A combination of silver nanoparticles and visible blue light enhances the antibacterial efficacy of ineffective antibiotics against methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (MRSA)

Background

Silver nanoparticles (AgNPs) are potential antimicrobials agents, which can be considered as an alternative to antibiotics for the treatment of infections caused by multi-drug resistant bacteria. The antimicrobial effects of double and triple combinations of AgNPs, visible blue light, and the conventional antibiotics amoxicillin, azithromycin, clarithromycin, linezolid, and vancomycin, against ten clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were investigated.

Methods

The antimicrobial activity of AgNPs, applied in combination with blue light, against selected isolates of MRSA was investigated at 1/2–1/128 of its minimal inhibitory concentration (MIC) in 24-well plates. The wells were exposed to blue light source at 460 nm and 250 mW for 1 h using a photon emitting diode. Samples were taken at different time intervals, and viable bacterial counts were determined. The double combinations of AgNPs and each of the antibiotics were assessed by the checkerboard method. The killing assay was used to test possible synergistic effects when blue light was further combined to AgNPs and each antibiotic at a time against selected isolates of MRSA.

Results

The bactericidal activity of AgNPs, at sub-MIC, and blue light was significantly (p < 0.001) enhanced when both agents were applied in combination compared to each agent alone. Similarly, synergistic interactions were observed when AgNPs were combined with amoxicillin, azithromycin, clarithromycin or linezolid in 30–40 % of the double combinations with no observed antagonistic interaction against the tested isolates. Combination of the AgNPs with vancomycin did not result in enhanced killing against all isolates tested. The antimicrobial activity against MRSA isolates was significantly enhanced in triple combinations of AgNPs, blue light and antibiotic, compared to treatments involving one or two agents. The bactericidal activities were highest when azithromycin or clarithromycin was included in the triple therapy compared to the other antibiotics tested.

Conclusions

A new strategy can be used to combat serious infections caused by MRSA by combining AgNPs, blue light, and antibiotics. This triple therapy may include antibiotics, which have been proven to be ineffective against MRSA. The suggested approach would be useful to face the fast-growing drug-resistance with the slow development of new antimicrobial agents, and to preserve last resort antibiotics such as vancomycin.

     

The genetic basis of spectral reflectance indices in drought-stressed wheat

Drought imposes a major constraint over the productivity of wheat, particularly in arid and semi-arid production zones. Here, the genetic basis of spectral reflectance indices was investigated in drought-stressed wheat by comparing, under two contrasting moisture regimes, the performance of an F₆ recombinant inbred line (RIL) population bred from a cross between the drought tolerant cultivar Pavon76 and the sensitive cultivar Yecora Rojo. The parents and RILs were genotyped with respect to both a set of microsatellite (SSR) loci and a number of known drought-responsive genes. In all, 28 quantitative trait loci (QTL) controlling dry weight per plant, water content of the above-ground biomass, leaf water potential, canopy temperature, and spectral reflectance indices traits were identified. The loci were distributed over 11 chromosomes, belonging to each of the three wheat sub-genomes. There were important location-flanking markers Barc109 and Barac4 on chromosome 5B relating to dry weight per plant accumulation under the limited irrigation regime. The same region-harbored QTL associated with leaf water potential, canopy temperature, and ratio index under the limited irrigation regime. Linkage between the known drought-responsive genes and aspects of the drought response was established. Some of QTL were of substantial enough effect for their linked markers to be likely usable for the marker-assisted breeding of drought tolerance in wheat.     

Association of IL‐37 gene polymorphisms with susceptibility to tuberculosis in Saudi subjects

Tuberculosis (TB) is one of the most common infectious diseases worldwide. IL‐37, a novel member of the IL‐1 family, has anti‐inflammatory activity. Various cytokine genes polymorphisms are reportedly associated with susceptibility to TB infection. However, an association between genetic variations in the IL‐37 gene and susceptibility to TB infection has not been investigated. The aim of this case‐control study was therefore to identify such an association in Saudi subjects, in which five single‐nucleotide polymorphisms (SNPs) in the IL‐37 gene were assessed. Serum concentrations of IL‐37 were evaluated using ELISA, and genetic variants genotyped by multiplex PCR and ligase detection reaction. It was found that the C/C genotype of rs2723176 (–6962 A/C) occurs significantly more frequently in patients with active TB and that the C allele of this SNP is associated with TB. In addition, the C allele of rs2723176 SNP was associated with high circulating concentrations of IL‐37. However, the genotype and allele frequency of the other four SNPs (rs3811046, rs3811047, rs2723186 and rs2723187) were not significantly associated with TB infection. In conclusion, the present data suggest that rs2723176 SNP of IL‐37 is involved in the development of TB infection. Furthermore, high circulating concentrations of IL‐37 may have a negative effect on protective immunity against TB infection.     

Phylogeography of the marbled crab Pachygrapsus marmoratus (Decapoda,Grapsidae) along part of the African Mediterranean coast reveals genetic homogeneity across the Siculo-Tunisian Strait versus heterogeneity across the Gibraltar Strait

We investigate the influence of previously postulated biogeographic barriers in the Mediterranean Sea on the population genetic structure of a highly dispersive and continuously distributed coastal species. In particular, we examine nuclear and mitochondrial genetic variation in the marbled crab, Pachygrapsus marmoratus, across part of the African Mediterranean coast in order to assess the influence of the Siculo-Tunisian Strait on its population genetic structure. Four polymorphic microsatellite loci were genotyped for 110 individuals, collected from eight locations covering parts of the Algerian, Tunisian and Libyan coasts. In addition, mtDNA corresponding to the Cox1 gene was sequenced for 80 samples. The corresponding results show contrasting patterns of genetic differentiation. While mtDNA results revealed a homogeneous haplotype composition in our study area, microsatellite data depicted genetic differentiation among populations, but not associated with any geographic barrier. This pattern, already recorded for this species from different geographic regions, may hint at the involvement of a complex series of abiotic and biotic factors in determining genetic structure. Demographic history reconstruction, inferred from mtDNA data, supports demographic and spatial expansion for the North African metapopulation dating back to the Mid-Pleistocene and following an historical bottleneck. Comparison of these African mitochondrial sequences with new sequences from a Turkish population and previously published sequences revealed a weak but significant separation of Atlantic and Mediterranean populations across the Gibraltar Strait, which was not recorded in previous studies of this grapsid species.     

Complexes of polyadenylic acid and the methyl esters of amino acids

This report includes studies of the binding of the methyl esters of a series of amino acids to polyadenylic acid. The principal data were obtained using proton NMR; however, some additional data were obtained through the study of insoluble complexes and through ultraviolet spectroscopy. The binding constants are in the order Phe>Ile?Leu>Val>Gly, and show a direct correlation with the hydrophobicities of the amino acids. In most cases they are essentially double the binding constants found by Reuben and Polk (1980) for monomeric AMP. All of these amino acids, except Gly, have A as the middle letter of their anticodons, and Phe is the only one with XAA as its only anticodon. It has the anticodon richest in A and has the highest binding constant for A. These results, coupled with other data, continue to support a model of the origin of the code which is based on weak, but selective affinities between amino acids and their anticodons.     

ACE inhibitors hypothesis generation for selective design,synthesis and biological evaluation of 3-mercapto-2-methyl-propanoyl-pyrrolidine-3-imine derivatives as antihypertensive agents

A series of new 3-mercapto-2-methyl-propanoyl-pyrrolidine derivatives (V, VIa–e) were designed. A new validated ACE inhibitors pharmacophore model (hypothesis) was generated for the first time in this research from the biologically active (frozen) conformation of Lisinopril–Human ACE complex that was downloaded from PDB, using stepwise technique of CATALYST modules. The molecular modeling compare–fit study of the designed molecules (V, VIa–e), with such ACE inhibitors hypothesis was fulfilled, and several compounds showed significant high simulation fit values. The compounds with high fit values were synthesized and biologically evaluated in vivo as hypotensive agents. It appears that the in vivo hypotensive activity of compounds V, VIa, VIb, and VIe was consistent with their molecular modeling results, and compound VIe showed the highest activity in comparison to Captopril.     

Phylogeny of six oligohymenophoreans (Protozoa, Ciliophora) inferred from small subunit rRNA gene sequences

The small subunit rRNA (SSrRNA) genes of six marine oligohymenophoreans, namely Uronemella filificum , Schizocalyptra sp.-WYG07060701, Schizocalyptra aeschtae , Pleuronema sinica , P. czapikae and Paratetrahymena sp., were sequenced. Phylogenetic trees were constructed with four different methods to assess the inter- and intrageneric relationships among the scuticociliates and the phylogenetic assignment of the order Loxocephalida. The SSrRNA phylogeny indicates that: (i) Paratetrahymena is most closely related to Cardiostomatella ; (ii) the order Loxocephalida and the family Uronematidae both appear to be polyphyletic; (iii) the order Philasterida is a well-defined taxon; (iv) Cyclidium porcatum falls outside the order Pleuronematida in all analyses; (v) the validity of the genus Uronemella is confirmed; (vi) Schizocalyptra is a member of the family Pleuronematidae. Furthermore, the predicted secondary structures of the variable region 4 of the SSrRNA gene sequences show that the size of the terminal bulge in Helix E23–7 is probably different for the orders Philasterida and Pleuronematida. Also, compared to Uronema and Homalogastra , Uronemella has distinct patterns in Helices E23–1, E23–7, E23–8 and E23–9.     

Applying Ligands Profiling Using Multiple Extended Electron Distribution Based Field Templates and Feature Trees Similarity Searching in the Discovery of New Generation of Urea-Based Antineoplastic Kinase Inhibitors

This study provides a comprehensive computational procedure for the discovery of novel urea-based antineoplastic kinase inhibitors while focusing on diversification of both chemotype and selectivity pattern. It presents a systematic structural analysis of the different binding motifs of urea-based kinase inhibitors and the corresponding configurations of the kinase enzymes. The computational model depends on simultaneous application of two protocols. The first protocol applies multiple consecutive validated virtual screening filters including SMARTS, support vector-machine model (ROC = 0.98), Bayesian model (ROC = 0.86) and structure-based pharmacophore filters based on urea-based kinase inhibitors complexes retrieved from literature. This is followed by hits profiling against different extended electron distribution (XED) based field templates representing different kinase targets. The second protocol enables cancericidal activity verification by using the algorithm of feature trees (Ftrees) similarity searching against NCI database. Being a proof-of-concept study, this combined procedure was experimentally validated by its utilization in developing a novel series of urea-based derivatives of strong anticancer activity. This new series is based on 3-benzylbenzo[d]thiazol-2(3H)-one scaffold which has interesting chemical feasibility and wide diversification capability. Antineoplastic activity of this series was assayed in vitro against NCI 60 tumor-cell lines showing very strong inhibition of GI₅₀ as low as 0.9 uM. Additionally, its mechanism was unleashed using KINEX™ protein kinase microarray-based small molecule inhibitor profiling platform and cell cycle analysis showing a peculiar selectivity pattern against Zap70, c-src, Mink1, csk and MeKK2 kinases. Interestingly, it showed activity on syk kinase confirming the recent studies finding of the high activity of diphenyl urea containing compounds against this kinase. Allover, the new series, which is based on a new kinase scaffold with interesting chemical diversification capabilities, showed that it exhibits its “emergent” properties by perturbing multiple unexplored kinase pathways.