Rapid molecular diagnosis of group a streptococcus with a novel loop mediated isothermal amplification method

Abstract

Background: Group A Streptococcus (GAS) is the most common bacterial cause of acute tonsillopharyngitis. In this study, it was aimed to evaluate the performance of a novel Loop Mediated Isothermal Amplification (LAMP) method in the rapid diagnosis of GAS in samples taken from children with a pre-diagnosis of acute bacterial tonsillopharyngitis by comparing it with culture and rapid antigen test (RAT) methods. Methods: A total of 100 throat swab samples taken from children at the pediatrics outpatient clinic with suspected tonsillopharyngitis were included in the study. Throat swab samples were analyzed by RAT, throat culture, and LAMP method. GAS suspected colonies were identified with MALDI-TOF MS system. The isothermal amplification reaction for LAMP was conducted by a novel LAMP instrument. Results: According to the results of throat cultures; 53 of them were positive and 47 were negative in terms of GAS. Six (11.32%) of the culture positive samples were found to be negative by the RAT (sensitivity; 88.68%, specificity 100%). While the antigen test was positive, no culture negative sample was detected. One of the culture positive samples was found negative by LAMP. In two samples, while throat culture was negative, it was observed that LAMP was positive (sensitivity; 98.11%, specificity; 95.74%). In one of these samples, the bacteria grown in the culture were identified as Streptococcus dysgalactiae by mass spectrophotometry. Conclusions: In this study, it was determined that the LAMP method used in the diagnosis of throat infections caused by GAS has high sensitivity and specificity. We believe that the instrument is easy to use, low cost, portable, and adaptable to point of care tests. There are very few studies in the literature regarding the use of the instrument in this field, and it should be evaluated in terms of its usability in daily practice with new studies.