Biochemical Characterization of b-Lactamases from Mycobacterium abscessus Complex and Genetic Environment of the b-Lactamase-Encoding Gene

A. RAMIREZ; M. RUGGIERO; C. ARANAGA; A. CATALDI; G. GUTKIND; J. H. DE WAARD; M. ARAQUE; P. POWER

MICROBIAL DRUG RESISTANCE-MECHANISMS EPIDEMIOLOGY AND DISEASE

MARY ANN LIEBERT INC

Lugar: New York; Año: 2016

1076-6294

The objectives of this study were to determine the kinetic parameters of purified recombinant Bla Mab andBla Mmas by spectrophotometry, analyze the genetic environment of the bla Mab and bla Mmas genes in both speciesby polymerase chain reaction and sequencing, furthermore, in silico models of both enzymes in complex withimipenem were obtained by modeling tools. Our results showed that Bla Mab and Bla Mmas have a similarhydrolysis behavior, displaying high catalytic efficiencies toward penams, cephalothin, and nitrocefin; none ofthe enzymes are well inhibited by clavulanate. Bla Mmas hydrolyzes imipenem at higher efficiency than cefo-taxime and aztreonam. Bla Mab and Bla Mmas showed that their closest structural homologs are KPC-2 and SFC-1,which correlate to the mild carbapenemase activity toward imipenem observed at least for BlaMmas. They alsoseem to differ from other class A b-lactamases by the presence of a more flexible O loop, which could impact inthe hydrolysis efficiency against some antibiotics. A -35 consensus sequence (TCGACA) and embedded at the3¢ end of MAB_2874, which may constitute the bla Mab and bla Mmas promoter. Our results suggest that theresistance mechanisms in fast-growing mycobacteria could be probably evolving toward the production of b-lactamases that have improved catalytic efficiencies against some of the drugs commonly used for the treatmentof mycobacterial infections, endangering the use of important drugs like the carbapenems.