Growth inhibition of <i>Acinetobacter</i> by 5-chloro-indole-3-acetic acid

The <i>Acinetobacter calcoaceticus-baumannii</i> complex includes high-priority, multidrug-resistant pathogens for which novel antibiotics are urgently needed. Many bacterial strains from this complex harbor a so-called <i>iac</i> gene cluster that codes for the catabolism of indole-3-acetic acid (IAA). Here, we demonstrate that possession and expression of <i>iac</i> genes represent an Achilles' heel for <i>Acinetobacter</i> species, which can be exploited to suppress bacterial growth by treatment with IAA and its analog 5-chloro-IAA.IMPORTANCE<i>Acinetobacter baumannii</i> is a deadly bacterial pathogen and one of the leading causes of hospital-acquired infections worldwide. It is also known for its resistance to many antibiotics currently available. In this study, we show that <i>Acinetobacter</i> bacteria choke on a mixture of IAA and 5-chloro-IAA, offering a path to the discovery and development of a novel drug treatment.