ABSTRACT
OBJECTIVES: Rapid and accurate sexually transmitted infection diagnosis can reduce onward transmission and improve treatment efficacy. We evaluated the accuracy of a 15-minute run-time recombinase polymerase amplification-based prototype point-of-care test (TwistDx) for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG). METHODS: Prospective, multicentre study of symptomatic and asymptomatic patients attending three English sexual health clinics. Research samples provided were additional self-collected vulvovaginal swab (SCVS) (female participants) and first-catch urine (FCU) aliquot (female and male participants). Samples were processed blind to the comparator (routine clinic CT/NG nucleic acid amplification test (NAAT)) results. Discrepancies were resolved using Cepheid CT/NG GeneXpert. RESULTS: Both recombinase polymerase amplification and routine clinic NAAT results were available for 392 male and 395 female participants. CT positivity was 8.9% (35/392) (male FCU), 7.3% (29/395) (female FCU) and 7.1% (28/395) (SCVS). Corresponding NG positivity was 3.1% (12/392), 0.8% (3/395) and 0.8% (3/395). Specificity and positive predictive values were 100% for all sample types and both organisms, except male CT FCU (99.7% specificity (95% confidence interval (CI) 98.4-100.0; 356/357), 97.1% positive predictive value (95% CI 84.7-99.9; 33/34)). For CT, sensitivity was ≥94.3% for FCU and SCVS. CT sensitivity for female FCU was higher (100%; 95% CI, 88.1-100; 29/29) than for SCVS (96.4%; 95% CI, 81.7-99.9; 27/28). NG sensitivity and negative predictive values were 100% in FCU (male and female). CONCLUSIONS: This prototype test has excellent performance characteristics, comparable to currently used NAATs, and fulfils several World Health Organization ASSURED criteria. Its rapidity without loss of performance suggests that once further developed and commercialized, this test could positively affect clinical practice and public health.
Subject(s)
Chlamydia trachomatis/isolation & purification , Neisseria gonorrhoeae/isolation & purification , Nucleic Acid Amplification Techniques/standards , Point-of-Care Testing , Sexually Transmitted Diseases/diagnosis , Adolescent , Adult , Aged , Ambulatory Care Facilities , Cross-Sectional Studies , Female , Humans , Male , Middle Aged , Prospective Studies , Sensitivity and Specificity , Specimen Handling , Young AdultABSTRACT
Body structures of Drosophila develop through transient developmental units, termed parasegments, with boundaries lying between the adjacent expression domains of wingless and engrailed. Parasegments are transformed into the morphologically distinct segments that remain fixed. Segment borders are established adjacent and posterior to each engrailed domain. They are marked by single rows of stripe expressing cells that develop into epidermal muscle attachment sites. We show that the positioning of these cells is achieved through repression of Hedgehog signal transduction by Wingless signaling at the parasegment boundary. The nuclear mediators of the two signaling pathways, Cubitus interruptus and Pangolin, function as activator and symmetry-breaking repressor of stripe expression, respectively.
Subject(s)
Drosophila Proteins , Drosophila/growth & development , Drosophila/physiology , Insect Proteins/physiology , Proto-Oncogene Proteins/physiology , Animals , Animals, Genetically Modified , Base Sequence , DNA/genetics , DNA Primers/genetics , Drosophila/genetics , Gene Expression Regulation, Developmental , Genes, Insect , Genes, Reporter , Hedgehog Proteins , Insect Proteins/genetics , Proto-Oncogene Proteins/genetics , Signal Transduction , Transcriptional Activation , Wnt1 ProteinABSTRACT
GTP hydrolysis by elongation factor Tu (EF-Tu) on the ribosome is induced by codon recognition. The mechanism by which a signal is transmitted from the site of codon-anticodon interaction in the decoding center of the 30S ribosomal subunit to the site of EF-Tu binding on the 50S subunit is not known. Here we examine the role of the tRNA in this process. We have used two RNA fragments, one which contains the anticodon and D hairpin domains (ACD oligomer) derived from tRNA(Phe) and the second which comprises the acceptor stem and T hairpin domains derived from tRNA(Ala) (AST oligomer) that aminoacylates with alanine and forms a ternary complex with EF-Tu. GTP. While the ACD oligomer and the ternary complex containing the Ala-AST oligomer interact with the 30S and 50S A site, respectively, no rapid GTP hydrolysis was observed when both were bound simultaneously. The presence of paromomycin, an aminoglycoside antibiotic that binds to the decoding site and stabilizes codon-anticodon interaction in unfavorable coding situations, did not increase the rate of GTP hydrolysis. These results suggest that codon recognition as such is not sufficient for GTPase activation and that an intact tRNA molecule is required for transmitting the signal created by codon recognition to EF-Tu.
