■ RESULTS AND DISCUSSIONSelective M. tuberculosis MenA Inhibitors: AssayStrategy. Antimicrobial spectrum focused against Mtb(selective antimycobacterial agent) is preferable for TBchemotherapy. 27 We realized that the peptide sequences ofthe Mtb menA and S. aureus menA gene products are only 32%identity and 50% similarity in the BLAST experiment. 28 Indeed,we have identified several molecules that exhibit selective MenAenzyme and bacterial growth inhibitory activities against Mtb,more than a 10-fold higher inhibitory activity against Mtb thanS. aureus. To develop MenA inhibitors which are selectiveagainst Mtb, molecules generated in this program were firstevaluated in MenA enzyme inhibitory assays. Only moleculesexhibited Mtb MenA activity over S. aureus MenA (IC50 < 20μM, >60 μM against Mtb MenA and S. aureus MenA,respectively) were evaluated in bacterial growth inhibitoryassays (MICs) using Mtb, S. aureus, and Escherichia coli (Figure3). The molecules exhibited good activity only against Mtb(MICs for Mtb, S. aureus, and E. coli are <12.5, >60, and >125μg/mL, respectively) were evaluated in E. coli growth inhibitoryassays under anaerobic conditions followed by menaquinonesupplementation assays (E. coli utilize only menaquinone in

E. coli Growth Inhibitory Assays under AnaerobicConditions. M. tuberculosis or S. aureus treated with the MenAinhibitors could not be rescued completely even at higherconcentrations of exogenous menaquinone (VK 2). In contrast,growth inhibition of E. coli by the MenA inhibitor could berescued by supplementation of VK2 (50 μM) under “anaerobicconditions” (vide supra). 46 E. coli growth inhibition rescued byaddition of VK2 may be attributed to the degree of permeabilityof VK 2 through the cell envelop. Although lack of activity ofMenA inhibitors against Gram-negative bacteria grown underaerobic conditions have been demonstrated, all MenAinhibitors identified in this program showed growth inhibitionof E. coli at 5−10 μg/mL concentrations under anaerobicconditions, and the inhibitory effect of MenA inhibitor wasrescued by supplementation of VK 2 . Therefore, theseconvenient cell-based assays using E. coli under anaerobicconditions can be utilized to confirm that the inhibitormolecules kill Gram-positive bacteria including Mtb bytargeting MenA biosynthesis or bacterial electron transportsystems

How many different "lines" of antibiotics against TB are there?Multiple Choiceonetwothreefourfive or more

What do MDR TB and MRSA have in common?Multiple ChoiceBoth are transmitted by mosquitoes.Both cause tuberculosis.Both are multidrug-resistant bacteria.Both have seen their numbers of infections decline dramatically in recent years.Both are viruses.

In some cases, a single antimicrobial agent is not sufficient to destroy all the pathogens that develop during the course of a disease; thus, two or more drugs may be used simultaneously to kill all the pathogens and to prevent resistant mutant pathogens from emerging. In tuberculosis, for example, in which multidrug-resistant strains of Mycobacterium tuberculosis are frequently encountered, four drugs (isoniazid, rifampin, pyrazinamide, and ethambutol) are routinely prescribed, and as many as 10 drugs may be required for especially resistant strains.(1 Point)TrueFalse

What is a bacterium that causes tuberculosis?