e We report here a series of five chemically diverse scaffolds that have in vitro activities on replicating and hypoxic nonreplicating bacilli by targeting the respiratory bc 1 complex in Mycobacterium tuberculosis in a strain-dependent manner. Deletion of the cytochrome bd oxidase generated a hypersusceptible mutant in which resistance was acquired by a mutation in qcrB. These results highlight the promiscuity of the bc 1 complex and the risk of targeting energy metabolism with new drugs.

The nonmevalonate pathway (NMP) of isoprene biosynthesis is an exciting new route toward novel antibiotic development. Inhibitors against several enzymes in this pathway are currently under examination. A significant liability of many of these agents is poor cell penetration. To overcome and improve our understanding of this problem, we have synthesized a series of lipophilic, prodrug analogs of fosmidomycin and FR900098, inhibitors of the NMP enzyme Dxr. Several of these compounds show improved antibacterial activity against a panel of organisms relative to the parent compound, including activity against Mycobacterium tuberculosis (Mtb). Our results show that this strategy can be an effective way for improving whole cell activity of NMP inhibitors.

Bacteria, plants, and algae produce isoprenoids through the methylerythritol phosphate (MEP) pathway, an attractive pathway for antimicrobial drug development as it is present in prokaryotes and some lower eukaryotes but absent from human cells. The first committed step of the MEP pathway is catalyzed by 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR/MEP synthase). MEP pathway genes have been identified in many biothreat agents, including Francisella, Brucella, Bacillus, Burkholderia, and Yersinia. The importance of the MEP pathway to Francisella is demonstrated by the fact that MEP pathway mutations are lethal. We have previously established that fosmidomycin inhibits purified MEP synthase (DXR) from F. tularensis LVS. FR900098, the acetyl derivative of fosmidomycin, was found to inhibit the activity of purified DXR from F. tularensis LVS (IC50 = 230 nM). Fosmidomycin and FR900098 are effective against purified DXR from Mycobacterium tuberculosis as well, but have no effect on whole cells because the compounds are too polar to penetrate the thick cell wall. Fosmidomycin requires the GlpT transporter to enter cells, and this is absent in some pathogens, including M. tuberculosis. In this study, we have identified the GlpT homologs in F. novicida and tested transposon insertion mutants of glpT. We showed that FR900098 also requires GlpT for full activity against F. novicida. Thus, we synthesized several FR900098 prodrugs that have lipophilic groups to facilitate their passage through the bacterial cell wall and bypass the requirement for the GlpT transporter. One compound, that we termed “compound 1,” was found to have GlpT-independent antimicrobial activity. We tested the ability of this best performing prodrug to inhibit F. novicida intracellular infection of eukaryotic cell lines and the caterpillar Galleria mellonella as an in vivo infection model. As a lipophilic GlpT-independent DXR inhibitor, compound 1 has the potential to be a broad-spectrum antibiotic, and should be effective against most MEP-dependent organisms.

In most bacteria, the nonmevalonate pathway is used to synthesize isoprene units. Dxr, the second step in the pathway, catalyzes the NADPH-dependent reductive isomerization of 1-deoxy-D-xylulose-5-phosphate (DXP) to 2-C-methyl-D-erythritol-4-phosphate (MEP). Dxr is inhibited by natural products fosmidomycin and FR900098, which bind in the DXP binding site. These compounds, while potent inhibitors of Dxr, lack whole cell activity against Mycobacterium tuberculosis (Mtb) due to their polarity. Our goal was to use the Mtb Dxr-fosmidomycin co-crystal structure to design bisubstrate ligands to bind to both the DXP and NADPH sites. Such compounds would be expected to demonstrate improved whole cell activity due to increased lipophilicity. Two series of compounds were designed and synthesized. Compounds from both series inhibited Mtb Dxr. The most potent compound (8) has an IC50 of 17.8 µM. Analysis shows 8 binds to Mtb Dxr via a novel, non-bisubstrate mechanism. Further, the diethyl ester of 8 inhibits Mtb growth making this class of compounds interesting lead molecules in the search for new antitubercular agents.

Page 6963, left column, second paragraph: the following text in lines 5 to 10 should be deleted. "We deleted this oxidase in H37Rv by replacing a 221-bp MluI fragment in the cydABDC operon with the aph gene encoding an aminoglycoside phosphotransferase. The mutant lacks the 3' end of the cydB gene (encoding subunit II of the cytochrome bd oxidase), the entire cydD gene, and the 5' end of cydC (where cydDC encodes a transporter involved in cytochrome biogenesis)." The cytochrome bd oxidase strain used was the cydC::aph strain mutant reported in

No abstract

1543 Background: Lung cancer is the leading cause of cancer death in the United States (US) and worldwide. Chest X-ray (CXR) is ineffective in reducing lung cancer mortality. National Lung Cancer Screening Trail (NLST) reported 20% reduction in mortality with the use of low-dose computed tomography (LDCT) scan to screen high risk individuals. Therefore, major organizations including US Preventive Services Task Force has adopted LDCT for lung cancer screening in high risk populations. However, The generalizability of this approach in community setting is yet to be confirmed. Our objective is to assess the ability of LDCT in detection of lung nodules and lung cancer in the community setting and compare the results to those reported in the NLST. Methods: Charts of subjects who underwent LDCT screening between 2013 and 2016 at SJHMC were retrospectively reviewed. Demographic data, the results of the LDCT scans, interventions performed, complications of procedures and pathology findings were collected. All cancer cases found by LDCT and the stage of cancers were documented. The results of our study were statistically compared to the results of both arms of the NLST (CT and CXR arms). Since CXR is ineffective for lung cancer screening, CXR arm serves equivalently to no screening. Results: The baseline characteristics of the subjects are significantly different between this study and NLST. LDCT in our study detected significantly higher positive findings. There are more cancers detected in this study compared to NLST CT and CXR arms, which could reflect higher incidence of cancer in this community or higher proportion of current smokers in our study. In this study, LDCT detected cancers at higher stages compared to that of the NLST CT arm but similar stages to NLST CXR arm. This may indicate that LDCT when performed in the community is less effective in detecting cancer at early stages. Conclusions: The community population have different characteristics compared those enrolled in clinical trials. This may limit the generalizability of the results. Population-based studies are needed to confirm the results of the NLST. [Table: see text]