Infectious diseases remain the world's top contributors to death and disability, and, with recent outbreaks of Zika virus infections there has been an urgency for simple, sensitive and easily translatable point-of-care tests. Here we demonstrate a novel point-of-care platform to diagnose infectious diseases from whole blood samples. A microfluidic platform performs minimal sample processing in a user-friendly diagnostics card followed by real-time reverse-transcription loop-mediated isothermal amplification (RT-LAMP) on the same card with pre-dried primers specific to viral targets. Our point-of-care platform uses a commercial smartphone to acquire real-time images of the amplification reaction and displays a visual read-out of the assay. We apply this system to detect closely related Zika, Dengue (types 1 and 3) and Chikungunya virus infections from whole blood on the same pre-printed chip with high specificity and clinically relevant sensitivity. Limit of detection of 1.56e5 PFU/mL of Zika virus from whole blood was achieved through our platform. With the ability to quantitate the target nucleic acid, this platform can also perform point-of-care patient surveillance for pathogen load or select biomarkers in whole blood.
Genetic studies of Phialophora gregata f. sp. sojae, the causal agent of brown stem rot (BSR) of soybean, have led to the development of species-specific primers capable of separating isolates into two distinct genotypes, A and B. To determine whether genotypic characterization could be related to differences in BSR symptom expression, five soybean cultivars, Pioneer 9234, Corsoy 79 (both BSR susceptible), Williams, BSR 101, and Jack and plant introduction (PI) 437970 (all BSR resistant), were inoculated with a total of 27 isolates of each genotype in four greenhouse experiments conducted from February to November 2000. BSR severity was calculated as the percentage of symptomatic foliar, internal stem, and internal root tissue. Genotype A isolates caused significantly more severe (P < 0.0001) BSR foliar symptoms than genotype B isolates on Pioneer 9234, Corsoy 79, Williams, and BSR 101, while Jack and PI 437970 expressed minimal foliar symptoms regardless of isolate genotype. Overall, internal stem symptoms caused by genotype A isolates were more severe than those caused by genotype B isolates on Pioneer 9234, Corsoy 79, Williams, and BSR 101. Conversely, Jack and PI 437970 did not differ significantly in severity of stem symptoms when inoculated with isolates of genotype A or B. Internal root symptoms for genotype A isolates were generally more severe than for genotype B isolates on all soybean genotypes tested. Our data strongly suggest that A and B genotypes of P. gregata f. sp. sojae differ in the severity of symptoms they cause, and that these genotypes correspond to the Type I (defoliating) and Type II (nondefoliating), respectively, pathotypes previously proposed for this vascular pathogen of soybean.
Phialophora gregata f.sp. sojae , a soilborne vascular pathogen causing brown stem rot of soybean, has been divided into A and B populations based on variation in the intergenic spacer region of nuclear rDNA (rDNA marker). The A and B populations correlate with defoliating and nondefoliating pathotypes, respectively. In this study, eight additional polymorphic anonymous marker loci (five inter simple sequence repeat loci and three long-primer random amplified polymorphic DNA loci) were identified and applied to a total of 189 isolates. Alleles of these eight loci were invariant within, but different between the A and B populations, providing further evidence that the rDNA marker identifies genetically distinct populations. The two populations were sympatric, residing not only in the same field, but also in the same plants under field conditions. Representative strains of the two populations, when used individually in inoculations, infected both resistant cv. Bell and susceptible cv. Sturdy. However, when the same representatives of the two populations were mixed in a 1 : 1 ratio and used as a mixed inoculum in a competitive bioassay, differential cultivar preference was revealed using PCR detection of populations in infected plants. Population A was detected significantly more often (18 out of 24 plants) in the susceptible cv. Sturdy, whereas population B was detected significantly more often (17 out of 24 plants) in the resistant cv. Bell, corroborating earlier field studies. This is the first controlled experiment to demonstrate a differential host preference of P. gregata f.sp. sojae toward different cultivars of the same host species. Unification of terminologies used in P. gregata f.sp. sojae is discussed.
A novel random laser, integrating a passive optical fiber with a phase separated aluminosilicate core–silica cladding as the feedback medium, is proposed and presented. The core exhibits greatly enhanced Rayleigh scattering, therefore requiring a significantly reduced length of scattering fiber (4 m) for lasing. With a Yb-doped fiber as the gain medium, the fiber laser operates at 1050 nm with low threshold power and possesses an output that can be amplified through conventional means. Furthermore, the laser was found to have a high degree of spatial coherence, spectral broadening with increasing input power, and temporal spectral variation. The facile setup and results herein pave the way for further study and applications based on low threshold random fiber lasers.
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