Lanthipeptides from <i>Chitinophaga pinensis</i> re-potentiating β-lactams against metallo-β-lactamase-producing Enterobacterales <i>in vitro</i>

ABSTRACT During a screening of secondary metabolites produced by soil bacteria, we identified two lanthipeptides from Chitinophaga pinensis , pinensin A and pinensin B, that exhibit strong in vitro synergy with β-lactams against metallo-β-lactamase (MβL)-producing Enterobacterales. Both compounds restored meropenem sensitivity in 30 MβL-producing Enterobacterales to levels below the clinical breakpoint. Mechanistic analysis identified pinensins as high-affinity zinc binders, exhibiting nanomolar dissociation constants, explaining the synergistic effect. The properties of pinensins warrant their further evaluation as β-lactam potentiators and highlight specific microbial taxa as promising sources for metalloenzyme inhibitor discovery. IMPORTANCE Resistance of clinical Enterobacterales to last resort drugs, such as carbapenems and newer cephalosporins, requires urgent measures. Production of metallo-β-lactamases is an important factor contributing to the problem, as there is no available therapeutic option against them. As with many of our currently utilized antibiotic classes, the environment has proven to be a valuable source of novel compounds, and naturally occurring inhibitors of metallo-β-lactamases may still await discovery. Herein, we show that such examples are two lanthipeptides produced by the soil bacterium Chitinophaga pinensis, which were able to counter the action of metallo-β-lactamases during the in vitro inhibition of clinical strains by β-lactams. The two compounds, previously identified as potent antifungal agents, exhibit strong binding and a degree of specificity for the enzymes’ cofactor (i.e., zinc), indicating that there is a potential for therapeutic applications.