KatG and KatE confer Acinetobacter resistance to hydrogen peroxide but sensitize bacteria to killing by phagocytic respiratory burst.

Abstract Aims Catalase catalyzes the degradation of H 2 O 2 . Acinetobacter species have four predicted catalase genes, katA , katE , katG , and katX . The aims of the present study seek to determine which catalase(s) plays a predominant role in determining the resistance to H 2 O 2 , and to assess the role of catalase in Acinetobacter virulence. Main methods Mutants of Acinetobacter baumannii and Acinetobacter nosocomialis with deficiencies in katA , katE , katG , and katX were tested for sensitivity to H 2 O 2 , either by halo assays or by liquid culture assays. Respiratory burst of neutrophils, in response to A. nosocomialis , was assessed by chemiluminescence to examine the effects of catalase on the production of reactive oxygen species (ROS) in neutrophils. Bacterial virulence was assessed using a Galleria mellonella larva infection model. Key findings The capacities of A. baumannii and A. nosocomialis to degrade H 2 O 2 are largely dependent on katE . The resistance of both A. baumannii and A. nosocomialis to H 2 O 2 is primarily determined by the katG gene, although katE also plays a minor role in H 2 O 2 resistance. Bacteria lacking both the katG and katE genes exhibit the highest sensitivity to H 2 O 2 . While A. nosocomialis bacteria with katE and/or katG were able to decrease ROS production by neutrophils, these cells also induced a more robust respiratory burst in neutrophils than did cells deficient in both katE and katG . We also found that A. nosocomialis deficient in both katE and katG was more virulent than the wildtype A. nosocomialis strain. Significance Our findings suggest that inhibition of Acinetobacter catalase may help to overcome the resistance of Acinetobacter species to microbicidal H 2 O 2 and facilitate bacterial disinfection.