Analytical performances of a point-of-care loop-mediated isothermal amplification assay to detect Group B Streptococcus in intrapartum pregnant women living in the Democratic Republic of the Congo.

OBJECTIVES: Group B Streptococcus (GBS) is the leading infectious cause of stillbirth and neonatal morbidity and mortality in sub-Saharan Africa. METHODS: Vaginal and rectovaginal swab samples were obtained from 274 intrapartum pregnant women in the Democratic Republic of the Congo to be analyzed for GBS DNA detection in parallel by the point-of-care BIOSYNEX AMPLIFLASH® GBS assay (Biosynex SA, Illkirch-Graffenstaden, France) and by reference quantitative polymerase chain reaction (qPCR). RESULTS: Rectovaginal swabbing, nearly two-fold more positive for GBS than vaginal swabbing alone, showed a high prevalence of GBS DNA positivity in 20.1% of eligible intrapartum pregnant women. In the event of significant bacterial carriage (i.e., cycle threshold ≤33 by reference qPCR), the AMPLIFLASH® GBS assay with rectovaginal swabbing showed high sensitivity (98.1%) and specificity (100.0%) for GBS DNA detection, with excellent concordance, reliability, and accuracy with the reference qPCR, and positive predictive values and negative predictive values above 99.0%. CONCLUSIONS: The study demonstrates a high rate of female rectogenital GBS colonization in pregnant Congolese women. The AMPLIFLASH® GBS assay harbored excellent analytical performances in the field, which makes it suitable to be used as point-of-care molecular assay in various hospital and non-hospital settings where rapid diagnosis of GBS is necessary.

Analytical performance of the point-of-care BIOSYNEX COVID-19 Ag BSS for the detection of SARS-CoV-2 nucleocapsid protein in nasopharyngeal swabs: a prospective field evaluation during the COVID-19 third wave in France.

BACKGROUND: The accuracy and reliability of rapid diagnostic tests are critical for monitoring and diagnosing SARS-CoV-2 infection in the general population. This study aimed to evaluate the analytical performance of the BIOSYNEX COVID-19 Ag BSS (Biosynex Swiss SA, Fribourg, Switzerland) antigen rapid diagnostic test (BIOSYNEX Ag-RDT), which targets the SARS-CoV-2 N-nucleocapsid protein for the diagnosis of COVID-19. The Ag-RDT was compared with a real-time RT-PCR (rtRT-PCR) as gold standard for performance measurement. METHODS: Two nasopharyngeal flocked swabs were prospectively collected simultaneously in March and April 2021 from 967 individuals aged ≥ 18 years tested for SARS-CoV-2 in two private laboratories, Paris, France. RESULTS: Overall, the Ag-RDT demonstrated high sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 81.8%, 99.6%, 96.6%, and 97.5%, respectively. The agreement (97.0%), reliability assessed using Cohen's κ-coefficient (0.87), and accuracy evaluated using Youden index (J) (81.6%) in detecting SARS-CoV-2 were high. The analytical performance of the Ag-RDT remained high when there was significant viral shedding (i.e., N gene Ct values ≤ 33 on reference RT-PCR). The sensitivity was only 55.2% in case of low or very low viral excretion (Ct > 33). CONCLUSIONS: The BIOSYNEX Ag-RDT is a promising, potentially simple diagnostic tool, especially in symptomatic COVID-19 patients with substantial viral excretion in the nasopharynx.

Evaluation of the Practicability of Biosynex Antigen Self-Test COVID-19 AG+ for the Detection of SARS-CoV-2 Nucleocapsid Protein from Self-Collected Nasal Mid-Turbinate Secretions in the General Public in France.

Due to their ease-of-use, lateral flow assay SARS-CoV-2 antigen-detecting rapid diagnostic tests could be suitable candidates for antigen-detecting rapid diagnostic self-test (Ag-RDST). We evaluated the practicability of the Ag-RDST BIOSYNEX Antigen Self-Test COVID-19 Ag+ (Biosynex Swiss SA, Freiburg, Switzerland), using self-collected nasal secretions from the turbinate medium (NMT), in 106 prospectively included adult volunteers living in Paris, France. The majority of the participants correctly understood the instructions for use (94.4%; 95% confidence interval (CI): 88.3-97.4), showing a great ability to perform the entire self-test procedure to obtain a valid and interpretable result (100%; 95% CI: 96.5-100), and demonstrated the ability to correctly interpret test results (96.2%; 95% CI: 94.2-97.5) with a high level of general satisfaction. About one in eight participants (# 15%) needed verbal help to perform or interpret the test, and only 3.8% of test results were misinterpreted. By reference to multiplex real-time RT-PCR, the Ag-RDST showed 90.9% and 100% sensitivity and specificity, respectively, and high agreement (98.1%), reliability (0.94), and accuracy (90.9%) to detect SARS-CoV-2 antigen. Taken together, our study demonstrates the high usability and accuracy of BIOSYNEX Antigen Self-Test COVID-19 Ag+ for supervised self-collected NMT sampling in an unselected adult population living in France.

Performances of the VitaPCR™ SARS-CoV-2 Assay during the second wave of the COVID-19 epidemic in France.

To assess the practicability (usability and satisfaction) and analytical performances of the VitaPCR™ SARS-CoV-2 Assay (Credo Diagnostics Biomedical Pte. Ltd.), a rapid point-of-care nucleic acid amplification test (NAAT), by reference to real-time reverse-transcription polymerase chain reaction (rRT-PCR) for respiratory viruses. The practicability of the VitaPCR™ Assay and Instrument was assessed from usability evaluation and a satisfaction questionnaire. Nasopharyngeal swabs were collected from 239 patients with coronavirus disease 2019 (COVID-19)-like illness during the second epidemic wave, in Paris, France. Overall, the usability of the VitaPCR™ Instrument was high. The satisfaction questionnaire indicated a high appreciation of the VitaPCR™ NAAT mainly for the short duration of analysis in only 20 min. A total of 140 and 99 samples were positive and negative for SARS-CoV-2 RNA by rRT-PCR, respectively. In the event of significant viral load (i.e., N gene Ct values 33), the platform's analytical performances dropped significantly, with lower sensitivity, concordance, and accuracy, while its specificity remained high. The VitaPCR™ SARS-CoV-2 Assay is an accurate rapid point-of-care NAAT, suitable for clinical practice for the rapid diagnosis of COVID-19, especially in patients with COVID-19-suspected symptoms.

Capillary whole-blood IgG-IgM COVID-19 self-test as a serological screening tool for SARS-CoV-2 infection adapted to the general public.

The practicability of a prototype capillary whole-blood IgG-IgM COVID-19 self-test (Exacto® COVID-19 self-test, Biosynex Swiss SA, Freiburg, Switzerland) as a serological screening tool for SARS-CoV-2 infection adapted to the general public was evaluated in a cross-sectional, general adult population study performed between April and May 2020 in Strasbourg, France, consisting of face-to-face, paper-based, semi-structured, and self-administrated questionnaires. Practicability was defined as the correct use of the self-test and the correct interpretation of the result. The correct use of self-test was conditioned by the presence of the control band after 15-min of migration. The correct interpretation of the tests was defined by the percent agreement between the tests results read and interpret by the participants compared to the expected results coded by the numbers and verified by trained observers. A total of 167 participants (52.7% female; median age, 35.8 years; 82% with post-graduate level) were enrolled, including 83 and 84 for usability and test results interpretation substudies, respectively. All participants (100%; 95% CI: 95.6-100) correctly used the self-test. However, 12 (14.5%; 95% CI: 8.5-23.6) asked for verbal help. The percent agreement between the tests results read and interpret by the participants compared to the expected results was 98.5% (95% CI: 96.5-99.4). However, misinterpretation occurred in only 2.3% of positive and 1.2% of invalid test results. Finally, all (100%) participants found that performing the COVID-19 self-test was easy; and 98.8% found the interpretation of the self-test results easy. Taken together, these pilot observations demonstrated for the first-time, high practicability and satisfaction of COVID-19 self-testing for serological IgG and IgM immune status, indicating its potential for use by the general public to complete the arsenal of available SARS-CoV-2 serological assays in the urgent context of the COVID-19 epidemic.

Comparative study and improvement of current cell micro-patterning techniques.

The original micropatterning technique on gold, although very efficient, is not accessible to most biology labs and is not compatible with their techniques for image acquisition. Other solutions have been developed on silanized glass coverslips. These methods are still hardly accessible to biology labs and do not provide sufficient reproducibility to become incorporated in routine biological protocols. Here, we analyzed cell behavior on micro-patterns produced by various alternative techniques. Distinct cell types displayed different behavior on micropatterns, while some were easily constrained by the patterns others escaped or ripped off the patterned adhesion molecules. We report methods to overcome some of these limitations on glass coverslips and on plastic dishes which are compatible with our experimental biological applications. Finally, we present a new method based on UV crosslinking of adhesion proteins with benzophenone to easily and rapidly produce highly reproducible micropatterns without the use of a microfabricated elastomeric stamp.

Importance of competition mechanisms in successive invasions by polyphagous tephritids in La Reunion.

Understanding the strength and modes of interspecific interactions between introduced and resident species (native or previously introduced) is necessary to predict invasion success. We evaluated different mechanisms of interspecific competition among four species of polyphagous fruit flies (Diptera: Tephritidae) from the island of La Reunion: one endemic species, Ceratitis catoirii, and three exotic species, C. capitata, C. rosa, and Bactrocera zonata, that have successively invaded the island. Larval competition experiments, i.e., co-infestations of the same fruit, and behavioral interference experiments measuring the ability of one female to displace another from a fruit, were performed among all pairs of the four species. We observed asymmetric and hierarchical interactions among species in both larval and adult interference competition. In agreement with the hypothesis that invasion is competition-limited, the competitive hierarchy coincided with the temporal sequence of establishment on the island, i.e., each newly established species tended to be competitively dominant over previously established ones.

Miniaturization and validation of a sensitive multiparametric cell-based assay for the concomitant detection of microtubule-destabilizing and microtubule-stabilizing agents.

The authors describe a cell-based assay for anti-microtubule compounds suitable for automation. This assay allows the identification, in a single screening campaign, of both microtubule-destabilizing and microtubule-stabilizing agents. Its rationale is based on the substrate properties of the tubulin-modifying enzymes involved in the tubulin tyrosination cycle. This cycle involves the removal of the C-terminal tyrosine of the tubulin alpha-subunit by an ill-defined tubulin carboxypeptidase and its readdition by tubulin tyrosine ligase. Because of the substrate properties of these enzymes, dynamic microtubules, sensitive to depolymerizing drugs, are composed of tyrosinated tubulin, whereas non-dynamic, stabilized microtubules are composed of detyrosinated tubulin. Thus depolymerization or stabilization of the microtubule network can easily be detected with double-immunofluorescence staining using antibodies specific to tyrosinated and detyrosinated tubulin. The authors have scaled this assay to the 96-well plate format and adapted its process for an automated handling, including a readout using a microplate reader. They describe the different steps of this adaptation. This assay was validated using known compounds. This new cell-based assay represents an alternative to both global cytotoxicity assays and in vitro tubulin assembly assays commonly used for the detection of microtubule poisons.