Streptococcus pneumoniae galU gene mutation has a direct effect on biofilm growth, adherence and phagocytosis in vitro and pathogenicity in vivo.

Streptococcus pneumoniae, the most common cause of bacterial pneumonia, has developed a wide range of virulence factors to evade the immune system of which the polysaccharide capsule is the most important one. Formation of this capsule is dependent on the cps gene locus, but also involves other genes-like galU. The pyrophosphorylase encoded by galU plays a role in the UDP-glucose metabolism of prokaryotes and is required for the biosynthesis of capsular polysaccharides. In this paper, the effect of a galU mutation leading to a dysfunctional UDP-glucose pyrophosphorylase (UDPG:PP) on in vitro biofilm biomass, adherence to lung epithelial cells and macrophage phagocytosis is studied. Last, in vivo virulence using a Galleria mellonella model has been studied. We show that the mutation improves streptococcal adherence to epithelial cells and macrophage phagocytosis in vitro, while there is no definitive correlation on biofilm formation between parent and mutant strains. Moreover, in vivo virulence is attenuated for all mutated strains. Together, these results demonstrate that a galU mutation in S. pneumoniae influences host cell interactions in vitro and in vivo and can strongly influence the outcome of a streptococcal infection. As such, UDPG:PP is worth investigating further as a potential drug target.

Synthesis and anti-tubercular activity of N(2)-arylbenzo[g]isoquinoline-5,10-dione-3-iminium bromides.

Tuberculosis has remained a challenge for medicinal chemists worldwide. In the framework of a collaborative program to identify and evaluate novel antitubercular candidate compounds, the biological properties of benzo[g]isoquinoline-5,10-diones have been found to be very promising. In this paper we have further expanded the library by incorporation of an amidinium moiety into the benzo[g]isoquinoline-5,10-dione scaffold. The presence of this functional group also increased the solubility of the quinones in polar solvents. To this purpose N(2)-arylbenzo[g]isoquinoline-5,10-dione-3-iminium bromides were synthesized in a straightforward way by means of a reaction of anilines with 2-(bromomethyl)-3-(cyanomethyl)-1,4-dimethoxynaphthalene. Following the biological evaluation, N(2)-(4-chlorophenyl)-5,10-dioxobenzo[g]isoquinoline-3(2H)-iminium bromide (MIC = 1.16 µM, CC50 = 28.51 µM, SI = 24.58) was selected as the most promising representative. Apart from the nano-molar anti-mycobacterial activity, the compound was able to target intracellular residing Mycobacterium tuberculosis and the susceptibility of a multi-drug-resistant strain towards the compound was confirmed.

1,4-diarylpiperazines and analogs as anti-tubercular agents: synthesis and biological evaluation.

Despite progress in modern chemotherapy to combat tuberculosis, the causative pathogen Mycobacterium tuberculosis (M.tb.) is far from eradicated. Bacillary resistance to anti-mycobacterial agents, bacillary persistence and human immunodeficiency virus (HIV) co-infection hamper current drug treatment to completely cure the infection, generating a constant demand for novel drug candidates to tackle these problems. A small library of novel heterocyclic compounds was screened in a rapid luminometric in vitro assay against the laboratory M.tb. strain H37Rv. A group of amidines was found to have the highest potency and was further evaluated for acute toxicity against C3A hepatocytes. Next, the most promising compounds were evaluated for activity against a multi-drug resistant clinical isolate. The group of amidines was also tested for their ability to kill intracellular M.tb. residing in mouse J774A.1 macrophages. Finally, we report on a correlation between the structural differences of the compounds and their anti-mycobacterial activity.