Loraine V Fabri1,2, Kristy I Azzopardi1, Joshua Osowicki3,4,5, Hannah R Frost1, Pierre R Smeesters1,2,6,7, Andrew C Steer1,8,9. 1. Tropical Diseases Research Group, Murdoch Children's Research Institute, Melbourne, Victoria, Australia. 2. Department of Paediatrics, Université Libre de Bruxelles, Brussels, Belgium. 3. Tropical Diseases Research Group, Murdoch Children's Research Institute, Melbourne, Victoria, Australia. joshua.osowicki@rch.org.au. 4. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia. joshua.osowicki@rch.org.au. 5. Infectious Diseases Unit, Department of General Medicine, The Royal Children's Hospital Melbourne, Melbourne, Victoria, Australia. joshua.osowicki@rch.org.au. 6. Academic Children Hospital Queen Fabiola, Université Libre de Bruxelles, Brussels, Belgium. 7. Molecular Bacteriology Laboratory, Université Libre de Bruxelles, Brussels, Belgium. 8. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia. 9. Infectious Diseases Unit, Department of General Medicine, The Royal Children's Hospital Melbourne, Melbourne, Victoria, Australia.
Abstract
BACKGROUND: Streptococcus pyogenes causes a profound global burden of morbidity and mortality across its diverse clinical spectrum. To support a new controlled human infection ('challenge') model seeking to accelerate S. pyogenes vaccine development, we aimed to develop an accurate and reliable molecular method for quantifying bacterial load from pharyngeal swabs collected during experimental human pharyngitis. METHODS: Combined sequential RNA + DNA extraction from throat swabs was compared to traditional separate RNA-only and DNA-only extractions. An emm-type specific qPCR was developed to detect the emm75 challenge strain. Results from the qPCR were compared to culture, using throat swab samples collected in a human challenge study. RESULTS: The qPCR was 100% specific for the emm75 challenge strain when tested against a panel of S. pyogenes emm-types and other respiratory pathogens. Combined RNA + DNA extraction had similar yield to traditional separate extractions. The combined extraction method and emm75 qPCR had 98.8% sensitivity compared to culture for throat swabs collected from challenge study participants. CONCLUSIONS: We have developed a reliable molecular method for measuring S. pyogenes bacterial load from throat swabs collected in a controlled human infection model of S. pyogenes pharyngitis. TRIAL REGISTRATION: NCT03361163 on 4th December 2017.
BACKGROUND:Streptococcus pyogenes causes a profound global burden of morbidity and mortality across its diverse clinical spectrum. To support a new controlled humaninfection ('challenge') model seeking to accelerate S. pyogenes vaccine development, we aimed to develop an accurate and reliable molecular method for quantifying bacterial load from pharyngeal swabs collected during experimental humanpharyngitis. METHODS: Combined sequential RNA + DNA extraction from throat swabs was compared to traditional separate RNA-only and DNA-only extractions. An emm-type specific qPCR was developed to detect the emm75 challenge strain. Results from the qPCR were compared to culture, using throat swab samples collected in a human challenge study. RESULTS: The qPCR was 100% specific for the emm75 challenge strain when tested against a panel of S. pyogenes emm-types and other respiratory pathogens. Combined RNA + DNA extraction had similar yield to traditional separate extractions. The combined extraction method and emm75 qPCR had 98.8% sensitivity compared to culture for throat swabs collected from challenge study participants. CONCLUSIONS: We have developed a reliable molecular method for measuring S. pyogenes bacterial load from throat swabs collected in a controlled humaninfection model of S. pyogenespharyngitis. TRIAL REGISTRATION: NCT03361163 on 4th December 2017.
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