The study found that the drug avibactam, which is usually paired with antibiotics, can make a tough, drug‑resistant Klebsiella pneumoniae strain more vulnerable to the body’s natural defenses, especially the antimicrobial peptide LL‑37 and immune cells like neutrophils. In mice, giving avibactam alone lowered the bacteria in the lungs, showing it helps the immune system clear the infection even though it doesn’t directly kill the bacteria on its own.

Infections caused by New Delhi metallo-β-lactamase (NDM)-producing strains of multidrug-resistant Klebsiella pneumoniae are a global public health threat lacking reliable therapies. NDM is impervious to all existing β-lactamase inhibitor (BLI) drugs, including the non-β-lactam BLI avibactam (AVI). Though lacking direct activity against NDMs, AVI can interact with penicillin-binding protein 2 in a manner that may influence cell wall dynamics. We found that exposure of NDM-1-producing K. pneumoniae to AVI led to striking bactericidal interactions with human cathelicidin antimicrobial peptide LL-37, a frontline component of host innate immunity. Moreover, AVI markedly sensitized NDM-1-producing K. pneumoniae to killing by freshly isolated human neutrophils, platelets, and serum when complement was active. Finally, AVI monotherapy reduced lung counts of NDM-1-producing K. pneumoniae in a murine pulmonary challenge model. AVI sensitizes NDM-1-producing K. pneumoniae to innate immune clearance in ways that are not appreciated by standard antibiotic testing and that merit further study.