity toward ?-lactams (i.e., nitrocefin and cephalothin). Moreover, avibactam was a poor inhibitor of AmpC1 (Kiapp > 600 ?M), and acyl-enzyme complex formation with AmpC1 was slow, likely due to lack of productive interactions with active-site residues. Interestingly, immunoblotting using a polyclonal anti-AmpC antibody revealed that protein expression of AmpC1 was inducible in Bmultivorans ATCC 17616 after growth in subinhibitory concentrations of imipenem (1 ?g/ml). AmpC is a unique inducible class C cephalosporinase that may play an ancillary role in Bmultivorans compared to PenA, which is the dominant ?-lactamase in Bmultivorans ATCC 17616.

SUBMITTER: Becka SA 

PROVIDER: S-EPMC6153817 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature