In vitro evaluation and comparison of 5 rapid antigen detection tests for the diagnosis of beta-hemolytic group A streptococcal pharyngitis

Nanozyme linked multi-array gas driven sensor for real-time quantitative detection of Group A streptococcus

Group A streptococcus (GAS) is a pathogen typically transmitted through respiratory droplets and skin contact, causing an estimated 700 million mild non-invasive infections worldwide each year. There are approximately 650 000 infections that progress to severe invasive infections, even resulting in death. Therefore, the ability to detect GAS rapidly, accurately and in real time is important. Herein, we developed a nanozyme linked multi-array gas driven sensor (NLMAGS) to point-of-care testing of GAS within 2 h. The NLMAGS demonstrated excellent performance as it combined the advantages of nanozyme techniques, immunoassay techniques, and 3D printing techniques. Platinum- and palladium-rich nanozyme particles (Au@Pt@PdNPs) were synthesized and used to label monocloning antibodies as detection probes. Magnetic beads were labeled with monocloning antibodies as capture probes to establish a double-antibody sandwich immunoassay for the detection of GAS. The sandwich immune complex can catalyze the H2O2 substrate and produce O2. GAS quantification can be achieved by measuring the distance that the O2 pushes the ink drops forward in the sensor. Under optimized conditions, the NLMAGS quantitatively detected 24 spiked samples with a limit of detection (LOD) of 62 CFU mL-1, which was 5 times lower than that of ELISA (334 CFU mL-1). A strong correlation with the conventional ELISA was found (r = 0.99, P < 0.001). In comparison, the traditional lateral flow immunoassay based on Au@Pt@PdNPs-mAb2 (Au@Pt@PdNPs-LFIA) had a LOD of 104 CFU mL-1, which was significantly higher than that of NLMAGS. The NLMAGS demonstrated excellent sensitivity to GAS. The intra- and inter-assay precisions of the sensor were below 15%. Overall, the established NLMAGS has promising potential as a rapid and quantitative method for detecting GAS and can also be used to detect various pathogens.

Recent Advances in the Rheumatic Fever and Rheumatic Heart Disease Continuum

Nearly a century after rheumatic fever (RF) and rheumatic heart disease (RHD) was eradicated from the developed world, the disease remains endemic in many low- and middle-income countries (LMICs), with grim health and socioeconomic impacts. The neglect of RHD which persisted for a semi-centennial was further driven by competing infectious diseases, particularly the human immunodeficiency virus (HIV) pandemic. However, over the last two-decades, slowly at first but with building momentum, there has been a resurgence of interest in RF/RHD. In this narrative review, we present the advances that have been made in the RF/RHD continuum over the past two decades since the re-awakening of interest, with a more concise focus on the last decade's achievements. Such primary advances include understanding the genetic predisposition to RHD, group A Streptococcus (GAS) vaccine development, and improved diagnostic strategies for GAS pharyngitis. Echocardiographic screening for RHD has been a major advance which has unearthed the prevailing high burden of RHD and the recent demonstration of benefit of secondary antibiotic prophylaxis on halting progression of latent RHD is a major step forward. Multiple befitting advances in tertiary management of RHD have also been realized. Finally, we summarize the research gaps and provide illumination on profitable future directions towards global eradication of RHD.

Retrospective study of group A Streptococcus oropharyngeal infection diagnosis using a rapid antigenic detection test in a paediatric population from the central region of Portugal

Group A Streptococcus (GAS) is one of the most important agents of oropharyngeal infection. To avoid unnecessary antibiotic prescription, it is recommended the confirmation of GAS infection in pharyngeal swabs using culture or rapid antigen detection test (RADT). This study aimed to retrospectively analyse the incidence of GAS oropharyngeal infection, detected by RADT, in a paediatric population in the Centre of Portugal. Data was collected from the database of the Paediatric Hospital Emergency Department (ED) regarding patients admitted with symptoms suggesting acute pharyngitis, from January 2013 to December 2018, in a total of 18,304 cases. Among these, 130 clinical files were searched for symptoms, complications and additional visits to the ED. The results showed an average GAS infection prevalence of 33%, with seasonal variation. In preschool children, especially in patients less than 3 years old, where the guidelines do not routinely encourage RADT, GAS tonsillitis assumed an unexpected importance, with 731 positive tests in a total of 3128 cases. Scarlatiniform rash and oral cavity petechiae had significant correlation with streptococcal aetiology (p < 0.05). The statistical analysis also showed that different signs and symptoms assume different weights depending on the age group of the patient. The main conclusion is that the incidence of GAS infection in the studied population is higher than generally described in preschool children, suggesting the need for a more cautious approach to children under 3 years presenting acute pharyngitis, and that RADT in this age group would contribute to a decrease in the number of unnoticed cases.

Diagnostic Methods, Clinical Guidelines, and Antibiotic Treatment for Group A Streptococcal Pharyngitis: A Narrative Review

The most common bacterial cause of pharyngitis is infection by Group A β-hemolytic streptococcus (GABHS), commonly known as strep throat. 5-15% of adults and 15-35% of children in the United States with pharyngitis have a GABHS infection. The symptoms of GABHS overlap with non-GABHS and viral causes of acute pharyngitis, complicating the problem of diagnosis. A careful physical examination and patient history is the starting point for diagnosing GABHS. After a physical examination and patient history is completed, five types of diagnostic methods can be used to ascertain the presence of a GABHS infection: clinical scoring systems, rapid antigen detection tests, throat culture, nucleic acid amplification tests, and machine learning and artificial intelligence. Clinical guidelines developed by professional associations can help medical professionals choose among available techniques to diagnose strep throat. However, guidelines for diagnosing GABHS created by the American and European professional associations vary significantly, and there is substantial evidence that most physicians do not follow any published guidelines. Treatment for GABHS using analgesics, antipyretics, and antibiotics seeks to provide symptom relief, shorten the duration of illness, prevent nonsuppurative and suppurative complications, and decrease the risk of contagion, while minimizing the unnecessary use of antibiotics. There is broad agreement that antibiotics with narrow spectrums of activity are appropriate for treating strep throat. But whether and when patients should be treated with antibiotics for GABHS remains a controversial question. There is no clearly superior management strategy for strep throat, as significant controversy exists regarding the best methods to diagnose GABHS and under what conditions antibiotics should be prescribed.

Comparison of 3 Nucleic Acid Amplification Tests and a Rapid Antigen Test with Culture for the Detection of Group A Streptococci from Throat Swabs

Background

Recently, the US Food and Drug Administration cleared 3 nucleic acid amplification test (NAAT) assays for detection of Streptococcus pyogenes [group A Streptococcus (GAS)] in pharyngeal specimens. However, there are limited studies evaluating the performance of these NAAT assays.

Methods

We compared the results of 3 NAATs (cobas Liat, Luminex Aries, and Cepheid Xpert Xpress) and a rapid antigen assay (Quidel QuickVue in-line strep A) with the accepted gold standard method, bacterial culture.

Results

Sixty-eight throat swab specimens collected between August and October 2017 were tested. Compared to bacterial culture, the sensitivities, specificities, positive predictive value, and negative predictive value for detecting GAS were as follows: cobas Liat: 100%, 97.4%, 96.7%, and 100%; Cepheid Xpert: 100%, 97.4%, 96.7%, and 100%; Luminex Aries: 95.2%, 100%, 100%, and 95.5%. The Quidel QuickVue in-line strep A assay showed poor sensitivity, detecting only 5.2% of culture-positive specimens.

Conclusion

The 3 NAATs have high sensitivity when compared with bacterial culture for detection of GAS. With rapid turnaround time and ease of use, these tests can be considered as reliable point-of-care tests for the diagnosis of GAS, replacing the need for back-up culture.

SERS-based rapid assay for sensitive detection of Group AStreptococcusby evaluation of the swab sampling technique

This study combines the accuracy of the gold standard with the sensitivity of SERS for fast detection of Group AStreptococcus pyogenes.

Detección de la colonización asintomática en orofaringe por Streptococcus pyogenes mediante dos métodos diagnósticos

Introducción. La Streptococcus pyogenes causa infecciones supurativas en la piel, en las mucosas y de carácter sistémico. Su detección oportuna es importante para evitar el desarrollo de complicaciones no supurativas. Además, el estado de portador puede ser una fuente potencial de autoinoculación o de brotes infecciosos.Objetivo. Determinar la presencia de estudiantes de medicina en estado de portador de S. pyogenes mediante dos métodos diagnósticos.Materiales y métodos. Se realizó un estudio de corte transversal con muestreo por conveniencia donde se analizaron muestras de orofaringe por inmunoensayo enzimático StrepA y cultivo bacteriano en agar base sangre de cordero al 5% más pruebas diferenciales con el objetivo de detectar la presencia de S. pyogenes.Resultados. De 77 muestras incluidas en el análisis, 3 (3.9%) fueron positivas por el cultivo microbiológico para S. pyogenes y ninguna por el método StrepA.Conclusión. El hallazgo de la bacteria S. pyogenes entre los estudiantes de medicina asintomáticos alerta de un potencial infeccioso. En la comparación de los métodos diagnósticos para su detección, los hallazgos validan el uso del cultivo sobre el del StrepA, en el caso de que se desee estimar la presencia de portadores de dicho agente.

Peritonsillar abscess (PTA): clinical characteristics, microbiology, drug exposures and outcomes of a large multicenter cohort survey of 412 patients hospitalized in 13 French university hospitals

The aim of this study was to describe the epidemiology of hospitalized patients with peritonsillar abscess (PTA). We conducted a multicenter survey in 13 French university hospitals in 2009-2012 describing 412 patients. Median age was 29 year (range, 2-84) and current smoking habit was reported by 177 (43 %) patients. Most of the patients (92 %) had consulted a physician for sore throat within 10 days before admission for PTA diagnosis. Additional symptoms such as visible tonsil abnormalities (83 %), tender cervical adenopathy (57 %) and fever ≥ 38.5 °C (53 %) were also reported. A total of 65 % patients (269/412) reported recent systemic anti-inflammatory agents (AIAs) exposure by medical prescription (70 %), self-medication (22 %), or both (8 %); 61 % and 27 % reported recent exposure to antibiotic and topical treatments for sore throat, respectively. Non-steroidal AIAs were used most often (45 %), particularly arylpropionic derivatives. A rapid diagnosis antigen test (RDT) for Streptococcus pyogenes was performed in 70 (17 %) patients and was positive in 17 (24 %), of whom 9 (53 %) were exposed to AIAs and 14 (82 %) to antibiotics. To treat PTA, antibiotic therapy was given to 392 (95 %) patients. Of 333 antibiotic prescriptions, amoxicillin-clavulanic acid and metronidazole were the most prescribed antibiotics (42 and 17 %, respectively). Surgical drainage of the abscess was performed in 119 (29 %) cases and tonsillectomy in 75 (18 %) cases. The clinical outcome was favorable during the hospital stay in 404 (98 %) patients. In conclusion, patients with sore throat are often exposed to AIAs before PTA diagnosis, and antibiotic prescription was not often based on the RDT positivity.