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 H2O2. 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 H2O2, and to assess the role of catalase in Acinetobacter virulence. Main Methods Mutants of A. baumannii and A. nosocomialis with deficiencies in katA, katE, katG, and katX were tested for sensitivity to H2O2, 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)1 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 H2O2 are largely dependent on katE. The resistance of both A. baumannii and A. nosocomialis to H2O2 is primarily determined by the katG gene, although katE also plays a minor role in H2O2 resistance. Bacteria lacking both the katG and katE genes exhibit the highest sensitivity to H2O2. 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 H2O2 and facilitate bacterial disinfection.

Assessment of Insertion Sequence Mobilization as an Adaptive Response to Oxidative Stress in Acinetobacter baumannii Using IS-seq

“…The significant differences in expression of iron acquisition genes seen here are consistent with those previously observed in A. baumannii (25) and other bacteria (26) and provide evidence for coordinated expression of genes related to iron homeostasis.…”

Erwinia amylovora catalases KatA and KatG are virulence factors and delay the starvation‐induced viable but non‐culturable (VBNC) response

“…It is worth mentioning that, similar to the observations in Xanthomonas campestris (Jittawuttipoka et al ., ), although several assays revealed that KatA was the major catalase in E. amylovora , the KatG‐deficient mutant was more affected during plant–pathogen interactions. In this sense, the importance of KatG might be related to functions other than catalase activity, such as the neutralization of toxic peroxide compounds produced after H 2 O 2 exposure (McLean et al ., ; Sun et al ., ). Our results correlate well with katG induction during fruit infection (Fig.…”

Biofilm inhibitory efficiency of phytol in combination with cefotaxime against nosocomial pathogen Acinetobacter baumannii

“…The antioxidant enzyme catalase plays a vital role in protecting A. baumannii from damage produced by reactive oxygen species through hydrolyzing hydrogen peroxide (Jones et al 2017). The katE gene is responsible for catalase enzyme production in A. baumannii, which is under the control of QS (Bhargava et al 2015;Montagu et al 2016;Sun et al 2016). The real-time data exposed notable down regulation of katE gene expression in PCCs treated A. baumannii (Fig.…”

“…; Sun et al . ). The real‐time data exposed notable down regulation of katE gene expression in PCCs treated A. baumannii (Fig.…”