Putrescine Reduces Antibiotic-Induced Oxidative Stress as a Mechanism of Modulation of Antibiotic Resistance in Burkholderia cenocepacia

Abstract

cCommunication of antibiotic resistance among bacteria via small molecules is implicated in transient reduction of bacterial susceptibility to antibiotics, which could lead to therapeutic failures aggravating the problem of antibiotic resistance. Released putrescine from the extremely antibiotic-resistant bacterium Burkholderia cenocepacia protects less-resistant cells from different species against the antimicrobial peptide polymyxin B (PmB). Exposure of B. cenocepacia to sublethal concentrations of PmB and other bactericidal antibiotics induces reactive oxygen species (ROS) production and expression of the oxidative stress response regulator OxyR. We evaluated whether putrescine alleviates antibiotic-induced oxidative stress. The accumulation of intracellular ROS, such as superoxide ion and hydrogen peroxide, was assessed fluorometrically with dichlorofluorescein diacetate, while the expression of OxyR and putrescine synthesis enzymes was determined in luciferase assays using chromosomal promoter-lux reporter system fusions. We evaluated wild-type and isogenic deletion mutant strains with defects in putrescine biosynthesis after exposure to sublethal concentrations of PmB and other bactericidal antibiotics. Exogenous putrescine protected against oxidative stress induced by PmB and other antibiotics, whereas reduced putrescine synthesis resulted in increased ROS generation and a parallel increased sensitivity to PmB. Of the 3 B. cenocepacia putrescine-synthesizing enzymes, PmB induced only BCAL2641, an ornithine decarboxylase. This study reveals BCAL2641 as a critical component of the putrescine-mediated communication of antibiotic resistance and as a plausible target for designing inhibitors that would block the communication of such resistance among different bacteria, ultimately reducing the window of therapeutic failure in treating bacterial infections.

Fumarate-Mediated Persistence of Escherichia coli against Antibiotics

“…Interpretation of FACS results should be cautious, though, as the role of reactive oxygen species (ROS) in antibiotic-mediated bacterial killing and the use of HPF in measuring ·OH have recently become matters of debate (47)(48)(49)(50). Nevertheless, we have established a relationship between fumarate-mediated persisters and ·OH generation, because substantial amounts of evidence still support the use of HPF and the role of ·OH in antibiotic-induced cell death (26,32,33,40,51).…”

Metabolomics of tomato xylem sap during bacterial wilt reveals Ralstonia solanacearum produces abundant putrescine, a metabolite that accelerates wilt disease

“…Polyamines are essential for biofilm formation in Yersinia pestis and induce type 3 secretion gene expression and function in Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa (Patel et al, 2006;Zhou et al, 2007;Jelsbak et al, 2012). Polyamines protect bacteria against many membrane stresses, including oxidative damage and cationic peptides like polymyxin B and the histones of neutrophil extracellular traps (NETs) (Goytia and Shafer, 2010;El-Halfawy and Valvano, 2014;Halverson et al, 2015). Putrescine enrichment in xylem sap may affect R. solanacearum biofilm, type 3 secretion and resistance to host ROS.…”

Antimicrobial Heteroresistance: an Emerging Field in Need of Clarity

“…Exposure to host-derived putrescine and other polyamines led to a transient increase in resistance to antimicrobial peptides in the urogenital pathogen Neisseria gonorrhoeae (154), suggesting that communication of resistance mediated by polyamines is likely a general phenomenon. Putrescine protected the surfaces of bacteria from the initial binding of polymyxin B (6) and reduced antibiotic-induced oxidative stress (155), while YceI could bind and sequester polymyxin B, thus potentially reducing its levels in the bacterial milieu (6).…”