Biology subjects

Tawiah, P. O.

Publications and source records attributed to Tawiah, P. O..

6 recordsLinked to original sources

bioRxiv2026

A newly identified detoxification system protects uropathogenic Escherichia coli from reactive chlorine species

Neutrophils eliminate invading pathogens through the production of reactive oxygen and chlorine species (ROS/RCS), with hypochlorous acid (HOCl) representing the most abundant and bactericidal oxidant produced in this process. Compared to bacterial defenses against ROS, which are well studied, little is known about how pathogens respond to and counter RCS, including HOCl. Here, we identify and mechanistically characterize RcrB, a protein of the uncharacterized DUF417 protein family, for which no role in oxidative stress defense has been described yet. We report a previously unrecognized role as an RCS detoxification system that confers high-level resistance to uropathogenic Escherichia coli (UPEC). We show that RcrB is an inner membrane protein and strongly induced during RCS exposure and phagocytosis. Loss of RcrB results in profound HOCl hypersensitivity, accompanied by elevated macromolecular damage and severe metabolic perturbations, establishing RcrB as a central determinant of UPECs RCS stress resistance. Heterologous expression of RcrB in HOCl-sensitive intestinal E. coli strains is sufficient to restore resistance but requires functional glutathione biosynthesis. Quantitative HOCl trapping assays demonstrate that RcrB expression protects the bacterial population by significantly reducing extracellular HOCl, indicating active chemical quenching rather than passive membrane protection. Structure-function analysis of RcrB confirms this conclusion and demonstrate that conserved, redox-active amino acids facing the periplasm are essential for its detoxification activity. In summary, our study reveals a hitherto unknown bacterial strategy for mitigating RCS and reveal a distinct mechanism by which UPEC may survive the mammalian host defense. Significance StatementDuring infection, human immune cells such as neutrophils kill bacteria by releasing powerful oxidants, including hypochlorous acid (HOCl), the active ingredient of household bleach. How pathogenic bacteria survive this chemical attack is still poorly understood. This study identifies a membrane protein in uropathogenic Escherichia coli as a key defense factor that neutralizes HOCl before it can damage the cell. RcrB acts at the bacterial cell envelope, where it detoxifies HOCl in a glutathione-dependent manner to maintain a balanced redox homeostasis and cellular integrity, thereby even protect neighboring bacteria. These findings reveal a previously unrecognized frontline defense strategy that helps pathogens survive immune attack and may represent a new target for antimicrobial therapies.

microbiology↗

bioRxiv2025

The Synergy between a Silver-Ruthenium Antimicrobial and aminoglycosides is based on severe macromolecular damage

The rise of multidrug-resistant (MDR) bacterial pathogens, including uropathogenic Escherichia coli (UPEC), highlights the urgent need for alternative treatment strategies to restore antibiotic efficacy. The silver-ruthenium antimicrobial AGXX(R) exerts potent bactericidal effects through the production of reactive oxygen species (ROS); however, its potential synergy with antibiotics has not been thoroughly investigated. Here, we show that sublethal concentrations of AGXX(R) strongly enhance aminoglycoside-mediated killing across a diverse panel of Gram-negative and Gram-positive MDR clinical isolates, including highly aminoglycoside-resistant strains. Combinational treatments significantly reduced the effective concentrations of gentamicin, tobramycin, kanamycin, and amikacin required for bacterial killing. Mechanistic analyses revealed that AGXX(R)/aminoglycoside co-treatment induces pronounced intracellular ROS accumulation, resulting in severe proteotoxic stress, extensive protein aggregation, and DNA damage. Scavenging ROS abolished synergistic killing, establishing oxidative imbalance as the primary driver of the synergy between both antimicrobials. We further identify polyphosphate as a key bacterial defense mechanism that mitigates ROS accumulation, proteotoxicity, and genotoxic stress during combinational treatment. Moreover, AGXX(R)-aminoglycoside synergy was preserved in an artificial urine medium and across clinical UPEC isolates, underscoring its relevance to urinary tract infections. Together, these findings position AGXX(R) as a potent aminoglycoside adjuvant that restores antibiotic efficacy through ROS-driven macromolecular damage, supporting its development for combination therapies against MDR bacterial infections.

microbiology↗

bioRxiv2025

A Novel Silver-Ruthenium-Based Antimicrobial Kills Gram-Negative Bacteria Through Oxidative Stress-Induced Macromolecular Damage

Amplified by the decline in antibiotic discovery, the rise of antibiotic resistance has become a significant global challenge in infectious disease control. Extraintestinal Escherichia coli (ExPEC), known to be the most common instigators of urinary tract infections (UTIs), represent such global threat. Novel strategies for more efficient treatments are therefore desperately needed. These include silver nanoparticles, which have been used as antimicrobial surface-coatings on catheters to eliminate biofilm-forming uropathogens and reduce the risk of nosocomial infections. AGXX(R) is a promising silver coating that presumably kills bacteria through the generation of reactive oxygen species (ROS) but is more potent than silver. However, neither is AGXX(R)s mode of action fully understood, nor have its effects on Gram-negative bacteria or bacterial response and defense mechanisms towards AGXX(R) been studied in detail. Here, we report that the bactericidal effects of AGXX(R) are primarily based on ROS formation, as supplementation of the media with a ROS scavenger completely abolished AGXX(R)-induced killing. We further show that AGXX(R) impairs the integrity of the bacterial cell envelope and causes substantial protein aggregation and DNA damage already at sublethal concentrations. ExPEC strains appear to be more resistant to the proteotoxic effects of AGXX(R) compared to non-pathogenic E. coli, indicating improved defense capabilities of the uropathogen. Global transcriptomic studies of AGXX(R)-stressed ExPEC revealed a strong oxidative stress response, perturbations in metal homeostasis, as well as the activation of heat shock and DNA damage responses. Finally, we present evidence that ExPEC counter AGXX(R) damage through the production of the chaperone polyphosphate.

microbiology↗

bioRxiv2023

Carbapenem- and cefiderocol-resistant Enterobacterales in surface waters in Kumasi, Ashanti Region, Ghana

This study investigated the presence of extended-spectrum {beta}-lactamase-producing Enterobacterales in selected surface waters in the Ashanti Region in Ghana. Subsequent genomic analysis revealed that one-fifth of the isolates were genotypically carbapenem-resistant. Phenotypic susceptibility testing not only confirmed their carbapenem resistance, but also uncovered two cefiderocol-resistant isolates.

microbiology↗

bioRxiv2023

Expression of RcrB confers resistance to hypochlorous acid in uropathogenic Escherichia coli

To eradicate bacterial pathogens, neutrophils are recruited to the sites of infection, where they engulf and kill microbes through the production of reactive oxygen and chlorine species (ROS/RCS). The most prominent RCS is antimicrobial oxidant hypochlorous acid (HOCl), which rapidly reacts with various amino acids side chains, including those containing sulfur and primary/tertiary amines, causing significant macromolecular damage. Pathogens like uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections (UTIs), have developed sophisticated defense systems to protect themselves from HOCl. We recently identified the RcrR regulon as a novel HOCl defense strategy in UPEC. The regulon is controlled by the HOCl-sensing transcriptional repressor RcrR, which is oxidatively inactivated by HOCl resulting in the expression of its target genes, including rcrB. rcrB encodes the putative membrane protein RcrB, deletion of which substantially increases UPECs susceptibility to HOCl. However, many questions regarding RcrBs role remain open including whether (i) the proteins mode of action requires additional help, (ii) rcrARB expression is induced by physiologically relevant oxidants other than HOCl, and (iii) expression of this defense system is limited to specific media and/or cultivation conditions. Here, we provide evidence that RcrB expression is sufficient to E. colis protection from HOCl and induced by and protects from several RCS but not from ROS. RcrB plays a protective role for RCS-stressed planktonic cells under various growth and cultivation conditions but appears to be irrelevant for UPECs biofilm formation. IMPORTANCEBacterial infections pose an increasing threat to human health exacerbating the demand for alternative treatment options. UPEC, the most common etiological agent of urinary tract infections (UTIs), are confronted by neutrophilic attacks in the bladder, and must therefore be well equipped with powerful defense systems to fend off the toxic effects of RCS. How UPEC deal with the negative consequences of the oxidative burst in the neutrophil phagosome remains unclear. Our study sheds light on the requirements for the expression and protective effects of RcrB, which we recently identified as UPECs most potent defense system towards HOCl-stress and phagocytosis. Thus, this novel HOCl-stress defense system could potentially serve as an attractive drug target to increase the bodys own capacity to fight UTIs.

microbiology↗

bioRxiv2023

The Novel Silver-Containing Antimicrobial Potentiates Aminoglycoside Activity Against Pseudomonas aeruginosa.

The rapid dissemination of antibiotic resistance combined with the decline in the discovery of novel antibiotics represents a major challenge for infectious disease control that can only be mitigated by investments into novel treatment strategies. Alternative antimicrobials, including silver, have regained interest due to their diverse mechanisms of inhibiting microbial growth. One such example is AGXX(R), a broad-spectrum silver containing antimicrobial that produces highly cytotoxic reactive oxygen species (ROS) to inflict extensive macromolecular damage. Due to connections identified between ROS production and antibiotic lethality, we hypothesized that AGXX(R) could potentially increase the activity of conventional antibiotics. Using the gram-negative pathogen Pseudomonas aeruginosa, we screened possible synergistic effects of AGXX(R) on several antibiotic classes. We found that the combination of AGXX(R) and aminoglycosides tested at sublethal concentrations led to a rapid exponential decrease in bacterial survival and restored sensitivity of a kanamycin-resistant strain. ROS production contributes significantly to the bactericidal effects of AGXX(R)/aminoglycoside treatments, which is dependent on oxygen availability and can be reduced by the addition of ROS scavengers. Additionally, P. aeruginosa strains deficient in ROS detoxifying/repair genes were more susceptible to AGXX(R)/aminoglycoside treatment. We further demonstrate that this synergistic interaction was associated with significant increase in outer and inner membrane permeability, resulting in increased antibiotic influx. Our study also revealed that AGXX(R)/aminoglycoside-mediated killing requires an active proton motive force across the bacterial membrane. Overall, our findings provide an understanding of cellular targets that could be inhibited to increase the activity of conventional antimicrobials. IMPORTANCEThe emergence of drug-resistant bacteria coupled with the decline in antibiotic development highlights the need for novel alternatives. Thus, new strategies aimed at repurposing conventional antibiotics have gained significant interest. The necessity of these interventions is evident especially in gram-negative pathogens as they are particularly difficult to treat due to their outer membrane. This study highlights the effectiveness of the silver containing antimicrobial AGXX(R) in potentiating aminoglycoside activities against P. aeruginosa. The combination of AGXX(R) and aminoglycosides not only reduces bacterial survival rapidly but also significantly re-sensitizes aminoglycoside-resistant P. aeruginosa strains. In combination with gentamicin, AGXX(R) induces increased endogenous oxidative stress, membrane damage and iron sulfur cluster disruption. These findings emphasize AGXX(R)s potential as a route of antibiotic adjuvant development and shed light into potential targets to enhance aminoglycoside activity.

microbiology↗