Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures

Abstract

bDetection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-␣-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrroline N-oxide) to assess free radical formation in the human pathogen Staphylococcus aureus treated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that when S. aureus was exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However, S. aureus cells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reduced katA expression and catalase activity in the presence of either antibiotic. Therefore, our results show that in S. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals.

The Role of Reactive Oxygen Species in Antibiotic-Induced Cell Death in Burkholderia cepacia Complex Bacteria

“…A specific way to directly measure the production of ROS without the need of functional translation is Electron Paramagnetic Resonance (EPR) [ 30 ]. Since free radicals have short half-lives, EPR is used in combination with spin traps or spin probes to yield relatively long-lived and detectable radical adducts.…”

Green and Red Brazilian Propolis: Antimicrobial Potential and Anti‐Virulence against ATCC and Clinically Isolated Multidrug‐Resistant Bacteria

“…The catalase enzyme produced by S. aureus inhibits the formation of free hydroxyl radicals, which are implicated in antibiotic mediated killing of this microorganism. Thus, catalase is an excellent target for creating structures capable of inhibiting the development of the S. aureus bacteria [41] . Due to this fact, a molecular docking investigation was performed with guttiferone E and xanthochymol to understand better the mechanism interaction between these compounds and S. aureus catalase enzyme.…”

Coatings with Natural Products—One Perspective on the Challenges Related to New Coatings’ Development

“…A considerable number of peptides have been discovered in recent decades, either inducible or constitutive, with activity against different types of microorganisms, characteristic of virtually all groups. These findings were preceded by the establishment of the role of thionines in plants as an example of antimicrobial peptides that protect the host from agents such as pathogenic microorganisms [13][14][15][16][17]. Thousands of peptide structures are currently known to possess a certain type of antimicrobial activity.…”

“…Linear peptides in turn form two distinct subgroups: (a) linear peptides with a tendency to adopt an α-helical amphipathic conformation; (b) linear peptides of unusual composition, rich in amino acids such as Pro, Arg, or (occasionally) Trp. The second group, which includes cysteine-containing peptides, can also be divided into two subgroups: (a) with a single disulfide structure and (b) with multiple disulfide structures [17]. There are currently a variety of approaches to classifying antimicrobial peptides.…”

“…There are currently a variety of approaches to classifying antimicrobial peptides. There are seven main criteria based on the classification of these valuable compounds: biosynthetic equipment used in their synthesis, biological source, biological functions, physicochemical properties, covalent bond pattern, 3D structure, and molecular targets [17][18][19].…”