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Top1. Introduction
Antimicrobial resistance is a frightening problem spread around the world. It is responsible for the increase of the death risk, specifically in hospitalized patients due to multidrug-resistant (MDR) bacteria (Giske et al., 2008; Maragakis et al., 2008; Nelson et al., 2017). The number of new MDR strains increased as a result of the combination of different factors, such as the indiscriminate use of antibiotics (Fleming-Dutra et al., 2016; Centers for Disease Control and Prevention (U.S.), 2019). During the COVID-19 pandemic, despite the rareness of bacterial co-infections, most patients were treated with antibiotics (Calderón-Parra et al., 2021). Additionally, agriculture and livestock play an important role in this problem (Boeckel et al., 2015; Manyi-Loh et al., 2018; Van Boeckel et al., 2019). Annually, the global human death estimative is 700,000 and in 2050 will expect to reach 10 million (Ghosh et al., 2019). Besides this unfavorable scenario, pharmaceutical companies' lack of new antibiotics could represent a major risk to humankind leading to a new “pre-antibiotic era” (Gajdács, 2019).
To help overcoming this need, in 2017, the World Health Organization (WHO) set the priorities to antibacterial development. This priority list classified pathogens into three classes according to their urgency: critical priority, high priority (where the methicillin-resistant Staphylococcus aureus [MRSA] is included), and medium priority (World Health Organization, 2017). For the development of new antibacterial drugs, it is desired a high selectivity against the pathogen to avoid toxicity in the host. The simplest way to achieve this property is to use essential targets in the bacteria metabolism that is absent in the human organism. Following these guidelines are the S. aureus DNA gyrase, an essential enzyme for genetic material replication and has no direct counterpart in mammalian cells. This enzyme is responsible for introducing negative supercoils into DNA in advance of the replication fork. The DNA gyrase displays the biological activity as heterotetrameric structures containing two substructures A (GyrA) and B (GyrB) for DNA gyrase, where GyrB is responsible for ATP hydrolysis and provides the energy required for the reaction catalyzed by GyrA. The other two substructures are for topoisomerase IV (Collin et al., 2011; Gross et al., 2003).
Recently, drug design companies have been successful in showing DNA gyrase inhibition through the use of different chemical scaffolds such as Schiff bases (Salem, Ragab, El-Khalafawy, et al., 2020), quinoxalines (Ammar et al., 2020), coumarin-thiazolyl esters (Liu et al., 2020), and others (Kolarič et al., 2021; Salem, Ragab, Askar, et al., 2020; Werner et al., 2015). In 2020, a series of N-thiadiazole-4-hydroxy-2-quinolone-3-carboxamides was synthesized and tested against S. aureus and several other gram-positive species (Xue et al., 2020). One of the most active compounds showed, beyond the DNA gyrase B inhibition, antibacterial activity, and a viable pharmacokinetic profile, being metabolically stable as well as orally active. Following these results, this work aimed to understand and predict the DNA gyrase inhibition and the bactericidal activity of this moiety derivatives, using classification Random Forest (RF) models for these two endpoints.