Purpose: Imipenem is one of the very few effective options for treating Mycobacterium abscessus  (M. abscessus ) infections; the development of imipenem resistance is a major health concern.
Materials and Methods: The susceptibility of 194 clinical M. abscessus  isolates to imipenem was determined. The ability of imipenem to synergize with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a zinc chelator and a metallo-β-lactamases (MBLs) inhibitor, to inhibit M. abscessus  growth was also assessed.
Results: M. abscessus  exhibited an elevated resistance to imipenem (MIC₅₀ = 16 mg/L, MIC₉₀ = 64 mg/L). A combination of TPEN and imipenem synergized to inhibit the growth of 100% of imipenem-resistant and 79.2% of imipenem-resistance intermediate isolates; no synergy was observed treating imipenem-sensitive isolates. A remarkable decrease in the MIC₅₀ (from 16 to 4 mg/L) and MIC₉₀ (from 64 to 8 mg/L) of imipenem was observed when it was combined with TPEN; the portion of imipenem-resistant isolates also decreased (from 48.4% to 0%). Consistent with these results demonstrating synergy, a time-kill assay showed the addition of TPEN significantly improved the bactericidal activity of imipenem toward M. abscessus . Similarly, EDTA (a potent MBLs inhibitor) promoted the anti-M. abscessus  activity of imipenem in a disk assay, corroborating the effect of TPEN and supporting the role of MBLs in imipenem resistance exhibited by some isolates.
Conclusion: These findings demonstrate that TPEN can reduce the resistance of M. abscessus  to imipenem and suggest that the inhibition of MBLs activity is the underlying mechanism.
Keywords: Mycobacterium abscessus , TPEN, imipenem resistance, metallo-β-lactamases