Inhibition of the β-Lactamase Bla by Avibactam Improves the and Efficacy of Imipenem against Mycobacterium abscessus.

pulmonary infections are treated with a macrolide (clarithromycin or azithromycin), an aminoglycoside (amikacin), and a β-lactam (cefoxitin or imipenem). The triple combination is used without any β-lactamase inhibitor, even though produces the broad-spectrum β-lactamase Bla We determine whether inhibition of Bla by avibactam improves the activity of imipenem against The bactericidal activity of drug combinations was assayed in broth and in human macrophages. The efficacy of the drugs was tested by monitoring the survival of infected zebrafish embryos. The level of Bla production in broth and in macrophages was compared by quantitative reverse transcription-PCR and Western blotting. The triple combination of imipenem (8 or 32 μg/ml), amikacin (32 μg/ml), and avibactam (4 μg/ml) was bactericidal in broth (<0.1% survival), with 3.2- and 4.3-log reductions in the number of CFU being achieved at 72 h when imipenem was used at 8 and 32 μg/ml, respectively. The triple combination achieved significant intracellular killing, with the bacterial survival rates being 54% and 7% with the low (8 μg/ml) and high (32 μg/ml) dosages of imipenem, respectively. inhibition of Bla by avibactam improved the survival of zebrafish embryos treated with imipenem. Expression of the gene encoding Bla was induced (20-fold) in the infected macrophages. Inhibition of Bla by avibactam improved the efficacy of imipenem against , in macrophages, and in zebrafish embryos, indicating that this β-lactamase inhibitor should be clinically evaluated. The evaluation of imipenem may underestimate the impact of Bla, since the production of the β-lactamase is inducible in macrophages.