Abstract
Antibiotic resistance is a major public health challenge, and Gram-negative multidrug-resistant bacteria are particularly dangerous. The threat of running out of active molecules is accelerated by the extensive use of antibiotics in the context of the COVID-19 pandemic, and new antibiotics are urgently needed. Colistin and polymyxin B are natural antibiotics considered as last resort drugs for multi-resistant infections, but their use is limited because of neuro- and nephrotoxicity. We previously reported a series of synthetic analogues inspired in natural polymyxins with a flexible scaffold that allows multiple modifications to improve activity and reduce toxicity. In this work, we focus on modifications in the hydrophobic domains, describing analogues that broaden or narrow the spectrum of activity including both Gram-positive and Gram-negative bacteria, with MICs in the low µM range and low hemolytic activity. Using biophysical methods, we explore the interaction of the new molecules with model membranes that mimic the bacterial inner and outer membranes, finding a selective effect on anionic membranes and a mechanism of action based on the alteration of membrane function. Transmission electron microscopy observation confirms that polymyxin analogues kill microbial cells primarily by damaging membrane integrity. Redistribution of the hydrophobicity within the polymyxin molecule seems a plausible approach for the design and development of safer and more selective antibiotics.
Highlights
The convergence of antibiotic resistance and the collapse in the antibiotics R&D pipeline calls for urgent action [1,2]
One of the risk factors associated with COVID-19 is secondary bacterial pneumonia, resulting in worst outcomes [9]
9.3 μM, it is necessary to design new with better therapeutic combining remains below
Summary
The convergence of antibiotic resistance and the collapse in the antibiotics R&D pipeline calls for urgent action [1,2]. There are different factors associated with the emergence of resistance, and the extensive use of broad-spectrum antibiotics is one of them. The large pharmaceutical companies have abandoned antibiotic research and development due to economic reasons; the antimicrobial pipeline is getting dry, with the last original class of antibiotic discovered in the late 1980s [1,4–6]. COVID-19 pandemic has caused an increase in antibiotic use, contributing significantly to the development of resistances [7]. Bacterial co-pathogens and secondary infections are commonly identified in hospitalized, severely ill COVID-19 patients, encompassing between ≈10 and 30% of cases with much greater frequency in the ICU setting [8]. One of the risk factors associated with COVID-19 is secondary bacterial pneumonia, resulting in worst outcomes [9]. Severely ill patients are more likely to receive treatment with invasive catheters, resulting in an increased risk of secondary infections with
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