Probing the dissonance among the diagnostic outputs of multiple approaches used for detection of Methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin resistant staphylococcus aureus (MRSA) is an extremely infectious hospital acquired bacterial pathogen often found in post-surgical patients globally. Early detection of such pathogens is a critical requirement to eliminate or reduce the incidence of anti-microbial resistance as well as for effective management of the disease. Despite the development of multiple biochemical, microbiological and nucleic acid amplifications techniques (NAATs), conventional culture methods are widely used clinically owing to high variability between the methods, technical skills and infrastructural needs. Further, multiple reports suggest significant variation among diagnostic output for MRSA detection. This work attempts to probe the discordance among the diagnostic output of three commonly used methods, while trying to understand the underlying cause of variability. MRSA detection on 217 clinical pus isolates was carried out using three different methods namely, conventional culture method, qPCR-based amplification and a modern LAMP based detection approach. Also, to confirm the presence of MRSA and distinguish from coagulase-negative staphylococci (CoNS), as well as to investigate the observed differences between qPCR and LAMP outputs, melt curve analysis was performed on discordant samples. LAMP based MRSA detection was found to be the optimum method. In summary, this study evaluates the diagnostic efficiency of the different detection methods, while probing for possible explanations for the observed differences.