The cell envelope of the Gram-negative Burkholderia cepacia complex (Bcc) presents unique restrictions to antibiotic penetration. As a consequence, Bcc species are notorious for causing recalcitrant multidrug-resistant infections in immunocompromised individuals, such as those living with cystic fibrosis. To systematically identify cell envelope-associated resistance and susceptibility determinants at the genome level, we constructed a high-density, randomly-barcoded transposon mutant library in the clinical isolate B. cenocepacia K56-2 and exposed it to a panel of more than twenty cell envelope-targeting antibiotics. By quantifying relative mutant fitness with BarSeq, followed by validation with CRISPR-interference, we profiled over a hundred new functional associations and identified novel mediators of antibiotic susceptibility in the Bcc cell envelope. We revealed new connections between β-lactam susceptibility, peptidoglycan synthesis, and blockages in undecaprenyl phosphate metabolism, which highlight a vulnerability in sharing this lipid intermediate. We then show that the clinically relevant synergy of the β-lactam/β-lactamase inhibitor combination ceftazidime/avibactam is primarily mediated by inhibition of the PenB carbapenemase. Importantly, we found that avibactam more strongly potentiates the activity of aztreonam and meropenem than ceftazidime in a panel of Bcc clinical isolates. Finally, we characterize for first time in the Bcc the iron and receptor-dependent activity of the novel siderophore-cephalosporin antibiotic, cefiderocol. Overall, our work has implications for antibiotic target prioritization, and for using additional combinations of β-lactam/β-lactamase inhibitors that can extend the utility of our current clinical arsenal of antibacterial therapies.
Bacteria of the genus Burkholderia include pathogenic Burkholderia mallei, Burkholderia pseudomallei and the Burkholderia cepacia complex (Bcc). These Gram-negative pathogens have intrinsic drug resistance, which makes treatment of infections difficult. Bcc affects individuals with cystic fibrosis (CF) and the species B. cenocepacia is associated with one of the worst clinical outcomes. Following the repurposing of auranofin as an antibacterial against Gram-positive bacteria, we previously synthetized auranofin analogs with activity against Gram-negatives. In this work, we show that two auranofin analogs, MS-40S and MS-40, have antibiotic activity against Burkholderia clinical isolates. The compounds are bactericidal against B. cenocepacia and kill stationary-phase cells and persisters without selecting for multistep resistance. Caenorhabditis elegans and Galleria mellonella tolerated high concentrations of MS-40S and MS-40, demonstrating that these compounds have low toxicity in these model organisms. In summary, we show that MS-40 and MS-40S have antimicrobial properties that warrant further investigations to determine their therapeutic potential against Burkholderia infections.
The cell envelope of the Gram-negativeBurkholderia cepaciacomplex (Bcc) presents unique restrictions to antibiotic penetration. As a consequence, Bcc species are notorious for causing recalcitrant multidrug-resistant infections in immunocompromised individuals, such as those living with cystic fibrosis. To systematically identify cell envelope-associated resistance and susceptibility determinants at the genome level, we constructed a high-density, randomly-barcoded transposon mutant library in the clinical isolateB. cenocepaciaK56-2 and exposed it to a panel of more than twenty cell envelope-targeting antibiotics. By quantifying relative mutant fitness with BarSeq, followed by validation with CRISPR-interference, we profiled over a hundred new chemical-genetic interactions and identified novel mediators of antibiotic susceptibility in the Bcc cell envelope. We first reveal new connections between broad-spectrum β-lactam susceptibility, peptidoglycan synthesis, and blockages in undecaprenyl phosphate metabolism, highlighting a β-lactam critical vulnerability associated with sharing this common lipid intermediate. We then show that the clinically relevant synergy of the β-lactam/ β-lactamase inhibitor combination ceftazidime/avibactam is primarily mediated by inhibition of the PenB carbapenemase, over more than twenty other putative β-lactamases. Importantly, avibactam more strongly potentiates the activity of aztreonam and meropenem than ceftazidime in a panel of Bcc clinical isolates. Finally, we characterize for first time in the Bcc the iron and receptor-dependent activity of the novel siderophore cephalosporin antibiotic, cefiderocol. Overall, our work has implications for antibiotic target prioritization, and for using additional combinations of β-lactam/ β-lactamase inhibitors that can extend the utility of our current clinical arsenal of antibacterial therapies.
Electrochemical sensors are gaining attention for the detection and quantification of pharmaceuticals in the environment. To that end, there is an interest in understanding the electrochemical characteristics of drugs. Herein, the multi-purpose drug auranofin is investigated for the first time in aqueous media. This compound offers therapeutic benefits in strains of cancer, parasites, bacteria and fungi, which have grown immune to many antibiotics. Auranofin detection was optimized at carbon black-modified electrodes. Voltammetry provides information about redox potentials, levels of detection and quantification, and pH dependence. Parameters identified in this study will be useful for auranofin sensing in environmental samples, and for studies related to drug resistance.
The increase of antibiotic resistance (AR) is a global concern for patients with acute infections as well as chronic illnesses, such as cystic fibrosis. Few antibiotics are effective, in particular against Gram-negative bacteria, due to their inherent cell membrane impermeability and high number of efflux pumps. Consequently, there is a dire need for innovative strategies to understand the underlying causes of low drug uptake and high efflux in bacteria. Electrochemistry has attracted immense attention over the past decade, because its methods are cost efficient and sensitive. This presentation highlights bioelectrochemical approaches to recognize and quantify antibiotic resistance. Following the characterization of antibacterials, the monitoring of drug efflux, the detection of antibiotic resistance through cell metabolites and the measurement of drug retention in bacteria are possible strategies to quantify antibiotic resistance in pathogens. The presented research forms the basis for the future development of a point-of-care biosensor to identify antibiotic resistance in patient samples. Such technology would advance clinical treatment from the current trial-and-error approach to the prescription of evidence based personalized drug regimens and benefit patients around the world.
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