An evolution of antibiotic-resistant bacteria has resulted in the need for new antibiotics. β-Lactam based drugs are the most predominantly prescribed antibiotics to combat bacterial infections; however, production of β-lactamases, which catalyze the hydrolysis of the β-lactam bond of this class of antibiotics, by pathogenic bacteria such as Bacillus cereus, are rendering them useless. Some inhibitors of β-lactamases have been found, but there are no inhibitors against a class of β-lactamases known as metallo-β-lactamases, and it has been reported that the number of bacteria that produce metallo-β-lactamases is on the rise. Finding inhibitors of metallo-β-lactamases is thus an urgent necessity. One way to approach the problem is by employing the combinatorial method SELEX. The SELEX method is significant in discovering and producing new classes of inhibitors, as well as providing insight into the development of these inhibitors and paves the way for future aptamer applications that further novel drug discovery.

Anthrax is caused by Bacillus anthracis, a bacterium that is able to secrete the toxins protective antigen, edema factor and lethal factor. Due to the high level of secretion from the bacteria and its severe virulence, lethal factor (LF) has been sought as a biomarker for detecting bacterial infection and as an effective target to neutralize toxicity. In this study, we found three aptamers, and binding affinity was determined by fluorescently labeled aptamers. One of the aptamers exhibited high affinity, with a K value of 11.0 ± 2.7 nM, along with low cross reactivity relative to bovine serum albumin and protective antigen. The therapeutic functionality of the aptamer was examined by assessing the inhibition of LF protease activity against a mitogen-activated protein kinase kinase. The aptamer appears to be an effective inhibitor of LF with an IC value of 15 ± 1.5 μM and approximately 85% cell viability, suggesting that this aptamer provides a potential clue for not only development of a sensitive diagnostic device of B. anthracis infection but also the design of novel inhibitors of LF.

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Metallo-b-lactamases (MBLs) that catalyze hydrolysis of b-lactam antibiotics are an emerging threat due to their rapid spread. A strain of the bacterium Bacillus anthracis has its ability to produce and secrete a MBL, referred to Bla2. To address this challenge, novel hydroxamic acidcontaining compounds such as 3-(heptyloxy)-N-hydroxybenzamide (compound 4) and Nhydroxy-3-((6-(hydroxyamino)-6-oxohexyl)oxy)benzamide (compound 7) were synthesized. Kinetic analysis of microbial inhibition indicated that the both sides of hydroxamic acids containing compound 7 revealed a reversible, competitive inhibition with a K i value of 0.18 ± 0.06 mM. The result has reflected that the both sides of dihydroxamic acids in a molecule play a crucial role in the binding affinity rather than monohydroxamic containing compound 4 which was unable to inhibit Bla2. In addition, in silico analysis suggested that compound 7 was coordinated with a zinc ion in the active site of enzyme. These observations suggest that the dihydroxamic acid-containing compound may be a promising drug candidate, and a further implication for designing new inhibitors of Bla2.