The role of the DSB system in antimicrobial resistance

Extensive use of antibiotics in medicine and agriculture has led to increasing emergence of antimicrobial resistance in bacterial populations. Dwindling resources in the discovery of novel active compound leads and the increasing demands for safety and efficacy of new drugs mean that we are now faced with treatment failures due to multi-drug resistant pathogens. In the quest for new targets that will enable us to counter antibiotic resistance, it is often ignored that many resistance mechanisms precede the clinical use of antibiotics. Instead, the ability to adapt, survive and bypass the toxicity of many chemical compounds is wired within the bacterial genome. Continuous inter-strain and inter-species competition have given microorganisms tools to thrive under conditions of chemical warfare. Recognising this is important when characterising mechanisms underpinning bacterial antimicrobial resistance, as it can lead to novel strategies that can help us bypass it. The work described here explores the connection between the disulfide bond formation system, a key oxidative protein folding pathway in the cell envelope of Gram-negative bacteria, and two widespread antimicrobial resistance mechanisms, b-lactamase catalysed hydrolysis of b-lactam antibiotics and efflux-mediated drug expulsion. It is demonstrated that oxidative-protein-folding-mediated proteostasis is crucial for both resistance mechanisms, and its inhibition can sensitise multidrug-resistant pathogens to existing antibiotics. Preliminary results from an experimental evolution approach, set the scene for future exploration of the importance of disulfide linkages for the capacity of b-lactamase enzymes to evolve under selective pressure. Together, these findings aim to address the mechanistic basis of a new avenue for antibiotic adjuvant therapy, whereby targeting a non-essential process would allow us to potentiate existing antibiotics towards previously resistant bacterial strains. With novel essential targets against bacteria being scarce, adjuvant approaches like this one could prolong the use and efficacy of existing drugs against some of the most resistant Gram-negative pathogens.Open Acces

Breaking antimicrobial resistance by disrupting extracytoplasmic protein folding

Antimicrobial resistance in Gram-negative bacteria is one of the greatest threats to global health. New antibacterial strategies are urgently needed, and the development of antibiotic adjuvants that either neutralize resistance proteins or compromise the integrity of the cell envelope is of ever-growing interest. Most available adjuvants are only effective against specific resistance proteins. Here we demonstrate that disruption of cell envelope protein homeostasis simultaneously compromises several classes of resistance determinants. In particular, we find that impairing DsbA-mediated disulfide bond formation incapacitates diverse β-lactamases and destabilizes mobile colistin resistance enzymes. Furthermore, we show that chemical inhibition of DsbA sensitizes multidrug-resistant clinical isolates to existing antibiotics and that the absence of DsbA, in combination with antibiotic treatment, substantially increases the survival of Galleria mellonella larvae infected with multidrug-resistant Pseudomonas aeruginosa. This work lays the foundation for the development of novel antibiotic adjuvants that function as broad-acting resistance breakers.British Society for Antimicrobial Chemotherapy BSAC-2018-0095NC3Rs NC/V001582/1Biological Sciences Research Council BB/V007823/1Academy of Medical Sciences SBF006\104

Breaking antimicrobial resistance by disrupting extracytoplasmic protein folding

Antimicrobial resistance in Gram-negative bacteria is one of the greatest threats to global health. New antibacterial strategies are urgently needed, and the development of antibiotic adjuvants that either neutralize resistance proteins or compromise the integrity of the cell envelope is of ever-growing interest. Most available adjuvants are only effective against specific resistance proteins. Here, we demonstrate that disruption of cell envelope protein homeostasis simultaneously compromises several classes of resistance determinants. In particular, we find that impairing DsbA-mediated disulfide bond formation incapacitates diverse β-lactamases and destabilizes mobile colistin resistance enzymes. Furthermore, we show that chemical inhibition of DsbA sensitizes multidrug-resistant clinical isolates to existing antibiotics and that the absence of DsbA, in combination with antibiotic treatment, substantially increases the survival of Galleria mellonella larvae infected with multidrug-resistant Pseudomonas aeruginosa. This work lays the foundation for the development of novel antibiotic adjuvants that function as broad-acting resistance breakers