Virulence of Streptococcus pneumoniae serotype 6C in experimental otitis media

Increases in colonization with serotypes of Streptococcus pneumoniae not contained within the 7-valent pneumococcal conjugate vaccine (PCV) have been reported among children following introduction. Serotype 6C has emerged as prevalent in nasopharyngeal colonization and acute otitis media (AOM), though it is uncommonly recovered from children with invasive pneumococcal disease. Vaccine serotypes within PCV7 have been replaced by nonvaccine serotypes without significant changes in the overall carriage rate. We hypothesize 1) that serotypes vary in their ability to evade host defenses and establish AOM following colonization and 2) the observed reduction in pneumococcal otitis results from a reduced disease potential by some ‘replacement serotypes’. We compared the capacity of S. pneumoniae serotypes 6C and 19A to produce experimental otitis media (EOM) in a chinchilla model. The proportion of chinchillas that developed culture positive EOM and density of middle ear infection was evaluated. EOM was found in 28/82 (34%) ears challenged with 6C compared to 13/18(72.2%) with 19A [p = 0.0003]. When disease due to 6C did occur, it was characterized by low-density infection. Our findings demonstrate that challenge with serotype 6C results in EOM less frequently than 19A. These data support the need for greater knowledge regarding differences among serotypes to produce AOM.     

N-hydroxyethyl-piperidine and -pyrrolidine homoazasugars: preparation and evaluation of glycosidase inhibitory activity

An efficient and practical strategy for the synthesis of N-hydroxyethyl-1-deoxy-homonojirimycins 4 and 5 and N-hydroxyethyl-pyrrolidine homoazasugars 6 and 7 with full stereocontrol is being reported. The key step involved is the intermolecular Michael addition of benzylamine to D-glucose derived alpha,beta-unsaturated ester 8 followed by N-alkylation with ethyl bromoacetate. Reduction with LAH, acetylation, hydrogenation and protection with -Cbz group afforded compounds 14a and 14b. Removal of 1,2-acetonide functionality, hydrogenation and deacetylation afforded N-hydroxyethyl-D-gluco-1-deoxyhomonojirimycin (4) and N-hydroxyethyl-L-ido-1-deoxyhomonojirimycin (5), respectively. Compounds 14a and 14b on acetylation followed by removal of 1,2-acetonide functionality, sodium metaperiodate oxidation, hydrogenation and deacetylation gave 1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-D-arabino-hexitol (6) and 1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-L-xylo-hexitol (7), respectively. The glycosidase inhibition activity of compounds 4, 5, 6, 7, 16a and 16b was evaluated using sweet almond seed as a rich source of different glycosidases.     

1-Aza-sugars from D-glucose. Preparation of 1-deoxy-5-dehydroxymethyl-nojirimycin, its analogues and evaluation of glycosidase inhibitory activity

D-glucose derived pentodialdoses 11a-c on reduction followed by tosylation, azide displacement, hydrogenation and protection with -Cbz group gave N-Cbz protected compounds 14a-c, respectively, which on removal of 1,2-acetonide functionality and hydrogenation afforded corresponding 1-aza-sugars 3, 9 and 10 in good overall yields. The glycosidase inhibition activity of these 1-aza-sugars was tested with sweet almond as a rich source of different glycosidases.     

Biology and interactions of two distinct monopartite begomoviruses and betasatellites associated with radish leaf curl disease in India

Background

Emerging whitefly transmitted begomoviruses are major pathogens of vegetable and fibre crops throughout the world, particularly in tropical and sub-tropical regions. Mutation, pseudorecombination and recombination are driving forces for the emergence and evolution of new crop-infecting begomoviruses. Leaf curl disease of field grown radish plants was noticed in Varanasi and Pataudi region of northern India. We have identified and characterized two distinct monopartite begomoviruses and associated beta satellite DNA causing leaf curl disease of radish (Raphanus sativus) in India.

Results

We demonstrate that RaLCD is caused by a complex of two Old World begomoviruses and their associated betasatellites. Radish leaf curl virus-Varanasi is identified as a new recombinant species, Radish leaf curl virus (RaLCV) sharing maximum nucleotide identity of 87.7% with Tomato leaf curl Bangladesh virus-[Bangladesh:2] (Accession number AF188481) while the virus causing radish leaf curl disease-Pataudi is an isolate of Croton yellow vein mosaic virus-[India] (CYVMV-IN) (Accession number AJ507777) sharing 95.8% nucleotide identity. Further, RDP analysis revealed that the RaLCV has a hybrid genome, a putative recombinant between Euphorbia leaf curl virus and Papaya leaf curl virus. Cloned DNA of either RaLCV or CYVMV induced mild leaf curl symptoms in radish plants. However, when these clones (RaLCV or CYVMV) were individually co-inoculated with their associated cloned DNA betasatellite, symptom severity and viral DNA levels were increased in radish plants and induced typical RaLCD symptoms. To further extend these studies, we carried out an investigation of the interaction of these radish-infecting begomoviruses and their associated satellite, with two tomato infecting begomoviruses (Tomato leaf curl Gujarat virus and Tomato leaf curl New Delhi virus). Both of the tomato-infecting begomoviruses showed a contrasting and differential interaction with DNA satellites, not only in the capacity to interact with these molecules but also in the modulation of symptom phenotypes by the satellites.

Conclusion

This is the first report and experimental demonstration of Koch's postulate for begomoviruses associated with radish leaf curl disease. Further observations also provide direct evidence of lateral movement of weed infecting begomovirus in the cultivated crops and the present study also suggests that the exchange of betasatellites with other begomoviruses would create a new disease complex posing a serious threat to crop production.     

Production of Gibberellin-like substances by an autotrophically grown Thiobacillus

Summary Gibberellin-like substances were present in cell-free culture medium of autotrophically grown Thiobacillus novellus. Dwarf-pea and cucumber-hypocotyl bioassays indicate presence of two gibberellin-like compounds.